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[PATCH 5/5] aarch64: Allow overriding HWCAP_CPUID feature check using HWCAP_MASK
- From: Siddhesh Poyarekar <siddhesh at sourceware dot org>
- To: libc-alpha at sourceware dot org
- Cc: adhemerval dot zanella at linaro dot org
- Date: Fri, 19 May 2017 01:37:18 +0530
- Subject: [PATCH 5/5] aarch64: Allow overriding HWCAP_CPUID feature check using HWCAP_MASK
- Authentication-results: sourceware.org; auth=none
- References: <1495138038-32212-1-git-send-email-siddhesh@sourceware.org>
Now that LD_HWCAP_MASK (or glibc.tune.hwcap_mask) is read early enough
to influence cpu feature check in aarch64, use it to influence
multiarch selection. Setting LD_HWCAP_MASK such that it clears
HWCAP_CPUID will now disable multiarch for the binary.
* sysdeps/unix/sysv/linux/aarch64/cpu-features.c
(init_cpu_features): Use glibc.tune.hwcap_mask.
---
sysdeps/unix/sysv/linux/aarch64/cpu-features.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/sysdeps/unix/sysv/linux/aarch64/cpu-features.c b/sysdeps/unix/sysv/linux/aarch64/cpu-features.c
index 7025062..0478fcc 100644
--- a/sysdeps/unix/sysv/linux/aarch64/cpu-features.c
+++ b/sysdeps/unix/sysv/linux/aarch64/cpu-features.c
@@ -18,18 +18,25 @@
#include <cpu-features.h>
#include <sys/auxv.h>
+#include <elf/dl-tunables.h>
static inline void
init_cpu_features (struct cpu_features *cpu_features)
{
- if (GLRO(dl_hwcap) & HWCAP_CPUID)
+#if HAVE_TUNABLES
+ uint64_t hwcap_mask = TUNABLE_GET (glibc, tune, hwcap_mask, uint64_t);
+#else
+ uint64_t hwcap_mask = GLRO (dl_hwcap_mask);
+#endif
+
+ uint64_t hwcap = GLRO (dl_hwcap) & hwcap_mask;
+
+ if (hwcap & HWCAP_CPUID)
{
register uint64_t id = 0;
asm volatile ("mrs %0, midr_el1" : "=r"(id));
cpu_features->midr_el1 = id;
}
else
- {
- cpu_features->midr_el1 = 0;
- }
+ cpu_features->midr_el1 = 0;
}
--
2.7.4