From 7e5a8cc5230dcc027686813e51a1b001cee4c602 Mon Sep 17 00:00:00 2001
From: Elliott Hughes <enh@google.com>
Date: Tue, 18 Jun 2013 13:15:00 -0700
Subject: [PATCH] Make LD_PRELOAD failures just warnings.

This matches glibc and makes life easier for developers who want to
sometimes preload a library from init (which has no conditionals); they
can simply move/remove the library to disable.

Change-Id: I579b8633f958235af6e46bb53b378b9e363afb1f
---
 linker/linker.cpp | 15 ++++++++-------
 linker/linker.h   | 11 ++++++++++-
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/linker/linker.cpp b/linker/linker.cpp
index 80dc62437..c53d52f68 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -1492,18 +1492,19 @@ static bool soinfo_link_image(soinfo* si) {
         return false;
     }
 
-    /* if this is the main executable, then load all of the preloads now */
+    // If this is the main executable, then load all of the libraries from LD_PRELOAD now.
     if (si->flags & FLAG_EXE) {
         memset(gLdPreloads, 0, sizeof(gLdPreloads));
+        size_t preload_count = 0;
         for (size_t i = 0; gLdPreloadNames[i] != NULL; i++) {
             soinfo* lsi = find_library(gLdPreloadNames[i]);
-            if (lsi == NULL) {
-                strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf));
-                DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s",
-                       gLdPreloadNames[i], si->name, tmp_err_buf);
-                return false;
+            if (lsi != NULL) {
+                gLdPreloads[preload_count++] = lsi;
+            } else {
+                // As with glibc, failure to load an LD_PRELOAD library is just a warning.
+                DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s",
+                        gLdPreloadNames[i], si->name, linker_get_error_buffer());
             }
-            gLdPreloads[i] = lsi;
         }
     }
 
diff --git a/linker/linker.h b/linker/linker.h
index 61d623a96..200a68277 100644
--- a/linker/linker.h
+++ b/linker/linker.h
@@ -43,7 +43,16 @@
       __libc_format_buffer(linker_get_error_buffer(), linker_get_error_buffer_size(), fmt, ##x); \
       /* If LD_DEBUG is set high enough, log every dlerror(3) message. */ \
       DEBUG("%s\n", linker_get_error_buffer()); \
-    } while(0)
+    } while (false)
+
+#define DL_WARN(fmt, x...) \
+    do { \
+      __libc_format_log(ANDROID_LOG_WARN, "linker", fmt, ##x); \
+      __libc_format_fd(2, "WARNING: linker: "); \
+      __libc_format_fd(2, fmt, ##x); \
+      __libc_format_fd(2, "\n"); \
+    } while (false)
+
 
 // Returns the address of the page containing address 'x'.
 #define PAGE_START(x)  ((x) & PAGE_MASK)