1 files changed, 48 insertions, 59 deletions

diff --git a/lib/asan/asan_posix.cc b/lib/asan/asan_posix.cc
index bcc6b381a785..ad31458df28d 100644
--- a/lib/asan/asan_posix.cc
+++ b/lib/asan/asan_posix.cc
@@ -13,7 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "sanitizer_common/sanitizer_platform.h"
-#if SANITIZER_LINUX || SANITIZER_MAC
+#if SANITIZER_POSIX
 
 #include "asan_internal.h"
 #include "asan_interceptors.h"
@@ -30,70 +30,59 @@
 #include <sys/resource.h>
 #include <unistd.h>
 
-static const uptr kAltStackSize = SIGSTKSZ * 4;  // SIGSTKSZ is not enough.
-
 namespace __asan {
 
-static void MaybeInstallSigaction(int signum,
-                                  void (*handler)(int, siginfo_t *, void *)) {
-  if (!AsanInterceptsSignal(signum))
-    return;
-  struct sigaction sigact;
-  REAL(memset)(&sigact, 0, sizeof(sigact));
-  sigact.sa_sigaction = handler;
-  sigact.sa_flags = SA_SIGINFO;
-  if (flags()->use_sigaltstack) sigact.sa_flags |= SA_ONSTACK;
-  CHECK_EQ(0, REAL(sigaction)(signum, &sigact, 0));
-  if (common_flags()->verbosity >= 1) {
-    Report("Installed the sigaction for signal %d\n", signum);
-  }
-}
-
-static void     ASAN_OnSIGSEGV(int, siginfo_t *siginfo, void *context) {
-  uptr addr = (uptr)siginfo->si_addr;
-  // Write the first message using the bullet-proof write.
-  if (13 != internal_write(2, "ASAN:SIGSEGV\n", 13)) Die();
+SignalContext SignalContext::Create(void *siginfo, void *context) {
+  uptr addr = (uptr)((siginfo_t*)siginfo)->si_addr;
   uptr pc, sp, bp;
   GetPcSpBp(context, &pc, &sp, &bp);
-  ReportSIGSEGV(pc, sp, bp, addr);
+  return SignalContext(context, addr, pc, sp, bp);
 }
 
-void SetAlternateSignalStack() {
-  stack_t altstack, oldstack;
-  CHECK_EQ(0, sigaltstack(0, &oldstack));
-  // If the alternate stack is already in place, do nothing.
-  if ((oldstack.ss_flags & SS_DISABLE) == 0) return;
-  // TODO(glider): the mapped stack should have the MAP_STACK flag in the
-  // future. It is not required by man 2 sigaltstack now (they're using
-  // malloc()).
-  void* base = MmapOrDie(kAltStackSize, __FUNCTION__);
-  altstack.ss_sp = base;
-  altstack.ss_flags = 0;
-  altstack.ss_size = kAltStackSize;
-  CHECK_EQ(0, sigaltstack(&altstack, 0));
-  if (common_flags()->verbosity > 0) {
-    Report("Alternative stack for T%d set: [%p,%p)\n",
-           GetCurrentTidOrInvalid(),
-           altstack.ss_sp, (char*)altstack.ss_sp + altstack.ss_size);
+void AsanOnSIGSEGV(int, void *siginfo, void *context) {
+  ScopedDeadlySignal signal_scope(GetCurrentThread());
+  int code = (int)((siginfo_t*)siginfo)->si_code;
+  // Write the first message using the bullet-proof write.
+  if (13 != internal_write(2, "ASAN:SIGSEGV\n", 13)) Die();
+  SignalContext sig = SignalContext::Create(siginfo, context);
+
+  // Access at a reasonable offset above SP, or slightly below it (to account
+  // for x86_64 or PowerPC redzone, ARM push of multiple registers, etc) is
+  // probably a stack overflow.
+  bool IsStackAccess = sig.addr + 512 > sig.sp && sig.addr < sig.sp + 0xFFFF;
+
+#if __powerpc__
+  // Large stack frames can be allocated with e.g.
+  //   lis r0,-10000
+  //   stdux r1,r1,r0 # store sp to [sp-10000] and update sp by -10000
+  // If the store faults then sp will not have been updated, so test above
+  // will not work, becase the fault address will be more than just "slightly"
+  // below sp.
+  if (!IsStackAccess && IsAccessibleMemoryRange(sig.pc, 4)) {
+    u32 inst = *(unsigned *)sig.pc;
+    u32 ra = (inst >> 16) & 0x1F;
+    u32 opcd = inst >> 26;
+    u32 xo = (inst >> 1) & 0x3FF;
+    // Check for store-with-update to sp. The instructions we accept are:
+    //   stbu rs,d(ra)          stbux rs,ra,rb
+    //   sthu rs,d(ra)          sthux rs,ra,rb
+    //   stwu rs,d(ra)          stwux rs,ra,rb
+    //   stdu rs,ds(ra)         stdux rs,ra,rb
+    // where ra is r1 (the stack pointer).
+    if (ra == 1 &&
+        (opcd == 39 || opcd == 45 || opcd == 37 || opcd == 62 ||
+         (opcd == 31 && (xo == 247 || xo == 439 || xo == 183 || xo == 181))))
+      IsStackAccess = true;
   }
-}
-
-void UnsetAlternateSignalStack() {
-  stack_t altstack, oldstack;
-  altstack.ss_sp = 0;
-  altstack.ss_flags = SS_DISABLE;
-  altstack.ss_size = 0;
-  CHECK_EQ(0, sigaltstack(&altstack, &oldstack));
-  UnmapOrDie(oldstack.ss_sp, oldstack.ss_size);
-}
-
-void InstallSignalHandlers() {
-  // Set the alternate signal stack for the main thread.
-  // This will cause SetAlternateSignalStack to be called twice, but the stack
-  // will be actually set only once.
-  if (flags()->use_sigaltstack) SetAlternateSignalStack();
-  MaybeInstallSigaction(SIGSEGV, ASAN_OnSIGSEGV);
-  MaybeInstallSigaction(SIGBUS, ASAN_OnSIGSEGV);
+#endif // __powerpc__
+
+  // We also check si_code to filter out SEGV caused by something else other
+  // then hitting the guard page or unmapped memory, like, for example,
+  // unaligned memory access.
+  if (IsStackAccess && (code == si_SEGV_MAPERR || code == si_SEGV_ACCERR))
+    ReportStackOverflow(sig);
+  else
+    ReportSIGSEGV("SEGV", sig);
 }
 
 // ---------------------- TSD ---------------- {{{1
@@ -127,4 +116,4 @@ void PlatformTSDDtor(void *tsd) {
 }
 }  // namespace __asan
 
-#endif  // SANITIZER_LINUX || SANITIZER_MAC
+#endif  // SANITIZER_POSIX