[PATCH v2 4/4] ppc64le: Revert "powerpc: Optimized strcmp for power10" (CVE-2025-5702)
Siddhesh Poyarekar
siddhesh@gotplt.org
Mon Jun 16 21:58:26 GMT 2025
On 2025-06-16 16:20, Carlos O'Donell wrote:
> This reverts commit 3367d8e180848030d1646f088759f02b8dfe0d6f
>
> Reason for revert: Power10 strcmp clobbers non-volatile vector
> registers (Bug 33056)
>
> Tested on ppc64le without regression.
> ---
See 1/4 for context.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
> sysdeps/powerpc/powerpc64/le/power10/strcmp.S | 204 ------------------
> sysdeps/powerpc/powerpc64/multiarch/Makefile | 2 +-
> .../powerpc64/multiarch/ifunc-impl-list.c | 4 -
> .../powerpc64/multiarch/strcmp-power10.S | 26 ---
> sysdeps/powerpc/powerpc64/multiarch/strcmp.c | 4 -
> 5 files changed, 1 insertion(+), 239 deletions(-)
> delete mode 100644 sysdeps/powerpc/powerpc64/le/power10/strcmp.S
> delete mode 100644 sysdeps/powerpc/powerpc64/multiarch/strcmp-power10.S
>
> diff --git a/sysdeps/powerpc/powerpc64/le/power10/strcmp.S b/sysdeps/powerpc/powerpc64/le/power10/strcmp.S
> deleted file mode 100644
> index 8a654d8e56..0000000000
> --- a/sysdeps/powerpc/powerpc64/le/power10/strcmp.S
> +++ /dev/null
> @@ -1,204 +0,0 @@
> -/* Optimized strcmp implementation for PowerPC64/POWER10.
> - Copyright (C) 2021-2025 Free Software Foundation, Inc.
> - This file is part of the GNU C Library.
> -
> - The GNU C Library is free software; you can redistribute it and/or
> - modify it under the terms of the GNU Lesser General Public
> - License as published by the Free Software Foundation; either
> - version 2.1 of the License, or (at your option) any later version.
> -
> - The GNU C Library is distributed in the hope that it will be useful,
> - but WITHOUT ANY WARRANTY; without even the implied warranty of
> - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> - Lesser General Public License for more details.
> -
> - You should have received a copy of the GNU Lesser General Public
> - License along with the GNU C Library; if not, see
> - <https://www.gnu.org/licenses/>. */
> -#include <sysdep.h>
> -
> -#ifndef STRCMP
> -# define STRCMP strcmp
> -#endif
> -
> -/* Implements the function
> - int [r3] strcmp (const char *s1 [r3], const char *s2 [r4]). */
> -
> -/* TODO: Change this to actual instructions when minimum binutils is upgraded
> - to 2.27. Macros are defined below for these newer instructions in order
> - to maintain compatibility. */
> -
> -#define LXVP(xtp,dq,ra) \
> - .long(((6)<<(32-6)) \
> - | ((((xtp)-32)>>1)<<(32-10)) \
> - | ((1)<<(32-11)) \
> - | ((ra)<<(32-16)) \
> - | dq)
> -
> -#define COMPARE_16(vreg1,vreg2,offset) \
> - lxv vreg1+32,offset(r3); \
> - lxv vreg2+32,offset(r4); \
> - vcmpnezb. v7,vreg1,vreg2; \
> - bne cr6,L(different); \
> -
> -#define COMPARE_32(vreg1,vreg2,offset,label1,label2) \
> - LXVP(vreg1+32,offset,r3); \
> - LXVP(vreg2+32,offset,r4); \
> - vcmpnezb. v7,vreg1+1,vreg2+1; \
> - bne cr6,L(label1); \
> - vcmpnezb. v7,vreg1,vreg2; \
> - bne cr6,L(label2); \
> -
> -#define TAIL(vreg1,vreg2) \
> - vctzlsbb r6,v7; \
> - vextubrx r5,r6,vreg1; \
> - vextubrx r4,r6,vreg2; \
> - subf r3,r4,r5; \
> - blr; \
> -
> -#define CHECK_N_BYTES(reg1,reg2,len_reg) \
> - sldi r0,len_reg,56; \
> - lxvl 32+v4,reg1,r0; \
> - lxvl 32+v5,reg2,r0; \
> - add reg1,reg1,len_reg; \
> - add reg2,reg2,len_reg; \
> - vcmpnezb. v7,v4,v5; \
> - vctzlsbb r6,v7; \
> - cmpld cr7,r6,len_reg; \
> - blt cr7,L(different); \
> -
> - /* TODO: change this to .machine power10 when the minimum required
> - binutils allows it. */
> -
