[PATCH] perf: x86: fix callgraphs of 32-bit processes on 64-bit kernels.
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From: Török Edwin on 15 Mar 2010 11:40 When profiling a 32-bit process on a 64-bit kernel, callgraph tracing stopped after the first function, because it has seen a garbage memory address (tried to interpret the frame pointer, and return address as a 64-bit pointer). Fix this by using a struct stack_frame with 32-bit pointers when the TIF_IA32 flag is set. Note that TIF_IA32 flag must be used, and not is_compat_task(), because the latter is only set when the 32-bit process is executing a syscall, which may not always be the case (when tracing page fault events for example). Signed-off-by: Török Edwin <edwintorok(a)gmail.com> --- arch/x86/kernel/cpu/perf_event.c | 33 +++++++++++++++++++++++++++++++++ 1 files changed, 33 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index 8c1c070..13ee83a 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -2401,6 +2401,20 @@ static int copy_stack_frame(const void __user *fp, struct stack_frame *frame) return bytes == sizeof(*frame); } +struct stack_frame_ia32 { + u32 next_frame; + u32 return_address; +}; + +static int copy_stack_frame_ia32(u32 fp, struct stack_frame_ia32 *frame) +{ + unsigned long bytes; + + bytes = copy_from_user_nmi(frame, (const void __user*)(unsigned long)fp, sizeof(*frame)); + + return bytes == sizeof(*frame); +} + static void perf_callchain_user(struct pt_regs *regs, struct perf_callchain_entry *entry) { @@ -2414,6 +2428,25 @@ perf_callchain_user(struct pt_regs *regs, struct perf_callchain_entry *entry) callchain_store(entry, PERF_CONTEXT_USER); callchain_store(entry, regs->ip); + if (test_thread_flag(TIF_IA32)) { + /* 32-bit process in 64-bit kernel. */ + u32 fp = regs->bp; + struct stack_frame_ia32 frame; + while (entry->nr < PERF_MAX_STACK_DEPTH) { + frame.next_frame = 0; + frame.return_address = 0; + + if (!copy_stack_frame_ia32(fp, &frame)) + break; + + if ((unsigned long)fp < regs->sp) + break; + + callchain_store(entry, frame.return_address); + fp = frame.next_frame; + } + return; + } while (entry->nr < PERF_MAX_STACK_DEPTH) { frame.next_frame = NULL; -- 1.7.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |