Rabin,
New it works fine! Thanks!
Sagar
On Wed, Oct 19, 2016 at 3:36 PM, Rabin Vincent <rabin@xxxxxx> wrote:
> On Tue, Oct 18, 2016 at 04:10:51PM -0700, Sagar Borikar wrote:
>> I tried these patches but still don't get correct bt output.
>
> I think I see the problem now. Your EPC is 0 so we hit the if
> (!IS_KVADDR(current.pc)) condition on the first iteration of the
> backtrace loop and exit without trying futher.
>
> Could you please try the following patch? Please include a log with
> debugging enabled ("set debug 8") if it still doesn't work. Thanks.
>
> 8<------------------
> >From 4ae6ab8d181deea53ece847007d27d228166370d Mon Sep 17 00:00:00 2001
> From: Rabin Vincent <rabinv@xxxxxxxx>
> Date: Thu, 20 Oct 2016 00:19:33 +0200
> Subject: [PATCH] mips: allow one invalid PC at start or after exception
>
> Before:
>
> PID: 2810 TASK: 835e41a8 CPU: 1 COMMAND: "sh"
> #0 [8315bb00] crash_kexec at 800b26a4
> #1 [8315bbe0] panic at 800dc0fc
> #2 [8315bc20] die at 8001fa74
> #3 [8315bc50] __do_page_fault at 8002de74
> #4 [8315bd28] ret_from_irq at 80019624
> $ 0 : 00000000 00000001 80690000 00000000
> $ 4 : 00000063 812972dc 81297db8 000000c2
> $ 8 : 00004b38 00000001 80680000 80620000
> $12 : 00000104 00000002 00000000 00000000
> $16 : 80622530 80620000 00000063 80620000
> $20 : 80622470 00000001 00000000 00b9f322
> $24 : 00000003 00000000 00440000 800dca80
> $28 : 8315a000 8315bde0 00000000 80313b30
> Hi : 00000046
> Lo : 0f5c2a0e
> epc : 00000000
> ra : 80313b30 __handle_sysrq+0x144
> Status: 1100fc03
> Cause : 10800008
> BadVA : 00000000
>
> After:
>
> crash> bt
> PID: 2810 TASK: 835e41a8 CPU: 1 COMMAND: "sh"
> #0 [8315bb00] crash_kexec at 800b26a4
> #1 [8315bbe0] panic at 800dc0fc
> #2 [8315bc20] die at 8001fa74
> #3 [8315bc50] __do_page_fault at 8002de74
> #4 [8315bd28] ret_from_irq at 80019624
> $ 0 : 00000000 00000001 80690000 00000000
> $ 4 : 00000063 812972dc 81297db8 000000c2
> $ 8 : 00004b38 00000001 80680000 80620000
> $12 : 00000104 00000002 00000000 00000000
> $16 : 80622530 80620000 00000063 80620000
> $20 : 80622470 00000001 00000000 00b9f322
> $24 : 00000003 00000000 00440000 800dca80
> $28 : 8315a000 8315bde0 00000000 80313b30
> Hi : 00000046
> Lo : 0f5c2a0e
> epc : 00000000
> ra : 80313b30 __handle_sysrq+0x144
> Status: 1100fc03
> Cause : 10800008
> BadVA : 00000000
> #5 [8315bde0] (invalid) at 0
> #6 [8315bde0] __handle_sysrq at 80313b30
> #7 [8315be18] write_sysrq_trigger at 80313c24
> #8 [8315be38] proc_reg_write at 80178074
> #9 [8315be58] __vfs_write at 8011ea78
> #10 [8315bec0] vfs_write at 8011fe7c
> #11 [8315bef0] sys_write at 801201e8
> #12 [8315bf28] syscall_common at 800275c8
> ---
> mips.c | 35 +++++++++++++++++++++++++----------
> 1 file changed, 25 insertions(+), 10 deletions(-)
>
> diff --git a/mips.c b/mips.c
> index 6cd8d1f..1bb4d27 100644
> --- a/mips.c
> +++ b/mips.c
> @@ -413,7 +413,7 @@ mips_dump_backtrace_entry(struct bt_info *bt, struct syment *sym,
> struct mips_unwind_frame *current,
> struct mips_unwind_frame *previous, int level)
