diff --git a/include/arch/i386/include/archtypes.h b/include/arch/i386/include/archtypes.h
index cc3a6b478..22a2ed2bc 100644
--- a/include/arch/i386/include/archtypes.h
+++ b/include/arch/i386/include/archtypes.h
@@ -33,6 +33,7 @@ typedef struct segframe {
 	reg_t	p_cr3;		/* page table root */
 	u32_t	*p_cr3_v;
 	char	*fpu_state;
+	int	p_kern_trap_style;
 } segframe_t;
 
 struct cpu_info {
diff --git a/include/arch/i386/include/asm.h b/include/arch/i386/include/asm.h
index cb15ecf55..1b4c91de2 100644
--- a/include/arch/i386/include/asm.h
+++ b/include/arch/i386/include/asm.h
@@ -218,6 +218,13 @@
 #ifdef __minix
 #define IMPORT(sym)               \
         .extern _C_LABEL(sym)
+
+#define KERVEC_ORIG 32     /* syscall trap to kernel */
+#define IPCVEC_ORIG 33     /* ipc trap to kernel  */
+
+#define KERVEC_UM 34     /* syscall trap to kernel, user-mapped code */
+#define IPCVEC_UM 35     /* ipc trap to kernel, user-mapped code  */
+
 #endif
 
 #endif /* !_I386_ASM_H_ */
diff --git a/include/arch/i386/include/interrupt.h b/include/arch/i386/include/interrupt.h
index f7442f897..b725875c6 100644
--- a/include/arch/i386/include/interrupt.h
+++ b/include/arch/i386/include/interrupt.h
@@ -25,8 +25,10 @@
 #define OVERFLOW_VECTOR    4	/* from INTO */
 
 /* Fixed system call vector. */
-#define KERN_CALL_VECTOR  32	/* system calls are made with int SYSVEC */
-#define IPC_VECTOR        33	/* interrupt vector for ipc */
+#define KERN_CALL_VECTOR_ORIG  32 /* system calls are made with int SYSVEC */
+#define IPC_VECTOR_ORIG        33 /* interrupt vector for ipc */
+#define KERN_CALL_VECTOR_UM    34 /* user-mapped equivalent */
+#define IPC_VECTOR_UM          35 /* user-mapped equivalent */
 
 /* Hardware interrupt numbers. */
 #ifndef USE_APIC
diff --git a/include/arch/i386/include/vm.h b/include/arch/i386/include/vm.h
index 71104e0a2..5c0c3c109 100644
--- a/include/arch/i386/include/vm.h
+++ b/include/arch/i386/include/vm.h
@@ -73,6 +73,7 @@ i386/vm.h
 /* CPUID flags */
 #define CPUID1_EDX_FPU		(1L)		/* FPU presence */
 #define CPUID1_EDX_PSE 		(1L <<  3)	/* Page Size Extension */
+#define CPUID1_EDX_SYSENTER	(1L << 11)	/* Intel SYSENTER */
 #define CPUID1_EDX_PGE 		(1L << 13)	/* Page Global (bit) Enable */
 #define CPUID1_EDX_APIC_ON_CHIP (1L << 9)	/* APIC is present on the chip */
 #define CPUID1_EDX_TSC		(1L << 4)	/* Timestamp counter present */
@@ -85,6 +86,8 @@ i386/vm.h
 #define CPUID1_ECX_SSE4_1	(1L << 19)
 #define CPUID1_ECX_SSE4_2	(1L << 20)
 
+#define CPUID_EF_EDX_SYSENTER	(1L << 11)	/* Intel SYSENTER */
+
 #ifndef __ASSEMBLY__
 
 #include <minix/type.h>
diff --git a/include/minix/com.h b/include/minix/com.h
index 525e4bbc2..7ff70e30c 100644
--- a/include/minix/com.h
+++ b/include/minix/com.h
@@ -629,6 +629,7 @@
 #define VMCTL_VMINHIBIT_SET	30
 #define VMCTL_VMINHIBIT_CLEAR	31
 #define VMCTL_CLEARMAPCACHE	32
+#define VMCTL_BOOTINHIBIT_CLEAR	33
 
 /* Codes and field names for SYS_SYSCTL. */
 #define SYSCTL_CODE		m1_i1	/* SYSCTL_CODE_* below */
diff --git a/include/minix/const.h b/include/minix/const.h
index 2a2d634dc..0afebcf6c 100644
--- a/include/minix/const.h
+++ b/include/minix/const.h
@@ -173,4 +173,8 @@
 /* magic value to put in struct proc entries for sanity checks. */
 #define PMAGIC 0xC0FFEE1
 
+/* MINIX_KERNFLAGS flags */
+#define MKF_I386_INTEL_SYSENTER	(1L << 0) /* SYSENTER available and supported */
+#define MKF_I386_AMD_SYSCALL	(1L << 1) /* SYSCALL available and supported */
+
 #endif /* _MINIX_CONST_H */
diff --git a/include/minix/cpufeature.h b/include/minix/cpufeature.h
index e5f983893..4ceae56c5 100644
--- a/include/minix/cpufeature.h
+++ b/include/minix/cpufeature.h
@@ -21,6 +21,10 @@
 #define _CPUF_I386_HTT		13	/* Supports HTT */
 #define _CPUF_I386_HTT_MAX_NUM	14	/* Maximal num of threads */
 
+#define _CPUF_I386_MTRR		15
+#define _CPUF_I386_SYSENTER	16	/* Intel SYSENTER instrs */
+#define _CPUF_I386_SYSCALL	17	/* AMD SYSCALL instrs */
+
 int _cpufeature(int featureno);
 
 #endif
diff --git a/include/minix/ipc.h b/include/minix/ipc.h
index e07cdefb3..48a92da52 100644
--- a/include/minix/ipc.h
+++ b/include/minix/ipc.h
@@ -5,6 +5,7 @@
 #endif
 #include <minix/ipcconst.h>
 #include <minix/type.h>
+#include <minix/const.h>
 
 /*==========================================================================* 
  * Types relating to messages. 						    *
@@ -152,24 +153,37 @@ typedef struct asynmsg
 #define AMF_NOTIFY_ERR	020	/* Send a notification when AMF_DONE is set and
 				 * delivery of the message failed */
 
-/* Hide names to avoid name space pollution. */
-#define echo		_echo
-#define notify		_notify
-#define sendrec		_sendrec
-#define receive		_receive
-#define send		_send
-#define sendnb		_sendnb
-#define senda		_senda
+int _send_orig(endpoint_t dest, message *m_ptr);
+int _receive_orig(endpoint_t src, message *m_ptr, int *status_ptr);
+int _sendrec_orig(endpoint_t src_dest, message *m_ptr);
+int _sendnb_orig(endpoint_t dest, message *m_ptr);
+int _notify_orig(endpoint_t dest);
+int _senda_orig(asynmsg_t *table, size_t count);
+int _do_kernel_call_orig(message *m_ptr);
 
-int echo(message *m_ptr);
-int notify(endpoint_t dest);
-int sendrec(endpoint_t src_dest, message *m_ptr);
-int receive(endpoint_t src, message *m_ptr, int *status_ptr);
-int send(endpoint_t dest, message *m_ptr);
-int sendnb(endpoint_t dest, message *m_ptr);
-int senda(asynmsg_t *table, size_t count);
 int _minix_kernel_info_struct(struct minix_kerninfo **);
 
-int _do_kernel_call(message *m_ptr);
+struct minix_ipcvecs {
+	int (*send_ptr)(endpoint_t dest, message *m_ptr);
+	int (*receive_ptr)(endpoint_t src, message *m_ptr, int *st);
+	int (*sendrec_ptr)(endpoint_t src_dest, message *m_ptr);
+	int (*sendnb_ptr)(endpoint_t dest, message *m_ptr);
+	int (*notify_ptr)(endpoint_t dest);
+	int (*do_kernel_call_ptr)(message *m_ptr);
+	int (*senda_ptr)(asynmsg_t *table, size_t count);
+};
+
+/* kernel-set IPC vectors retrieved by a constructor in libc/sys-minix/init.c */
+extern struct minix_ipcvecs _minix_ipcvecs;
+
+#define CHOOSETRAP(name) (_minix_ipcvecs. name ## _ptr)
+
+#define send		CHOOSETRAP(send)
+#define receive		CHOOSETRAP(receive)
+#define sendrec		CHOOSETRAP(sendrec)
+#define sendnb		CHOOSETRAP(sendnb)
+#define notify		CHOOSETRAP(notify)
+#define do_kernel_call	CHOOSETRAP(do_kernel_call)
+#define senda		CHOOSETRAP(senda)
 
