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minix/kernel/arch/i386/mpx386.S
Tomas Hruby 5efa92f754 NMI watchdog is an awesome feature for debugging locked up kernels. 
There is not that much use for it on a single CPU, however, deadlock
between kernel and system task can be delected. Or a runaway loop.

If a kernel gets locked up the timer interrupts don't occure (as all
interrupts are disabled in kernel mode). The only chance is to
interrupt the kernel by a non-maskable interrupt.

This patch generates NMIs using performance counters. It uses the most
widely available performace counters. As the performance counters are 
highly model-specific this patch is not guaranteed to work on every
machine.  Unfortunately this is also true for KVM :-/ On the other
hand adding this feature for other models is not extremely difficult
and the framework makes it hopefully easy enough.

Depending on the frequency of the CPU an NMI is generated at most
about every 0.5s If the cpu's speed is less then 2Ghz it is generated
at most every 1s. In general an NMI is generated much less often as
the performance counter counts down only if the cpu is not idle.
Therefore the overhead of this feature is fairly minimal even if the
load is high.

Uppon detecting that the kernel is locked up the kernel dumps the 
state of the kernel registers and panics.

Local APIC must be enabled for the watchdog to work.

The code is _always_ compiled in, however, it is only enabled if  
watchdog=<non-zero> is set in the boot monitor.

One corner case is serial console debugging. As dumping a lot of stuff
to the serial link may take a lot of time, the watchdog does not 
detect lockups during this time!!! as it would result in too many
false positives. 10 nmi have to be handled before the lockup is
detected. This means something between ~5s to 10s.

Another corner case is that the watchdog is enabled only after the
paging is enabled as it would be pure madness to try to get it right.
2010-01-16 20:53:55 +00:00

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/*
* This file, mpx386.s, is included by mpx.s when Minix is compiled for
* 32-bit Intel CPUs. The alternative mpx88.s is compiled for 16-bit CPUs.
*
* This file is part of the lowest layer of the MINIX kernel. (The other part
* is "proc.c".) The lowest layer does process switching and message handling.
* Furthermore it contains the assembler startup code for Minix and the 32-bit
* interrupt handlers. It cooperates with the code in "start.c" to set up a
* good environment for main().
*
* Every transition to the kernel goes through this file. Transitions to the
* kernel may be nested. The initial entry may be with a system call (i.e.,
* send or receive a message), an exception or a hardware interrupt; kernel
* reentries may only be made by hardware interrupts. The count of reentries
* is kept in "k_reenter". It is important for deciding whether to switch to
* the kernel stack and for protecting the message passing code in "proc.c".
*
* For the message passing trap, most of the machine state is saved in the
* proc table. (Some of the registers need not be saved.) Then the stack is
* switched to "k_stack", and interrupts are reenabled. Finally, the system
* call handler (in C) is called. When it returns, interrupts are disabled
* again and the code falls into the restart routine, to finish off held-up
* interrupts and run the process or task whose pointer is in "proc_ptr".
*
* Hardware interrupt handlers do the same, except (1) The entire state must
* be saved. (2) There are too many handlers to do this inline, so the save
* routine is called. A few cycles are saved by pushing the address of the
* appropiate restart routine for a return later. (3) A stack switch is
* avoided when the stack is already switched. (4) The (master) 8259 interrupt
* controller is reenabled centrally in save(). (5) Each interrupt handler
* masks its interrupt line using the 8259 before enabling (other unmasked)
* interrupts, and unmasks it after servicing the interrupt. This limits the
* nest level to the number of lines and protects the handler from itself.
*
* For communication with the boot monitor at startup time some constant
* data are compiled into the beginning of the text segment. This facilitates
* reading the data at the start of the boot process, since only the first
* sector of the file needs to be read.
*
* Some data storage is also allocated at the end of this file. This data
* will be at the start of the data segment of the kernel and will be read
* and modified by the boot monitor before the kernel starts.
