2018-07-03 19:56:21

by Kees Cook

Subject: [PATCH] RAID/s390: Remove VLA usage

In the quest to remove all stack VLA usage from the kernel[1], this moves
the "$#" replacement from being an argument to being inside the function,
which avoids generating VLAs.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Cc: Martin Schwidefsky <[email protected]>
Cc: Philippe Ombredanne <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
---
Resend due to typo in To/Cc
---
lib/raid6/s390vx.uc | 34 ++++++++++++++++++----------------
1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/lib/raid6/s390vx.uc b/lib/raid6/s390vx.uc
index 140fa8bb5c23..914ebe98fc21 100644
--- a/lib/raid6/s390vx.uc
+++ b/lib/raid6/s390vx.uc
@@ -55,22 +55,24 @@ static inline void XOR(int x, int y, int z)
asm volatile ("VX %0,%1,%2" : : "i" (x), "i" (y), "i" (z));
}

-static inline void LOAD_DATA(int x, int n, u8 *ptr)
+static inline void LOAD_DATA(int x, u8 *ptr)
{
- typedef struct { u8 _[16*n]; } addrtype;
+ typedef struct { u8 _[16 * $#]; } addrtype;
register addrtype *__ptr asm("1") = (addrtype *) ptr;

asm volatile ("VLM %2,%3,0,%r1"
- : : "m" (*__ptr), "a" (__ptr), "i" (x), "i" (x + n - 1));
+ : : "m" (*__ptr), "a" (__ptr), "i" (x),
+ "i" (x + $# - 1));
}

-static inline void STORE_DATA(int x, int n, u8 *ptr)
+static inline void STORE_DATA(int x, u8 *ptr)
{
- typedef struct { u8 _[16*n]; } addrtype;
+ typedef struct { u8 _[16 * $#]; } addrtype;
register addrtype *__ptr asm("1") = (addrtype *) ptr;

asm volatile ("VSTM %2,%3,0,1"
- : "=m" (*__ptr) : "a" (__ptr), "i" (x), "i" (x + n - 1));
+ : "=m" (*__ptr) : "a" (__ptr), "i" (x),
+ "i" (x + $# - 1));
}

static inline void COPY_VEC(int x, int y)
@@ -93,19 +95,19 @@ static void raid6_s390vx$#_gen_syndrome(int disks, size_t bytes, void **ptrs)
q = dptr[z0 + 2]; /* RS syndrome */

for (d = 0; d < bytes; d += $#*NSIZE) {
- LOAD_DATA(0,$#,&dptr[z0][d]);
+ LOAD_DATA(0,&dptr[z0][d]);
COPY_VEC(8+$$,0+$$);
for (z = z0 - 1; z >= 0; z--) {
MASK(16+$$,8+$$);
AND(16+$$,16+$$,25);
SHLBYTE(8+$$,8+$$);
XOR(8+$$,8+$$,16+$$);
- LOAD_DATA(16,$#,&dptr[z][d]);
+ LOAD_DATA(16,&dptr[z][d]);
XOR(0+$$,0+$$,16+$$);
XOR(8+$$,8+$$,16+$$);
}
- STORE_DATA(0,$#,&p[d]);
- STORE_DATA(8,$#,&q[d]);
+ STORE_DATA(0,&p[d]);
+ STORE_DATA(8,&q[d]);
}
kernel_fpu_end(&vxstate, KERNEL_VXR);
}
@@ -127,14 +129,14 @@ static void raid6_s390vx$#_xor_syndrome(int disks, int start, int stop,

for (d = 0; d < bytes; d += $#*NSIZE) {
/* P/Q data pages */
- LOAD_DATA(0,$#,&dptr[z0][d]);
+ LOAD_DATA(0,&dptr[z0][d]);
COPY_VEC(8+$$,0+$$);
for (z = z0 - 1; z >= start; z--) {
MASK(16+$$,8+$$);
AND(16+$$,16+$$,25);
SHLBYTE(8+$$,8+$$);
XOR(8+$$,8+$$,16+$$);
- LOAD_DATA(16,$#,&dptr[z][d]);
+ LOAD_DATA(16,&dptr[z][d]);
XOR(0+$$,0+$$,16+$$);
XOR(8+$$,8+$$,16+$$);
}
@@ -145,12 +147,12 @@ static void raid6_s390vx$#_xor_syndrome(int disks, int start, int stop,
SHLBYTE(8+$$,8+$$);
XOR(8+$$,8+$$,16+$$);
}
- LOAD_DATA(16,$#,&p[d]);
+ LOAD_DATA(16,&p[d]);
XOR(16+$$,16+$$,0+$$);
- STORE_DATA(16,$#,&p[d]);
- LOAD_DATA(16,$#,&q[d]);
+ STORE_DATA(16,&p[d]);
+ LOAD_DATA(16,&q[d]);
XOR(16+$$,16+$$,8+$$);
- STORE_DATA(16,$#,&q[d]);
+ STORE_DATA(16,&q[d]);
}
kernel_fpu_end(&vxstate, KERNEL_VXR);
}
--
2.17.1


--
Kees Cook
Pixel Security

2018-07-04 06:50:31

by Martin Schwidefsky

Subject: Re: [PATCH] RAID/s390: Remove VLA usage

On Tue, 3 Jul 2018 12:52:21 -0700
Kees Cook <[email protected]> wrote:

> In the quest to remove all stack VLA usage from the kernel[1], this moves
> the "$#" replacement from being an argument to being inside the function,
> which avoids generating VLAs.
>
> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
>
> Signed-off-by: Kees Cook <[email protected]>
> ---
> lib/raid6/s390vx.uc | 34 ++++++++++++++++++----------------
> 1 file changed, 18 insertions(+), 16 deletions(-)

Added to s390:features for the next merge window. Thanks.

--
blue skies,
Martin.

"Reality continues to ruin my life." - Calvin.