x86: i386-show-unhandled-signals-v3
This patch makes the i386 behave the same way that x86_64 does when a
segfault happens. A line gets printed to the kernel log so that tools
that need to check for failures can behave more uniformly between
debug.show_unhandled_signals sysctl variable to 0 (or by doing echo 0 >
/proc/sys/debug/exception-trace)
Also, all of the lines being printed are now using printk_ratelimit() to
deny the ability of DoS from a local user with a program like the
following:
main()
{
while (1)
if (!fork()) *(int *)0 = 0;
}
This new revision also includes the fix that Andrew did which got rid of
new sysctl that was added to the system in earlier versions of this.
Also, 'show-unhandled-signals' sysctl has been renamed back to the old
'exception-trace' to avoid breakage of people's scripts.
AK: Enabling by default for i386 will be likely controversal, but let's see what happens
AK: Really folks, before complaining just fix your segfaults
AK: I bet this will find a lot of silent issues
Signed-off-by: Masoud Sharbiani <masouds@google.com>
Signed-off-by: Andi Kleen <ak@suse.de>
[ Personally, I've found the complaints useful on x86-64, so I'm all for
this. That said, I wonder if we could do it more prettily.. -Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/i386/kernel/signal.c b/arch/i386/kernel/signal.c
index d574e38..f5dd856 100644
--- a/arch/i386/kernel/signal.c
+++ b/arch/i386/kernel/signal.c
@@ -199,6 +199,13 @@
return eax;
badframe:
+ if (show_unhandled_signals && printk_ratelimit())
+ printk("%s%s[%d] bad frame in sigreturn frame:%p eip:%lx"
+ " esp:%lx oeax:%lx\n",
+ current->pid > 1 ? KERN_INFO : KERN_EMERG,
+ current->comm, current->pid, frame, regs->eip,
+ regs->esp, regs->orig_eax);
+
force_sig(SIGSEGV, current);
return 0;
}
diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index 57772a1..438949d 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -618,6 +618,13 @@
current->thread.error_code = error_code;
current->thread.trap_no = 13;
+ if (show_unhandled_signals && unhandled_signal(current, SIGSEGV) &&
+ printk_ratelimit())
+ printk(KERN_INFO
+ "%s[%d] general protection eip:%lx esp:%lx error:%lx\n",
+ current->comm, current->pid,
+ regs->eip, regs->esp, error_code);
+
force_sig(SIGSEGV, current);
return;
diff --git a/arch/i386/mm/fault.c b/arch/i386/mm/fault.c
index e92a101..01ffdd4 100644
--- a/arch/i386/mm/fault.c
+++ b/arch/i386/mm/fault.c
@@ -283,6 +283,8 @@
return 0;
}
+int show_unhandled_signals = 1;
+
/*
* This routine handles page faults. It determines the address,
* and the problem, and then passes it off to one of the appropriate
@@ -469,6 +471,14 @@
if (is_prefetch(regs, address, error_code))
return;
+ if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
+ printk_ratelimit()) {
+ printk("%s%s[%d]: segfault at %08lx eip %08lx "
+ "esp %08lx error %lx\n",
+ tsk->pid > 1 ? KERN_INFO : KERN_EMERG,
+ tsk->comm, tsk->pid, address, regs->eip,
+ regs->esp, error_code);
+ }
tsk->thread.cr2 = address;
/* Kernel addresses are always protection faults */
tsk->thread.error_code = error_code | (address >= TASK_SIZE);