2018-02-02 15:01:35

by Arnd Bergmann

Subject: [PATCH] kdb: use memmove instead of overlapping memcpy

gcc discovered that the memcpy() arguments in kdbnearsym() overlap, so
we should really use memmove(), which is defined to handle that correctly:

In function 'memcpy',
inlined from 'kdbnearsym' at /git/arm-soc/kernel/debug/kdb/kdb_support.c:132:4:
/git/arm-soc/include/linux/string.h:353:9: error: '__builtin_memcpy' accessing 792 bytes at offsets 0 and 8 overlaps 784 bytes at offset 8 [-Werror=restrict]
return __builtin_memcpy(p, q, size);

Signed-off-by: Arnd Bergmann <[email protected]>
---
kernel/debug/kdb/kdb_support.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/debug/kdb/kdb_support.c b/kernel/debug/kdb/kdb_support.c
index 5d8ef3a07ecd..1ad4370ccbf0 100644
--- a/kernel/debug/kdb/kdb_support.c
+++ b/kernel/debug/kdb/kdb_support.c
@@ -129,13 +129,13 @@ int kdbnearsym(unsigned long addr, kdb_symtab_t *symtab)
}
if (i >= ARRAY_SIZE(kdb_name_table)) {
debug_kfree(kdb_name_table[0]);
- memcpy(kdb_name_table, kdb_name_table+1,
+ memmove(kdb_name_table, kdb_name_table+1,
sizeof(kdb_name_table[0]) *
(ARRAY_SIZE(kdb_name_table)-1));
} else {
debug_kfree(knt1);
knt1 = kdb_name_table[i];
- memcpy(kdb_name_table+i, kdb_name_table+i+1,
+ memmove(kdb_name_table+i, kdb_name_table+i+1,
sizeof(kdb_name_table[0]) *
(ARRAY_SIZE(kdb_name_table)-i-1));
}
--
2.9.0

2018-02-02 15:10:31

by Jason Wessel

Subject: Re: [PATCH] kdb: use memmove instead of overlapping memcpy

On 02/02/2018 08:59 AM, Arnd Bergmann wrote:
> gcc discovered that the memcpy() arguments in kdbnearsym() overlap, so
> we should really use memmove(), which is defined to handle that correctly:
>
> In function 'memcpy',
> inlined from 'kdbnearsym' at /git/arm-soc/kernel/debug/kdb/kdb_support.c:132:4:
> /git/arm-soc/include/linux/string.h:353:9: error: '__builtin_memcpy' accessing 792 bytes at offsets 0 and 8 overlaps 784 bytes at offset 8 [-Werror=restrict]
> return __builtin_memcpy(p, q, size);
>
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> kernel/debug/kdb/kdb_support.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/debug/kdb/kdb_support.c b/kernel/debug/kdb/kdb_support.c
> index 5d8ef3a07ecd..1ad4370ccbf0 100644
> --- a/kernel/debug/kdb/kdb_support.c
> +++ b/kernel/debug/kdb/kdb_support.c
> @@ -129,13 +129,13 @@ int kdbnearsym(unsigned long addr, kdb_symtab_t *symtab)
> }
> if (i >= ARRAY_SIZE(kdb_name_table)) {
> debug_kfree(kdb_name_table[0]);
> - memcpy(kdb_name_table, kdb_name_table+1,
> + memmove(kdb_name_table, kdb_name_table+1,
> sizeof(kdb_name_table[0]) *
> (ARRAY_SIZE(kdb_name_table)-1));
> } else {
> debug_kfree(knt1);
> knt1 = kdb_name_table[i];
> - memcpy(kdb_name_table+i, kdb_name_table+i+1,
> + memmove(kdb_name_table+i, kdb_name_table+i+1,
> sizeof(kdb_name_table[0]) *
> (ARRAY_SIZE(kdb_name_table)-i-1));
> }
>


That is good by me. Many thanks! Added to queue.

Reviewed-by: Jason Wessel <[email protected]>

Jason.