[PATCH v5 11/19] x86, boot: Add checking for memcpy

Yinghai Lu
2015-03-18T07:28:18Z

parse_elf is using local memcpy to move section to running position.

That memcpy actually only support no overlapping or dest < src.

Add checking in memcpy to find out wrong with future use, at that time
we will need to have backward memcpy for it.

Also put comments in parse_elf about the fact.

Signed-off-by: Yinghai Lu <yinghai-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
arch/x86/boot/compressed/misc.c | 14 +++++++-------
arch/x86/boot/compressed/misc.h | 2 ++
arch/x86/boot/compressed/string.c | 28 ++++++++++++++++++++++++++--
3 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index f99c9c9..94e283c 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -106,9 +106,6 @@
#undef memset
#define memzero(s, n) memset((s), 0, (n))

-
-static void error(char *m);
-
/*
* This is set up by the setup-routine at boot-time
*/
@@ -218,7 +215,7 @@ void __putstr(const char *s)
outb(0xff & (pos >> 1), vidport+1);
}

-static void error(char *x)
+void error(char *x)
{
error_putstr("\n\n");
error_putstr(x);
@@ -353,9 +350,12 @@ static void parse_elf(void *output)
#else
dest = (void *)(phdr->p_paddr);
#endif
- memcpy(dest,
- output + phdr->p_offset,
- phdr->p_filesz);
+ /*
+ * simple version memcpy only can work when dest is
+ * smaller than src or no overlapping.
+ * Here dest is smaller than src always.
+ */
+ memcpy(dest, output + phdr->p_offset, phdr->p_filesz);
break;
default: /* Ignore other PT_* */ break;
}
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 98914a0..a7f3826 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -37,6 +37,8 @@ extern struct boot_params *real_mode; /* Pointer to real-mode data */
void __putstr(const char *s);
#define error_putstr(__x) __putstr(__x)

+void error(char *x);
+
#ifdef CONFIG_X86_VERBOSE_BOOTUP

#define debug_putstr(__x) __putstr(__x)
diff --git a/arch/x86/boot/compressed/string.c b/arch/x86/boot/compressed/string.c
index 00e788b..03805a4 100644
--- a/arch/x86/boot/compressed/string.c
+++ b/arch/x86/boot/compressed/string.c
@@ -1,7 +1,7 @@
#include "../string.c"

#ifdef CONFIG_X86_32
-void *memcpy(void *dest, const void *src, size_t n)
+void *__memcpy(void *dest, const void *src, size_t n)
{
int d0, d1, d2;
asm volatile(
@@ -15,7 +15,7 @@ void *memcpy(void *dest, const void *src, size_t n)
return dest;
}
#else
-void *memcpy(void *dest, const void *src, size_t n)
+void *__memcpy(void *dest, const void *src, size_t n)
{
long d0, d1, d2;
asm volatile(
@@ -30,6 +30,30 @@ void *memcpy(void *dest, const void *src, size_t n)
}
#endif

+void *memcpy(void *dest, const void *src, size_t n)
+{
+ unsigned long start_dest, end_dest;
+ unsigned long start_src, end_src;
+ unsigned long max_start, min_end;
+
+ if (dest < src)
+ return __memcpy(dest, src, n);
+
+ start_dest = (unsigned long)dest;
+ end_dest = (unsigned long)dest + n;
+ start_src = (unsigned long)src;
+ end_src = (unsigned long)src + n;
+ max_start = (start_dest > start_src) ? start_dest : start_src;
+ min_end = (end_dest < end_src) ? end_dest : end_src;
+
+ if (max_start >= min_end)
+ return __memcpy(dest, src, n);
+
+ error("memcpy does not support overlapping with dest > src!\n");
+
+ return dest;
+}
+
void *memset(void *s, int c, size_t n)
{
int i;
--
1.8.4.5