mirror of
https://github.com/jart/cosmopolitan.git
synced 2024-05-01 19:28:46 +00:00
49 lines
2.1 KiB
C
49 lines
2.1 KiB
C
#if 0
|
|
/*─────────────────────────────────────────────────────────────────╗
|
|
│ To the extent possible under law, Justine Tunney has waived │
|
|
│ all copyright and related or neighboring rights to this file, │
|
|
│ as it is written in the following disclaimers: │
|
|
│ • http://unlicense.org/ │
|
|
│ • http://creativecommons.org/publicdomain/zero/1.0/ │
|
|
╚─────────────────────────────────────────────────────────────────*/
|
|
#endif
|
|
#include "libc/calls/calls.h"
|
|
#include "libc/calls/struct/sigaction.h"
|
|
#include "libc/calls/struct/siginfo.h"
|
|
#include "libc/calls/ucontext.h"
|
|
#include "libc/stdio/stdio.h"
|
|
#include "libc/sysv/consts/sa.h"
|
|
#include "libc/sysv/consts/sig.h"
|
|
#include "third_party/xed/x86.h"
|
|
#ifdef __x86_64__
|
|
|
|
/**
|
|
* @fileoverview How to change CPU state on signal delivery
|
|
*
|
|
* This program redefines division by zero so that it has a definition.
|
|
* The definition is the meaning of life, the universe, and everything.
|
|
* Normally crash signals like `SIGSEGV`, `SIGILL`, and `SIGFPE` aren't
|
|
* recoverable. This example shows how it actually can be done with Xed
|
|
* and this example should work on all supported platforms even Windows
|
|
*/
|
|
|
|
void handler(int sig, siginfo_t *si, void *vctx) {
|
|
struct XedDecodedInst xedd;
|
|
struct ucontext *ctx = vctx;
|
|
xed_decoded_inst_zero_set_mode(&xedd, XED_MACHINE_MODE_LONG_64);
|
|
xed_instruction_length_decode(&xedd, (void *)ctx->uc_mcontext.rip, 15);
|
|
ctx->uc_mcontext.rip += xedd.length;
|
|
ctx->uc_mcontext.rax = 42; // set the DIV result registers rdx:rax
|
|
ctx->uc_mcontext.rdx = 0;
|
|
}
|
|
|
|
int main(int argc, char *argv[]) {
|
|
struct sigaction saint = {.sa_sigaction = handler, .sa_flags = SA_SIGINFO};
|
|
sigaction(SIGFPE, &saint, NULL);
|
|
volatile long x = 0;
|
|
printf("123/0 = %ld\n", 123 / x);
|
|
return 0;
|
|
}
|
|
|
|
#endif /* __x86_64__ */
|