Switch MemoryRemote to use ptrace.
Some processes will fail to read when using process_vm_read, so switch
back to ptrace for now. For example, the system_server process only
gets two frames without this fix.
Fix up some of the remote memory read unit tests to allow passing
even when using ptrace.
Bug: 70160908
Test: All unit tests pass, debuggerd -b <system_server pid> works.
Change-Id: I37c67bf9c480d7268c9fe32dad6a8d78a4020b85
diff --git a/libunwindstack/Memory.cpp b/libunwindstack/Memory.cpp
index 2479655..b1b39a0 100644
--- a/libunwindstack/Memory.cpp
+++ b/libunwindstack/Memory.cpp
@@ -198,8 +198,68 @@
return actual_len;
}
+static bool PtraceReadLong(pid_t pid, uint64_t addr, long* value) {
+ // ptrace() returns -1 and sets errno when the operation fails.
+ // To disambiguate -1 from a valid result, we clear errno beforehand.
+ errno = 0;
+ *value = ptrace(PTRACE_PEEKTEXT, pid, reinterpret_cast<void*>(addr), nullptr);
+ if (*value == -1 && errno) {
+ return false;
+ }
+ return true;
+}
+
+static size_t ReadWithPtrace(pid_t pid, uint64_t addr, void* dst, size_t bytes) {
+ // Make sure that there is no overflow.
+ uint64_t max_size;
+ if (__builtin_add_overflow(addr, bytes, &max_size)) {
+ return 0;
+ }
+
+ size_t bytes_read = 0;
+ long data;
+ size_t align_bytes = addr & (sizeof(long) - 1);
+ if (align_bytes != 0) {
+ if (!PtraceReadLong(pid, addr & ~(sizeof(long) - 1), &data)) {
+ return 0;
+ }
+ size_t copy_bytes = std::min(sizeof(long) - align_bytes, bytes);
+ memcpy(dst, reinterpret_cast<uint8_t*>(&data) + align_bytes, copy_bytes);
+ addr += copy_bytes;
+ dst = reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(dst) + copy_bytes);
+ bytes -= copy_bytes;
+ bytes_read += copy_bytes;
+ }
+
+ for (size_t i = 0; i < bytes / sizeof(long); i++) {
+ if (!PtraceReadLong(pid, addr, &data)) {
+ return bytes_read;
+ }
+ memcpy(dst, &data, sizeof(long));
+ dst = reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(dst) + sizeof(long));
+ addr += sizeof(long);
+ bytes_read += sizeof(long);
+ }
+
+ size_t left_over = bytes & (sizeof(long) - 1);
+ if (left_over) {
+ if (!PtraceReadLong(pid, addr, &data)) {
+ return bytes_read;
+ }
+ memcpy(dst, &data, left_over);
+ bytes_read += left_over;
+ }
+ return bytes_read;
+}
+
size_t MemoryRemote::Read(uint64_t addr, void* dst, size_t size) {
- return ProcessVmRead(pid_, dst, addr, size);
+#if !defined(__LP64__)
+ // Cannot read an address greater than 32 bits.
+ if (addr > UINT32_MAX) {
+ return 0;
+ }
+#endif
+ return ReadWithPtrace(pid_, addr, dst, size);
}
size_t MemoryLocal::Read(uint64_t addr, void* dst, size_t size) {