> - .machine power9
> -ENTRY_TOCLESS (STRCMP, 4)
> - li r11,16
> - /* eq bit of cr1 used as swap status flag to indicate if
> - source pointers were swapped. */
> - crclr 4*cr1+eq
> - vspltisb v19,-1
> - andi. r7,r3,15
> - sub r7,r11,r7 /* r7(nalign1) = 16 - (str1 & 15). */
> - andi. r9,r4,15
> - sub r5,r11,r9 /* r5(nalign2) = 16 - (str2 & 15). */
> - cmpld cr7,r7,r5
> - beq cr7,L(same_aligned)
> - blt cr7,L(nalign1_min)
> - /* Swap r3 and r4, and r7 and r5 such that r3 and r7 hold the
> - pointer which is closer to the next 16B boundary so that only
> - one CHECK_N_BYTES is needed before entering the loop below. */
> - mr r8,r4
> - mr r4,r3
> - mr r3,r8
> - mr r12,r7
> - mr r7,r5
> - mr r5,r12
> - crset 4*cr1+eq /* Set bit on swapping source pointers. */
> -
> - .p2align 5
> -L(nalign1_min):
> - CHECK_N_BYTES(r3,r4,r7)
> -
> - .p2align 5
> -L(s1_aligned):
> - /* r9 and r5 is number of bytes to be read after and before
> - page boundary correspondingly. */
> - sub r5,r5,r7
> - subfic r9,r5,16
> - /* Now let r7 hold the count of quadwords which can be
> - checked without crossing a page boundary. quadword offset is
> - (str2>>4)&0xFF. */
> - rlwinm r7,r4,28,0xFF
> - /* Below check is required only for first iteration. For second
> - iteration and beyond, the new loop counter is always 255. */
> - cmpldi r7,255
> - beq L(L3)
> - /* Get the initial loop count by 255-((str2>>4)&0xFF). */
> - subfic r11,r7,255
> -
> - .p2align 5
> -L(L1):
> - mtctr r11
> -
> - .p2align 5
> -L(L2):
> - COMPARE_16(v4,v5,0) /* Load 16B blocks using lxv. */
> - addi r3,r3,16
> - addi r4,r4,16
> - bdnz L(L2)
> - /* Cross the page boundary of s2, carefully. */
> -
> - .p2align 5
> -L(L3):
> - CHECK_N_BYTES(r3,r4,r5)
> - CHECK_N_BYTES(r3,r4,r9)
> - li r11,255 /* Load the new loop counter. */
> - b L(L1)
> -
> - .p2align 5
> -L(same_aligned):
> - CHECK_N_BYTES(r3,r4,r7)
> - /* Align s1 to 32B and adjust s2 address.
> - Use lxvp only if both s1 and s2 are 32B aligned. */
> - COMPARE_16(v4,v5,0)
> - COMPARE_16(v4,v5,16)
> - COMPARE_16(v4,v5,32)
> - COMPARE_16(v4,v5,48)
> - addi r3,r3,64
> - addi r4,r4,64
> - COMPARE_16(v4,v5,0)
> - COMPARE_16(v4,v5,16)
> -
> - clrldi r6,r3,59
> - subfic r5,r6,32
> - add r3,r3,r5
> - add r4,r4,r5
> - andi. r5,r4,0x1F
> - beq cr0,L(32B_aligned_loop)
> -
> - .p2align 5
> -L(16B_aligned_loop):
> - COMPARE_16(v4,v5,0)
> - COMPARE_16(v4,v5,16)
> - COMPARE_16(v4,v5,32)
> - COMPARE_16(v4,v5,48)
> - addi r3,r3,64
> - addi r4,r4,64
> - b L(16B_aligned_loop)
> -
> - /* Calculate and return the difference. */
> -L(different):
> - vctzlsbb r6,v7
> - vextubrx r5,r6,v4
> - vextubrx r4,r6,v5
> - bt 4*cr1+eq,L(swapped)
> - subf r3,r4,r5
> - blr
> -
> - /* If src pointers were swapped, then swap the
> - indices and calculate the return value. */
> -L(swapped):
> - subf r3,r5,r4
> - blr
> -
> - .p2align 5
> -L(32B_aligned_loop):
> - COMPARE_32(v14,v16,0,tail1,tail2)
> - COMPARE_32(v18,v20,32,tail3,tail4)
> - COMPARE_32(v22,v24,64,tail5,tail6)
> - COMPARE_32(v26,v28,96,tail7,tail8)
> - addi r3,r3,128
> - addi r4,r4,128
> - b L(32B_aligned_loop)
> -
> -L(tail1): TAIL(v15,v17)
> -L(tail2): TAIL(v14,v16)
> -L(tail3): TAIL(v19,v21)
> -L(tail4): TAIL(v18,v20)
> -L(tail5): TAIL(v23,v25)
> -L(tail6): TAIL(v22,v24)
> -L(tail7): TAIL(v27,v29)
> -L(tail8): TAIL(v26,v28)
> -
> -END (STRCMP)
> -libc_hidden_builtin_def (strcmp)
> diff --git a/sysdeps/powerpc/powerpc64/multiarch/Makefile b/sysdeps/powerpc/powerpc64/multiarch/Makefile
> index 818f287925..e321ce54e0 100644
> --- a/sysdeps/powerpc/powerpc64/multiarch/Makefile