 #endif /* _IPC_H */
diff --git a/include/minix/type.h b/include/minix/type.h
index dd1473209..dbcb23e1f 100644
--- a/include/minix/type.h
+++ b/include/minix/type.h
@@ -168,8 +168,8 @@ struct minix_kerninfo {
 	 */
 #define KERNINFO_MAGIC 0xfc3b84bf
 	u32_t kerninfo_magic;
-	u32_t minix_feature_flags;
-	u32_t flags_unused1;
+	u32_t minix_feature_flags;	/* features in minix kernel */
+	u32_t ki_flags;			/* what is present in this struct */
 	u32_t flags_unused2;
 	u32_t flags_unused3;
 	u32_t flags_unused4;
@@ -177,7 +177,10 @@ struct minix_kerninfo {
 	struct machine		*machine;
 	struct kmessages	*kmessages;
 	struct loadinfo		*loadinfo;
+	struct minix_ipcvecs	*minix_ipcvecs;
 } __packed;
 
+#define MINIX_KIF_IPCVECS	(1L << 0)
+
 #endif /* _TYPE_H */
 
diff --git a/kernel/arch/i386/Makefile.inc b/kernel/arch/i386/Makefile.inc
index 25f637c53..c9b9375cc 100644
--- a/kernel/arch/i386/Makefile.inc
+++ b/kernel/arch/i386/Makefile.inc
@@ -36,7 +36,7 @@ SRCS+=	mpx.S arch_clock.c arch_do_vmctl.c arch_system.c \
 	do_iopenable.c do_readbios.c do_sdevio.c exception.c i8259.c io_inb.S \
 	io_inl.S io_intr.S io_inw.S io_outb.S io_outl.S io_outw.S klib.S klib16.S memory.c \
 	oxpcie.c protect.c direct_tty_utils.c arch_reset.c \
-	pg_utils.c
+	pg_utils.c usermapped_glo_ipc.S usermapped_data_arch.c
 
 OBJS.kernel+=	${UNPAGED_OBJS}
 
diff --git a/kernel/arch/i386/apic.c b/kernel/arch/i386/apic.c
index 597650020..9ec3190c2 100644
--- a/kernel/arch/i386/apic.c
+++ b/kernel/arch/i386/apic.c
@@ -835,8 +835,10 @@ static struct gate_table_s gate_table_ioapic[] = {
 };
 
 static struct gate_table_s gate_table_common[] = {
-	{ ipc_entry, IPC_VECTOR, USER_PRIVILEGE },
-	{ kernel_call_entry, KERN_CALL_VECTOR, USER_PRIVILEGE },
+	{ ipc_entry_softint_orig, IPC_VECTOR_ORIG, USER_PRIVILEGE },
+	{ kernel_call_entry_orig, KERN_CALL_VECTOR_ORIG, USER_PRIVILEGE },
+	{ ipc_entry_softint_um, IPC_VECTOR_UM, USER_PRIVILEGE },
+	{ kernel_call_entry_um, KERN_CALL_VECTOR_UM, USER_PRIVILEGE },
 	{ NULL, 0, 0}
 };
 
diff --git a/kernel/arch/i386/apic_asm.S b/kernel/arch/i386/apic_asm.S
index 33a379d15..ae9e0b6ba 100644
--- a/kernel/arch/i386/apic_asm.S
+++ b/kernel/arch/i386/apic_asm.S
@@ -18,7 +18,7 @@
 ENTRY(apic_hwint##irq)							\
 	TEST_INT_IN_KERNEL(4, 0f)					;\
 									\
-	SAVE_PROCESS_CTX(0)						;\
+	SAVE_PROCESS_CTX(0, KTS_INT_HARD)				;\
 	push	%ebp							;\
 	call	_C_LABEL(context_stop)					;\
 	add	$4, %esp						;\
@@ -47,7 +47,7 @@ ENTRY(apic_hwint##irq)							\
 #define lapic_intr(func) \
 	TEST_INT_IN_KERNEL(4, 0f)					;\
 									\
-	SAVE_PROCESS_CTX(0)						;\
+	SAVE_PROCESS_CTX(0, KTS_INT_HARD)				;\
 	push	%ebp							;\
 	call	_C_LABEL(context_stop)					;\
 	add	$4, %esp						;\
diff --git a/kernel/arch/i386/arch_system.c b/kernel/arch/i386/arch_system.c
index 2296bf835..4b1812be8 100644
--- a/kernel/arch/i386/arch_system.c
+++ b/kernel/arch/i386/arch_system.c
@@ -7,6 +7,7 @@
 #include <string.h>
 #include <machine/cmos.h>
 #include <machine/bios.h>
+#include <machine/cpu.h>
 #include <minix/portio.h>
 #include <minix/cpufeature.h>
 #include <assert.h>
@@ -149,6 +150,7 @@ static char fpu_state[NR_PROCS][FPU_XFP_SIZE] __aligned(FPUALIGN);
 void arch_proc_reset(struct proc *pr)
 {
 	char *v = NULL;
+	struct stackframe_s reg;
 
 	assert(pr->p_nr < NR_PROCS);
 
@@ -161,11 +163,11 @@ void arch_proc_reset(struct proc *pr)
 	}
 
 	/* Clear process state. */
-        memset(&pr->p_reg, 0, sizeof(pr->p_reg));
+        memset(&reg, 0, sizeof(pr->p_reg));
         if(iskerneln(pr->p_nr))
-        	pr->p_reg.psw = INIT_TASK_PSW;
+        	reg.psw = INIT_TASK_PSW;
         else
-        	pr->p_reg.psw = INIT_PSW;
+        	reg.psw = INIT_PSW;
 
 	pr->p_seg.fpu_state = v;
 
@@ -178,6 +180,9 @@ void arch_proc_reset(struct proc *pr)
 	pr->p_reg.ss = 
 	pr->p_reg.es = 
 	pr->p_reg.ds = USER_DS_SELECTOR;
+
+	/* set full context and make sure it gets restored */
+	arch_proc_setcontext(pr, &reg, 0);
 }
 
 void arch_set_secondary_ipc_return(struct proc *p, u32_t val)
@@ -512,6 +517,94 @@ struct proc * arch_finish_switch_to_user(void)
 	return p;
 }
 