> {
> - const char *name = sym->name;
> + const char *name = sym ? sym->name : "(invalid)";
> struct load_module *lm;
> char *name_plus_offset;
> char buf[BUFSIZE];
> @@ -447,7 +447,7 @@ mips_dump_backtrace_entry(struct bt_info *bt, struct syment *sym,
> fprintf(fp, " %s\n", buf);
> }
>
> - if (mips_is_exception_entry(sym)) {
> + if (sym && mips_is_exception_entry(sym)) {
> char pt_regs[SIZE(pt_regs)];
>
> GET_STACK_DATA(current->sp, &pt_regs, SIZE(pt_regs));
> @@ -533,6 +533,7 @@ mips_back_trace_cmd(struct bt_info *bt)
> {
> struct mips_unwind_frame current, previous;
> int level = 0;
> + int invalid_ok = 1;
>
> if (bt->flags & BT_REGS_NOT_FOUND)
> return;
> @@ -549,22 +550,24 @@ mips_back_trace_cmd(struct bt_info *bt)
> }
>
> while (INSTACK(current.sp, bt)) {
> - struct syment *symbol;
> + struct syment *symbol = NULL;
> ulong offset;
>
> if (CRASHDEBUG(8))
> fprintf(fp, "level %d pc %#lx ra %#lx sp %lx\n",
> level, current.pc, current.ra, current.sp);
>
> - if (!IS_KVADDR(current.pc))
> + if (!IS_KVADDR(current.pc) && !invalid_ok)
> return;
>
> symbol = value_search(current.pc, &offset);
> - if (!symbol) {
> + if (!symbol && !invalid_ok) {
> error(FATAL, "PC is unknown symbol (%lx)", current.pc);
> return;
> }
>
> + invalid_ok = 0;
> +
> /*
> * If we get an address which points to the start of a
> * function, then it could one of the following:
> @@ -586,7 +589,7 @@ mips_back_trace_cmd(struct bt_info *bt)
> * * ret_from_fork
> * * ret_from_kernel_thread
> */
> - if (!current.ra && !offset && !STRNEQ(symbol->name, "ret_from")) {
> + if (!current.ra && !offset && symbol && !STRNEQ(symbol->name, "ret_from")) {
> if (CRASHDEBUG(8))
> fprintf(fp, "zero offset at %s, try previous symbol\n",
> symbol->name);
> @@ -598,7 +601,7 @@ mips_back_trace_cmd(struct bt_info *bt)
> }
> }
>
> - if (mips_is_exception_entry(symbol)) {
> + if (symbol && mips_is_exception_entry(symbol)) {
> struct mips_pt_regs_main *mains;
> struct mips_pt_regs_cp0 *cp0;
> char pt_regs[SIZE(pt_regs)];
> @@ -617,18 +620,30 @@ mips_back_trace_cmd(struct bt_info *bt)
> if (CRASHDEBUG(8))
> fprintf(fp, "exception pc %#lx ra %#lx sp %lx\n",
> previous.pc, previous.ra, previous.sp);
> - } else {
> +
> + /* The PC causing the exception may have been invalid */
> + invalid_ok = 1;
> + } else if (symbol) {
> mips_analyze_function(symbol->value, offset, ¤t, &previous);
> + } else {
> + /*
> + * The current PC is invalid. Assume that the code
> + * jumped through a invalid pointer and that the SP has
> + * not been adjusted.
> + */
> + previous.sp = current.sp;
> }
>
> mips_dump_backtrace_entry(bt, symbol, ¤t, &previous, level++);
> - if (!current.ra)
> - break;
>
> current.pc = current.ra;
> current.sp = previous.sp;
> current.ra = previous.ra;
>
> + if (CRASHDEBUG(8))
> + fprintf(fp, "next %d pc %#lx ra %#lx sp %lx\n",
> + level, current.pc, current.ra, current.sp);
> +
> previous.sp = previous.pc = previous.ra = 0;
> }
> }
> --
> 2.1.4
>
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