ARM: elf: add new hwcap for identifying atomic ldrd/strd instructions (a469abd0) · Commits · 戴 / test

CPUs implementing LPAE have atomic ldrd/strd instructions, meaning that userspace software can avoid having to use the exclusive variants of these instructions if they wish. This patch advertises the atomicity of these instructions via the hwcaps, so userspace can detect this CPU feature. Reported-by:

Vladimir Danushevsky <vladimir.danushevsky@oracle.com> Signed-off-by:

Will Deacon <will.deacon@arm.com>

arch/arm/include/uapi/asm/hwcap.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -25,6 +25,6 @@
		#define HWCAP_IDIVT (1 << 18)
		#define HWCAP_VFPD32 (1 << 19) /* set if VFP has 32 regs (not 16) */
		#define HWCAP_IDIV (HWCAP_IDIVA \| HWCAP_IDIVT)

		#define HWCAP_LPAE (1 << 20)

		#endif /* _UAPI__ASMARM_HWCAP_H */

arch/arm/kernel/setup.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -355,7 +355,7 @@ void __init early_print(const char *str, ...)

		static void __init cpuid_init_hwcaps(void)
		{
		unsigned int divide_instrs;
		unsigned int divide_instrs, vmsa;

		if (cpu_architecture() < CPU_ARCH_ARMv7)
		return;
		@@ -368,6 +368,11 @@ static void __init cpuid_init_hwcaps(void)
		case 1:
		elf_hwcap \|= HWCAP_IDIVT;
		}

		/* LPAE implies atomic ldrd/strd instructions */
		vmsa = (read_cpuid_ext(CPUID_EXT_MMFR0) & 0xf) >> 0;
		if (vmsa >= 5)
		elf_hwcap \|= HWCAP_LPAE;
		}

		static void __init feat_v6_fixup(void)
		@@ -872,6 +877,7 @@ static const char *hwcap_str[] = {
		"vfpv4",
		"idiva",
		"idivt",
		"lpae",
		NULL
		};

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