+void arch_proc_setcontext(struct proc *p, struct stackframe_s *state, int isuser)
+{
+	if(isuser) {
+		/* Restore user bits of psw from sc, maintain system bits
+		 * from proc.
+		 */
+		state->psw  =  (state->psw & X86_FLAGS_USER) |
+			(p->p_reg.psw & ~X86_FLAGS_USER);
+	}
+
+	/* someone wants to totally re-initialize process state */
+	assert(sizeof(p->p_reg) == sizeof(*state));
+	memcpy(&p->p_reg, state, sizeof(*state));
+
+	/* further code is instructed to not touch the context
+	 * any more
+	 */
+	p->p_misc_flags |= MF_CONTEXT_SET;
+
+	/* on x86 this requires returning using iret (KTS_INT)
+	 * so that the full context is restored instead of relying on
+	 * the userspace doing it (as it would do on SYSEXIT).
+	 * as ESP and EIP are also reset, userspace won't try to
+	 * restore bogus context after returning.
+	 *
+	 * if the process is not blocked, or the kernel will ignore
+	 * our trap style, we needn't panic but things will probably
+	 * not go well for the process (restored context will be ignored)
+	 * and the situation should be debugged.
+	 */
+	if(!(p->p_rts_flags)) {
+		printf("WARNINIG: setting full context of runnable process\n");
+		print_proc(p);
+		util_stacktrace();
+	}
+	if(p->p_seg.p_kern_trap_style == KTS_NONE)
+		printf("WARNINIG: setting full context of out-of-kernel process\n");
+	p->p_seg.p_kern_trap_style = KTS_FULLCONTEXT;
+}
+
+void restore_user_context(struct proc *p)
+{
+	int trap_style = p->p_seg.p_kern_trap_style;
+#if 0
+#define TYPES 10
+	static int restores[TYPES], n = 0;
+
+	p->p_seg.p_kern_trap_style = KTS_NONE;
+
+	if(trap_style >= 0 && trap_style < TYPES)
+		restores[trap_style]++;
+
+	if(!(n++ % 500000)) {
+		int t;
+		for(t = 0; t < TYPES; t++)
+			if(restores[t])
+				printf("%d: %d   ", t, restores[t]);
+		printf("\n");
+	}
+#endif
+
+	if(trap_style == KTS_SYSENTER) {
+		restore_user_context_sysenter(p);
+		NOT_REACHABLE;
+        }
+
+	if(trap_style == KTS_SYSCALL) {
+		restore_user_context_syscall(p);
+		NOT_REACHABLE;
+	}
+
+        switch(trap_style) {
+                case KTS_NONE:
+                        panic("no entry trap style known");
+                case KTS_INT_HARD:
+                case KTS_INT_UM:
+                case KTS_FULLCONTEXT:
+                case KTS_INT_ORIG:
+			restore_user_context_int(p);
+			NOT_REACHABLE;
+                default:
+                        panic("unknown trap style recorded");
+                        NOT_REACHABLE;
+        }
+
+        NOT_REACHABLE;
+}
+
 void fpu_sigcontext(struct proc *pr, struct sigframe *fr, struct sigcontext *sc)
 {
 	int fp_error;
diff --git a/kernel/arch/i386/arch_watchdog.c b/kernel/arch/i386/arch_watchdog.c
index b6884e4d4..80647af0d 100644
--- a/kernel/arch/i386/arch_watchdog.c
+++ b/kernel/arch/i386/arch_watchdog.c
@@ -9,11 +9,6 @@
 
 #define CPUID_UNHALTED_CORE_CYCLES_AVAILABLE	0
 
-#define INTEL_MSR_PERFMON_CRT0	0xc1
-#define INTEL_MSR_PERFMON_SEL0	0x186
-
-#define INTEL_MSR_PERFMON_SEL0_ENABLE	(1 << 22)
-
 /*
  * Intel architecture performance counters watchdog
  */
diff --git a/kernel/arch/i386/exception.c b/kernel/arch/i386/exception.c
index e10d6dd73..d885cfcd1 100644
--- a/kernel/arch/i386/exception.c
+++ b/kernel/arch/i386/exception.c
@@ -248,11 +248,6 @@ void exception_handler(int is_nested, struct exception_frame * frame)
 			frame->vector, (unsigned long)frame->errcode,
 			(unsigned long)frame->eip, frame->cs,
 			(unsigned long)frame->eflags);
-		printseg("cs: ", 1, saved_proc, frame->cs);
-		printseg("ds: ", 0, saved_proc, saved_proc->p_reg.ds);
-		if(saved_proc->p_reg.ds != saved_proc->p_reg.ss) {
-			printseg("ss: ", 0, saved_proc, saved_proc->p_reg.ss);
-		}
 		proc_stacktrace(saved_proc);
 	}
 
diff --git a/kernel/arch/i386/include/arch_proto.h b/kernel/arch/i386/include/arch_proto.h
index 3693ac460..9748b6c52 100644
--- a/kernel/arch/i386/include/arch_proto.h
+++ b/kernel/arch/i386/include/arch_proto.h
@@ -47,10 +47,25 @@ void alignment_check(void);
 void machine_check(void);
 void simd_exception(void);
 
+void restore_user_context_int(struct proc *);
+void restore_user_context_sysenter(struct proc *);
+void restore_user_context_syscall(struct proc *);
+
 /* Software interrupt handlers, in numerical order. */
 void trp(void);
-void ipc_entry(void);
-void kernel_call_entry(void);
+void ipc_entry_softint_orig(void);
+void ipc_entry_softint_um(void);
+void ipc_entry_sysenter(void);
+void ipc_entry_syscall_cpu0(void);
+void ipc_entry_syscall_cpu1(void);
+void ipc_entry_syscall_cpu2(void);
+void ipc_entry_syscall_cpu3(void);
+void ipc_entry_syscall_cpu4(void);
+void ipc_entry_syscall_cpu5(void);
+void ipc_entry_syscall_cpu6(void);
+void ipc_entry_syscall_cpu7(void);
+void kernel_call_entry_orig(void);
+void kernel_call_entry_um(void);
 void level0_call(void);
 
 /* exception.c */
@@ -111,6 +126,30 @@ void x86_load_es(u32_t);
 void x86_load_fs(u32_t);
 void x86_load_gs(u32_t);
 
+/* ipc functions in usermapped_ipc.S */
+int usermapped_send_softint(endpoint_t dest, message *m_ptr);
+int usermapped_receive_softint(endpoint_t src, message *m_ptr, int *status_ptr);
+int usermapped_sendrec_softint(endpoint_t src_dest, message *m_ptr);
+int usermapped_sendnb_softint(endpoint_t dest, message *m_ptr);
+int usermapped_notify_softint(endpoint_t dest);
+int usermapped_do_kernel_call_softint(message *m_ptr);
+int usermapped_senda_softint(asynmsg_t *table, size_t count);
+
+int usermapped_send_syscall(endpoint_t dest, message *m_ptr);
+int usermapped_receive_syscall(endpoint_t src, message *m_ptr, int *status_ptr);
+int usermapped_sendrec_syscall(endpoint_t src_dest, message *m_ptr);
+int usermapped_sendnb_syscall(endpoint_t dest, message *m_ptr);
+int usermapped_notify_syscall(endpoint_t dest);
+int usermapped_do_kernel_call_syscall(message *m_ptr);
+int usermapped_senda_syscall(asynmsg_t *table, size_t count);
+
+int usermapped_send_sysenter(endpoint_t dest, message *m_ptr);
+int usermapped_receive_sysenter(endpoint_t src, message *m_ptr, int *status_ptr);
+int usermapped_sendrec_sysenter(endpoint_t src_dest, message *m_ptr);
+int usermapped_sendnb_sysenter(endpoint_t dest, message *m_ptr);
+int usermapped_notify_sysenter(endpoint_t dest);
+int usermapped_do_kernel_call_sysenter(message *m_ptr);
+int usermapped_senda_sysenter(asynmsg_t *table, size_t count);
 
 void switch_k_stack(void * esp, void (* continuation)(void));
 
diff --git a/kernel/arch/i386/include/archconst.h b/kernel/arch/i386/include/archconst.h
index 6ae9de784..88fff3c59 100644
--- a/kernel/arch/i386/include/archconst.h
+++ b/kernel/arch/i386/include/archconst.h
@@ -150,4 +150,26 @@
 
 #define PG_ALLOCATEME ((phys_bytes)-1)
 
+/* MSRs */
+#define INTEL_MSR_PERFMON_CRT0         0xc1
+#define INTEL_MSR_SYSENTER_CS         0x174
+#define INTEL_MSR_SYSENTER_ESP        0x175
+#define INTEL_MSR_SYSENTER_EIP        0x176
+#define INTEL_MSR_PERFMON_SEL0        0x186
+
+#define INTEL_MSR_PERFMON_SEL0_ENABLE (1 << 22)
+
+#define AMD_EFER_SCE		(1L << 0) /* SYSCALL/SYSRET enabled */
+#define AMD_MSR_EFER		0xC0000080	/* extended features msr */
+#define AMD_MSR_STAR		0xC0000081	/* SYSCALL params msr */
+
+/* trap styles recorded on kernel entry and exit */
+#define KTS_NONE	1 /* invalid */
+#define KTS_INT_HARD	2 /* exception / hard interrupt */
+#define KTS_INT_ORIG	3 /* soft interrupt from libc */
+#define KTS_INT_UM	4 /* soft interrupt from usermapped code */
+#define KTS_FULLCONTEXT	5 /* must restore full context */
+#define KTS_SYSENTER	6 /* SYSENTER instruction (usermapped) */
+#define KTS_SYSCALL	7 /* SYSCALL instruction (usermapped) */
+
 #endif /* _I386_ACONST_H */
diff --git a/kernel/arch/i386/memory.c b/kernel/arch/i386/memory.c
index 542084f5f..776fec03a 100644
--- a/kernel/arch/i386/memory.c
+++ b/kernel/arch/i386/memory.c
@@ -883,7 +883,10 @@ int arch_phys_map_reply(const int index, const vir_bytes addr)
 	}
 #endif
 	if(index == first_um_idx) {
-		u32_t usermapped_offset;
+		extern struct minix_ipcvecs minix_ipcvecs_sysenter,
+			minix_ipcvecs_syscall,
+			minix_ipcvecs_softint;
+		extern u32_t usermapped_offset;
 		assert(addr > (u32_t) &usermapped_start);
 		usermapped_offset = addr - (u32_t) &usermapped_start;
 		memset(&minix_kerninfo, 0, sizeof(minix_kerninfo));
@@ -895,13 +898,44 @@ int arch_phys_map_reply(const int index, const vir_bytes addr)
 		ASSIGN(kmessages);
 		ASSIGN(loadinfo);
 
