arch/tile: support signal "exception-trace" hook
This change adds support for /proc/sys/debug/exception-trace to tile.
Like x86 and sparc, by default it is set to "1", generating a one-line
printk whenever a user process crashes. By setting it to "2", we get
a much more complete userspace diagnostic at crash time, including
a user-space backtrace, register dump, and memory dump around the
address of the crash.
Some vestiges of the Tilera-internal version of this support are
removed with this patch (the show_crashinfo variable and the
arch_coredump_signal function). We retain a "crashinfo" boot parameter
which allows you to set the boot-time value of exception-trace.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
diff --git a/arch/tile/kernel/signal.c b/arch/tile/kernel/signal.c
index 1260321..bedaf4e 100644
--- a/arch/tile/kernel/signal.c
+++ b/arch/tile/kernel/signal.c
@@ -39,7 +39,6 @@
#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
-
SYSCALL_DEFINE3(sigaltstack, const stack_t __user *, uss,
stack_t __user *, uoss, struct pt_regs *, regs)
{
@@ -78,6 +77,13 @@
return err;
}
+void signal_fault(const char *type, struct pt_regs *regs,
+ void __user *frame, int sig)
+{
+ trace_unhandled_signal(type, regs, (unsigned long)frame, SIGSEGV);
+ force_sigsegv(sig, current);
+}
+
/* The assembly shim for this function arranges to ignore the return value. */
SYSCALL_DEFINE1(rt_sigreturn, struct pt_regs *, regs)
{
@@ -105,7 +111,7 @@
return 0;
badframe:
- force_sig(SIGSEGV, current);
+ signal_fault("bad sigreturn frame", regs, frame, 0);
return 0;
}
@@ -231,7 +237,7 @@
return 0;
give_sigsegv:
- force_sigsegv(sig, current);
+ signal_fault("bad setup frame", regs, frame, sig);
return -EFAULT;
}
@@ -245,7 +251,6 @@
{
int ret;
-
/* Are we from a system call? */
if (regs->faultnum == INT_SWINT_1) {
/* If so, check system call restarting.. */
@@ -363,3 +368,118 @@
/* Avoid double syscall restart if there are nested signals. */
regs->faultnum = INT_SWINT_1_SIGRETURN;
}
+
+int show_unhandled_signals = 1;
+
+static int __init crashinfo(char *str)
+{
+ unsigned long val;
+ const char *word;
+
+ if (*str == '\0')
+ val = 2;
+ else if (*str != '=' || strict_strtoul(++str, 0, &val) != 0)
+ return 0;
+ show_unhandled_signals = val;
+ switch (show_unhandled_signals) {
+ case 0:
+ word = "No";
+ break;
+ case 1:
+ word = "One-line";
+ break;
+ default:
+ word = "Detailed";
+ break;
+ }
+ pr_info("%s crash reports will be generated on the console\n", word);
+ return 1;
+}
+__setup("crashinfo", crashinfo);
+
+static void dump_mem(void __user *address)
+{
+ void __user *addr;
+ enum { region_size = 256, bytes_per_line = 16 };
+ int i, j, k;
+ int found_readable_mem = 0;
+
+ pr_err("\n");
+ if (!access_ok(VERIFY_READ, address, 1)) {
+ pr_err("Not dumping at address 0x%lx (kernel address)\n",
+ (unsigned long)address);
+ return;
+ }
+
+ addr = (void __user *)
+ (((unsigned long)address & -bytes_per_line) - region_size/2);
+ if (addr > address)
+ addr = NULL;
+ for (i = 0; i < region_size;
+ addr += bytes_per_line, i += bytes_per_line) {
+ unsigned char buf[bytes_per_line];
+ char line[100];
+ if (copy_from_user(buf, addr, bytes_per_line))
+ continue;
+ if (!found_readable_mem) {
+ pr_err("Dumping memory around address 0x%lx:\n",
+ (unsigned long)address);
+ found_readable_mem = 1;
+ }
+ j = sprintf(line, REGFMT":", (unsigned long)addr);
+ for (k = 0; k < bytes_per_line; ++k)
+ j += sprintf(&line[j], " %02x", buf[k]);
+ pr_err("%s\n", line);
+ }
+ if (!found_readable_mem)
+ pr_err("No readable memory around address 0x%lx\n",
+ (unsigned long)address);
+}
+
+void trace_unhandled_signal(const char *type, struct pt_regs *regs,
+ unsigned long address, int sig)
+{
+ struct task_struct *tsk = current;
+
+ if (show_unhandled_signals == 0)
+ return;
+
+ /* If the signal is handled, don't show it here. */
+ if (!is_global_init(tsk)) {
+ void __user *handler =
+ tsk->sighand->action[sig-1].sa.sa_handler;
+ if (handler != SIG_IGN && handler != SIG_DFL)
+ return;
+ }
+
+ /* Rate-limit the one-line output, not the detailed output. */
+ if (show_unhandled_signals <= 1 && !printk_ratelimit())
+ return;
+
+ printk("%s%s[%d]: %s at %lx pc "REGFMT" signal %d",
+ task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
+ tsk->comm, task_pid_nr(tsk), type, address, regs->pc, sig);
+
+ print_vma_addr(KERN_CONT " in ", regs->pc);
+
+ printk(KERN_CONT "\n");
+
+ if (show_unhandled_signals > 1) {
+ switch (sig) {
+ case SIGILL:
+ case SIGFPE:
+ case SIGSEGV:
+ case SIGBUS:
+ pr_err("User crash: signal %d,"
+ " trap %ld, address 0x%lx\n",
+ sig, regs->faultnum, address);
+ show_regs(regs);
+ dump_mem((void __user *)address);
+ break;
+ default:
+ pr_err("User crash: signal %d, trap %ld\n",
+ sig, regs->faultnum);
+ break;
+ }
+ }
+}