*/
#include "../../kernel.h" /* configures the kernel */
/* sections */
#include <sys/vm_i386.h>
#ifdef __ACK__
.text
begtext:
#ifdef __ACK__
.rom
#else
.data
#endif
begrom:
.data
begdata:
.bss
begbss:
#endif
#include <minix/config.h>
#include <minix/const.h>
#include <minix/com.h>
#include <ibm/interrupt.h>
#include <archconst.h>
#include "../../const.h"
#include "../../proc.h"
#include "sconst.h"
/* Selected 386 tss offsets. */
#define TSS3_S_SP0 4
/*
* Exported functions
* Note: in assembly language the .define statement applied to a function name
* is loosely equivalent to a prototype in C code -- it makes it possible to
* link to an entity declared in the assembly code but does not create
* the entity.
*/
.globl restart
.globl reload_cr3
.globl write_cr3
.globl divide_error
.globl single_step_exception
.globl nmi
.globl breakpoint_exception
.globl overflow
.globl bounds_check
.globl inval_opcode
.globl copr_not_available
.globl double_fault
.globl copr_seg_overrun
.globl inval_tss
.globl segment_not_present
.globl stack_exception
.globl general_protection
.globl page_fault
.globl copr_error
.globl alignment_check
.globl machine_check
.globl simd_exception
.globl params_size
.globl params_offset
.globl mon_ds
.globl schedcheck
.globl dirtypde
.globl lazy_fpu
.globl hwint00 /* handlers for hardware interrupts */
.globl hwint01
.globl hwint02
.globl hwint03
.globl hwint04
.globl hwint05
.globl hwint06
.globl hwint07
.globl hwint08
.globl hwint09
.globl hwint10
.globl hwint11
.globl hwint12
.globl hwint13
.globl hwint14
.globl hwint15
.globl level0_call
/* Exported variables. */
.globl begbss
.globl begdata
.text
/*===========================================================================*/
/* MINIX */
/*===========================================================================*/
.global MINIX
MINIX:
/* this is the entry point for the MINIX kernel */
jmp over_flags /* skip over the next few bytes */
.short CLICK_SHIFT /* for the monitor: memory granularity */
flags:
/* boot monitor flags:
* call in 386 mode, make bss, make stack,
* load high, don't patch, will return,
* uses generic INT, memory vector,
* new boot code return
*/
.short 0x01FD
nop /* extra byte to sync up disassembler */
over_flags:
/* Set up a C stack frame on the monitor stack. (The monitor sets cs and ds */
/* right. The ss descriptor still references the monitor data segment.) */
movzwl %sp, %esp /* monitor stack is a 16 bit stack */
push %ebp
mov %esp, %ebp
push %esi
push %edi
cmp $0, 4(%ebp) /* monitor return vector is */
je noret /* nonzero if return possible */
incl mon_return
noret:
movl %esp, mon_sp /* save stack pointer for later return */
/* Copy the monitor global descriptor table to the address space of kernel and */
/* switch over to it. Prot_init() can then update it with immediate effect. */
sgdt gdt+GDT_SELECTOR /* get the monitor gdtr */
movl gdt+GDT_SELECTOR+2, %esi /* absolute address of GDT */
mov $gdt, %ebx /* address of kernel GDT */
mov $8*8, %ecx /* copying eight descriptors */
copygdt:
movb %es:(%esi), %al
movb %al, (%ebx)
inc %esi
inc %ebx
loop copygdt
movl gdt+DS_SELECTOR+2, %eax /* base of kernel data */
and $0x00FFFFFF, %eax /* only 24 bits */
add $gdt, %eax /* eax = vir2phys(gdt) */
movl %eax, gdt+GDT_SELECTOR+2 /* set base of GDT */
lgdt gdt+GDT_SELECTOR /* switch over to kernel GDT */
/* Locate boot parameters, set up kernel segment registers and stack. */
