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Subject[PATCH] 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>
---
Arnd Bergmann originally requested this (see parent email in thread)
in code review of an early batch of arch/tile code.

arch/tile/include/asm/processor.h | 7 --
arch/tile/include/asm/signal.h | 4 +
arch/tile/kernel/compat_signal.c | 4 +-
arch/tile/kernel/signal.c | 128 +++++++++++++++++++++++++++++++++++-
arch/tile/kernel/single_step.c | 4 +
arch/tile/kernel/traps.c | 1 +
arch/tile/mm/fault.c | 24 ++++---
kernel/sysctl.c | 2 +-
8 files changed, 151 insertions(+), 23 deletions(-)

diff --git a/arch/tile/include/asm/processor.h b/arch/tile/include/asm/processor.h
index d6b43dd..34c1e01 100644
--- a/arch/tile/include/asm/processor.h
+++ b/arch/tile/include/asm/processor.h
@@ -257,10 +257,6 @@ static inline void cpu_relax(void)
barrier();
}

-struct siginfo;
-extern void arch_coredump_signal(struct siginfo *, struct pt_regs *);
-#define arch_coredump_signal arch_coredump_signal
-
/* Info on this processor (see fs/proc/cpuinfo.c) */
struct seq_operations;
extern const struct seq_operations cpuinfo_op;
@@ -271,9 +267,6 @@ extern char chip_model[64];
/* Data on which physical memory controller corresponds to which NUMA node. */
extern int node_controller[];

-/* Do we dump information to the console when a user application crashes? */
-extern int show_crashinfo;
-
#if CHIP_HAS_CBOX_HOME_MAP()
/* Does the heap allocator return hash-for-home pages by default? */
extern int hash_default;
diff --git a/arch/tile/include/asm/signal.h b/arch/tile/include/asm/signal.h
index 81d92a4..1e1e616 100644
--- a/arch/tile/include/asm/signal.h
+++ b/arch/tile/include/asm/signal.h
@@ -28,6 +28,10 @@ struct pt_regs;
int restore_sigcontext(struct pt_regs *, struct sigcontext __user *);
int setup_sigcontext(struct sigcontext __user *, struct pt_regs *);
void do_signal(struct pt_regs *regs);
+void signal_fault(const char *type, struct pt_regs *,
+ void __user *frame, int sig);
+void trace_unhandled_signal(const char *type, struct pt_regs *regs,
+ unsigned long address, int signo);
#endif

#endif /* _ASM_TILE_SIGNAL_H */
diff --git a/arch/tile/kernel/compat_signal.c b/arch/tile/kernel/compat_signal.c
index dbb0dfc..a7869ad 100644
--- a/arch/tile/kernel/compat_signal.c
+++ b/arch/tile/kernel/compat_signal.c
@@ -317,7 +317,7 @@ long compat_sys_rt_sigreturn(struct pt_regs *regs)
return 0;

badframe:
- force_sig(SIGSEGV, current);
+ signal_fault("bad sigreturn frame", regs, frame, 0);
return 0;
}

@@ -431,6 +431,6 @@ int compat_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
return 0;

give_sigsegv:
- force_sigsegv(sig, current);
+ signal_fault("bad setup frame", regs, frame, sig);
return -EFAULT;
}
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 @@ int restore_sigcontext(struct pt_regs *regs,
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 @@ SYSCALL_DEFINE1(rt_sigreturn, struct pt_regs *, regs)
return 0;

badframe:
- force_sig(SIGSEGV, current);
+ signal_fault("bad sigreturn frame", regs, frame, 0);
return 0;
}

@@ -231,7 +237,7 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
return 0;

give_sigsegv:
- force_sigsegv(sig, current);
+ signal_fault("bad setup frame", regs, frame, sig);
return -EFAULT;
}

@@ -245,7 +251,6 @@ static int handle_signal(unsigned long sig, siginfo_t *info,
{
int ret;

