[PATCH] aarch64: fix off-by-one in reading cpuinfo

[PATCH] aarch64: fix off-by-one in reading cpuinfo

[Philipp Tomsich]

Fixes: 341573406b39

Don't subtract one from the result of strnlen() when trying to point
to the first character after the current string.  This issue would
cause individual characters (where the 128 byte buffers are stitched
together) to be lost.

gcc/ChangeLog:

	* config/aarch64/driver-aarch64.cc (readline): Fix off-by-one.

Signed-off-by: Philipp Tomsich <philipp.tomsich@vrull.eu>

---

 gcc/config/aarch64/driver-aarch64.cc | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/gcc/config/aarch64/driver-aarch64.cc b/gcc/config/aarch64/driver-aarch64.cc
index 52ff537908e..48250e68034 100644
--- a/gcc/config/aarch64/driver-aarch64.cc
+++ b/gcc/config/aarch64/driver-aarch64.cc
@@ -203,9 +203,9 @@ readline (FILE *f)
 	return std::string ();
       /* If we're not at the end of the line then override the
 	 \0 added by fgets.  */
-      last = strnlen (buf, size) - 1;
+      last = strnlen (buf, size);
     }
-  while (!feof (f) && buf[last] != '\n');
+  while (!feof (f) && (last > 0 && buf[last - 1] != '\n'));
 
   std::string result (buf);
   free (buf);
-- 
2.34.1

Re: [PATCH] aarch64: fix off-by-one in reading cpuinfo

[Richard Sandiford]

Philipp Tomsich <philipp.tomsich@vrull.eu> writes:
> Fixes: 341573406b39
>
> Don't subtract one from the result of strnlen() when trying to point
> to the first character after the current string.  This issue would
> cause individual characters (where the 128 byte buffers are stitched
> together) to be lost.
>
> gcc/ChangeLog:
>
> 	* config/aarch64/driver-aarch64.cc (readline): Fix off-by-one.
>
> Signed-off-by: Philipp Tomsich <philipp.tomsich@vrull.eu>

Thanks for the patch.  Would it be possible to create a testcase along
the lines of gcc.target/aarch64/cpunative/native_cpu_15.c?

Richard

> ---
>
>  gcc/config/aarch64/driver-aarch64.cc | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/gcc/config/aarch64/driver-aarch64.cc b/gcc/config/aarch64/driver-aarch64.cc
> index 52ff537908e..48250e68034 100644
> --- a/gcc/config/aarch64/driver-aarch64.cc
> +++ b/gcc/config/aarch64/driver-aarch64.cc
> @@ -203,9 +203,9 @@ readline (FILE *f)
>  	return std::string ();
>        /* If we're not at the end of the line then override the
>  	 \0 added by fgets.  */
> -      last = strnlen (buf, size) - 1;
> +      last = strnlen (buf, size);
>      }
> -  while (!feof (f) && buf[last] != '\n');
> +  while (!feof (f) && (last > 0 && buf[last - 1] != '\n'));
>  
>    std::string result (buf);
>    free (buf);