jmp_sp.cpp
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/*
# see: https://github.com/winlinvip/simple-rtmp-server/issues/190
# see: https://github.com/winlinvip/simple-rtmp-server/wiki/v1_CN_SrsLinuxArm
g++ -g -O0 -o jmp_sp jmp_sp.cpp
arm-linux-gnueabi-g++ -g -o jmp_sp jmp_sp.cpp -static
arm-linux-gnueabi-strip jmp_sp
*/
#include <stdio.h>
#include <stdlib.h>
#include <setjmp.h>
jmp_buf env_func1;
void func1()
{
#if defined(__amd64__) || defined(__x86_64__)
register long int rsp0 asm("rsp");
int ret = setjmp(env_func1);
printf("setjmp func0 ret=%d, rsp=%#lx\n", ret, rsp0);
#endif
}
void func0()
{
/**
the definition of jmp_buf:
typedef struct __jmp_buf_tag jmp_buf[1];
struct __jmp_buf_tag {
__jmp_buf __jmpbuf;
int __mask_was_saved;
__sigset_t __saved_mask;
};
*/
#if defined(__amd64__) || defined(__x86_64__)
/**
here, the __jmp_buf is 8*8=64 bytes
# if __WORDSIZE == 64
typedef long int __jmp_buf[8];
*/
/**
the layout for setjmp of x86_64
#
# The jmp_buf is assumed to contain the following, in order:
# %rbx
# %rsp (post-return)
# %rbp
# %r12
# %r13
# %r14
# %r15
# <return address>
#
*/
register long int rsp0 asm("rsp");
int ret = setjmp(env_func1);
printf("setjmp func0 ret=%d, rsp=%#lx\n", ret, rsp0);
printf("after setjmp: ");
for (int i = 0; i < 8; i++) {
printf("env[%d]=%#x, ", i, (int)env_func1[0].__jmpbuf[i]);
}
printf("\n");
func1();
#else
/**
/usr/arm-linux-gnueabi/include/bits/setjmp.h
#ifndef _ASM
The exact set of registers saved may depend on the particular core
in use, as some coprocessor registers may need to be saved. The C
Library ABI requires that the buffer be 8-byte aligned, and
recommends that the buffer contain 64 words. The first 28 words
are occupied by v1-v6, sl, fp, sp, pc, d8-d15, and fpscr. (Note
that d8-15 require 17 words, due to the use of fstmx.)
typedef int __jmp_buf[64] __attribute__((__aligned__ (8)));
the layout of setjmp for arm:
0-5: v1-v6
6: sl
7: fp
8: sp
9: pc
10-26: d8-d15 17words
27: fpscr
*/
/**
For example, on raspberry-pi, armv6 cpu:
(gdb) x /64 env_func1[0].__jmpbuf
v1, 0: 0x00 0x00 0x00 0x00
v2, 1: 0x00 0x00 0x00 0x00
v3, 2: 0x2c 0x84 0x00 0x00
v4, 3: 0x00 0x00 0x00 0x00
v5, 4: 0x00 0x00 0x00 0x00
v6, 5: 0x00 0x00 0x00 0x00
sl, 6: 0x00 0xf0 0xff 0xb6
fp, 7: 0x9c 0xfb 0xff 0xbe
sp, 8: 0x88 0xfb 0xff 0xbe
pc, 9: 0x08 0x85 0x00 0x00
(gdb) p /x $sp
$5 = 0xbefffb88
(gdb) p /x $pc
$4 = 0x850c
*/
int ret = setjmp(env_func1);
printf("setjmp func1 ret=%d\n", ret);
printf("after setjmp: ");
for (int i = 0; i < 64; i++) {
printf("env[%d]=%#x, ", i, (int)env_func1[0].__jmpbuf[i]);
}
printf("func0 terminated\n");
#endif
}
int main(int argc, char** argv) {
#if defined(__amd64__) || defined(__x86_64__)
printf("x86_64 sizeof(long int)=%d, sizeof(long)=%d, sizeof(int)=%d, __WORDSIZE=%d\n",
(int)sizeof(long int), (int)sizeof(long), (int)sizeof(int), (int)__WORDSIZE);
#else
printf("arm sizeof(long int)=%d, sizeof(long)=%d, sizeof(int)=%d\n",
(int)sizeof(long int), (int)sizeof(long), (int)sizeof(int));
#endif
func0();
printf("terminated\n");
return 0;
}