uprobes/x86: Fix the wrong ->si_addr when xol triggers a trap
If the probed insn triggers a trap, ->si_addr = regs->ip is technically
correct, but this is not what the signal handler wants; we need to pass
the address of the probed insn, not the address of xol slot.
Add the new arch-agnostic helper, uprobe_get_trap_addr(), and change
fill_trap_info() and math_error() to use it. !CONFIG_UPROBES case in
uprobes.h uses a macro to avoid include hell and ensure that it can be
compiled even if an architecture doesn't define instruction_pointer().
Test-case:
#include <signal.h>
#include <stdio.h>
#include <unistd.h>
extern void probe_div(void);
void sigh(int sig, siginfo_t *info, void *c)
{
int passed = (info->si_addr == probe_div);
printf(passed ? "PASS\n" : "FAIL\n");
_exit(!passed);
}
int main(void)
{
struct sigaction sa = {
.sa_sigaction = sigh,
.sa_flags = SA_SIGINFO,
};
sigaction(SIGFPE, &sa, NULL);
asm (
"xor %ecx,%ecx\n"
".globl probe_div; probe_div:\n"
"idiv %ecx\n"
);
return 0;
}
it fails if probe_div() is probed.
Note: show_unhandled_signals users should probably use this helper too,
but we need to cleanup them first.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 73b3ea3..3fdb205 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -23,6 +23,7 @@
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/ptrace.h>
+#include <linux/uprobes.h>
#include <linux/string.h>
#include <linux/delay.h>
#include <linux/errno.h>
@@ -148,11 +149,11 @@
case X86_TRAP_DE:
sicode = FPE_INTDIV;
- siaddr = regs->ip;
+ siaddr = uprobe_get_trap_addr(regs);
break;
case X86_TRAP_UD:
sicode = ILL_ILLOPN;
- siaddr = regs->ip;
+ siaddr = uprobe_get_trap_addr(regs);
break;
case X86_TRAP_AC:
sicode = BUS_ADRALN;
@@ -531,7 +532,7 @@
task->thread.error_code = error_code;
info.si_signo = SIGFPE;
info.si_errno = 0;
- info.si_addr = (void __user *)regs->ip;
+ info.si_addr = (void __user *)uprobe_get_trap_addr(regs);
if (trapnr == X86_TRAP_MF) {
unsigned short cwd, swd;
/*