[libunwind][SystemZ] Use process_vm_readv to avoid potential segfaults
Fix potential crashes during unwind when checking for signal frames
and the current PC is invalid.
The same bug was fixed for aarch64 in https://reviews.llvm.org/D126343.
Reviewed by: MaskRay
Differential Revision: https://reviews.llvm.org/D129856
GitOrigin-RevId: 24ec521cd7bb51447f4ab03460d91c57378d49f7
diff --git a/src/UnwindCursor.hpp b/src/UnwindCursor.hpp
index e363f9e..b8bd9bc 100644
--- a/src/UnwindCursor.hpp
+++ b/src/UnwindCursor.hpp
@@ -2695,8 +2695,14 @@
// own restorer function, though, or user-mode QEMU might write a trampoline
// onto the stack.
const pint_t pc = static_cast<pint_t>(this->getReg(UNW_REG_IP));
- const uint16_t inst = _addressSpace.get16(pc);
- if (inst == 0x0a77 || inst == 0x0aad) {
+ // The PC might contain an invalid address if the unwind info is bad, so
+ // directly accessing it could cause a segfault. Use process_vm_readv to
+ // read the memory safely instead.
+ uint16_t inst;
+ struct iovec local_iov = {&inst, sizeof inst};
+ struct iovec remote_iov = {reinterpret_cast<void *>(pc), sizeof inst};
+ long bytesRead = process_vm_readv(getpid(), &local_iov, 1, &remote_iov, 1, 0);
+ if (bytesRead == sizeof inst && (inst == 0x0a77 || inst == 0x0aad)) {
_info = {};
_info.start_ip = pc;
_info.end_ip = pc + 2;
diff --git a/test/bad_unwind_info.pass.cpp b/test/bad_unwind_info.pass.cpp
index 97427ea..06017d1 100644
--- a/test/bad_unwind_info.pass.cpp
+++ b/test/bad_unwind_info.pass.cpp
@@ -10,7 +10,7 @@
// Ensure that libunwind doesn't crash on invalid info; the Linux aarch64
// sigreturn frame check would previously attempt to access invalid memory in
// this scenario.
-// REQUIRES: linux && (target={{aarch64-.+}} || target={{x86_64-.+}})
+// REQUIRES: linux && (target={{aarch64-.+}} || target={{s390x-.+}} || target={{x86_64-.+}})
// GCC doesn't support __attribute__((naked)) on AArch64.
// UNSUPPORTED: gcc
@@ -36,6 +36,20 @@
".cfi_def_cfa_offset 0\n"
".cfi_restore x30\n"
"ret\n");
+#elif defined(__s390x__)
+ __asm__("stmg %r14,%r15,112(%r15)\n"
+ "mvghi 104(%r15),4\n"
+ "# purposely use incorrect offset for %r14\n"
+ ".cfi_offset 14, -56\n"
+ ".cfi_offset 15, -40\n"
+ "lay %r15,-160(%r15)\n"
+ ".cfi_def_cfa_offset 320\n"
+ "brasl %r14,stepper\n"
+ "lmg %r14,%r15,272(%r15)\n"
+ ".cfi_restore 15\n"
+ ".cfi_restore 14\n"
+ ".cfi_def_cfa_offset 160\n"
+ "br %r14\n");
#elif defined(__x86_64__)
__asm__("pushq %rbx\n"
".cfi_def_cfa_offset 16\n"
@@ -48,7 +62,7 @@
".cfi_def_cfa_offset 8\n"
"ret\n");
#else
-#error This test is only supported on aarch64 or x86-64
+#error This test is only supported on aarch64, s390x, or x86-64
#endif
}