+		/* select the right set of IPC routines to map into processes */
+		if(minix_feature_flags & MKF_I386_INTEL_SYSENTER) {
+			printf("kernel: selecting intel sysenter ipc style\n");
+			minix_kerninfo.minix_ipcvecs = &minix_ipcvecs_sysenter;
+		} else  if(minix_feature_flags & MKF_I386_AMD_SYSCALL) {
+			printf("kernel: selecting amd syscall ipc style\n");
+			minix_kerninfo.minix_ipcvecs = &minix_ipcvecs_syscall;
+		} else	{
+			printf("kernel: selecting fallback (int) ipc style\n");
+			minix_kerninfo.minix_ipcvecs = &minix_ipcvecs_softint;
+		}
+
 		/* adjust the pointers of the functions and the struct
 		 * itself to the user-accessible mapping
 		 */
+		FIXPTR(minix_kerninfo.minix_ipcvecs->send_ptr);
+		FIXPTR(minix_kerninfo.minix_ipcvecs->receive_ptr);
+		FIXPTR(minix_kerninfo.minix_ipcvecs->sendrec_ptr);
+		FIXPTR(minix_kerninfo.minix_ipcvecs->senda_ptr);
+		FIXPTR(minix_kerninfo.minix_ipcvecs->sendnb_ptr);
+		FIXPTR(minix_kerninfo.minix_ipcvecs->notify_ptr);
+		FIXPTR(minix_kerninfo.minix_ipcvecs->do_kernel_call_ptr);
+		FIXPTR(minix_kerninfo.minix_ipcvecs);
+
 		minix_kerninfo.kerninfo_magic = KERNINFO_MAGIC;
 		minix_kerninfo.minix_feature_flags = minix_feature_flags;
 		minix_kerninfo_user = (vir_bytes) FIXEDPTR(&minix_kerninfo);
 
+		/* if libc_ipc is set, disable usermapped ipc functions
+		 * and force binaries to use in-libc fallbacks.
+		 */
+		if(env_get("libc_ipc")) {
+			printf("kernel: forcing in-libc fallback ipc style\n");
+			minix_kerninfo.minix_ipcvecs = NULL;
+		} else {
+			minix_kerninfo.ki_flags |= MINIX_KIF_IPCVECS;
+		}
+
 		return OK;
 	}
 
diff --git a/kernel/arch/i386/mpx.S b/kernel/arch/i386/mpx.S
index 44af169d0..75305e7aa 100644
--- a/kernel/arch/i386/mpx.S
+++ b/kernel/arch/i386/mpx.S
@@ -47,6 +47,7 @@
 /* Selected 386 tss offsets. */
 #define TSS3_S_SP0	4
 
+IMPORT(usermapped_offset)
 IMPORT(copr_not_available_handler)
 IMPORT(params_size)
 IMPORT(params_offset)
@@ -72,7 +73,7 @@ IMPORT(multiboot_init)
 #define hwint_master(irq) \
 	TEST_INT_IN_KERNEL(4, 0f)					;\
 									\
-	SAVE_PROCESS_CTX(0)						;\
+	SAVE_PROCESS_CTX(0, KTS_INT_HARD)				;\
 	push	%ebp							;\
 	movl	$0, %ebp	/* for stack trace */			;\
 	call	_C_LABEL(context_stop)					;\
@@ -132,7 +133,7 @@ ENTRY(hwint07)
 #define hwint_slave(irq)	\
 	TEST_INT_IN_KERNEL(4, 0f)					;\
 									\
-	SAVE_PROCESS_CTX(0)						;\
+	SAVE_PROCESS_CTX(0, KTS_INT_HARD)				;\
 	push	%ebp							;\
 	movl	$0, %ebp	/* for stack trace */			;\
 	call	_C_LABEL(context_stop)					;\
@@ -187,13 +188,83 @@ ENTRY(hwint15)
 /* Interrupt routine for irq 15 */
 	hwint_slave(15)
 
+/* differences with sysenter:
+ *   - we have to find our own per-cpu stack (i.e. post-SYSCALL
+ *     %esp is not configured)
+ *   - we have to save the post-SYSRET %eip, provided by the cpu
+ *     in %ecx
+ *   - the system call parameters are passed in %ecx, so we userland
+ *     code that executes SYSCALL copies %ecx to %edx. So the roles
+ *     of %ecx and %edx are reversed
+ *   - we can use %esi as a scratch register
+ */
+#define ipc_entry_syscall_percpu(cpu)			;\
+ENTRY(ipc_entry_syscall_cpu ## cpu)			;\
+	xchg	%ecx, %edx				;\
+	mov	k_percpu_stacks+4*cpu, %esi		;\
+	mov	(%esi), %ebp 				;\
+	movl	$KTS_SYSCALL, P_KERN_TRAP_STYLE(%ebp)	;\
+	xchg	%esp, %esi				;\
+	jmp	syscall_sysenter_common
+
+ipc_entry_syscall_percpu(0)
+ipc_entry_syscall_percpu(1)
+ipc_entry_syscall_percpu(2)
+ipc_entry_syscall_percpu(3)
+ipc_entry_syscall_percpu(4)
+ipc_entry_syscall_percpu(5)
+ipc_entry_syscall_percpu(6)
+ipc_entry_syscall_percpu(7)
+
+ENTRY(ipc_entry_sysenter)
+	/* SYSENTER simply sets kernel segments, EIP to here, and ESP
+	 * to tss->sp0 (through MSR). so no automatic context saving is done.
+	 * interrupts are disabled.
+	 *
+	 * register usage:
+	 * edi: call type (IPCVEC, KERVEC)
+	 * ebx, eax, ecx: syscall params, set by userland
+	 * esi, edx: esp, eip to restore, set by userland
+	 *
+	 * no state is automatically saved; userland does all of that.
+	 */
+	mov	(%esp), %ebp /* get proc saved by arch_finish_switch_to_user */
+
+	/* inform kernel we entered by sysenter and should
+	 * therefore exit through restore_user_context_sysenter
+	 */
+	movl	$KTS_SYSENTER, P_KERN_TRAP_STYLE(%ebp)
+	add	usermapped_offset, %edx	/* compensate for mapping difference */
+
+syscall_sysenter_common:
+	mov	%esi, SPREG(%ebp)	/* esi is return esp */
+	mov	%edx, PCREG(%ebp)	/* edx is return eip */
+
+	/* check for call type; do_ipc? */
+	cmp	$IPCVEC_UM, %edi
+	jz	ipc_entry_common
+
+	/* check for kernel trap */
+	cmp	$KERVEC_UM, %edi
+	jz	kernel_call_entry_common
+
+	/* unrecognized call number; restore user with error */
+	movl	$-1, AXREG(%ebp)
+	push	%ebp	
+	call	restore_user_context	/* restore_user_context(%ebp); */
+
 /*
  * IPC is only from a process to kernel
  */
-ENTRY(ipc_entry)
+ENTRY(ipc_entry_softint_orig)
+	SAVE_PROCESS_CTX(0, KTS_INT_ORIG)
+	jmp ipc_entry_common
 
-	SAVE_PROCESS_CTX(0)
+ENTRY(ipc_entry_softint_um)
+	SAVE_PROCESS_CTX(0, KTS_INT_UM)
+	jmp ipc_entry_common
 
+ENTRY(ipc_entry_common)
 	/* save the pointer to the current process */
 	push	%ebp
 
