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/* This file is part of the Spring engine (GPL v2 or later), see LICENSE.html */
#include "thread_backtrace.h"
#include <vector>
#include <stdint.h>
#include <string.h> // memcpy
#if defined(__FreeBSD__)
#include <pthread_np.h> // pthread_attr_get_np
#endif
#define FP_OFFSET 1 //! in sizeof(void*)
#define MAX(a,b) (a>b)?a:b
#define INSTACK(a) ((a) >= stack_buffer && (a) <= (stack_buffer + stack_size))
//TODO Our custom thread_backtrace() only works on the mainthread.
// Use to gdb's libthread_db to get the stacktraces of all threads.
// note, the stacktrace of non-mainthreads is disabled in CrashHandler.cpp:450 (date: 2012-03)
static uint8_t* TranslateStackAddrToBufferAddr(uint8_t* p, uint8_t* stackbot, uint8_t* stack_buffer)
{
uintptr_t addr = *(uintptr_t*)(p);
uintptr_t pos = addr - (uintptr_t)stackbot;
uint8_t* frame = stack_buffer + pos;
return frame;
}
static void internal_pthread_backtrace(pthread_t thread, void** buffer, size_t max, size_t* depth, size_t skip)
{
*depth = 0;
//! Get information about the stack (pos & size).
uint8_t* stackbot;
size_t stack_size; //! in bytes
size_t guard_size; //! in bytes
#if defined(__FreeBSD__)
pthread_attr_t attr;
pthread_attr_init(&attr);
pthread_attr_get_np(thread, &attr);
pthread_attr_getstack(&attr, (void**)&stackbot, &stack_size);
pthread_attr_getguardsize(&attr, &guard_size);
pthread_attr_destroy(&attr);
#elif defined(__APPLE__)
stackbot = (uint8_t*)pthread_get_stackaddr_np(thread);
stack_size = pthread_get_stacksize_np(thread);
guard_size = 0; //FIXME anyway to get that?
#else
pthread_attr_t attr;
pthread_getattr_np(thread, &attr);
pthread_attr_getstack(&attr, (void**)&stackbot, &stack_size);
pthread_attr_getguardsize(&attr, &guard_size);
pthread_attr_destroy(&attr);
#endif
stack_size -= guard_size;
//! The thread is is still running!!!
//! So make a buffer copy of the stack, else it gets changed while we reading from it!
std::vector<uint8_t> sbuffer(stack_size);
uint8_t* stack_buffer = &sbuffer[0];
memcpy(stack_buffer, stackbot, stack_size);
//! It is impossible to get the current frame (the current function pos) on the stack
//! for other pthreads, so we need to find it ourself. The beneath method is very naive
//! and just searchs for the starting address that gives us the longest stackdepth.
unsigned longest_stack = 0;
unsigned longest_offset = 0;
int check_area = MAX(0, stack_size - 1024*sizeof(uintptr_t));
check_area *= 0.8f; //! only check ~20% from the top of the stack
for (int offset = stack_size - sizeof(uintptr_t); offset >= check_area; offset -= sizeof(uintptr_t)) {
unsigned stack_depth = 0;
uint8_t* frame = stack_buffer + offset;
frame = TranslateStackAddrToBufferAddr(frame, stackbot, stack_buffer);
uint8_t* last_frame = frame;
while (INSTACK(frame) && (frame > last_frame)) {
last_frame = frame;
frame = TranslateStackAddrToBufferAddr(frame, stackbot, stack_buffer);
stack_depth++;
}
if (stack_depth > longest_stack) {
longest_stack = stack_depth;
longest_offset = offset;
}
}
//! Now get the list of function addresses from the stack.
uint8_t* frame = stack_buffer + longest_offset;
if(!INSTACK(frame))
return;
while (skip--) {
uint8_t* next = TranslateStackAddrToBufferAddr(frame, stackbot, stack_buffer);
if(!INSTACK(next))
return;
frame = next;
}
while (max--) {
uint8_t* next = TranslateStackAddrToBufferAddr(frame, stackbot, stack_buffer);
buffer[*depth] = (void*)*((uintptr_t*)frame + FP_OFFSET);
(*depth)++;
if(!INSTACK(next))
return;
frame = next;
}
}
int thread_backtrace(pthread_t thread, void** buffer, int size)
{
size_t num_frames;
internal_pthread_backtrace(thread, buffer, size, &num_frames, 0);
while (num_frames >= 1 && buffer[num_frames-1] == NULL) num_frames -= 1;
return num_frames;
}
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