mirrors/glibc
1
0
Fork 0
mirror of https://sourceware.org/git/glibc.git synced 2024-11-23 09:43:32 +08:00
Code Issues Actions Packages Projects Releases Wiki Activity

aarch64: Remove HWCAP_CPUID from HWCAP_IMPORTANT

Browse Source 
This partially reverts

commit f82e9672ad
Author:     Siddhesh Poyarekar <siddhesh@sourceware.org>

    aarch64: Allow overriding HWCAP_CPUID feature check using HWCAP_MASK

The idea was to make it possible to disable cpuid based ifunc resolution
in glibc by changing the hwcap mask which the user could already control.

However the hwcap mask has an orthogonal role: it specifies additional
library search paths for the dynamic linker.  So "cpuid" got added to
the search paths when it was set in the default mask (HWCAP_IMPORTANT),
which is not useful behaviour, the hwcap masking should not be reused
in the cpu features code.

Meanwhile there is a tunable to set the cpu explicitly so it is possible
to disable the cpuid based dispatch without using a hwcap mask:

  GLIBC_TUNABLES=glibc.tune.cpu=generic

	* sysdeps/unix/sysv/linux/aarch64/cpu-features.c (init_cpu_features):
	Use dl_hwcap without masking.
	* sysdeps/unix/sysv/linux/aarch64/dl-procinfo.h (HWCAP_IMPORTANT):
	Remove HWCAP_CPUID.
This commit is contained in:
Szabolcs Nagy 2018-06-28 14:43:07 +01:00
parent ddb3c626b0
commit d0cd798071
3 changed files with 10 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
ChangeLog
View File

@ -1,3 +1,10 @@
2018-07-06 Szabolcs Nagy <szabolcs.nagy@arm.com>
* sysdeps/unix/sysv/linux/aarch64/cpu-features.c (init_cpu_features):
Use dl_hwcap without masking.
* sysdeps/unix/sysv/linux/aarch64/dl-procinfo.h (HWCAP_IMPORTANT):
Remove HWCAP_CPUID.
2018-07-06 Florian Weimer <fweimer@redhat.com>
* conform/conformtest.pl (checknamespace): Escape literal braces

5
sysdeps/unix/sysv/linux/aarch64/cpu-features.c
View File

@ -53,9 +53,6 @@ get_midr_from_mcpu (const char *mcpu)
static inline void
init_cpu_features (struct cpu_features *cpu_features)
{
uint64_t hwcap_mask = GET_HWCAP_MASK();
uint64_t hwcap = GLRO (dl_hwcap) & hwcap_mask;
register uint64_t midr = UINT64_MAX;
#if HAVE_TUNABLES
@ -69,7 +66,7 @@ init_cpu_features (struct cpu_features *cpu_features)
allows it. */
if (midr == UINT64_MAX)
{
if (hwcap & HWCAP_CPUID)
if (GLRO (dl_hwcap) & HWCAP_CPUID)
asm volatile ("mrs %0, midr_el1" : "=r"(midr));
else
midr = 0;

5
sysdeps/unix/sysv/linux/aarch64/dl-procinfo.h
View File

@ -27,9 +27,8 @@
/* We cannot provide a general printing function. */
#define _dl_procinfo(type, word) -1
/* HWCAP_CPUID should be available by default to influence IFUNC as well as
library search. */
#define HWCAP_IMPORTANT HWCAP_CPUID
/* No additional library search paths. */
#define HWCAP_IMPORTANT 0
static inline const char *
__attribute__ ((unused))