@@ -226,10 +297,15 @@ ENTRY(ipc_entry)
 /*
  * kernel call is only from a process to kernel
  */
-ENTRY(kernel_call_entry)
+ENTRY(kernel_call_entry_orig)
+	SAVE_PROCESS_CTX(0, KTS_INT_ORIG)
+	jmp	kernel_call_entry_common
 
-	SAVE_PROCESS_CTX(0)
+ENTRY(kernel_call_entry_um)
+	SAVE_PROCESS_CTX(0, KTS_INT_UM)
+	jmp	kernel_call_entry_common
 
+ENTRY(kernel_call_entry_common)
 	/* save the pointer to the current process */
 	push	%ebp
 
@@ -270,7 +346,7 @@ exception_entry:
 	TEST_INT_IN_KERNEL(12, exception_entry_nested)
 
 exception_entry_from_user:
-	SAVE_PROCESS_CTX(8)
+	SAVE_PROCESS_CTX(8, KTS_INT_HARD)
 
 	/* stop user process cycles */
 	push	%ebp
@@ -306,10 +382,37 @@ exception_entry_nested:
 	/* resume execution at the point of exception */
 	iret
 
-/*===========================================================================*/
-/*				restart					     */
-/*===========================================================================*/
-ENTRY(restore_user_context)
+ENTRY(restore_user_context_sysenter)
+	/* return to userspace using sysexit.
+	 * most of the context saving the userspace process is
+	 * responsible for, we just have to take care of the right EIP
+	 * and ESP restoring here to resume execution, and set EAX and
+	 * EBX to the saved status values.
+	 */
+	mov	4(%esp), %ebp		/* retrieve proc ptr arg */
+	movw	$USER_DS_SELECTOR, %ax
+	movw	%ax, %ds
+	mov	PCREG(%ebp), %edx	/* sysexit restores EIP using EDX */
+	mov	SPREG(%ebp), %ecx	/* sysexit restores ESP using ECX */
+	mov	AXREG(%ebp), %eax	/* trap return value */
+	mov	BXREG(%ebp), %ebx	/* secondary return value */
+	sti				/* enable interrupts */
+	sysexit				/* jump to EIP in user */
+
+ENTRY(restore_user_context_syscall)
+	/* return to userspace using sysret.
+	 * the procedure is very similar to sysexit; it requires
+	 * manual %esp restoring, new EIP in ECX, does not require
+	 * enabling interrupts, and of course sysret instead of sysexit.
+	 */
+	mov	4(%esp), %ebp		/* retrieve proc ptr arg */
+	mov	PCREG(%ebp), %ecx	/* sysret restores EIP using ECX */
+	mov	SPREG(%ebp), %esp	/* restore ESP directly */
+	mov	AXREG(%ebp), %eax	/* trap return value */
+	mov	BXREG(%ebp), %ebx	/* secondary return value */
+	sysret				/* jump to EIP in user */
+
+ENTRY(restore_user_context_int)
 	mov	4(%esp), %ebp	/* will assume P_STACKBASE == 0 */
 
 	/* reconstruct the stack for iret */
@@ -415,7 +518,7 @@ LABEL(inval_opcode)
 LABEL(copr_not_available)
 	TEST_INT_IN_KERNEL(4, copr_not_available_in_kernel)
 	cld			/* set direction flag to a known value */
-	SAVE_PROCESS_CTX(0)
+	SAVE_PROCESS_CTX(0, KTS_INT_HARD)
 	/* stop user process cycles */
 	push	%ebp
 	mov	$0, %ebp
@@ -505,6 +608,7 @@ ENTRY(startup_ap_32)
 
 .data
 .short	0x526F	/* this must be the first data entry (magic #) */
+
 .bss
 k_initial_stack:
 .space	K_STACK_SIZE
diff --git a/kernel/arch/i386/procoffsets.cf b/kernel/arch/i386/procoffsets.cf
index d39772157..e460650dc 100644
--- a/kernel/arch/i386/procoffsets.cf
+++ b/kernel/arch/i386/procoffsets.cf
@@ -16,3 +16,5 @@ member CSREG p_reg.cs
 member PSWREG p_reg.psw
 member SPREG p_reg.sp
 member P_CR3 p_seg.p_cr3
+member P_KERN_TRAP_STYLE p_seg.p_kern_trap_style
+member P_MAGIC p_magic
diff --git a/kernel/arch/i386/protect.c b/kernel/arch/i386/protect.c
index 23f566107..8dc050220 100644
--- a/kernel/arch/i386/protect.c
+++ b/kernel/arch/i386/protect.c
@@ -5,6 +5,7 @@
 
 #include <string.h>
 #include <assert.h>
+#include <minix/cpufeature.h>
 #include <machine/multiboot.h>
 
 #include "kernel/kernel.h"
@@ -25,6 +26,8 @@ struct segdesc_s gdt[GDT_SIZE] __aligned(DESC_SIZE);
 struct gatedesc_s idt[IDT_SIZE] __aligned(DESC_SIZE);
 struct tss_s tss[CONFIG_MAX_CPUS];
 
+u32_t k_percpu_stacks[CONFIG_MAX_CPUS];
+
 int prot_init_done = 0;
 
 phys_bytes vir2phys(void *vir)
@@ -141,8 +144,10 @@ static struct gate_table_s gate_table_exceptions[] = {
 	{ alignment_check, ALIGNMENT_CHECK_VECTOR, INTR_PRIVILEGE },
 	{ machine_check, MACHINE_CHECK_VECTOR, INTR_PRIVILEGE },
 	{ simd_exception, SIMD_EXCEPTION_VECTOR, INTR_PRIVILEGE },
-	{ ipc_entry, IPC_VECTOR, USER_PRIVILEGE },
-	{ kernel_call_entry, KERN_CALL_VECTOR, USER_PRIVILEGE },
+	{ ipc_entry_softint_orig, IPC_VECTOR_ORIG, USER_PRIVILEGE },
+	{ kernel_call_entry_orig, KERN_CALL_VECTOR_ORIG, USER_PRIVILEGE },
+	{ ipc_entry_softint_um, IPC_VECTOR_UM, USER_PRIVILEGE },
+	{ kernel_call_entry_um, KERN_CALL_VECTOR_UM, USER_PRIVILEGE },
 	{ NULL, 0, 0}
 };
 
@@ -168,13 +173,45 @@ int tss_init(unsigned cpu, void * kernel_stack)
 	 * make space for process pointer and cpu id and point to the first
 	 * usable word
 	 */
-	t->sp0 = ((unsigned) kernel_stack) - X86_STACK_TOP_RESERVED;
+	k_percpu_stacks[cpu] = t->sp0 = ((unsigned) kernel_stack) - X86_STACK_TOP_RESERVED;
 	/* 
 	 * set the cpu id at the top of the stack so we know on which cpu is
 	 * this stak in use when we trap to kernel
 	 */
 	*((reg_t *)(t->sp0 + 1 * sizeof(reg_t))) = cpu;
 
+	/* Set up Intel SYSENTER support if available. */
+	if(minix_feature_flags & MKF_I386_INTEL_SYSENTER) {
+	  ia32_msr_write(INTEL_MSR_SYSENTER_CS, 0, KERN_CS_SELECTOR);
+  	  ia32_msr_write(INTEL_MSR_SYSENTER_ESP, 0, t->sp0);
+  	  ia32_msr_write(INTEL_MSR_SYSENTER_EIP, 0, (u32_t) ipc_entry_sysenter);
+  	}
+
+	/* Set up AMD SYSCALL support if available. */
+	if(minix_feature_flags & MKF_I386_AMD_SYSCALL) {
+		u32_t msr_lo, msr_hi;
+
+		/* set SYSCALL ENABLE bit in EFER MSR */
+		ia32_msr_read(AMD_MSR_EFER, &msr_hi, &msr_lo);
+		msr_lo |= AMD_EFER_SCE;
+		ia32_msr_write(AMD_MSR_EFER, msr_hi, msr_lo);
+
+		/* set STAR register value */
+#define set_star_cpu(forcpu) if(cpu == forcpu) {				\
+		ia32_msr_write(AMD_MSR_STAR,					\
+		  ((u32_t)USER_CS_SELECTOR << 16) | (u32_t)KERN_CS_SELECTOR,	\
+		  (u32_t) ipc_entry_syscall_cpu ## forcpu); }
+		set_star_cpu(0);
+		set_star_cpu(1);
+		set_star_cpu(2);
+		set_star_cpu(3);
+		set_star_cpu(4);
+		set_star_cpu(5);
+		set_star_cpu(6);
+		set_star_cpu(7);
+		assert(CONFIG_MAX_CPUS <= 8);
+  	}
+
 	return SEG_SELECTOR(index);
 }
 