mov 8(%ebp), %ebx /* boot parameters offset */
mov 12(%ebp), %edx /* boot parameters length */
mov 16(%ebp), %eax /* address of a.out headers */
movl %eax, aout
mov %ds, %ax /* kernel data */
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
mov %ax, %ss
mov $k_boot_stktop, %esp /* set sp to point to the top of kernel stack */
/* Save boot parameters into these global variables for i386 code */
movl %edx, params_size
movl %ebx, params_offset
movl $SS_SELECTOR, mon_ds
/* Call C startup code to set up a proper environment to run main(). */
push %edx
push %ebx
push $SS_SELECTOR
push $DS_SELECTOR
push $CS_SELECTOR
call cstart /* cstart(cs, ds, mds, parmoff, parmlen) */
add $5*4, %esp
/* Reload gdtr, idtr and the segment registers to global descriptor table set */
/* up by prot_init(). */
lgdt gdt+GDT_SELECTOR
lidt gdt+IDT_SELECTOR
ljmp $CS_SELECTOR, $csinit
csinit:
movw $DS_SELECTOR, %ax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
mov %ax, %ss
movw $TSS_SELECTOR, %ax /* no other TSS is used */
ltr %ax
push $0 /* set flags to known good state */
popf /* esp, clear nested task and int enable */
jmp main /* main() */
/*===========================================================================*/
/* interrupt handlers */
/* interrupt handlers for 386 32-bit protected mode */
/*===========================================================================*/
#define PIC_IRQ_HANDLER(irq) \
push $irq ;\
call irq_handle /* intr_handle(irq_handlers[irq]) */ ;\
add $4, %esp ;
/*===========================================================================*/
/* hwint00 - 07 */
/*===========================================================================*/
/* Note this is a macro, it just looks like a subroutine. */
#define hwint_master(irq) \
TEST_INT_IN_KERNEL(4, 0f) ;\
\
SAVE_PROCESS_CTX(0) ;\
movl $0, %ebp /* for stack trace */ ;\
PIC_IRQ_HANDLER(irq) ;\
movb $END_OF_INT, %al ;\
outb $INT_CTL /* reenable interrupts in master pic */ ;\
jmp restart ;\
\
0: \
pusha ;\
PIC_IRQ_HANDLER(irq) ;\
movb $END_OF_INT, %al ;\
outb $INT_CTL /* reenable interrupts in master pic */ ;\
popa ;\
iret ;
/* Each of these entry points is an expansion of the hwint_master macro */
.balign 16
hwint00:
/* Interrupt routine for irq 0 (the clock). */
hwint_master(0)
.balign 16
hwint01:
/* Interrupt routine for irq 1 (keyboard) */
hwint_master(1)
.balign 16
hwint02:
/* Interrupt routine for irq 2 (cascade!) */
hwint_master(2)
.balign 16
hwint03:
/* Interrupt routine for irq 3 (second serial) */
hwint_master(3)
.balign 16
hwint04:
/* Interrupt routine for irq 4 (first serial) */
hwint_master(4)
.balign 16
hwint05:
/* Interrupt routine for irq 5 (XT winchester) */
hwint_master(5)
.balign 16
hwint06:
/* Interrupt routine for irq 6 (floppy) */
hwint_master(6)
.balign 16
hwint07:
/* Interrupt routine for irq 7 (printer) */
hwint_master(7)
/*===========================================================================*/
/* hwint08 - 15 */
/*===========================================================================*/
/* Note this is a macro, it just looks like a subroutine. */
#define hwint_slave(irq) \
TEST_INT_IN_KERNEL(4, 0f) ;\
\
SAVE_PROCESS_CTX(0) ;\
movl $0, %ebp /* for stack trace */ ;\
PIC_IRQ_HANDLER(irq) ;\
movb $END_OF_INT, %al ;\
outb $INT_CTL /* reenable interrupts in master pic */ ;\
outb $INT2_CTL /* reenable slave 8259 */ ;\
jmp restart ;\
\
0: \
