From 441ccc3580f45340715fd8f5c4db795b06326404 Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Fri, 18 May 2018 08:47:10 +0200 Subject: [PATCH] x86/stacktrace: Clarify the reliable success paths Make clear which path is for user tasks and for kthreads and idle tasks. This will allow easier plug-in of the ORC unwinder in the next patches. Note that we added a check for unwind error to the top of the loop, so that an error is returned also for user tasks (the 'goto success' would skip the check after the loop otherwise). Signed-off-by: Jiri Slaby Acked-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: https://lkml.kernel.org/lkml/20180518064713.26440-3-jslaby@suse.cz Signed-off-by: Ingo Molnar --- arch/x86/kernel/stacktrace.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c index f9dacf6d4667..6acf1d5ca832 100644 --- a/arch/x86/kernel/stacktrace.c +++ b/arch/x86/kernel/stacktrace.c @@ -89,21 +89,24 @@ __save_stack_trace_reliable(struct stack_trace *trace, struct pt_regs *regs; unsigned long addr; - for (unwind_start(&state, task, NULL, NULL); !unwind_done(&state); + for (unwind_start(&state, task, NULL, NULL); + !unwind_done(&state) && !unwind_error(&state); unwind_next_frame(&state)) { regs = unwind_get_entry_regs(&state, NULL); if (regs) { + /* Success path for user tasks */ + if (user_mode(regs)) + goto success; + /* * Kernel mode registers on the stack indicate an * in-kernel interrupt or exception (e.g., preemption * or a page fault), which can make frame pointers * unreliable. */ - if (!user_mode(regs)) - return -EINVAL; - break; + return -EINVAL; } addr = unwind_get_return_address(&state); @@ -124,6 +127,11 @@ __save_stack_trace_reliable(struct stack_trace *trace, if (unwind_error(&state)) return -EINVAL; + /* Success path for non-user tasks, i.e. kthreads and idle tasks */ + if (!(task->flags & (PF_KTHREAD | PF_IDLE))) + return -EINVAL; + +success: if (trace->nr_entries < trace->max_entries) trace->entries[trace->nr_entries++] = ULONG_MAX;