@@ -285,6 +322,11 @@ void prot_init()
 {
   extern char k_boot_stktop;
 
+  if(_cpufeature(_CPUF_I386_SYSENTER))
+	minix_feature_flags |= MKF_I386_INTEL_SYSENTER;
+  if(_cpufeature(_CPUF_I386_SYSCALL))
+	minix_feature_flags |= MKF_I386_AMD_SYSCALL;
+
   memset(gdt, 0, sizeof(gdt));
   memset(idt, 0, sizeof(idt));
 
diff --git a/kernel/arch/i386/sconst.h b/kernel/arch/i386/sconst.h
index 1262f6cd6..6138e4402 100644
--- a/kernel/arch/i386/sconst.h
+++ b/kernel/arch/i386/sconst.h
@@ -73,7 +73,7 @@
  * displ is the stack displacement. In case of an exception, there are two extra
  * value on the stack - error code and the exception number
  */
-#define SAVE_PROCESS_CTX(displ) \
+#define SAVE_PROCESS_CTX(displ, trapcode) \
 								\
 	cld /* set the direction flag to a known state */	;\
 								\
@@ -82,6 +82,7 @@
 	movl	(CURR_PROC_PTR + 4 + displ)(%esp), %ebp	;\
 							\
 	SAVE_GP_REGS(%ebp)				;\
+        movl	$trapcode, P_KERN_TRAP_STYLE(%ebp)	;\
 	pop	%esi			/* get the orig %ebp and save it */ ;\
 	mov	%esi, BPREG(%ebp)			;\
 							\
diff --git a/kernel/arch/i386/usermapped_data_arch.c b/kernel/arch/i386/usermapped_data_arch.c
new file mode 100644
index 000000000..837836a21
--- /dev/null
+++ b/kernel/arch/i386/usermapped_data_arch.c
@@ -0,0 +1,33 @@
+#include "kernel.h"
+#include "arch_proto.h"
+
+struct minix_ipcvecs minix_ipcvecs_softint = {
+	.send_ptr = usermapped_send_softint,
+	.receive_ptr = usermapped_receive_softint,
+	.sendrec_ptr = usermapped_sendrec_softint,
+	.sendnb_ptr = usermapped_sendnb_softint,
+	.notify_ptr = usermapped_notify_softint,
+	.do_kernel_call_ptr = usermapped_do_kernel_call_softint,
+	.senda_ptr = usermapped_senda_softint
+};
+
+struct minix_ipcvecs minix_ipcvecs_sysenter = {
+	.send_ptr = usermapped_send_sysenter,
+	.receive_ptr = usermapped_receive_sysenter,
+	.sendrec_ptr = usermapped_sendrec_sysenter,
+	.sendnb_ptr = usermapped_sendnb_sysenter,
+	.notify_ptr = usermapped_notify_sysenter,
+	.do_kernel_call_ptr = usermapped_do_kernel_call_sysenter,
+	.senda_ptr = usermapped_senda_sysenter
+};
+
+struct minix_ipcvecs minix_ipcvecs_syscall = {
+	.send_ptr = usermapped_send_syscall,
+	.receive_ptr = usermapped_receive_syscall,
+	.sendrec_ptr = usermapped_sendrec_syscall,
+	.sendnb_ptr = usermapped_sendnb_syscall,
+	.notify_ptr = usermapped_notify_syscall,
+	.do_kernel_call_ptr = usermapped_do_kernel_call_syscall,
+	.senda_ptr = usermapped_senda_syscall
+};
+
diff --git a/kernel/arch/i386/usermapped_glo_ipc.S b/kernel/arch/i386/usermapped_glo_ipc.S
new file mode 100644
index 000000000..3df59df36
--- /dev/null
+++ b/kernel/arch/i386/usermapped_glo_ipc.S
@@ -0,0 +1,94 @@
+#include <minix/ipcconst.h>
+#include <machine/asm.h>
+
+/**========================================================================* */
+/*                           IPC assembly routines			  * */
+/**========================================================================* */
+/* all message passing routines save ebx, but destroy eax and ecx. */
+
+#define IPCFUNC(name,SETARGS,VEC,POSTTRAP)			 \
+ENTRY(usermapped_ ## name ## _softint)					;\
+	push	%ebp							;\
+	movl	%esp, %ebp						;\
+	push	%ebx							;\
+	SETARGS								;\
+	int	$VEC	/* trap to the kernel */			;\
+	mov	%ebx, %ecx	/* save %ebx */				;\
+	POSTTRAP							;\
+	pop	%ebx							;\
+	pop	%ebp							;\
+	ret								;\
+ENTRY(usermapped_ ## name ## _sysenter)					;\
+	push	%ebp							;\
+	movl	%esp, %ebp						;\
+	push	%ebp							;\
+	push	%edx							;\
+	push	%ebx							;\
+	push	%esi							;\
+	push	%edi							;\
+	movl	%esp, %esi	/* kernel uses %esi for restored %esp */;\
+	movl	$0f, %edx	/* kernel uses %edx for restored %eip */;\
+	movl	$VEC, %edi	/* %edi to distinguish ipc/kerncall */	;\
+	SETARGS			/* call-specific register setup */	;\
+	sysenter		/* disappear into kernel */		;\
+0:									;\
+	mov	%ebx, %ecx	/* return w. state mangled; save %ebx */;\
+	pop	%edi							;\
+	pop	%esi							;\
+	pop	%ebx							;\
+	pop	%edx							;\
+	pop	%ebp							;\
+	POSTTRAP							;\
+	pop	%ebp							;\
+	ret								;\
+ENTRY(usermapped_ ## name ## _syscall)					;\
+	push	%ebp							;\
+	movl	%esp, %ebp						;\
+	push	%ebp							;\
+	push	%edx							;\
+	push	%ebx							;\
+	push	%esi							;\
+	push	%edi							;\
+	movl	$VEC, %edi	/* %edi to distinguish ipc/kerncall */	;\
+	SETARGS			/* call-specific register setup */	;\
+	movl	%ecx, %edx	/* %ecx is clobbered by SYSCALL */	;\
+	syscall			/* disappear into kernel */		;\
+	mov	%ebx, %ecx	/* return w. state mangled; save %ebx */;\
+	pop	%edi							;\
+	pop	%esi							;\
+	pop	%ebx							;\
+	pop	%edx							;\
+	pop	%ebp							;\
+	POSTTRAP							;\
+	pop	%ebp							;\
+	ret
+
+#define IPCARGS(opcode)							\
+	movl	8(%ebp), %eax	/* eax = dest-src */			;\
+	movl	12(%ebp), %ebx	/* ebx = message pointer */		;\
+	movl	$opcode, %ecx						;\
+
+#define SENDA_ARGS		\
+	movl	12(%ebp), %eax	/* eax = count */			;\
+	movl	8(%ebp), %ebx	/* ebx = table */			;\
+	movl	$SENDA, %ecx						;\
+
+#define GETSTATUS							\
+	push	%eax							;\
+	movl    16(%ebp), %eax      /* ecx = saved %ebx */		;\
+	movl	%ecx,  (%eax)						;\
+	pop	%eax
+
+#define KERNARGS mov 8(%ebp), %eax
+
+IPCFUNC(send,IPCARGS(SEND),IPCVEC_UM,)
+IPCFUNC(receive,IPCARGS(RECEIVE),IPCVEC_UM,GETSTATUS)
+IPCFUNC(sendrec,IPCARGS(SENDREC),IPCVEC_UM,)
+IPCFUNC(sendnb,IPCARGS(SENDNB),IPCVEC_UM,)
+IPCFUNC(notify,IPCARGS(NOTIFY),IPCVEC_UM,)
+IPCFUNC(senda,SENDA_ARGS,IPCVEC_UM,)
+IPCFUNC(do_kernel_call,KERNARGS,KERVEC_UM,)
+
+.data
+LABEL(usermapped_offset)
+.space 4
diff --git a/kernel/main.c b/kernel/main.c
index 9dff7251c..652f68f5b 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -240,8 +240,10 @@ void kmain(kinfo_t *local_cbi)
 		get_cpulocal_var(proc_ptr) = rp;
 
