[PATCH v1 1/2] String: Add three more overflow tests cases to test-strnlen.c

[PATCH v1 1/2] String: Add three more overflow tests cases to test-strnlen.c

[Noah Goldstein]

No bug. Just seem like relevant cases given that strnlen will
use s + maxlen in many implementations.

Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
---
 string/test-strnlen.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/string/test-strnlen.c b/string/test-strnlen.c
index f53e09263f..bb5d9b5f04 100644
--- a/string/test-strnlen.c
+++ b/string/test-strnlen.c
@@ -117,6 +117,10 @@ do_overflow_tests (void)
           do_test (0, i, ~len + i, BIG_CHAR);
           do_test (0, i, ~len - buf_addr - i, BIG_CHAR);
           do_test (0, i, ~len - buf_addr + i, BIG_CHAR);
+
+          do_test (0, i, -buf_addr, BIG_CHAR);
+          do_test (0, i, j - buf_addr, BIG_CHAR);
+          do_test (0, i, -buf_addr - j, BIG_CHAR);
         }
     }
 }
-- 
2.25.1

[PATCH v1 2/2] x86: Remove unnecessary overflow check from wcsnlen-sse4_1.S

[Noah Goldstein]

No bug. The way wcsnlen will check if near the end of maxlen
is the following macro:

	mov	%r11, %rsi;	\
	subq	%rax, %rsi;	\
	andq	$-64, %rax;	\
	testq	$-64, %rsi;	\
	je	L(strnlen_ret)

Which words independently of s + maxlen overflowing. So the
second overflow check is unnecissary for correctness and
just extra overhead in the common no overflow case.

test-strlen.c, test-wcslen.c, test-strnlen.c and test-wcsnlen.c are
all passing

Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
---
Sorry I didn't notice this earlier before my last commit. As
of submitting this patch

	a775a7a3eb1e85b54af0b4ee5ff4dcf66772a1fb

Is HEAD of master to maybe rebase so commit history isnt messy?

        
 sysdeps/x86_64/multiarch/strlen-vec.S | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/sysdeps/x86_64/multiarch/strlen-vec.S b/sysdeps/x86_64/multiarch/strlen-vec.S
index 439e486a43..b7657282bd 100644
--- a/sysdeps/x86_64/multiarch/strlen-vec.S
+++ b/sysdeps/x86_64/multiarch/strlen-vec.S
@@ -71,19 +71,12 @@ L(n_nonzero):
    suffice.  */
 	mov	%RSI_LP, %R10_LP
 	sar	$62, %R10_LP
-	test	%R10_LP, %R10_LP
 	jnz	__wcslen_sse4_1
 	sal	$2, %RSI_LP
 # endif
 
-
 /* Initialize long lived registers.  */
-
 	add	%RDI_LP, %RSI_LP
-# ifdef AS_WCSLEN
-/* Check for overflow again from s + maxlen * sizeof(wchar_t).  */
-	jbe	__wcslen_sse4_1
-# endif
 	mov	%RSI_LP, %R10_LP
 	and	$-64, %R10_LP
 	mov	%RSI_LP, %R11_LP
-- 
2.25.1

Re: [PATCH v1 1/2] String: Add three more overflow tests cases to test-strnlen.c

[H.J. Lu]

On Wed, Jun 23, 2021 at 4:59 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> No bug. Just seem like relevant cases given that strnlen will
> use s + maxlen in many implementations.
>
> Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> ---
>  string/test-strnlen.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/string/test-strnlen.c b/string/test-strnlen.c
> index f53e09263f..bb5d9b5f04 100644
> --- a/string/test-strnlen.c
> +++ b/string/test-strnlen.c
> @@ -117,6 +117,10 @@ do_overflow_tests (void)
>            do_test (0, i, ~len + i, BIG_CHAR);
>            do_test (0, i, ~len - buf_addr - i, BIG_CHAR);
>            do_test (0, i, ~len - buf_addr + i, BIG_CHAR);
> +
> +          do_test (0, i, -buf_addr, BIG_CHAR);
> +          do_test (0, i, j - buf_addr, BIG_CHAR);
> +          do_test (0, i, -buf_addr - j, BIG_CHAR);
>          }
>      }
>  }
> --
> 2.25.1
>

LGTM.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Thanks.

-- 
H.J.