-
/* Are we from a system call? */
if (regs->faultnum == INT_SWINT_1) {
/* If so, check system call restarting.. */
@@ -363,3 +368,118 @@ done:
/* 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;
+ }
+ }
+}
diff --git a/arch/tile/kernel/single_step.c b/arch/tile/kernel/single_step.c
index 86df5a2..4032ca8 100644
--- a/arch/tile/kernel/single_step.c
+++ b/arch/tile/kernel/single_step.c
@@ -186,6 +186,8 @@ static tile_bundle_bits rewrite_load_store_unaligned(
.si_code = SEGV_MAPERR,
.si_addr = addr
};
+ trace_unhandled_signal("segfault", regs,
+ (unsigned long)addr, SIGSEGV);
force_sig_info(info.si_signo, &info, current);
return (tile_bundle_bits) 0;
}
@@ -196,6 +198,8 @@ static tile_bundle_bits rewrite_load_store_unaligned(
.si_code = BUS_ADRALN,
.si_addr = addr
};
+ trace_unhandled_signal("unaligned trap", regs,
+ (unsigned long)addr, SIGBUS);
force_sig_info(info.si_signo, &info, current);
return (tile_bundle_bits) 0;
}
diff --git a/arch/tile/kernel/traps.c b/arch/tile/kernel/traps.c
index 5474fc2..f9803df 100644
--- a/arch/tile/kernel/traps.c
+++ b/arch/tile/kernel/traps.c
@@ -308,6 +308,7 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
info.si_addr = (void __user *)address;
if (signo == SIGILL)
info.si_trapno = fault_num;
+ trace_unhandled_signal("trap", regs, address, signo);
force_sig_info(signo, &info, current);
}

diff --git a/arch/tile/mm/fault.c b/arch/tile/mm/fault.c
index 24ca54a..25b7b90 100644
--- a/arch/tile/mm/fault.c
+++ b/arch/tile/mm/fault.c
@@ -43,8 +43,11 @@

#include <arch/interrupts.h>

-static noinline void force_sig_info_fault(int si_signo, int si_code,
- unsigned long address, int fault_num, struct task_struct *tsk)
+static noinline void force_sig_info_fault(const char *type, int si_signo,
+ int si_code, unsigned long address,
+ int fault_num,
+ struct task_struct *tsk,
+ struct pt_regs *regs)
{
siginfo_t info;

@@ -59,6 +62,7 @@ static noinline void force_sig_info_fault(int si_signo, int si_code,
info.si_code = si_code;
info.si_addr = (void __user *)address;
info.si_trapno = fault_num;
+ trace_unhandled_signal(type, regs, address, si_signo);
force_sig_info(si_signo, &info, tsk);
}

@@ -71,11 +75,12 @@ SYSCALL_DEFINE2(cmpxchg_badaddr, unsigned long, address,
struct pt_regs *, regs)
{
if (address >= PAGE_OFFSET)
- force_sig_info_fault(SIGSEGV, SEGV_MAPERR, address,
- INT_DTLB_MISS, current);
+ force_sig_info_fault("atomic segfault", SIGSEGV, SEGV_MAPERR,
+ address, INT_DTLB_MISS, current, regs);
else
- force_sig_info_fault(SIGBUS, BUS_ADRALN, address,
- INT_UNALIGN_DATA, current);
+ force_sig_info_fault("atomic alignment fault", SIGBUS,
+ BUS_ADRALN, address,
+ INT_UNALIGN_DATA, current, regs);

/*
* Adjust pc to point at the actual instruction, which is unusual
@@ -471,8 +476,8 @@ bad_area_nosemaphore:
*/
local_irq_enable();

- force_sig_info_fault(SIGSEGV, si_code, address,
- fault_num, tsk);
+ force_sig_info_fault("segfault", SIGSEGV, si_code, address,
+ fault_num, tsk, regs);
return 0;
}

@@ -547,7 +552,8 @@ do_sigbus:
if (is_kernel_mode)
goto no_context;

- force_sig_info_fault(SIGBUS, BUS_ADRERR, address, fault_num, tsk);
+ force_sig_info_fault("bus error", SIGBUS, BUS_ADRERR, address,
+ fault_num, tsk, regs);
return 0;
}

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c0bb324..aaec934 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1496,7 +1496,7 @@ static struct ctl_table fs_table[] = {

static struct ctl_table debug_table[] = {
#if defined(CONFIG_X86) || defined(CONFIG_PPC) || defined(CONFIG_SPARC) || \
- defined(CONFIG_S390)
+ defined(CONFIG_S390) || defined(CONFIG_TILE)
{
.procname = "exception-trace",
.data = &show_unhandled_signals,
--
1.6.5.2


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