From 172955a4e30b88ce8239a7ef426b4e8903e9923c Mon Sep 17 00:00:00 2001
From: Christopher Ferris <cferris@google.com>
Date: Tue, 26 Aug 2014 20:48:11 -0700
Subject: [PATCH] Replace snprintf calls in linker.

When enabling debug malloc, the snprintf calls in the linker fails to
update the buffer.

The problem is that snprintf makes a call to pthread_getspecific that
returns a valid pointer, but the data it points to is zero. This should
never happen and causes the snprintf to stop and do nothing.

Temporarily replace snprintf with a different implementation to work
around this issue.

Bug: 16874447
Bug: 17302493
Change-Id: I7a500f28adf153150cf2812fae745ff41f1c48d3
---
 linker/debugger.cpp |  4 ++--
 linker/linker.cpp   | 16 +++++++++++++++-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/linker/debugger.cpp b/linker/debugger.cpp
index 079682cab..c31615171 100644
--- a/linker/debugger.cpp
+++ b/linker/debugger.cpp
@@ -170,9 +170,9 @@ static void log_signal_summary(int signum, const siginfo_t* info) {
   if (info != NULL) {
     // For a rethrown signal, this si_code will be right and the one debuggerd shows will
     // always be SI_TKILL.
-    snprintf(code_desc, sizeof(code_desc), ", code %d", info->si_code);
+    __libc_format_buffer(code_desc, sizeof(code_desc), ", code %d", info->si_code);
     if (has_address) {
-      snprintf(addr_desc, sizeof(addr_desc), ", fault addr %p", info->si_addr);
+      __libc_format_buffer(addr_desc, sizeof(addr_desc), ", fault addr %p", info->si_addr);
     }
   }
   __libc_format_log(ANDROID_LOG_FATAL, "libc",
diff --git a/linker/linker.cpp b/linker/linker.cpp
index 52eb56ab8..2d8e07eb4 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -866,7 +866,21 @@ static void soinfo_unload(soinfo* si) {
 }
 
 void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
-  snprintf(buffer, buffer_size, "%s:%s", kDefaultLdPaths[0], kDefaultLdPaths[1]);
+  // Use basic string manipulation calls to avoid snprintf.
+  // snprintf indirectly calls pthread_getspecific to get the size of a buffer.
+  // When debug malloc is enabled, this call returns 0. This in turn causes
+  // snprintf to do nothing, which causes libraries to fail to load.
+  // See b/17302493 for further details.
+  // Once the above bug is fixed, this code can be modified to use
+  // snprintf again.
+  size_t required_len = strlen(kDefaultLdPaths[0]) + strlen(kDefaultLdPaths[1]) + 2;
+  if (buffer_size < required_len) {
+    __libc_fatal("android_get_LD_LIBRARY_PATH failed, buffer too small: buffer len %zu, required len %zu",
+                 buffer_size, required_len);
+  }
+  char* end = stpcpy(buffer, kDefaultLdPaths[0]);
+  *end = ':';
+  strcpy(end + 1, kDefaultLdPaths[1]);
 }
 
 void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) {