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Commit abd4f750 authored by Masoud Asgharifard Sharbiani's avatar Masoud Asgharifard Sharbiani Committed by Linus Torvalds
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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: default avatarMasoud Sharbiani <masouds@google.com>
Signed-off-by: default avatarAndi 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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5fa63fcc

arch/i386/kernel/signal.c

+7 −0
Original line number Diff line number Diff line
@@ -199,6 +199,13 @@ asmlinkage int sys_sigreturn(unsigned long __unused) 
	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;

}

arch/i386/kernel/traps.c

+7 −0
Original line number Diff line number Diff line
@@ -618,6 +618,13 @@ fastcall void __kprobes do_general_protection(struct pt_regs * regs, 


	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;

arch/i386/mm/fault.c

+10 −0
Original line number Diff line number Diff line
@@ -283,6 +283,8 @@ static inline int vmalloc_fault(unsigned long address) 
	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 @@ bad_area_nosemaphore: 
		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);

arch/x86_64/kernel/signal.c

+1 −1
Original line number Diff line number Diff line
@@ -487,7 +487,7 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags) 
void signal_fault(struct pt_regs *regs, void __user *frame, char *where)

{ 

	struct task_struct *me = current; 

	if (exception_trace)

	if (show_unhandled_signals && printk_ratelimit())

		printk("%s[%d] bad frame in %s frame:%p rip:%lx rsp:%lx orax:%lx\n",

	       me->comm,me->pid,where,frame,regs->rip,regs->rsp,regs->orig_rax);

arch/x86_64/kernel/traps.c

+4 −2
Original line number Diff line number Diff line
@@ -584,7 +584,8 @@ static void __kprobes do_trap(int trapnr, int signr, char *str, 
		tsk->thread.error_code = error_code;

		tsk->thread.trap_no = trapnr;



		if (exception_trace && unhandled_signal(tsk, signr))

		if (show_unhandled_signals && unhandled_signal(tsk, signr) &&

		    printk_ratelimit())

			printk(KERN_INFO

			       "%s[%d] trap %s rip:%lx rsp:%lx error:%lx\n",

			       tsk->comm, tsk->pid, str,
@@ -688,7 +689,8 @@ asmlinkage void __kprobes do_general_protection(struct pt_regs * regs, 
		tsk->thread.error_code = error_code;

		tsk->thread.trap_no = 13;



		if (exception_trace && unhandled_signal(tsk, SIGSEGV))

		if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&

		    printk_ratelimit())

			printk(KERN_INFO

		       "%s[%d] general protection rip:%lx rsp:%lx error:%lx\n",

			       tsk->comm, tsk->pid,