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ARM: 9274/1: Add hwcap for Speculative Store Bypassing Safe

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Speculative Store Bypassing Safe(FEAT_SSBS) is a feature present in
AArch32 state for Armv8 and is represented by ID_PFR2_EL1.SSBS
identification register.

This feature denotes the presence of PSTATE.ssbs bit and hence adding a
hwcap will enable the userspace to check it before trying to set/unset
this PSTATE.

This commit adds the ID feature bit detection, and uses elf_hwcap2
accordingly.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Amit Daniel Kachhap 2022-11-17 07:10:35 +01:00 committed by Russell King (Oracle)
parent 3bda6d8848
commit fea53546be
2 changed files with 9 additions and 0 deletions
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1
arch/arm/include/uapi/asm/hwcap.h
View File

@ -44,5 +44,6 @@
#define HWCAP2_SHA2 (1 << 3) #define HWCAP2_SHA2 (1 << 3)
#define HWCAP2_CRC32 (1 << 4) #define HWCAP2_CRC32 (1 << 4)
#define HWCAP2_SB (1 << 5) #define HWCAP2_SB (1 << 5)
#define HWCAP2_SSBS (1 << 6)
#endif /* _UAPI__ASMARM_HWCAP_H */ #endif /* _UAPI__ASMARM_HWCAP_H */

8
arch/arm/kernel/setup.c
View File

@ -451,6 +451,7 @@ static void __init cpuid_init_hwcaps(void)
int block; int block;
u32 isar5; u32 isar5;
u32 isar6; u32 isar6;
u32 pfr2;
if (cpu_architecture() < CPU_ARCH_ARMv7) if (cpu_architecture() < CPU_ARCH_ARMv7)
return; return;
@ -492,6 +493,12 @@ static void __init cpuid_init_hwcaps(void)
block = cpuid_feature_extract_field(isar6, 12); block = cpuid_feature_extract_field(isar6, 12);
if (block >= 1) if (block >= 1)
elf_hwcap2 |= HWCAP2_SB; elf_hwcap2 |= HWCAP2_SB;
/* Check for Speculative Store Bypassing control */
pfr2 = read_cpuid_ext(CPUID_EXT_PFR2);
block = cpuid_feature_extract_field(pfr2, 4);
if (block >= 1)
elf_hwcap2 |= HWCAP2_SSBS;
} }
static void __init elf_hwcap_fixup(void) static void __init elf_hwcap_fixup(void)
@ -1272,6 +1279,7 @@ static const char *hwcap2_str[] = {
"sha2", "sha2",
"crc32", "crc32",
"sb", "sb",
"ssbs",
NULL NULL
}; };