Re: [PATCH v1 2/2] x86: Remove unnecessary overflow check from wcsnlen-sse4_1.S

[H.J. Lu]

On Wed, Jun 23, 2021 at 5:00 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> No bug. The way wcsnlen will check if near the end of maxlen
> is the following macro:
>
>         mov     %r11, %rsi;     \
>         subq    %rax, %rsi;     \
>         andq    $-64, %rax;     \
>         testq   $-64, %rsi;     \
>         je      L(strnlen_ret)
>
> Which words independently of s + maxlen overflowing. So the
> second overflow check is unnecissary for correctness and
> just extra overhead in the common no overflow case.
>
> test-strlen.c, test-wcslen.c, test-strnlen.c and test-wcsnlen.c are
> all passing
>
> Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> ---
> Sorry I didn't notice this earlier before my last commit. As
> of submitting this patch
>
>         a775a7a3eb1e85b54af0b4ee5ff4dcf66772a1fb
>
> Is HEAD of master to maybe rebase so commit history isnt messy?
>
>
>  sysdeps/x86_64/multiarch/strlen-vec.S | 7 -------
>  1 file changed, 7 deletions(-)
>
> diff --git a/sysdeps/x86_64/multiarch/strlen-vec.S b/sysdeps/x86_64/multiarch/strlen-vec.S
> index 439e486a43..b7657282bd 100644
> --- a/sysdeps/x86_64/multiarch/strlen-vec.S
> +++ b/sysdeps/x86_64/multiarch/strlen-vec.S
> @@ -71,19 +71,12 @@ L(n_nonzero):
>     suffice.  */
>         mov     %RSI_LP, %R10_LP
>         sar     $62, %R10_LP
> -       test    %R10_LP, %R10_LP
>         jnz     __wcslen_sse4_1
>         sal     $2, %RSI_LP
>  # endif
>
> -
>  /* Initialize long lived registers.  */
> -
>         add     %RDI_LP, %RSI_LP
> -# ifdef AS_WCSLEN
> -/* Check for overflow again from s + maxlen * sizeof(wchar_t).  */
> -       jbe     __wcslen_sse4_1
> -# endif
>         mov     %RSI_LP, %R10_LP
>         and     $-64, %R10_LP
>         mov     %RSI_LP, %R11_LP
> --
> 2.25.1
>

LGTM.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Thanks.

-- 
H.J.

Re: [PATCH v1 2/2] x86: Remove unnecessary overflow check from wcsnlen-sse4_1.S

[Sunil Pandey]

On Wed, Jun 23, 2021 at 5:42 PM H.J. Lu via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> On Wed, Jun 23, 2021 at 5:00 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > No bug. The way wcsnlen will check if near the end of maxlen
> > is the following macro:
> >
> >         mov     %r11, %rsi;     \
> >         subq    %rax, %rsi;     \
> >         andq    $-64, %rax;     \
> >         testq   $-64, %rsi;     \
> >         je      L(strnlen_ret)
> >
> > Which words independently of s + maxlen overflowing. So the
> > second overflow check is unnecissary for correctness and
> > just extra overhead in the common no overflow case.
> >
> > test-strlen.c, test-wcslen.c, test-strnlen.c and test-wcsnlen.c are
> > all passing
> >
> > Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> > ---
> > Sorry I didn't notice this earlier before my last commit. As
> > of submitting this patch
> >
> >         a775a7a3eb1e85b54af0b4ee5ff4dcf66772a1fb
> >
> > Is HEAD of master to maybe rebase so commit history isnt messy?
> >
> >
> >  sysdeps/x86_64/multiarch/strlen-vec.S | 7 -------
> >  1 file changed, 7 deletions(-)
> >
> > diff --git a/sysdeps/x86_64/multiarch/strlen-vec.S b/sysdeps/x86_64/multiarch/strlen-vec.S
> > index 439e486a43..b7657282bd 100644
> > --- a/sysdeps/x86_64/multiarch/strlen-vec.S
> > +++ b/sysdeps/x86_64/multiarch/strlen-vec.S
> > @@ -71,19 +71,12 @@ L(n_nonzero):
> >     suffice.  */
> >         mov     %RSI_LP, %R10_LP
> >         sar     $62, %R10_LP
> > -       test    %R10_LP, %R10_LP
> >         jnz     __wcslen_sse4_1
> >         sal     $2, %RSI_LP
> >  # endif
> >
> > -
> >  /* Initialize long lived registers.  */
> > -
> >         add     %RDI_LP, %RSI_LP
> > -# ifdef AS_WCSLEN
> > -/* Check for overflow again from s + maxlen * sizeof(wchar_t).  */
> > -       jbe     __wcslen_sse4_1
> > -# endif
> >         mov     %RSI_LP, %R10_LP
> >         and     $-64, %R10_LP
> >         mov     %RSI_LP, %R11_LP
> > --
> > 2.25.1
> >
>
> LGTM.
>
> Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
>
> Thanks.
>
> --
> H.J.

I would like to backport this patch to release branches.
Any comments or objections?

--Sunil