 	/* Process isn't scheduled until VM has set up a pagetable for it. */
-	if(rp->p_nr != VM_PROC_NR && rp->p_nr >= 0)
+	if(rp->p_nr != VM_PROC_NR && rp->p_nr >= 0) {
 		rp->p_rts_flags |= RTS_VMINHIBIT;
+		rp->p_rts_flags |= RTS_BOOTINHIBIT;
+	}
 
 	rp->p_rts_flags |= RTS_PROC_STOP;
 	rp->p_rts_flags &= ~RTS_SLOT_FREE;
diff --git a/kernel/proc.h b/kernel/proc.h
index 9b792b931..0a32d022d 100644
--- a/kernel/proc.h
+++ b/kernel/proc.h
@@ -159,6 +159,7 @@ struct proc {
 				   pick a new one. Process was dequeued and
 				   should be enqueued at the end of some run
 				   queue again */
+#define RTS_BOOTINHIBIT	0x10000	/* not ready until VM has made it */
 
 /* A process is runnable iff p_rts_flags == 0. */
 #define rts_f_is_runnable(flg)	((flg) == 0)
diff --git a/kernel/proto.h b/kernel/proto.h
index 28dbba4a6..aa9702480 100644
--- a/kernel/proto.h
+++ b/kernel/proto.h
@@ -59,6 +59,7 @@ void enqueue(struct proc *rp);
 void dequeue(struct proc *rp);
 void switch_to_user(void);
 void arch_proc_reset(struct proc *rp);
+void arch_proc_setcontext(struct proc *rp, struct stackframe_s *state, int user);
 struct proc * arch_finish_switch_to_user(void);
 struct proc *endpoint_lookup(endpoint_t ep);
 #if DEBUG_ENABLE_IPC_WARNINGS
diff --git a/kernel/system/do_sigreturn.c b/kernel/system/do_sigreturn.c
index 090557fd0..f96a727be 100644
--- a/kernel/system/do_sigreturn.c
+++ b/kernel/system/do_sigreturn.c
@@ -49,7 +49,7 @@ int do_sigreturn(struct proc * caller, message * m_ptr)
 #endif
 
   /* Restore the registers. */
-  memcpy(&rp->p_reg, &sc.sc_regs, sizeof(sigregs));
+  arch_proc_setcontext(rp, &sc.sc_regs, 1);
 #if defined(__i386__)
   if(sc.sc_flags & MF_FPU_INITIALIZED)
   {
@@ -60,8 +60,6 @@ int do_sigreturn(struct proc * caller, message * m_ptr)
   }
 #endif
 
-  rp->p_misc_flags |= MF_CONTEXT_SET;
-
   return(OK);
 }
 #endif /* USE_SIGRETURN */
diff --git a/kernel/system/do_vmctl.c b/kernel/system/do_vmctl.c
index f3a9b980e..7ecc5e30b 100644
--- a/kernel/system/do_vmctl.c
+++ b/kernel/system/do_vmctl.c
@@ -174,6 +174,9 @@ int do_vmctl(struct proc * caller, message * m_ptr)
 		/* VM says: forget about old mappings we have cached. */
 		mem_clear_mapcache();
 		return OK;
+	case VMCTL_BOOTINHIBIT_CLEAR:
+		RTS_UNSET(p, RTS_BOOTINHIBIT);
+		return OK;
   }
 
   /* Try architecture-specific vmctls. */
diff --git a/lib/libc/arch/i386/sys-minix/_ipc.S b/lib/libc/arch/i386/sys-minix/_ipc.S
index 4e828d749..bcb70a20c 100644
--- a/lib/libc/arch/i386/sys-minix/_ipc.S
+++ b/lib/libc/arch/i386/sys-minix/_ipc.S
@@ -9,40 +9,40 @@
 /*                           IPC assembly routines			  * */
 /**========================================================================* */
 /* all message passing routines save ebx, but destroy eax and ecx. */
-ENTRY(_send)
+ENTRY(_send_orig)
 	push	%ebp
 	movl	%esp, %ebp
 	push	%ebx
 	movl	SRC_DST(%ebp), %eax	/* eax = dest-src */
 	movl	MESSAGE(%ebp), %ebx	/* ebx = message pointer */
 	movl	$SEND, %ecx	/* _send(dest, ptr) */
-	int	$IPCVEC	/* trap to the kernel */
+	int	$IPCVEC_ORIG	/* trap to the kernel */
 	pop	%ebx
 	pop	%ebp
 	ret
 
-ENTRY(_receive)
+ENTRY(_receive_orig)
 	push	%ebp
 	movl	%esp, %ebp
 	push	%ebx
 	movl	SRC_DST(%ebp), %eax	/* eax = dest-src */
 	movl	MESSAGE(%ebp), %ebx	/* ebx = message pointer */
 	movl	$RECEIVE, %ecx	/* _receive(src, ptr) */
-	int	$IPCVEC	/* trap to the kernel */
+	int	$IPCVEC_ORIG	/* trap to the kernel */
 	movl	STATUS(%ebp), %ecx	/* ecx = status pointer */
 	movl	%ebx, (%ecx)
 	pop	%ebx
 	pop	%ebp
 	ret
 
-ENTRY(_sendrec)
+ENTRY(_sendrec_orig)
 	push	%ebp
 	movl	%esp, %ebp
 	push	%ebx
 	movl	SRC_DST(%ebp), %eax	/* eax = dest-src */
 	movl	MESSAGE(%ebp), %ebx	/* ebx = message pointer */
 	movl	$SENDREC, %ecx	/* _sendrec(srcdest, ptr) */
-	int	$IPCVEC	/* trap to the kernel */
+	int	$IPCVEC_ORIG	/* trap to the kernel */
 	pop	%ebx
 	pop	%ebp
 	ret
@@ -54,38 +54,38 @@ ENTRY(_minix_kernel_info_struct)
 	movl	$0, %eax
 	movl	$0, %ebx
 	movl	$MINIX_KERNINFO, %ecx
-	int	$IPCVEC	/* trap to the kernel */
+	int	$IPCVEC_ORIG	/* trap to the kernel */
 	movl	8(%ebp), %ecx	/* ecx = return struct ptr */
 	movl	%ebx, (%ecx)
 	pop	%ebx
 	pop	%ebp
 	ret
 
-ENTRY(_notify)
+ENTRY(_notify_orig)
 	push	%ebp
 	movl	%esp, %ebp
 	push	%ebx
 	movl	SRC_DST(%ebp), %eax	/* eax = destination  */
 	movl	$NOTIFY, %ecx	/* _notify(srcdst) */
-	int	$IPCVEC	/* trap to the kernel */
+	int	$IPCVEC_ORIG	/* trap to the kernel */
 	pop	%ebx
 	pop	%ebp
 	ret
 
-ENTRY(_sendnb)
+ENTRY(_sendnb_orig)
 	push	%ebp
 	movl	%esp, %ebp
 	push	%ebx
 	movl	SRC_DST(%ebp), %eax	/* eax = dest-src */
 	movl	MESSAGE(%ebp), %ebx	/* ebx = message pointer */
 	movl	$SENDNB, %ecx	/* _sendnb(dest, ptr) */
-	int	$IPCVEC	/* trap to the kernel */
+	int	$IPCVEC_ORIG	/* trap to the kernel */
 	pop	%ebx
 	pop	%ebp
 	ret
 
-ENTRY(_do_kernel_call)
+ENTRY(_do_kernel_call_orig)
 	/* pass the message pointer to kernel in the %eax register */
 	movl	4(%esp), %eax
-	int	$KERVEC
+	int	$KERVEC_ORIG
 	ret
diff --git a/lib/libc/arch/i386/sys-minix/_senda.S b/lib/libc/arch/i386/sys-minix/_senda.S
index 9a2cb6d81..256d85180 100644
--- a/lib/libc/arch/i386/sys-minix/_senda.S
+++ b/lib/libc/arch/i386/sys-minix/_senda.S
@@ -4,7 +4,7 @@
 	MSGTAB = 8	/* message table */
 	TABCOUNT = 12	/* number of entries in message table */
 