pusha ;\
PIC_IRQ_HANDLER(irq) ;\
movb $END_OF_INT, %al ;\
outb $INT_CTL /* reenable interrupts in master pic */ ;\
outb $INT2_CTL /* reenable slave 8259 */ ;\
popa ;\
iret ;
/* Each of these entry points is an expansion of the hwint_slave macro */
.balign 16
hwint08:
/* Interrupt routine for irq 8 (realtime clock) */
hwint_slave(8)
.balign 16
hwint09:
/* Interrupt routine for irq 9 (irq 2 redirected) */
hwint_slave(9)
.balign 16
hwint10:
/* Interrupt routine for irq 10 */
hwint_slave(10)
.balign 16
hwint11:
/* Interrupt routine for irq 11 */
hwint_slave(11)
.balign 16
hwint12:
/* Interrupt routine for irq 12 */
hwint_slave(12)
.balign 16
hwint13:
/* Interrupt routine for irq 13 (FPU exception) */
hwint_slave(13)
.balign 16
hwint14:
/* Interrupt routine for irq 14 (AT winchester) */
hwint_slave(14)
.balign 16
hwint15:
/* Interrupt routine for irq 15 */
hwint_slave(15)
/*
* syscall is only from a process to kernel
*/
.balign 16
.globl syscall_entry
syscall_entry:
SAVE_PROCESS_CTX(0)
/* save the pointer to the current process */
push %ebp
/*
* pass the syscall arguments from userspace to the handler.
* SAVE_PROCESS_CTX() does not clobber these registers, they are still
* set as the userspace have set them
*/
push %edx
push %ebx
push %eax
push %ecx
/* for stack trace */
movl $0, %ebp
call sys_call
/* restore the current process pointer and save the return value */
add $4 * 4, %esp
pop %esi
mov %eax, AXREG(%esi)
jmp restart
.balign 16
/*
* called by the exception interrupt vectors. If the exception does not push
* errorcode, we assume that the vector handler pushed 0 instead. Next pushed
* thing is the vector number. From this point on we can continue as if every
* exception pushes an error code
*/
exception_entry:
/*
* check if it is a nested trap by comparing the saved code segment
* descriptor with the kernel CS first
*/
TEST_INT_IN_KERNEL(12, exception_entry_nested)
exception_entry_from_user:
cld
SAVE_PROCESS_CTX(8)
/* for stack trace clear %ebp */
movl $0, %ebp
/*
* push a pointer to the interrupt state pushed by the cpu and the
* vector number pushed by the vector handler just before calling
* exception_entry and call the exception handler.
*/
push %esp
push $0 /* it's not a nested exception */
call exception_handler
jmp restart
exception_entry_nested:
pusha
mov %esp, %eax
add $(8 * 4), %eax
push %eax
pushl $1 /* it's a nested exception */
call exception_handler
add $8, %esp
popa
/* clear the error code and the exception number */
add $8, %esp
/* resume execution at the point of exception */
iret
/*===========================================================================*/
/* restart */
/*===========================================================================*/
restart:
call schedcheck
/* %eax is set by schedcheck() to the process to run */
mov %eax, %ebp /* will assume P_STACKBASE == 0 */
cmpl $0, P_CR3(%ebp)
jz 0f
/*
* test if the cr3 is loaded with the current value to avoid unnecessary
* TLB flushes
*/
mov P_CR3(%ebp), %eax
mov %cr3, %ecx
cmp %ecx, %eax
jz 0f
mov %eax, %cr3
mov %ebp, ptproc
movl $0, dirtypde
0:
/* reconstruct the stack for iret */
movl SSREG(%ebp), %eax
push %eax
movl SPREG(%ebp), %eax
push %eax
movl PSWREG(%ebp), %eax
push %eax
movl CSREG(%ebp), %eax
push %eax
movl PCREG(%ebp), %eax
push %eax
RESTORE_GP_REGS(%ebp)
lldt P_LDT_SEL(%ebp) /* enable process' segment descriptors */
RESTORE_SEGS(%ebp)
movl %ss:BPREG(%ebp), %ebp
