131 строка
4.1 KiB
C
131 строка
4.1 KiB
C
//
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// monotouch-fixes.c:
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//
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// Author:
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// Rolf Bjarne Kvinge
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//
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// Copyright 2011 Xamarin Inc.
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//
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#include <stdio.h>
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#include <dlfcn.h>
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#include <signal.h>
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#include <sys/mman.h>
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#include <string.h>
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#include <unistd.h>
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#include <stdint.h>
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#include <errno.h>
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// Apple uses LLVM to implement OpenGL ES on the iPhone Simulator, unfortunately
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// LLVM has a race condition in their signal handling - they set one-shot
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// signal handlers and restore the previous handler in those handlers. The
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// problem is that they set SA_RESETHAND|SA_NODEFER when setting their signal
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// handler, which means that if another signal arrives before their signal handler
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// has been able to restore our signal handler, the default signal handler will
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// be called (which just exits the process without any diagnostics at all).
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//
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// For the 32bit simulator we inject our own sigaction method, which takes precedence
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// over the system one, and reset the flags to 0 if flags is SA_RESETHAND|SA_NODEFER.
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//
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// Unfortunately this technique does not seem to work for the 64bit simulator, so there
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// we patch the system sigaction instead.
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//
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typedef int (*SigAction) (int sig, const struct sigaction *__restrict act, struct sigaction *__restrict oact);
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static SigAction system_sigaction = sigaction;
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static int
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my_sigaction (int sig, const struct sigaction *__restrict act, struct sigaction *__restrict oact)
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{
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//fprintf (stderr, "my_sigaction (%i, %p: handler = %p mask = %i flags = %i, %p)\n", sig, act, act ? act->sa_handler : NULL, act ? act->sa_mask : -1, act ? act->sa_flags : -1, oact);
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if (act && act->sa_flags == (SA_NODEFER | SA_RESETHAND)) {
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switch (sig) {
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case SIGUSR1:
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case SIGUSR2:
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case SIGFPE:
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// fprintf (stderr, "fixed up sicaction (%i, %p: handler = %p mask = %i flags = %i, %p)\n", sig, act, act ? act->sa_handler : NULL, act ? act->sa_mask : -1, act ? act->sa_flags : -1, oact);
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((struct sigaction *) act)->sa_flags = 0;
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break;
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}
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}
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return system_sigaction (sig, act, oact);
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}
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#if defined(__i386__)
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typedef struct interpose_s {
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void *new_func;
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void *orig_func;
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} interpose_t;
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static const interpose_t interposers[] __attribute__ ((unused)) \
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__attribute__ ((section("__DATA, __interpose"))) = {
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{ (void *) &my_sigaction, (void *) &sigaction },
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};
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#elif defined(__x86_64__)
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static void
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patch_sigaction ()
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{
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// Sanity check.
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uint64_t * func = (uint64_t *) &sigaction;
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uint64_t first = 0x20ec8348e5894855; // first 8 bytes of sigaction
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uint64_t second = 0x0a771ef883ff478d; // second 8 bytes of sigaction
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if (func [0] != first || func [1] != second) {
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fprintf (stderr, "MonoTouch: Could not install sigaction override, unexpected sigaction implementation.\n");
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return;
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}
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// allocate executable memory
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uint64_t pagesize = (uint64_t) getpagesize ();
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void *exec = mmap (NULL, pagesize, PROT_EXEC | PROT_WRITE | PROT_READ, MAP_ANON | MAP_PRIVATE, -1, 0);
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if (exec == NULL) {
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fprintf (stderr, "MonoTouch: Could not allocate memory for sigaction override: %s\n", strerror (errno));
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return;
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}
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// create a trampoline that jumps to the real sigaction (to just after where we modified it).
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uint64_t *i64 = (uint64_t *) exec;
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i64 [0] = first;
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i64 [1] = second;
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uint16_t *i16 = (uint16_t *) exec;
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// movabsq &sigaction + 14,%r11
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i16 [7] = 0xbb49;
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i64 [2] = (uint64_t) (14 + (char *) &sigaction);
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// jmpq *%r11
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i16 [12] = 0xff41;
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i16 [13] = 0x00e3;
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// make sigaction patchable.
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uint64_t symbol = (uint64_t) (char *) &sigaction;
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void *aligned_symbol = (void *) (symbol & ~(pagesize - 1));
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int ret;
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ret = mprotect (aligned_symbol, pagesize * 2, PROT_READ | PROT_WRITE | PROT_EXEC);
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if (ret != 0) {
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fprintf (stderr, "MonoTouch: could not patch sigaction: %s\n", strerror (errno));
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munmap (exec, pagesize);
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return;
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}
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// patch sigaction to call my_sigaction instead.
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uint16_t *f16 = (uint16_t *) &sigaction;
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// movabsq my_sigaction,%r11
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f16 [0] = 0xbb49;
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uint64_t *f64 = (uint64_t *) (f16 + 1);
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f64 [0] = (uint64_t) &my_sigaction;
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// jmpq *%r11
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f16 [5] = 0xff41;
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f16 [6] = 0x00e3;
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// Make sigaction non-writeable again.
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mprotect (aligned_symbol, pagesize * 2, PROT_READ | PROT_EXEC);
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system_sigaction = (SigAction) exec;
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}
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#endif
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