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);
diff --git a/arch/x86_64/kernel/signal.c b/arch/x86_64/kernel/signal.c
index 4886afc..739175b 100644
--- a/arch/x86_64/kernel/signal.c
+++ b/arch/x86_64/kernel/signal.c
@@ -487,7 +487,7 @@
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);
diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index 8713ad4..0388842 100644
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -584,7 +584,8 @@
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 @@
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,
diff --git a/arch/x86_64/mm/fault.c b/arch/x86_64/mm/fault.c
index 2074bdd..5e9ac70 100644
--- a/arch/x86_64/mm/fault.c
+++ b/arch/x86_64/mm/fault.c
@@ -221,16 +221,6 @@
return 0;
}
-int unhandled_signal(struct task_struct *tsk, int sig)
-{
- if (is_init(tsk))
- return 1;
- if (tsk->ptrace & PT_PTRACED)
- return 0;
- return (tsk->sighand->action[sig-1].sa.sa_handler == SIG_IGN) ||
- (tsk->sighand->action[sig-1].sa.sa_handler == SIG_DFL);
-}
-
static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs,
unsigned long error_code)
{
@@ -302,7 +292,7 @@
}
static int page_fault_trace;
-int exception_trace = 1;
+int show_unhandled_signals = 1;
/*
* This routine handles page faults. It determines the address,
@@ -494,7 +484,8 @@
(address >> 32))
return;
- if (exception_trace && unhandled_signal(tsk, SIGSEGV)) {
+ if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
+ printk_ratelimit()) {
printk(
"%s%s[%d]: segfault at %016lx rip %016lx rsp %016lx error %lx\n",
tsk->pid > 1 ? KERN_INFO : KERN_EMERG,
diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c
index 381c2ec..88678e8 100644
--- a/arch/x86_64/mm/init.c
+++ b/arch/x86_64/mm/init.c
@@ -697,39 +697,6 @@
return pfn_valid(pte_pfn(*pte));
}
-#ifdef CONFIG_SYSCTL
-#include <linux/sysctl.h>
-
-static ctl_table debug_table2[] = {
- {
- .ctl_name = 99,
- .procname = "exception-trace",
- .data = &exception_trace,
- .maxlen = sizeof(int),
- .mode = 0644,
- .proc_handler = proc_dointvec
- },
- {}
-};
-
-static ctl_table debug_root_table2[] = {
- {
- .ctl_name = CTL_DEBUG,
- .procname = "debug",
- .mode = 0555,
- .child = debug_table2
- },
- {}
-};
-
-static __init int x8664_sysctl_init(void)
-{
- register_sysctl_table(debug_root_table2);
- return 0;
-}
-__initcall(x8664_sysctl_init);
-#endif
-
/* A pseudo VMA to allow ptrace access for the vsyscall page. This only
covers the 64bit vsyscall page now. 32bit has a real VMA now and does
not need special handling anymore. */