From df4200e8c255fca1d03855b971b57036b9ccaa94 Mon Sep 17 00:00:00 2001 From: Elliott Hughes Date: Thu, 14 Feb 2013 14:41:57 -0800 Subject: [PATCH] Add a "smash-stack" option to crasher. bionic's __stack_chk_fail was preventing debuggerd from dumping stacks, which was not helpful. Bug: 2487269 Change-Id: Idba2a274037b960dfb2ac1c21686323268c4b372 --- debuggerd/Android.mk | 1 + debuggerd/crasher.c | 13 +++++++++++++ 2 files changed, 14 insertions(+) diff --git a/debuggerd/Android.mk b/debuggerd/Android.mk index e48b9af51..3fca64f4b 100644 --- a/debuggerd/Android.mk +++ b/debuggerd/Android.mk @@ -37,6 +37,7 @@ LOCAL_SRC_FILES += $(TARGET_ARCH)/crashglue.S LOCAL_MODULE := crasher LOCAL_MODULE_PATH := $(TARGET_OUT_OPTIONAL_EXECUTABLES) LOCAL_MODULE_TAGS := optional +LOCAL_CFLAGS += -fstack-protector-all #LOCAL_FORCE_STATIC_EXECUTABLE := true LOCAL_SHARED_LIBRARIES := libcutils libc include $(BUILD_EXECUTABLE) diff --git a/debuggerd/crasher.c b/debuggerd/crasher.c index 74eaa4983..134fe8033 100644 --- a/debuggerd/crasher.c +++ b/debuggerd/crasher.c @@ -35,6 +35,18 @@ static void debuggerd_connect() } } +int smash_stack(int i) { + printf("crasher: deliberately corrupting stack...\n"); + // Unless there's a "big enough" buffer on the stack, gcc + // doesn't bother inserting checks. + char buf[8]; + // If we don't write something relatively unpredicatable + // into the buffer and then do something with it, gcc + // optimizes everything away and just returns a constant. + *(int*)(&buf[7]) = (uintptr_t) &buf[0]; + return *(int*)(&buf[0]); +} + void test_call1() { *((int*) 32) = 1; @@ -95,6 +107,7 @@ int do_action(const char* arg) return do_action_on_thread(arg + strlen("thread-")); } + if(!strcmp(arg,"smash-stack")) return smash_stack(42); if(!strcmp(arg,"nostack")) crashnostack(); if(!strcmp(arg,"ctest")) return ctest(); if(!strcmp(arg,"exit")) exit(1);