[POWERPC] Implement logging of unhandled signals

Implement show_unhandled_signals sysctl + support to print when a process
is killed due to unhandled signals just as i386 and x86_64 does.

Default to having it off, unlike x86 that defaults on.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>

4 files changed, 70 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
index c434d6c4e4e6..a65a44fbe523 100644
--- a/arch/powerpc/kernel/signal.c
+++ b/arch/powerpc/kernel/signal.c
@@ -16,6 +16,12 @@
 
 #include "signal.h"
 
+/* Log an error when sending an unhandled signal to a process. Controlled
+ * through debug.exception-trace sysctl.
+ */
+
+int show_unhandled_signals = 0;
+
 /*
  * Allocate space for the signal frame
  */
diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 590057e9e987..6126bca8b70a 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -705,11 +705,13 @@ int handle_rt_signal32(unsigned long sig, struct k_sigaction *ka,
 {
         struct rt_sigframe __user *rt_sf;
         struct mcontext __user *frame;
+        void __user *addr;
         unsigned long newsp = 0;
 
         /* Set up Signal Frame */
         /* Put a Real Time Context onto stack */
         rt_sf = get_sigframe(ka, regs, sizeof(*rt_sf));
+        addr = rt_sf;
         if (unlikely(rt_sf == NULL))
                 goto badframe;
 
@@ -728,6 +730,7 @@ int handle_rt_signal32(unsigned long sig, struct k_sigaction *ka,
 
         /* Save user registers on the stack */
         frame = &rt_sf->uc.uc_mcontext;
+        addr = frame;
         if (vdso32_rt_sigtramp && current->mm->context.vdso_base) {
                 if (save_user_regs(regs, frame, 0))
                         goto badframe;
@@ -742,6 +745,7 @@ int handle_rt_signal32(unsigned long sig, struct k_sigaction *ka,
 
         /* create a stack frame for the caller of the handler */
         newsp = ((unsigned long)rt_sf) - (__SIGNAL_FRAMESIZE + 16);
+        addr = (void __user *)regs->gpr[1];
         if (put_user(regs->gpr[1], (u32 __user *)newsp))
                 goto badframe;
 
@@ -762,6 +766,12 @@ badframe:
         printk("badframe in handle_rt_signal, regs=%p frame=%p newsp=%lx\n",
                regs, frame, newsp);
 #endif
+        if (show_unhandled_signals && printk_ratelimit())
+                printk(KERN_INFO "%s[%d]: bad frame in handle_rt_signal32: "
+                        "%p nip %08lx lr %08lx\n",
+                        current->comm, current->pid,
+                        addr, regs->nip, regs->link);
+
         force_sigsegv(sig, current);
         return 0;
 }
@@ -886,6 +896,12 @@ long sys_rt_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8,
         return 0;
 
  bad:
+        if (show_unhandled_signals && printk_ratelimit())
+                printk(KERN_INFO "%s[%d]: bad frame in sys_rt_sigreturn: "
+                        "%p nip %08lx lr %08lx\n",
+                        current->comm, current->pid,
+                        rt_sf, regs->nip, regs->link);
+
         force_sig(SIGSEGV, current);
         return 0;
 }
@@ -967,6 +983,13 @@ int sys_debug_setcontext(struct ucontext __user *ctx,
          * We kill the task with a SIGSEGV in this situation.
          */
         if (do_setcontext(ctx, regs, 1)) {
+                if (show_unhandled_signals && printk_ratelimit())
+                        printk(KERN_INFO "%s[%d]: bad frame in "
+                                "sys_debug_setcontext: %p nip %08lx "
+                                "lr %08lx\n",
+                                current->comm, current->pid,
+                                ctx, regs->nip, regs->link);
+
                 force_sig(SIGSEGV, current);
                 goto out;
         }
@@ -1048,6 +1071,12 @@ badframe:
         printk("badframe in handle_signal, regs=%p frame=%p newsp=%lx\n",
                regs, frame, newsp);
 #endif
+        if (show_unhandled_signals && printk_ratelimit())
+                printk(KERN_INFO "%s[%d]: bad frame in handle_signal32: "
+                        "%p nip %08lx lr %08lx\n",
+                        current->comm, current->pid,
+                        frame, regs->nip, regs->link);
+
         force_sigsegv(sig, current);
         return 0;
 }
@@ -1061,12 +1090,14 @@ long sys_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8,
         struct sigcontext __user *sc;
         struct sigcontext sigctx;
         struct mcontext __user *sr;
+        void __user *addr;
         sigset_t set;
 
