From a469abd0f868c902b75532579bf87553dcf1b360 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Mon, 8 Apr 2013 17:13:12 +0100 Subject: ARM: elf: add new hwcap for identifying atomic ldrd/strd instructions 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 Signed-off-by: Will Deacon --- arch/arm/kernel/setup.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'arch/arm/kernel/setup.c') diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c index 1522c7ae31b0..bdcd4dd13230 100644 --- a/arch/arm/kernel/setup.c +++ b/arch/arm/kernel/setup.c @@ -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 }; -- cgit