Re: [LTP] [PATCH] mmap04: Make sure the scanf address format is at least 8 hex chars

[Cyril Hrubis <chrubis@suse.cz>]

Hi!
> The addresses in /proc/self/maps are at least 8 hex chars. Zeros are
> added to the front of the address when shorted (both on 32bit and
> 64bit systems.
> 
> Under valgrind the mmaps used in kernel/syscalls/mmap/mmap04.c come
> out very low in the address space and might be shorter than 8 hex
> chars. This causes the scanf to fail:
> mmap04.c:62: TBROK: Expected 1 conversions got 0 FILE '/proc/self/maps'

I guess I do not understand the problem here. The PRIxPTR translates to
"x", "lx", or "llx" depending on architecture and as far as I can tell
the %x modifier handles leading zeroes just fine.

> Fix this by using "%08" PRIxPTR when creating the fmt used.

Unfortunately this is not universally true. For example the vsyscall
page is mapped at very high address on x86_64:

ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0                  [vsyscall]

> Signed-off-by: Mark Wielaard <mark@klomp.org>
> ---
>  testcases/kernel/syscalls/mmap/mmap04.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/testcases/kernel/syscalls/mmap/mmap04.c b/testcases/kernel/syscalls/mmap/mmap04.c
> index 4a050b7b50da..5b28180df29b 100644
> --- a/testcases/kernel/syscalls/mmap/mmap04.c
> +++ b/testcases/kernel/syscalls/mmap/mmap04.c
> @@ -58,7 +58,8 @@ static void run(unsigned int i)
>  
>  	addr2 = SAFE_MMAP(addr1 + pagesize, pagesize, tc->prot, tc->flags | MAP_FIXED, -1, 0);
>  
> -	sprintf(fmt, "%" PRIxPTR "-%%*x %%s", (uintptr_t)addr2);
> +	/* A /proc/self/maps address is at least 8 hex (left zero padded) */
> +	sprintf(fmt, "%08" PRIxPTR "-%%*x %%s", (uintptr_t)addr2);
>  	SAFE_FILE_LINES_SCANF("/proc/self/maps", fmt, perms);
>  
>  	if (!strcmp(perms, tc->exp_perms)) {
> -- 
> 2.51.0
> 
> 
> -- 
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-- 
Cyril Hrubis
chrubis@suse.cz

-- 
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