kernel: add safememset() kernel call

include/minix/com.h

@@ -352,8 +352,10 @@
 #  define SYS_SCHEDCTL (KERNEL_CALL + 54)	/* sys_schedctl() */
 #  define SYS_STATECTL (KERNEL_CALL + 55)	/* sys_statectl() */
 
+#  define SYS_SAFEMEMSET (KERNEL_CALL + 56)	/* sys_safememset() */
+
 /* Total */
-#define NR_SYS_CALLS	56	/* number of kernel calls */
+#define NR_SYS_CALLS	57	/* number of kernel calls */
 
 #define SYS_CALL_MASK_SIZE BITMAP_CHUNKS(NR_SYS_CALLS)
 
@@ -361,7 +363,7 @@
 #define SYS_BASIC_CALLS \
     SYS_EXIT, SYS_SAFECOPYFROM, SYS_SAFECOPYTO, SYS_VSAFECOPY, SYS_GETINFO, \
     SYS_TIMES, SYS_SETALARM, SYS_SETGRANT, SYS_SAFEMAP, SYS_SAFEREVMAP, \
-    SYS_SAFEUNMAP, SYS_PROFBUF, SYS_SYSCTL, SYS_STATECTL
+    SYS_SAFEUNMAP, SYS_PROFBUF, SYS_SYSCTL, SYS_STATECTL, SYS_SAFEMEMSET
 
 /* Field names for SYS_MEMSET. */
 #define MEM_PTR		m2_p1	/* base */
@@ -561,6 +563,13 @@
 #define	SCP_ADDRESS	m2_p1	/* my own address */
 #define	SCP_BYTES	m2_l2	/* bytes from offset */
 
+/* SYS_SAFEMEMSET */
+#define SMS_DST		m2_i1	/* dst endpoint */
+#define SMS_GID		m2_i3	/* grant id */
+#define SMS_OFFSET	m2_l1	/* offset within grant */
+#define	SMS_BYTES	m2_l2	/* bytes from offset */
+#define SMS_PATTERN     m2_i2	/* memset() pattern */
+
 /* Field names for SYS_VSAFECOPY* */
 #define VSCP_VEC_ADDR	m2_p1	/* start of vector */
 #define VSCP_VEC_SIZE	m2_l2	/* elements in vector */

kernel/system.c

@@ -226,6 +226,9 @@ void system_init(void)
   map(SYS_SAFECOPYTO, do_safecopy_to);	/* copy with pre-granted permission */
   map(SYS_VSAFECOPY, do_vsafecopy);	/* vectored safecopy */
 
+  /* safe memset */
+  map(SYS_SAFEMEMSET, do_safememset);	/* safememset */
+
   /* Mapping. */
   map(SYS_SAFEMAP, do_safemap);		/* map pages from other process */
   map(SYS_SAFEREVMAP, do_saferevmap);	/* grantor revokes the map grant */

kernel/system.h

@@ -178,6 +178,8 @@ int do_vmctl(struct proc * caller, message *m_ptr);
 int do_setgrant(struct proc * caller, message *m_ptr);
 int do_readbios(struct proc * caller, message *m_ptr);
 
+int do_safememset(struct proc * caller, message *m_ptr);
+
 int do_safemap(struct proc * caller, message *m_ptr);
 int do_saferevmap(struct proc * caller, message *m_ptr);
 int do_safeunmap(struct proc * caller, message *m_ptr);

kernel/system/Makefile.inc

@@ -25,6 +25,7 @@ SRCS+= 	\
 	do_setgrant.c \
 	do_privctl.c \
 	do_safecopy.c \
+	do_safememset.c \
 	do_safemap.c \
 	do_sysctl.c \
 	do_getksig.c \

kernel/system/do_safememset.c

@@ -0,0 +1,58 @@
+/* The kernel call implemented in this file:
+ *   m_type:	SYS_SAFEMEMSET
+ *
+ * The parameters for this kernel call are:
+ *	SMS_DST		dst endpoint
+ *	SMS_GID		grant id
+ *	SMS_OFFSET	offset within grant
+ *	SMS_PATTERN     memset pattern byte
+ *	SMS_BYTES	bytes from offset
+ */
+#include <assert.h>
+
+#include <minix/safecopies.h>
+
+#include "kernel/system.h"
+#include "kernel.h"
+
+/*===========================================================================*
+ *                              do_safememset                                *
+ *===========================================================================*/
+int do_safememset(struct proc *caller, message *m_ptr) {
+	/* Implementation of the do_safememset() kernel call */
+
+	/* Extract parameters */
+	endpoint_t dst_endpt = m_ptr->SMS_DST;
+	endpoint_t caller_endpt = caller->p_endpoint;
+	cp_grant_id_t grantid = m_ptr->SMS_GID;
+	vir_bytes g_offset = m_ptr->SMS_OFFSET;
+	int pattern = m_ptr->SMS_PATTERN;
+	size_t len = (size_t)m_ptr->SMS_BYTES;
+
+	struct proc *dst_p;
+	endpoint_t new_granter;
+	static vir_bytes v_offset;
+	int r;
+
+	if (dst_endpt == NONE || caller_endpt == NONE)
+		return EFAULT;
+
+	if (!(dst_p = endpoint_lookup(dst_endpt)))
+		return EINVAL;
+
+	if (!(priv(dst_p) && priv(dst_p)->s_grant_table)) {
+		printf("safememset: dst %d has no grant table\n", dst_endpt);
+		return EINVAL;
+	}
+
+	/* Verify permission exists, memset always requires CPF_WRITE */
+	r = verify_grant(dst_endpt, caller_endpt, grantid, len, CPF_WRITE,
+			 g_offset, &v_offset, &new_granter);
+
+	if (r != OK) {
+		printf("safememset: grant %d verify failed %d", grantid, r);
+		return r;
+	}
+
+	return vm_memset(caller, new_granter, v_offset, pattern, len);
+}