From 41bc866d58821eaebb72b0ee5117c8b5ca3b9cbe Mon Sep 17 00:00:00 2001
From: Wez Furlong <wez@netevil.org>
Date: Sun, 18 Mar 2007 01:37:02 +0000
Subject: [PATCH] be more libc friendly when replacing malloc().

Use our own getenv() on glibc platforms, as the glibc implementation calls
malloc() internally.  This allows the use of env vars to enable debugging modes
in the app.
---
 envvar.c | 26 ++++++++++++++++++++++++++
 malloc.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/envvar.c b/envvar.c
index 77518d2..e3769a8 100644
--- a/envvar.c
+++ b/envvar.c
@@ -93,6 +93,26 @@ typedef struct umem_env_item {
 static arg_process_t umem_backend_process;
 #endif
 
+#ifdef __GLIBC__
+/* replace getenv() with a specialized version that doesn't
+ * need to allocate memory.  We can't use strlen or strcmp
+ * here. */
+#include <unistd.h>
+static char *safe_getenv(const char *name)
+{
+	int i, l;
+	for (l = 0; name[l]; l++)
+		;
+	for (i = 0; __environ[i]; i++) {
+		if (!memcmp(__environ[i], name, l) && __environ[i][l] == '=') {
+			return &__environ[i][l+1];
+		}
+	}
+	return NULL;
+}
+#define getenv(x) safe_getenv(x)
+#endif
+
 static arg_process_t umem_log_process;
 
 const char *____umem_environ_msg_options = "-- UMEM_OPTIONS --";
@@ -553,6 +573,7 @@ umem_setup_envvars(int invalid)
 	static volatile enum {
 		STATE_START,
 		STATE_GETENV,
+		STATE_DLOPEN,
 		STATE_DLSYM,
 		STATE_FUNC,
 		STATE_DONE
@@ -577,6 +598,10 @@ umem_setup_envvars(int invalid)
 			where = "during getenv(3C) calls -- "
 			    "getenv(3C) results ignored.";
 			break;
+		case STATE_DLOPEN:
+			where = "during dlopen(3C) call -- "
+			    "_umem_*() results ignored.";
+			break;
 		case STATE_DLSYM:
 			where = "during dlsym(3C) call -- "
 			    "_umem_*() results ignored.";
@@ -623,6 +648,7 @@ umem_setup_envvars(int invalid)
 # define dlclose(a)		0
 # define dlerror()		0
 #endif
+	state = STATE_DLOPEN;
 	/* get a handle to the "a.out" object */
 	if ((h = dlopen(0, RTLD_FIRST | RTLD_LAZY)) != NULL) {
 		for (cur_env = umem_envvars; cur_env->env_name != NULL;
diff --git a/malloc.c b/malloc.c
index 45fae6e..7eec207 100644
--- a/malloc.c
+++ b/malloc.c
@@ -41,6 +41,10 @@
 
 #include "misc.h"
 
+#ifdef __GLIBC__
+# include <malloc.h>
+#endif
+
 /*
  * malloc_data_t is an 8-byte structure which is located "before" the pointer
  * returned from {m,c,re}alloc and memalign.  The first four bytes give
@@ -58,8 +62,12 @@ typedef struct malloc_data {
 	uint32_t malloc_stat; /* = UMEM_MALLOC_ENCODE(state, malloc_size) */
 } malloc_data_t;
 
+#ifdef __GLIBC__
+static void *umem_malloc_hook(size_t size_arg, const void *caller)
+#else
 void *
 malloc(size_t size_arg)
+#endif
 {
 #ifdef _LP64
 	uint32_t high_size = 0;
@@ -120,6 +128,7 @@ malloc(size_t size_arg)
 	return ((void *)ret);
 }
 
+#ifndef __GLIBC__
 void *
 calloc(size_t nelem, size_t elsize)
 {
@@ -138,6 +147,7 @@ calloc(size_t nelem, size_t elsize)
 	(void) memset(retval, 0, size);
 	return (retval);
 }
+#endif
 
 /*
  * memalign uses vmem_xalloc to do its work.
@@ -146,8 +156,12 @@ calloc(size_t nelem, size_t elsize)
  * code.
  */
 
+#ifdef __GLIBC__
+static void *umem_memalign_hook(size_t size_arg, size_t align, const void *caller)
+#else
 void *
 memalign(size_t align, size_t size_arg)
+#endif
 {
 	size_t size;
 	uintptr_t phase;
@@ -226,11 +240,13 @@ memalign(size_t align, size_t size_arg)
 	return ((void *)ret);
 }
 
+#ifndef __GLIBC__
 void *
 valloc(size_t size)
 {
 	return (memalign(pagesize, size));
 }
+#endif
 
 /*
  * process_free:
@@ -376,8 +392,12 @@ process_memalign:
 	return (1);
 }
 
+#ifdef __GLIBC__
+static void umem_free_hook(void *buf, const void *caller)
+#else
 void
 free(void *buf)
+#endif
 {
 	if (buf == NULL)
 		return;
@@ -388,8 +408,12 @@ free(void *buf)
 	(void) process_free(buf, 1, NULL);
 }
 
+#ifdef __GLIBC__
+static void *umem_realloc_hook(void *buf_arg, size_t newsize, const void *caller)
+#else
 void *
 realloc(void *buf_arg, size_t newsize)
+#endif
 {
 	size_t oldsize;
 	void *buf;
@@ -417,8 +441,25 @@ realloc(void *buf_arg, size_t newsize)
 	return (buf);
 }
 
+#ifdef __GLIBC__
+static void __attribute__((constructor)) umem_malloc_init_hook(void)
+{
+	if (__malloc_hook != umem_malloc_hook) {
+		umem_startup(NULL, 0, 0, NULL, NULL);
+		__malloc_hook = umem_malloc_hook;
+		__free_hook = umem_free_hook;
+		__realloc_hook = umem_realloc_hook;
+		__memalign_hook = umem_memalign_hook;
+	}
+}
+
+void (*__malloc_initialize_hook)(void) = umem_malloc_init_hook;
+
+#else
 void __attribute__((constructor))
 __malloc_umem_init (void)
 {
-  umem_startup(NULL, 0, 0, NULL, NULL);
+	umem_startup(NULL, 0, 0, NULL, NULL);
 }
+#endif
+