lkml.org 
[lkml]   [2013]   [May]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] arch: arm64: kernel: sprintf(), 'str' needs additional 1 byte for failure processing
Hello,

On Mon, May 27, 2013 at 03:00:12AM +0100, Chen Gang wrote:
>
> When failure occurs at the last looping cycle (when 'i == 0'), it will
> print "bad PC value" instead of "(%08x) ", which needs additional 1
> byte.
>
> If not add 1 byte, the 'str' may be memory overflow.
>
>
> Signed-off-by: Chen Gang <gang.chen@asianux.com>
> ---
> arch/arm64/kernel/traps.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index 61d7dd2..c2f68d2 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -100,7 +100,7 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
> {
> unsigned long addr = instruction_pointer(regs);
> mm_segment_t fs;
> - char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
> + char str[sizeof("00000000 ") * 5 + 2 + 1 + 1], *p = str;
> int i;

Whilst this code is difficult to follow, I don't think it's incorrect.
The size of the str array is:

sizeof("00000000 ") = 8 ('0's) + 1 (space) + 1 (NUL) = 10 bytes
*5 = 50 bytes
+2 (for the two brackets when i == 0) = 52 bytes
+1 (this is for the "bad PC value") = 53 bytes

In the worst case (when the PC is bad) we print:

"%08x " x4 = (8 + 1 + 1) *4 = 40 bytes
"bad PC value" = 12 + 1 = 13 bytes

so again, 53 bytes.

... or have I missed a character somewhere?

Will


\
 
 \ /
  Last update: 2013-05-28 13:21    [W:0.059 / U:0.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site