         /* Always make any pending restarted system calls return -EINTR */
         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 
         sc = (struct sigcontext __user *)(regs->gpr[1] + __SIGNAL_FRAMESIZE);
+        addr = sc;
         if (copy_from_user(&sigctx, sc, sizeof(sigctx)))
                 goto badframe;
 
@@ -1083,6 +1114,7 @@ long sys_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8,
         restore_sigmask(&set);
 
         sr = (struct mcontext __user *)from_user_ptr(sigctx.regs);
+        addr = sr;
         if (!access_ok(VERIFY_READ, sr, sizeof(*sr))
             || restore_user_regs(regs, sr, 1))
                 goto badframe;
@@ -1091,6 +1123,12 @@ long sys_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8,
         return 0;
 
 badframe:
+        if (show_unhandled_signals && printk_ratelimit())
+                printk(KERN_INFO "%s[%d]: bad frame in sys_sigreturn: "
+                        "%p nip %08lx lr %08lx\n",
+                        current->comm, current->pid,
+                        addr, regs->nip, regs->link);
+
         force_sig(SIGSEGV, current);
         return 0;
 }
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index de895e6d8c62..faeb8f207ea4 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -64,6 +64,11 @@ struct rt_sigframe {
         char abigap[288];
 } __attribute__ ((aligned (16)));
 
+static const char fmt32[] = KERN_INFO \
+        "%s[%d]: bad frame in %s: %08lx nip %08lx lr %08lx\n";
+static const char fmt64[] = KERN_INFO \
+        "%s[%d]: bad frame in %s: %016lx nip %016lx lr %016lx\n";
+
 /*
  * Set up the sigcontext for the signal frame.
  */
@@ -315,6 +320,11 @@ badframe:
         printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
                regs, uc, &uc->uc_mcontext);
 #endif
+        if (show_unhandled_signals && printk_ratelimit())
+                printk(regs->msr & MSR_SF ? fmt64 : fmt32,
+                        current->comm, current->pid, "rt_sigreturn",
+                        (long)uc, regs->nip, regs->link);
+
         force_sig(SIGSEGV, current);
         return 0;
 }
@@ -398,6 +408,11 @@ badframe:
         printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
                regs, frame, newsp);
 #endif
+        if (show_unhandled_signals && printk_ratelimit())
+                printk(regs->msr & MSR_SF ? fmt64 : fmt32,
+                        current->comm, current->pid, "setup_rt_frame",
+                        (long)frame, regs->nip, regs->link);
+
         force_sigsegv(signr, current);
         return 0;
 }
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 2f1857c9819f..bf9e39c6e296 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -172,11 +172,21 @@ int die(const char *str, struct pt_regs *regs, long err)
 void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr)
 {
         siginfo_t info;
+        const char fmt32[] = KERN_INFO "%s[%d]: unhandled signal %d " \
+                        "at %08lx nip %08lx lr %08lx code %x\n";
+        const char fmt64[] = KERN_INFO "%s[%d]: unhandled signal %d " \
+                        "at %016lx nip %016lx lr %016lx code %x\n";
 
         if (!user_mode(regs)) {
                 if (die("Exception in kernel mode", regs, signr))
                         return;
-        }
+        } else if (show_unhandled_signals &&
+                    unhandled_signal(current, signr) &&
+                    printk_ratelimit()) {
+                        printk(regs->msr & MSR_SF ? fmt64 : fmt32,
+                                current->comm, current->pid, signr,
+                                addr, regs->nip, regs->link, code);
+                }
 
         memset(&info, 0, sizeof(info));
         info.si_signo = signr;