[PATCH 4/6] x86/dumpstack: print any pt_regs found on the stack

From: Josh Poimboeuf
Date: Thu Oct 20 2016 - 12:35:36 EST


Now that we can find pt_regs registers on the stack, print them. Here's
an example of what it looks like:

Call Trace:
<IRQ>
[<ffffffff8144b793>] dump_stack+0x86/0xc3
[<ffffffff81142c73>] hrtimer_interrupt+0xb3/0x1c0
[<ffffffff8105eb86>] local_apic_timer_interrupt+0x36/0x60
[<ffffffff818b27cd>] smp_apic_timer_interrupt+0x3d/0x50
[<ffffffff818b06ee>] apic_timer_interrupt+0x9e/0xb0
RIP: 0010:[<ffffffff818aef43>] [<ffffffff818aef43>] _raw_spin_unlock_irq+0x33/0x60
RSP: 0018:ffff880079c4f760 EFLAGS: 00000202
RAX: ffff880078738000 RBX: ffff88007d3da0c0 RCX: 0000000000000007
RDX: 0000000000006d78 RSI: ffff8800787388f0 RDI: ffff880078738000
RBP: ffff880079c4f768 R08: 0000002199088f38 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff81e0d540
R13: ffff8800369fb700 R14: 0000000000000000 R15: ffff880078738000
<EOI>
[<ffffffff810e1f14>] finish_task_switch+0xb4/0x250
[<ffffffff810e1ed6>] ? finish_task_switch+0x76/0x250
[<ffffffff818a7b61>] __schedule+0x3e1/0xb20
...
[<ffffffff810759c8>] trace_do_page_fault+0x58/0x2c0
[<ffffffff8106f7dc>] do_async_page_fault+0x2c/0xa0
[<ffffffff818b1dd8>] async_page_fault+0x28/0x30
RIP: 0010:[<ffffffff8145b062>] [<ffffffff8145b062>] __clear_user+0x42/0x70
RSP: 0018:ffff880079c4fd38 EFLAGS: 00010202
RAX: 0000000000000000 RBX: 0000000000000138 RCX: 0000000000000138
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 000000000061b640
RBP: ffff880079c4fd48 R08: 0000002198feefd7 R09: ffffffff82a40928
R10: 0000000000000001 R11: 0000000000000000 R12: 000000000061b640
R13: 0000000000000000 R14: ffff880079c50000 R15: ffff8800791d7400
[<ffffffff8145b043>] ? __clear_user+0x23/0x70
[<ffffffff8145b0fb>] clear_user+0x2b/0x40
[<ffffffff812fbda2>] load_elf_binary+0x1472/0x1750
[<ffffffff8129a591>] search_binary_handler+0xa1/0x200
[<ffffffff8129b69b>] do_execveat_common.isra.36+0x6cb/0x9f0
[<ffffffff8129b5f3>] ? do_execveat_common.isra.36+0x623/0x9f0
[<ffffffff8129bcaa>] SyS_execve+0x3a/0x50
[<ffffffff81003f5c>] do_syscall_64+0x6c/0x1e0
[<ffffffff818afa3f>] entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:[<00007fd2e2f2e537>] [<00007fd2e2f2e537>] 0x7fd2e2f2e537
RSP: 002b:00007ffc449c5fc8 EFLAGS: 00000246
RAX: ffffffffffffffda RBX: 00007ffc449c8860 RCX: 00007fd2e2f2e537
RDX: 000000000127cc40 RSI: 00007ffc449c8860 RDI: 00007ffc449c6029
RBP: 00007ffc449c60b0 R08: 65726f632d667265 R09: 00007ffc449c5e20
R10: 00000000000005a7 R11: 0000000000000246 R12: 000000000127cc40
R13: 000000000127ce05 R14: 00007ffc449c6029 R15: 000000000127ce01

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
arch/x86/kernel/dumpstack.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 3251177..64281a1 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -82,7 +82,7 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
* - softirq stack
* - hardirq stack
*/
- for (; stack; stack = stack_info.next_sp) {
+ for (regs = NULL; stack; stack = stack_info.next_sp) {
const char *str_begin, *str_end;

/*
@@ -119,6 +119,15 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
if (!__kernel_text_address(addr))
continue;

+ /*
+ * Don't print regs->ip again if it was already printed
+ * by __show_regs() below.
+ */
+ if (regs && stack == &regs->ip) {
+ unwind_next_frame(&state);
+ continue;
+ }
+
if (stack == ret_addr_p)
reliable = 1;

@@ -146,6 +155,11 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
* of the addresses will just be printed as unreliable.
*/
unwind_next_frame(&state);
+
+ /* if the frame has entry regs, print them */
+ regs = unwind_get_entry_regs(&state);
+ if (regs)
+ __show_regs(regs, 0);
}

if (str_end)
--
2.7.4