* [LTP] [PATCH] mmap04: Make sure the scanf address format is at least 8 hex chars
@ 2025-09-18 15:26 Mark Wielaard
2025-09-18 15:30 ` Mark Wielaard
2025-09-22 7:48 ` Cyril Hrubis
0 siblings, 2 replies; 6+ messages in thread
From: Mark Wielaard @ 2025-09-18 15:26 UTC (permalink / raw)
To: ltp; +Cc: Mark Wielaard, Martin Cermak
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'
Fix this by using "%08" PRIxPTR when creating the fmt used.
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
--
Mailing list info: https://lists.linux.it/listinfo/ltp
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [LTP] [PATCH] mmap04: Make sure the scanf address format is at least 8 hex chars
2025-09-18 15:26 [LTP] [PATCH] mmap04: Make sure the scanf address format is at least 8 hex chars Mark Wielaard
@ 2025-09-18 15:30 ` Mark Wielaard
2025-09-22 7:48 ` Cyril Hrubis
1 sibling, 0 replies; 6+ messages in thread
From: Mark Wielaard @ 2025-09-18 15:30 UTC (permalink / raw)
To: ltp; +Cc: Martin Cermak
Hi,
Sorry, I cannot type...
On Thu, 2025-09-18 at 17:26 +0200, Mark Wielaard wrote:
> 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
^ should be shorter.
> 64bit systems.
^ missing closing bracket ).
>
> 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'
>
> Fix this by using "%08" PRIxPTR when creating the fmt used.
>
> 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)) {
--
Mailing list info: https://lists.linux.it/listinfo/ltp
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [LTP] [PATCH] mmap04: Make sure the scanf address format is at least 8 hex chars
2025-09-18 15:26 [LTP] [PATCH] mmap04: Make sure the scanf address format is at least 8 hex chars Mark Wielaard
2025-09-18 15:30 ` Mark Wielaard
@ 2025-09-22 7:48 ` Cyril Hrubis
2025-09-22 8:24 ` Mark Wielaard
1 sibling, 1 reply; 6+ messages in thread
From: Cyril Hrubis @ 2025-09-22 7:48 UTC (permalink / raw)
To: Mark Wielaard; +Cc: Martin Cermak, ltp
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
>
>
> --
> Mailing list info: https://lists.linux.it/listinfo/ltp
--
Cyril Hrubis
chrubis@suse.cz
--
Mailing list info: https://lists.linux.it/listinfo/ltp
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [LTP] [PATCH] mmap04: Make sure the scanf address format is at least 8 hex chars
2025-09-22 7:48 ` Cyril Hrubis
@ 2025-09-22 8:24 ` Mark Wielaard
2025-09-22 8:33 ` Cyril Hrubis
0 siblings, 1 reply; 6+ messages in thread
From: Mark Wielaard @ 2025-09-22 8:24 UTC (permalink / raw)
To: Cyril Hrubis; +Cc: Martin Cermak, ltp
Hi Cyril,
On Mon, Sep 22, 2025 at 09:48:56AM +0200, Cyril Hrubis wrote:
> > 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.
The problem is that we want to match (scanf) an absolute address
(addr2) at the start of the line. It is this absolute/literal address
that doesn't match (because it might not have leading zeros).
e.g. We might want to match the address 403a000 and want to match
against: 0403a000-04048000 rw-p
When creating the fmt which we want to use for scanf we currently
generate: "403a000-%*x %s" Which doesn't match because it is missing
the leading zero (the "-%*x %s" would match the rest, except that the
start of the line doesn't). So with the "%08" fix we would generate:
"0403a000-%*x %s" which does match because it has the same number of
leading zeros.
> > 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]
Assuming we want to match the starting address ffffffffff600000 this
will work fine. "%08" PRIxPTR will generate that exact address without
extra leading zeros because it is already > 8 hex chars.
Hope that explains what is going on. The confusion might be because we
first use a patterns with sprintf to generate the pattern that we are
then going to use with scanf to parse both an actual/literal address
(plus hex address and perm string).
Cheers,
Mark
> > 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
> >
> >
> > --
> > Mailing list info: https://lists.linux.it/listinfo/ltp
>
> --
> Cyril Hrubis
> chrubis@suse.cz
--
Mailing list info: https://lists.linux.it/listinfo/ltp
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [LTP] [PATCH] mmap04: Make sure the scanf address format is at least 8 hex chars
2025-09-22 8:24 ` Mark Wielaard
@ 2025-09-22 8:33 ` Cyril Hrubis
2025-09-22 21:26 ` Petr Vorel
0 siblings, 1 reply; 6+ messages in thread
From: Cyril Hrubis @ 2025-09-22 8:33 UTC (permalink / raw)
To: Mark Wielaard; +Cc: Martin Cermak, ltp
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.
>
> The problem is that we want to match (scanf) an absolute address
> (addr2) at the start of the line. It is this absolute/literal address
> that doesn't match (because it might not have leading zeros).
>
> e.g. We might want to match the address 403a000 and want to match
> against: 0403a000-04048000 rw-p
>
> When creating the fmt which we want to use for scanf we currently
> generate: "403a000-%*x %s" Which doesn't match because it is missing
> the leading zero (the "-%*x %s" would match the rest, except that the
> start of the line doesn't). So with the "%08" fix we would generate:
> "0403a000-%*x %s" which does match because it has the same number of
> leading zeros.
Ah right, I'm blind, we generate the fmt on the fly. In that case
padding to eight zeroes will match what kernel does.
Reviewed-by: Cyril Hrubis <chrubis@suse.cz>
--
Cyril Hrubis
chrubis@suse.cz
--
Mailing list info: https://lists.linux.it/listinfo/ltp
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [LTP] [PATCH] mmap04: Make sure the scanf address format is at least 8 hex chars
2025-09-22 8:33 ` Cyril Hrubis
@ 2025-09-22 21:26 ` Petr Vorel
0 siblings, 0 replies; 6+ messages in thread
From: Petr Vorel @ 2025-09-22 21:26 UTC (permalink / raw)
To: Cyril Hrubis; +Cc: Mark Wielaard, Martin Cermak, ltp
Hi Mark, Cyril,
> 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.
> > The problem is that we want to match (scanf) an absolute address
> > (addr2) at the start of the line. It is this absolute/literal address
> > that doesn't match (because it might not have leading zeros).
> > e.g. We might want to match the address 403a000 and want to match
> > against: 0403a000-04048000 rw-p
> > When creating the fmt which we want to use for scanf we currently
> > generate: "403a000-%*x %s" Which doesn't match because it is missing
> > the leading zero (the "-%*x %s" would match the rest, except that the
> > start of the line doesn't). So with the "%08" fix we would generate:
> > "0403a000-%*x %s" which does match because it has the same number of
> > leading zeros.
> Ah right, I'm blind, we generate the fmt on the fly. In that case
> padding to eight zeroes will match what kernel does.
Mark, thanks for fixing our test! Merged.
Kind regards,
Petr
--
Mailing list info: https://lists.linux.it/listinfo/ltp
^ permalink raw reply [flat|nested] 6+ messages in thread
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2025-09-18 15:26 [LTP] [PATCH] mmap04: Make sure the scanf address format is at least 8 hex chars Mark Wielaard
2025-09-18 15:30 ` Mark Wielaard
2025-09-22 7:48 ` Cyril Hrubis
2025-09-22 8:24 ` Mark Wielaard
2025-09-22 8:33 ` Cyril Hrubis
2025-09-22 21:26 ` Petr Vorel
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