x86/dumpstack: Fix occasionally missing registers

If two consecutive stack frames have pt_regs, the oops dump code fails
to print the second frame's registers.  Fix that.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Fixes: 3b3fa11bc700 ("x86/dumpstack: Print any pt_regs found on the stack")
Link: http://lkml.kernel.org/r/269c5c00c7d45c699f3dcea42a3a594c6cf7a9a3.1499786555.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index dbce3cc..bd265a4 100644 (file)
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -94,6 +94,9 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
                if (stack_name)
                        printk("%s <%s>\n", log_lvl, stack_name);
 
+               if (regs && on_stack(&stack_info, regs, sizeof(*regs)))
+                       __show_regs(regs, 0);
+
                /*
                 * Scan the stack, printing any text addresses we find.  At the
                 * same time, follow proper stack frames with the unwinder.
@@ -118,10 +121,8 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
                         * 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 (regs && stack == &regs->ip)
+                               goto next;
 
                        if (stack == ret_addr_p)
                                reliable = 1;
@@ -144,6 +145,7 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
                        if (!reliable)
                                continue;
 
+next:
                        /*
                         * Get the next frame from the unwinder.  No need to
                         * check for an error: if anything goes wrong, the rest
@@ -153,7 +155,7 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
 
                        /* if the frame has entry regs, print them */
                        regs = unwind_get_entry_regs(&state);
-                       if (regs)
+                       if (regs && on_stack(&stack_info, regs, sizeof(*regs)))
                                __show_regs(regs, 0);
                }