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/*
* Copyright (C) 2020 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "platform/bionic/android_unsafe_frame_pointer_chase.h"
#include "pthread_internal.h"
#include "platform/bionic/mte.h"
/*
* Implement fast stack unwinding for stack frames with frame pointers. Stores at most num_entries
* return addresses to buffer buf. Returns the number of available return addresses, which may be
* greater than num_entries.
*
* This function makes no guarantees about its behavior on encountering a frame built without frame
* pointers, except that it should not crash or enter an infinite loop, and that any frames prior to
* the frame built without frame pointers should be correct.
*
* This function is only meant to be used with memory safety tools such as sanitizers which need to
* take stack traces efficiently. Normal applications should use APIs such as libunwindstack or
* _Unwind_Backtrace.
*/
__attribute__((no_sanitize("address", "hwaddress"))) size_t android_unsafe_frame_pointer_chase(
uintptr_t* buf, size_t num_entries) {
// Disable MTE checks for the duration of this function, since we can't be sure that following
// next_frame pointers won't cause us to read from tagged memory. ASAN/HWASAN are disabled here
// for the same reason.
ScopedDisableMTE x;
struct frame_record {
uintptr_t next_frame, return_addr;
};
auto begin = reinterpret_cast<uintptr_t>(__builtin_frame_address(0));
uintptr_t end = __get_thread()->stack_top;
stack_t ss;
if (sigaltstack(nullptr, &ss) == 0 && (ss.ss_flags & SS_ONSTACK)) {
end = reinterpret_cast<uintptr_t>(ss.ss_sp) + ss.ss_size;
}
size_t num_frames = 0;
while (1) {
auto* frame = reinterpret_cast<frame_record*>(begin);
if (num_frames < num_entries) {
buf[num_frames] = frame->return_addr;
}
++num_frames;
if (frame->next_frame < begin + sizeof(frame_record) || frame->next_frame >= end ||
frame->next_frame % sizeof(void*) != 0) {
break;
}
begin = frame->next_frame;
}
return num_frames;
}
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