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-rw-r--r--arch/um/sys-i386/ptrace.c15
1 files changed, 12 insertions, 3 deletions
diff --git a/arch/um/sys-i386/ptrace.c b/arch/um/sys-i386/ptrace.c
index e839ce65ad2..8032a105949 100644
--- a/arch/um/sys-i386/ptrace.c
+++ b/arch/um/sys-i386/ptrace.c
@@ -6,6 +6,7 @@
#include <linux/config.h>
#include <linux/compiler.h>
#include "linux/sched.h"
+#include "linux/mm.h"
#include "asm/elf.h"
#include "asm/ptrace.h"
#include "asm/uaccess.h"
@@ -26,9 +27,17 @@ int is_syscall(unsigned long addr)
n = copy_from_user(&instr, (void __user *) addr, sizeof(instr));
if(n){
- printk("is_syscall : failed to read instruction from 0x%lx\n",
- addr);
- return(0);
+ /* access_process_vm() grants access to vsyscall and stub,
+ * while copy_from_user doesn't. Maybe access_process_vm is
+ * slow, but that doesn't matter, since it will be called only
+ * in case of singlestepping, if copy_from_user failed.
+ */
+ n = access_process_vm(current, addr, &instr, sizeof(instr), 0);
+ if(n != sizeof(instr)) {
+ printk("is_syscall : failed to read instruction from "
+ "0x%lx\n", addr);
+ return(1);
+ }
}
/* int 0x80 or sysenter */
return((instr == 0x80cd) || (instr == 0x340f));