From 1bf4bdb11de75be3b8ecc38b3ba6b55b05c43ac5 Mon Sep 17 00:00:00 2001
From: Alberto Bertogli <albertito@blitiri.com.ar>
Date: Sun, 14 Jun 2009 22:23:41 -0300
Subject: [PATCH 24/48] preload: Add custom-made wrappers for malloc() and realloc()

They can't be made generic because, at least on glibc, they're used before
constructors are called.

See the comments inside the code for more details.

Signed-off-by: Alberto Bertogli <albertito@blitiri.com.ar>
---
 preload/modules/libc.mm.custom.c |  105 ++++++++++++++++++++++++++++++++++++++
 1 files changed, 105 insertions(+), 0 deletions(-)
 create mode 100644 preload/modules/libc.mm.custom.c

diff --git a/preload/modules/libc.mm.custom.c b/preload/modules/libc.mm.custom.c
new file mode 100644
index 0000000..8e0210b
--- /dev/null
+++ b/preload/modules/libc.mm.custom.c
@@ -0,0 +1,105 @@
+
+/*
+ * Custom-made wrappers for malloc() and realloc().
+ *
+ * They can't be made generic because, at least on glibc, they're used before
+ * constructors are called.
+ *
+ * We use __malloc_hook, the glibc-specific interface, so this is glibc-only.
+ */
+
+#include <features.h>
+
+#ifndef __GLIBC__
+  #warning "Not using glibc, so no malloc() wrappers will be available"
+#else
+
+#include "codegen.h"
+
+#include <malloc.h>
+
+
+/* Original glibc's hooks, saved in our init function */
+static void *(*old_malloc_hook)(size_t, const void *);
+static void *(*old_realloc_hook)(void *ptr, size_t size, const void *caller);
+
+/* Our own hooks, that will replace glibc's */
+static void *fiu_malloc_hook(size_t size, const void *caller);
+static void *fiu_realloc_hook(void *ptr, size_t size, const void *caller);
+
+
+/* We are not going to use __malloc_initialize_hook because it would be called
+ * before our library initialization functions, which include fiu_init().
+ * Instead, we will use a constructor just like the other wrappers, but it
+ * will run after them just to make things tidier (NOT because it is
+ * necessary). */
+
+static void __attribute__((constructor(202))) fiu_init_malloc(void)
+{
+	/* Save original hooks, used in ours to prevent unwanted recursion */
+	old_malloc_hook = __malloc_hook;
+	old_realloc_hook = __realloc_hook;
+
+	__malloc_hook = fiu_malloc_hook;
+	__realloc_hook = fiu_realloc_hook;
+}
+
+
+static void *fiu_malloc_hook(size_t size, const void *caller)
+{
+	void *r;
+	int fstatus;
+
+	/* fiu_fail() may call anything */
+	rec_inc();
+
+	/* See __malloc_hook(3) for details */
+	__malloc_hook = old_malloc_hook;
+
+	fstatus = fiu_fail("libc/mm/malloc");
+	if (fstatus != 0) {
+		r = NULL;
+		goto exit;
+	}
+
+	r = malloc(size);
+
+exit:
+	old_malloc_hook = __malloc_hook;
+	__malloc_hook = fiu_malloc_hook;
+
+	rec_dec();
+	return r;
+}
+
+
+static void *fiu_realloc_hook(void *ptr, size_t size, const void *caller)
+{
+	void *r;
+	int fstatus;
+
+	/* fiu_fail() may call anything */
+	rec_inc();
+
+	/* See __malloc_hook(3) for details */
+	__realloc_hook = old_realloc_hook;
+
+	fstatus = fiu_fail("libc/mm/realloc");
+	if (fstatus != 0) {
+		r = NULL;
+		goto exit;
+	}
+
+	r = realloc(ptr, size);
+
+exit:
+	old_realloc_hook = __realloc_hook;
+	__realloc_hook = fiu_realloc_hook;
+
+	rec_dec();
+	return r;
+}
+
+
+#endif // defined __GLIBC__
+
-- 
1.6.2.2.646.gb214