iret /* continue process */
/*===========================================================================*/
/* exception handlers */
/*===========================================================================*/
#define EXCEPTION_ERR_CODE(vector) \
push $vector ;\
jmp exception_entry
#define EXCEPTION_NO_ERR_CODE(vector) \
pushl $0 ;\
EXCEPTION_ERR_CODE(vector)
divide_error:
EXCEPTION_NO_ERR_CODE(DIVIDE_VECTOR)
single_step_exception:
EXCEPTION_NO_ERR_CODE(DEBUG_VECTOR)
nmi:
#ifndef CONFIG_WATCHDOG
EXCEPTION_NO_ERR_CODE(NMI_VECTOR)
#else
/*
* We have to be very careful as this interrupt can occur anytime. On
* the other hand, if it interrupts a user process, we will resume the
* same process which makes things a little simpler. We know that we are
* already on kernel stack whenever it happened and we can be
* conservative and save everything as we don't need to be extremely
* efficient as the interrupt is infrequent and some overhead is already
* expected.
*/
/*
* save the important registers. We don't save %cs and %ss and they are
* saved and restored by CPU
*/
pushw %ds
pushw %es
pushw %fs
pushw %gs
pusha
/*
* We cannot be sure about the state of the kernel segment register,
* however, we always set %ds and %es to the same as %ss
*/
mov %ss, %si
mov %si, %ds
mov %si, %es
push %esp
call nmi_watchdog_handler
add $4, %esp
/* restore all the important registers as they were before the trap */
popa
popw %gs
popw %fs
popw %es
popw %ds
iret
#endif
breakpoint_exception:
EXCEPTION_NO_ERR_CODE(BREAKPOINT_VECTOR)
overflow:
EXCEPTION_NO_ERR_CODE(OVERFLOW_VECTOR)
bounds_check:
EXCEPTION_NO_ERR_CODE(BOUNDS_VECTOR)
inval_opcode:
EXCEPTION_NO_ERR_CODE(INVAL_OP_VECTOR)
copr_not_available:
TEST_INT_IN_KERNEL(4, copr_not_available_in_kernel)
clts
cld /* set direction flag to a known value */
SAVE_PROCESS_CTX_NON_LAZY(0)
lea P_MISC_FLAGS(%ebp), %ebx
movw (%ebx), %cx
and $MF_FPU_INITIALIZED, %cx
jnz 0f /* jump if FPU is already initialized */
orw $MF_FPU_INITIALIZED, (%ebx)
fninit
jmp copr_return
0: /* load FPU context for current process */
mov %ss:FP_SAVE_AREA_P(%ebp), %eax
cmp $0, osfxsr_feature
jz fp_l_no_fxsr /* FXSR is not avaible. */
/* DO NOT CHANGE THE OPERAND!!! gas2ack does not handle it yet */
fxrstor (%eax)
jmp copr_return
fp_l_no_fxsr:
/* DO NOT CHANGE THE OPERAND!!! gas2ack does not handle it yet */
frstor (%eax)
copr_return:
orw $MF_USED_FPU, (%ebx) /* fpu was used during last execution */
jmp restart
copr_not_available_in_kernel:
movl $NO_NUM, 4(%esp)
movl $0, (%esp)
call minix_panic
double_fault:
EXCEPTION_ERR_CODE(DOUBLE_FAULT_VECTOR)
copr_seg_overrun:
EXCEPTION_NO_ERR_CODE(COPROC_SEG_VECTOR)
inval_tss:
EXCEPTION_ERR_CODE(INVAL_TSS_VECTOR)
segment_not_present:
EXCEPTION_ERR_CODE(SEG_NOT_VECTOR)
stack_exception:
EXCEPTION_ERR_CODE(STACK_FAULT_VECTOR)
general_protection:
EXCEPTION_ERR_CODE(PROTECTION_VECTOR)
page_fault:
EXCEPTION_ERR_CODE(PAGE_FAULT_VECTOR)
copr_error:
EXCEPTION_NO_ERR_CODE(COPROC_ERR_VECTOR)
alignment_check:
EXCEPTION_NO_ERR_CODE(ALIGNMENT_CHECK_VECTOR)
machine_check:
EXCEPTION_NO_ERR_CODE(MACHINE_CHECK_VECTOR)
simd_exception:
EXCEPTION_NO_ERR_CODE(SIMD_EXCEPTION_VECTOR)
/*===========================================================================*/
/* lazy_fpu */
/*===========================================================================*/
/* void lazy_fpu(struct proc *pptr)
* It's called, when we are on kernel stack.