-ENTRY(_senda)
+ENTRY(_senda_orig)
 	push	%ebp
 	movl	%esp, %ebp
 	push	%ebx
diff --git a/lib/libc/sys-minix/init.c b/lib/libc/sys-minix/init.c
index 7b21078ca..38974f39c 100644
--- a/lib/libc/sys-minix/init.c
+++ b/lib/libc/sys-minix/init.c
@@ -2,15 +2,29 @@
 #include <stdio.h>
 #include <minix/ipc.h>
 
+/* Minix kernel info, IPC functions pointers */
 struct minix_kerninfo *_minix_kerninfo = NULL;
 
 void    __minix_init(void) __attribute__((__constructor__, __used__));
 
+struct minix_ipcvecs _minix_ipcvecs = {
+	.sendrec_ptr = _sendrec_orig,
+	.send_ptr = _send_orig,
+	.notify_ptr = _notify_orig,
+	.senda_ptr = _senda_orig,
+	.sendnb_ptr = _sendnb_orig,
+	.receive_ptr = _receive_orig,
+	.do_kernel_call_ptr = _do_kernel_call_orig,
+};
+
 void __minix_init(void)
 {
 	if((_minix_kernel_info_struct(&_minix_kerninfo)) != 0
 	  || _minix_kerninfo->kerninfo_magic != KERNINFO_MAGIC) {
 		_minix_kerninfo = NULL;
-	}
+         } else if((_minix_kerninfo->ki_flags & MINIX_KIF_IPCVECS) &&
+         	_minix_kerninfo->minix_ipcvecs) {
+		_minix_ipcvecs = *_minix_kerninfo->minix_ipcvecs;
+         }
 }
 
diff --git a/lib/libc/sys-minix/syscall.c b/lib/libc/sys-minix/syscall.c
index 522810835..c1b53e31c 100644
--- a/lib/libc/sys-minix/syscall.c
+++ b/lib/libc/sys-minix/syscall.c
@@ -11,7 +11,7 @@ int _syscall(endpoint_t who, int syscallnr, message *msgptr)
   int status;
 
   msgptr->m_type = syscallnr;
-  status = _sendrec(who, msgptr);
+  status = sendrec(who, msgptr);
   if (status != 0) {
 	/* 'sendrec' itself failed. */
 	/* XXX - strerror doesn't know all the codes */
diff --git a/lib/libexec/exec_general.c b/lib/libexec/exec_general.c
index 20d3ca9ee..2ac942df9 100644
--- a/lib/libexec/exec_general.c
+++ b/lib/libexec/exec_general.c
@@ -13,6 +13,7 @@
 #include <minix/com.h>
 #include <minix/callnr.h>
 #include <minix/vm.h>
+#include <minix/ipc.h>
 #include <minix/syslib.h>
 #include <sys/mman.h>
 #include <machine/elf.h>
diff --git a/lib/libminlib/i386/_cpufeature.c b/lib/libminlib/i386/_cpufeature.c
index 52d8db2dc..1a7c011d5 100644
--- a/lib/libminlib/i386/_cpufeature.c
+++ b/lib/libminlib/i386/_cpufeature.c
@@ -3,10 +3,14 @@
 #include <minix/minlib.h>
 #include <minix/cpufeature.h>
 #include <machine/vm.h>
+#include <string.h>
 
 int _cpufeature(int cpufeature)
 {
 	u32_t eax, ebx, ecx, edx;
+	u32_t ef_eax = 0, ef_ebx = 0, ef_ecx = 0, ef_edx = 0;
+	unsigned int family, model, stepping;
+	int is_intel = 0, is_amd = 0;
 
 	eax = ebx = ecx = edx = 0;
 
@@ -14,8 +18,34 @@ int _cpufeature(int cpufeature)
 	eax = 0;
 	_cpuid(&eax, &ebx, &ecx, &edx);
 	if(eax > 0) {
+		char vendor[12];
+		memcpy(vendor,   &ebx, sizeof(ebx));
+		memcpy(vendor+4, &edx, sizeof(edx));
+		memcpy(vendor+8, &ecx, sizeof(ecx));
+		if(!strncmp(vendor, "GenuineIntel", sizeof(vendor)))
+			is_intel = 1;
+		if(!strncmp(vendor, "AuthenticAMD", sizeof(vendor)))
+			is_amd = 1;
 		eax = 1;
 		_cpuid(&eax, &ebx, &ecx, &edx);
+	} else return 0;
+
+	stepping   =  eax        & 0xf;
+	model    = (eax >>  4) & 0xf;
+
+	if(model == 0xf || model == 0x6) {
+		model += ((eax >> 16) & 0xf) << 4;
+	}
+
+	family   = (eax >>  8) & 0xf;
+
+	if(family == 0xf) {
+		family += (eax >> 20) & 0xff;
+	}
+
+	if(is_amd) {
+		ef_eax = 0x80000001;
+		_cpuid(&ef_eax, &ef_ebx, &ef_ecx, &ef_edx);
 	}
 
 	switch(cpufeature) {
@@ -53,6 +83,15 @@ int _cpufeature(int cpufeature)
 			return edx & CPUID1_EDX_HTT;
 		case _CPUF_I386_HTT_MAX_NUM:
 			return (ebx >> 16) & 0xff;
+		case _CPUF_I386_SYSENTER:
+			if(!is_intel) return 0;
+			if(!(edx & CPUID1_EDX_SYSENTER)) return 0;
+			if(family == 6 && model < 3 && stepping < 3) return 0;
+			return 1;
+		case _CPUF_I386_SYSCALL:
+			if(!is_amd) return 0;
+			if(!(ef_edx & CPUID_EF_EDX_SYSENTER)) return 0;
+			return 1;
 	}
 
 	return 0;
diff --git a/lib/libsys/kernel_call.c b/lib/libsys/kernel_call.c
index 264547325..856e45aa6 100644
--- a/lib/libsys/kernel_call.c
+++ b/lib/libsys/kernel_call.c
@@ -4,6 +4,6 @@
 int _kernel_call(int syscallnr, message *msgptr)
 {
   msgptr->m_type = syscallnr;
-  _do_kernel_call(msgptr);
+  do_kernel_call(msgptr);
   return(msgptr->m_type);
 }
diff --git a/lib/libsys/taskcall.c b/lib/libsys/taskcall.c
index f6778699a..b547471b7 100644
--- a/lib/libsys/taskcall.c
+++ b/lib/libsys/taskcall.c
@@ -14,7 +14,7 @@ register message *msgptr;
   int status;
 
   msgptr->m_type = syscallnr;
-  status = _sendrec(who, msgptr);
+  status = sendrec(who, msgptr);
   if (status != 0) return(status);
   return(msgptr->m_type);
 }
diff --git a/servers/vm/main.c b/servers/vm/main.c
index 25a0b862d..dbcae012e 100644
--- a/servers/vm/main.c
+++ b/servers/vm/main.c
@@ -294,6 +294,10 @@ void exec_bootproc(struct vmproc *vmp, struct boot_image *ip)
         if(sys_exec(vmp->vm_endpoint, (char *) execi->stack_high - 12,
 		(char *) ip->proc_name, execi->pc) != OK)
 		panic("vm: boot process exec of %d failed\n", vmp->vm_endpoint);
+
+	/* make it runnable */
+	if(sys_vmctl(vmp->vm_endpoint, VMCTL_BOOTINHIBIT_CLEAR, 0) != OK)
+		panic("VMCTL_BOOTINHIBIT_CLEAR failed");
 }
 
 void init_vm(void)
@@ -301,6 +305,7 @@ void init_vm(void)
 	int s, i;
 	static struct memory mem_chunks[NR_MEMS];
 	static struct boot_image *ip;
+	extern void __minix_init(void);
 
 #if SANITYCHECKS
 	incheck = nocheck = 0;
@@ -414,6 +419,11 @@ void init_vm(void)
 
 	/* Initialize the structures for queryexit */
 	init_query_exit();
+
+	/* Acquire kernel ipc vectors that weren't available
+	 * before VM had determined kernel mappings
+	 */
+	__minix_init();
 }
 
 /*===========================================================================*