From 9d87d7695731ed27ab80da71d5e162982eeeda3a Mon Sep 17 00:00:00 2001
From: Jonas 'Sortie' Termansen <sortie@maxsi.org>
Date: Wed, 13 May 2015 20:27:49 +0200
Subject: [PATCH] Abort on overlapping memcpy.

---
 kernel/libk.cpp      |  6 ++++++
 libc/include/libk.h  |  2 ++
 libc/string/memcpy.c | 28 +++++++++++++++++++++++++++-
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/kernel/libk.cpp b/kernel/libk.cpp
index 0bd4cf31..baa301a9 100644
--- a/kernel/libk.cpp
+++ b/kernel/libk.cpp
@@ -96,6 +96,12 @@ void libk_abort(void)
 	Sortix::PanicF("abort()");
 }
 
+extern "C"
+void libk_overlapping_memcpy(void)
+{
+	Sortix::PanicF("Overlapping memcpy detected");
+}
+
 extern "C"
 void libk_random_lock(void)
 {
diff --git a/libc/include/libk.h b/libc/include/libk.h
index 32a11987..498c766d 100644
--- a/libc/include/libk.h
+++ b/libc/include/libk.h
@@ -41,6 +41,8 @@ __attribute__((noreturn))
 void libk_stack_chk_fail(void);
 __attribute__((noreturn))
 void libk_abort(void);
+__attribute__((noreturn))
+void libk_overlapping_memcpy(void);
 void libk_random_lock(void);
 void libk_random_unlock(void);
 bool libk_hasentropy(size_t);
diff --git a/libc/string/memcpy.c b/libc/string/memcpy.c
index ede0db88..6ee6fda3 100644
--- a/libc/string/memcpy.c
+++ b/libc/string/memcpy.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2012, 2014 Jonas 'Sortie' Termansen.
+ * Copyright (c) 2011, 2012, 2014, 2015, 2016 Jonas 'Sortie' Termansen.
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -17,9 +17,15 @@
  * Copy memory between non-overlapping regions.
  */
 
+#include <scram.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 
+#if defined(__is_sortix_libk)
+#include <libk.h>
+#endif
+
 inline static
 void* memcpy_slow(void* restrict dst_ptr,
                   const void* restrict src_ptr,
@@ -36,6 +42,26 @@ void* memcpy(void* restrict dst_ptr,
              const void* restrict src_ptr,
              size_t size)
 {
+	if ( dst_ptr == src_ptr || !size )
+		return dst_ptr;
+
+	void* dst_end = (char*) dst_ptr + size;
+	const void* src_end = (const const char*) src_ptr + size;
+	if ( (dst_ptr < src_ptr && src_ptr < dst_end) ||
+	     (src_ptr < dst_ptr && dst_ptr < src_end) )
+	{
+#if defined(__is_sortix_libk)
+		libk_overlapping_memcpy();
+#else
+		struct scram_undefined_behavior info;
+		info.filename = __FILE__;
+		info.line = __LINE__;
+		info.column = 0;
+		info.violation = "overlapping memcpy";
+		scram(SCRAM_UNDEFINED_BEHAVIOR, &info);
+#endif
+	}
+
 #if 8 < __SIZEOF_LONG__
 #warning "you should add support for your unexpectedly large unsigned long."
 	return memcpy_slow(dst_ptr, src_ptr, size);