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SubjectRe: [PATCH] arch/tile: support signal "exception-trace" hook
Resending with Andi Kleen's current email address (ak@suse.de was in the
git log for the x86 version of show-unhandled-signals).

On 5/16/2011 2:23 PM, Chris Metcalf wrote:
> 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,

--
Chris Metcalf, Tilera Corp.
http://www.tilera.com




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