[Lldb-commits] [PATCH] D62503: Add ReadCStringFromMemory for faster string reads

[António Afonso via Phabricator via lldb-commits]

aadsm updated this revision to Diff 203084.
aadsm added a comment.

Make sure we always return a null terminated string


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D62503/new/

https://reviews.llvm.org/D62503

Files:
  lldb/include/lldb/Host/common/NativeProcessProtocol.h
  lldb/source/Host/common/NativeProcessProtocol.cpp
  lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp


Index: lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp
===================================================================
--- lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp
+++ lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp
@@ -2189,11 +2189,12 @@
     return error;
 
   char name_buffer[PATH_MAX];
-  error = ReadMemory(link_map.l_name, &name_buffer, sizeof(name_buffer),
-                     bytes_read);
+  error = ReadCStringFromMemory(link_map.l_name,
+                                reinterpret_cast<char *>(&name_buffer),
+                                sizeof(name_buffer), bytes_read);
   if (!error.Success())
     return error;
-  name_buffer[PATH_MAX - 1] = '\0';
+
   info.name = std::string(name_buffer);
   info.link_map = link_map_addr;
   info.base_addr = link_map.l_addr;
Index: lldb/source/Host/common/NativeProcessProtocol.cpp
===================================================================
--- lldb/source/Host/common/NativeProcessProtocol.cpp
+++ lldb/source/Host/common/NativeProcessProtocol.cpp
@@ -16,6 +16,8 @@
 #include "lldb/Utility/State.h"
 #include "lldb/lldb-enumerations.h"
 
+#include "llvm/Support/Process.h"
+
 using namespace lldb;
 using namespace lldb_private;
 
@@ -659,6 +661,51 @@
   return Status();
 }
 
+Status NativeProcessProtocol::ReadCStringFromMemory(lldb::addr_t addr,
+                                                    char *buffer,
+                                                    size_t max_size,
+                                                    size_t &total_bytes_read) {
+  const size_t cache_line_size = llvm::sys::Process::getPageSizeEstimate();
+  size_t bytes_read = 0;
+  size_t bytes_left = max_size;
+  addr_t curr_addr = addr;
+  char *curr_buffer = buffer;
+  total_bytes_read = 0;
+  Status error;
+
+  while (bytes_left > 0 && error.Success()) {
+    addr_t cache_line_bytes_left =
+        cache_line_size - (curr_addr % cache_line_size);
+    addr_t bytes_to_read = std::min<addr_t>(bytes_left, cache_line_bytes_left);
+    error = ReadMemory(curr_addr, reinterpret_cast<void *>(curr_buffer),
+                       bytes_to_read, bytes_read);
+
+    if (bytes_read == 0)
+      break;
+
+    auto str_end = std::memchr(curr_buffer, '\0', bytes_read);
+    if (str_end != NULL) {
+      total_bytes_read = (size_t)(reinterpret_cast<char *>(str_end) - buffer);
+      error.Clear();
+      break;
+    }
+
+    total_bytes_read += bytes_read;
+    curr_buffer += bytes_read;
+    curr_addr = reinterpret_cast<addr_t>(reinterpret_cast<char *>(curr_addr) +
+                                         bytes_read);
+    bytes_left -= bytes_read;
+  }
+
+  // Make sure we return a null terminated string.
+  if (bytes_left == 0 && buffer[max_size - 1] != '\0') {
+    buffer[max_size - 1] = '\0';
+    total_bytes_read--;
+  }
+
+  return error;
+}
+
 lldb::StateType NativeProcessProtocol::GetState() const {
   std::lock_guard<std::recursive_mutex> guard(m_state_mutex);
   return m_state;
Index: lldb/include/lldb/Host/common/NativeProcessProtocol.h
===================================================================
--- lldb/include/lldb/Host/common/NativeProcessProtocol.h
+++ lldb/include/lldb/Host/common/NativeProcessProtocol.h
@@ -83,6 +83,9 @@
   Status ReadMemoryWithoutTrap(lldb::addr_t addr, void *buf, size_t size,
                                size_t &bytes_read);
 
+  Status ReadCStringFromMemory(lldb::addr_t addr, char *buffer, size_t max_size,
+                               size_t &total_bytes_read);
+
   virtual Status WriteMemory(lldb::addr_t addr, const void *buf, size_t size,
                              size_t &bytes_written) = 0;
 


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