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arm64: Support AT_HWCAP3

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We have filled all 64 bits of AT_HWCAP2 so in order to support discovery of
further features provide the framework to use the already defined AT_HWCAP3
for further CPU features.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20241004-arm64-elf-hwcap3-v2-2-799d1daad8b0@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Mark Brown 2024-10-04 21:26:30 +01:00 committed by Catalin Marinas
parent 4e6e8c2b75
commit ddadbcdaae
5 changed files with 20 additions and 5 deletions
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6
Documentation/arch/arm64/elf_hwcaps.rst
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@ -16,9 +16,9 @@ architected discovery mechanism available to userspace code at EL0. The
kernel exposes the presence of these features to userspace through a set
of flags called hwcaps, exposed in the auxiliary vector.
Userspace software can test for features by acquiring the AT_HWCAP or
AT_HWCAP2 entry of the auxiliary vector, and testing whether the relevant
flags are set, e.g.::
Userspace software can test for features by acquiring the AT_HWCAP,
AT_HWCAP2 or AT_HWCAP3 entry of the auxiliary vector, and testing
whether the relevant flags are set, e.g.::
bool floating_point_is_present(void)
{

3
arch/arm64/include/asm/cpufeature.h
View File

@ -12,7 +12,7 @@
#include <asm/hwcap.h>
#include <asm/sysreg.h>
#define MAX_CPU_FEATURES 128
#define MAX_CPU_FEATURES 192
#define cpu_feature(x) KERNEL_HWCAP_ ## x
#define ARM64_SW_FEATURE_OVERRIDE_NOKASLR 0
@ -438,6 +438,7 @@ void cpu_set_feature(unsigned int num);
bool cpu_have_feature(unsigned int num);
unsigned long cpu_get_elf_hwcap(void);
unsigned long cpu_get_elf_hwcap2(void);
unsigned long cpu_get_elf_hwcap3(void);
#define cpu_set_named_feature(name) cpu_set_feature(cpu_feature(name))
#define cpu_have_named_feature(name) cpu_have_feature(cpu_feature(name))

6
arch/arm64/include/asm/hwcap.h
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@ -159,17 +159,21 @@
#define KERNEL_HWCAP_SME_SF8DP2 __khwcap2_feature(SME_SF8DP2)
#define KERNEL_HWCAP_POE __khwcap2_feature(POE)
#define __khwcap3_feature(x) (const_ilog2(HWCAP3_ ## x) + 128)
/*
* This yields a mask that user programs can use to figure out what
* instruction set this cpu supports.
*/
#define ELF_HWCAP cpu_get_elf_hwcap()
#define ELF_HWCAP2 cpu_get_elf_hwcap2()
#define ELF_HWCAP3 cpu_get_elf_hwcap3()
#ifdef CONFIG_COMPAT
#define COMPAT_ELF_HWCAP (compat_elf_hwcap)
#define COMPAT_ELF_HWCAP2 (compat_elf_hwcap2)
extern unsigned int compat_elf_hwcap, compat_elf_hwcap2;
#define COMPAT_ELF_HWCAP3 (compat_elf_hwcap3)
extern unsigned int compat_elf_hwcap, compat_elf_hwcap2, compat_elf_hwcap3;
#endif
enum {

4
arch/arm64/include/uapi/asm/hwcap.h
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@ -124,4 +124,8 @@
#define HWCAP2_SME_SF8DP2 (1UL << 62)
#define HWCAP2_POE (1UL << 63)
/*
* HWCAP3 flags - for AT_HWCAP3
*/
#endif /* _UAPI__ASM_HWCAP_H */

6
arch/arm64/kernel/cpufeature.c
View File

@ -103,6 +103,7 @@ static DECLARE_BITMAP(elf_hwcap, MAX_CPU_FEATURES) __read_mostly;
COMPAT_HWCAP_LPAE)
unsigned int compat_elf_hwcap __read_mostly = COMPAT_ELF_HWCAP_DEFAULT;
unsigned int compat_elf_hwcap2 __read_mostly;
unsigned int compat_elf_hwcap3 __read_mostly;
#endif
DECLARE_BITMAP(system_cpucaps, ARM64_NCAPS);
@ -3499,6 +3500,11 @@ unsigned long cpu_get_elf_hwcap2(void)
return elf_hwcap[1];
}
unsigned long cpu_get_elf_hwcap3(void)
{
return elf_hwcap[2];
}
static void __init setup_boot_cpu_capabilities(void)
{
/*