> +++ b/sysdeps/powerpc/powerpc64/multiarch/Makefile
> @@ -32,7 +32,7 @@ sysdep_routines += memcpy-power8-cached memcpy-power7 memcpy-a2 memcpy-power6 \
> ifneq (,$(filter %le,$(config-machine)))
> sysdep_routines += memcmp-power10 memcpy-power10 memmove-power10 memset-power10 \
> rawmemchr-power9 rawmemchr-power10 \
> - strcmp-power9 strcmp-power10 strncmp-power9 \
> + strcmp-power9 strncmp-power9 \
> strcpy-power9 strcat-power10 stpcpy-power9 \
> strlen-power9 strncpy-power9 stpncpy-power9 strlen-power10
> endif
> diff --git a/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c b/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c
> index dde3bec709..016d05fd16 100644
> --- a/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c
> +++ b/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c
> @@ -366,10 +366,6 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> /* Support sysdeps/powerpc/powerpc64/multiarch/strcmp.c. */
> IFUNC_IMPL (i, name, strcmp,
> #ifdef __LITTLE_ENDIAN__
> - IFUNC_IMPL_ADD (array, i, strcmp,
> - (hwcap2 & PPC_FEATURE2_ARCH_3_1)
> - && (hwcap & PPC_FEATURE_HAS_VSX),
> - __strcmp_power10)
> IFUNC_IMPL_ADD (array, i, strcmp,
> hwcap2 & PPC_FEATURE2_ARCH_3_00
> && hwcap & PPC_FEATURE_HAS_ALTIVEC,
> diff --git a/sysdeps/powerpc/powerpc64/multiarch/strcmp-power10.S b/sysdeps/powerpc/powerpc64/multiarch/strcmp-power10.S
> deleted file mode 100644
> index 7b45fcd63a..0000000000
> --- a/sysdeps/powerpc/powerpc64/multiarch/strcmp-power10.S
> +++ /dev/null
> @@ -1,26 +0,0 @@
> -/* Optimized strcmp implementation for POWER10/PPC64.
> - Copyright (C) 2021-2025 Free Software Foundation, Inc.
> - This file is part of the GNU C Library.
> -
> - The GNU C Library is free software; you can redistribute it and/or
> - modify it under the terms of the GNU Lesser General Public
> - License as published by the Free Software Foundation; either
> - version 2.1 of the License, or (at your option) any later version.
> -
> - The GNU C Library is distributed in the hope that it will be useful,
> - but WITHOUT ANY WARRANTY; without even the implied warranty of
> - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> - Lesser General Public License for more details.
> -
> - You should have received a copy of the GNU Lesser General Public
> - License along with the GNU C Library; if not, see
> - <https://www.gnu.org/licenses/>. */
> -
> -#if defined __LITTLE_ENDIAN__ && IS_IN (libc)
> -#define STRCMP __strcmp_power10
> -
> -#undef libc_hidden_builtin_def
> -#define libc_hidden_builtin_def(name)
> -
> -#include <sysdeps/powerpc/powerpc64/le/power10/strcmp.S>
> -#endif /* __LITTLE_ENDIAN__ && IS_IN (libc) */
> diff --git a/sysdeps/powerpc/powerpc64/multiarch/strcmp.c b/sysdeps/powerpc/powerpc64/multiarch/strcmp.c
> index 3c636e3bbc..7c77c084a7 100644
> --- a/sysdeps/powerpc/powerpc64/multiarch/strcmp.c
> +++ b/sysdeps/powerpc/powerpc64/multiarch/strcmp.c
> @@ -29,16 +29,12 @@ extern __typeof (strcmp) __strcmp_power7 attribute_hidden;
> extern __typeof (strcmp) __strcmp_power8 attribute_hidden;
> # ifdef __LITTLE_ENDIAN__
> extern __typeof (strcmp) __strcmp_power9 attribute_hidden;
> -extern __typeof (strcmp) __strcmp_power10 attribute_hidden;
> # endif
>
> # undef strcmp
>
> libc_ifunc_redirected (__redirect_strcmp, strcmp,
> # ifdef __LITTLE_ENDIAN__
> - (hwcap2 & PPC_FEATURE2_ARCH_3_1
> - && hwcap & PPC_FEATURE_HAS_VSX)
> - ? __strcmp_power10 :
> (hwcap2 & PPC_FEATURE2_ARCH_3_00
> && hwcap & PPC_FEATURE_HAS_ALTIVEC)
> ? __strcmp_power9 :
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