[PATCH v4 45/57] x86/dumpstack: print any pt_regs found on the stack

[Josh Poimboeuf]

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 1c25a6d..9af8bb1 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -86,7 +86,7 @@ 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;
 
 		/*
@@ -123,6 +123,15 @@ 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;
 
@@ -150,6 +159,11 @@ 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