Commit-ID:  6fa81a12b3f1834a22167aa2d7b24dcc4bf884e3
Gitweb:     http://git.kernel.org/tip/6fa81a12b3f1834a22167aa2d7b24dcc4bf884e3
Author:     Josh Poimboeuf <[email protected]>
AuthorDate: Thu, 20 Oct 2016 11:34:45 -0500
Committer:  Ingo Molnar <[email protected]>
CommitDate: Fri, 21 Oct 2016 09:26:05 +0200

x86/dumpstack: Print orig_ax in __show_regs()

The value of regs->orig_ax contains potentially useful debugging data:
For syscalls it contains the syscall number.  For interrupts it contains
the (negated) vector number.  To reduce noise, print it only if it has a
useful value (i.e., something other than -1).

Here's what it looks like for a write syscall:

  RIP: 0033:[<00007f53ad7b1940>] 0x7f53ad7b1940
  RSP: 002b:00007fff8de66558 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
  RAX: ffffffffffffffda RBX: 0000000000000046 RCX: 00007f53ad7b1940
  RDX: 0000000000000002 RSI: 00007f53ae0ca000 RDI: 0000000000000001
  ...

Suggested-by: Andy Lutomirski <[email protected]>
Signed-off-by: Josh Poimboeuf <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: 
http://lkml.kernel.org/r/93f0fe0307a4af884d3fca00edabcc8cff236002.1476973742.git.jpoim...@redhat.com
Signed-off-by: Ingo Molnar <[email protected]>
---
 arch/x86/kernel/process_64.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index b3b50ac..f1c36da 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -63,8 +63,13 @@ void __show_regs(struct pt_regs *regs, int all)
 
        printk(KERN_DEFAULT "RIP: %04lx:[<%016lx>] %pS\n", regs->cs & 0xffff,
                        regs->ip, (void *)regs->ip);
-       printk(KERN_DEFAULT "RSP: %04lx:%016lx  EFLAGS: %08lx\n", regs->ss,
+       printk(KERN_DEFAULT "RSP: %04lx:%016lx EFLAGS: %08lx", regs->ss,
                        regs->sp, regs->flags);
+       if (regs->orig_ax != -1)
+               pr_cont(" ORIG_RAX: %016lx\n", regs->orig_ax);
+       else
+               pr_cont("\n");
+
        printk(KERN_DEFAULT "RAX: %016lx RBX: %016lx RCX: %016lx\n",
               regs->ax, regs->bx, regs->cx);
        printk(KERN_DEFAULT "RDX: %016lx RSI: %016lx RDI: %016lx\n",

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