* Actualy lazy code is just few lines, which check MF_USED_FPU,
* another part is save_init_fpu().
*/
lazy_fpu:
push %ebp
mov %esp, %ebp
push %eax
push %ebx
push %ecx
cmp $0, fpu_presence /* Do we have FPU? */
jz no_fpu_available
mov 8(%ebp), %eax /* Get pptr */
lea P_MISC_FLAGS(%eax), %ebx
movw (%ebx), %cx
and $MF_USED_FPU, %cx
jz 0f /* Don't save FPU */
mov %ss:FP_SAVE_AREA_P(%eax), %eax
cmp $0, osfxsr_feature
jz fp_s_no_fxsr /* FXSR is not avaible. */
/* DO NOT CHANGE THE OPERAND!!! gas2ack does not handle it yet */
fxsave (%eax)
fninit
jmp fp_saved
fp_s_no_fxsr:
/* DO NOT CHANGE THE OPERAND!!! gas2ack does not handle it yet */
fnsave (%eax)
fwait /* required for compatibility with processors prior pentium */
fp_saved:
andw $~MF_USED_FPU, (%ebx)
0: mov %cr0, %eax
or $0x00000008, %eax /* Set TS flag */
mov %eax, %cr0
no_fpu_available:
pop %ecx
pop %ebx
pop %eax
pop %ebp
ret
/*===========================================================================*/
/* write_cr3 */
/*===========================================================================*/
/* PUBLIC void write_cr3(unsigned long value); */
write_cr3:
push %ebp
mov %esp, %ebp
mov 8(%ebp), %eax
mov %cr3, %ecx
cmp %ecx, %eax
jz 0f
mov %eax, %cr3
movl $0, dirtypde
0:
pop %ebp
ret
/*===========================================================================*/
/* level0_call */
/*===========================================================================*/
level0_call:
/*
* which level0 function to call was passed here by putting it in %eax
*/
SAVE_PROCESS_CTX(0)
/* for stack trace */
movl $0, %ebp
/*
* the function to call is in %eax, set in userspace. SAVE_PROCESS_CTX()
* does not clobber this register so we can use it straightaway
*/
call *%eax
jmp restart
/*===========================================================================*/
/* reload_cr3 */
/*===========================================================================*/
/* PUBLIC void reload_cr3(void); */
reload_cr3:
push %ebp
mov %esp, %ebp
movl $0, dirtypde
mov %cr3, %eax
mov %eax, %cr3
pop %ebp
ret
/*===========================================================================*/
/* data */
/*===========================================================================*/
#ifdef __ACK__
.rom /* Before the string table please */
#else
.data
#endif
.short 0x526F /* this must be the first data entry (magic #) */
.bss
/*
* this stack is used temporarily for booting only. We switch to a proper kernel
* stack after the first trap to kernel
*/
.globl k_boot_stktop
k_boot_stack:
.space 4096 /* kernel stack */ /* FIXME use macro here */
k_boot_stktop: /* top of kernel stack */
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