diff mbox series

[v2,09/19] x86: Use dl-symbol-redir-ifunc.h on cpu-tunables

Message ID 20231017130526.2216827-10-adhemerval.zanella@linaro.org
State New
Headers show
Series Improve loader environment variable handling | expand

Commit Message

Adhemerval Zanella Netto Oct. 17, 2023, 1:05 p.m. UTC 
The dl-symbol-redir-ifunc.h redirects compiler-generated libcalls to
arch-specific memory implementations to avoid ifun calls where it is not
yet possible. The memcmp-isa-default-impl.h aims to fix the same issue
by calling the specific memset implementation directly.

Using the memcmp symbol directly allows the compile to inline the memset
calls (especially because _dl_tunable_set_hwcaps uses constants values),
generating better code.

For i386, _dl_writev with PIE requires to use the old 'int $0x80'
syscall mode because the calling the TLS register (gs) is not yet
initialized.

Checked on x86_64-linux-gnu.

Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
---
 .../i686/multiarch/dl-symbol-redir-ifunc.h    |  5 +++
 .../sysv/linux/i386/dl-writev.h}              | 18 ++++-----
 sysdeps/x86/cpu-tunables.c                    | 39 ++++++-------------
 .../x86_64/multiarch/dl-symbol-redir-ifunc.h  | 15 +++++++
 4 files changed, 39 insertions(+), 38 deletions(-)
 rename sysdeps/{x86_64/memcmp-isa-default-impl.h => unix/sysv/linux/i386/dl-writev.h} (62%)

Comments

Siddhesh Poyarekar Oct. 27, 2023, 10:32 a.m. UTC | #1 
On 2023-10-17 09:05, Adhemerval Zanella wrote:
> The dl-symbol-redir-ifunc.h redirects compiler-generated libcalls to
> arch-specific memory implementations to avoid ifun calls where it is not

ifunc

> yet possible. The memcmp-isa-default-impl.h aims to fix the same issue
> by calling the specific memset implementation directly.
> 
> Using the memcmp symbol directly allows the compile to inline the memset

compiler

> calls (especially because _dl_tunable_set_hwcaps uses constants values),
> generating better code.
> 
> For i386, _dl_writev with PIE requires to use the old 'int $0x80'
> syscall mode because the calling the TLS register (gs) is not yet
> initialized.
> 
> Checked on x86_64-linux-gnu.
> 
> Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

> ---
>   .../i686/multiarch/dl-symbol-redir-ifunc.h    |  5 +++
>   .../sysv/linux/i386/dl-writev.h}              | 18 ++++-----
>   sysdeps/x86/cpu-tunables.c                    | 39 ++++++-------------
>   .../x86_64/multiarch/dl-symbol-redir-ifunc.h  | 15 +++++++
>   4 files changed, 39 insertions(+), 38 deletions(-)
>   rename sysdeps/{x86_64/memcmp-isa-default-impl.h => unix/sysv/linux/i386/dl-writev.h} (62%)
> 
> diff --git a/sysdeps/i386/i686/multiarch/dl-symbol-redir-ifunc.h b/sysdeps/i386/i686/multiarch/dl-symbol-redir-ifunc.h
> index dee69d19db..220c586bd2 100644
> --- a/sysdeps/i386/i686/multiarch/dl-symbol-redir-ifunc.h
> +++ b/sysdeps/i386/i686/multiarch/dl-symbol-redir-ifunc.h
> @@ -19,6 +19,11 @@
>   #ifndef _DL_IFUNC_GENERIC_H
>   #define _DL_IFUNC_GENERIC_H
>   
> +#ifndef SHARED
> +
>   asm ("memset = __memset_ia32");
> +asm ("memcmp = __memcmp_ia32");
> +
> +#endif /* SHARED */
>   
>   #endif
> diff --git a/sysdeps/x86_64/memcmp-isa-default-impl.h b/sysdeps/unix/sysv/linux/i386/dl-writev.h
> similarity index 62%
> rename from sysdeps/x86_64/memcmp-isa-default-impl.h
> rename to sysdeps/unix/sysv/linux/i386/dl-writev.h
> index 0962e83c3d..624d0e46b0 100644
> --- a/sysdeps/x86_64/memcmp-isa-default-impl.h
> +++ b/sysdeps/unix/sysv/linux/i386/dl-writev.h
> @@ -1,5 +1,5 @@
> -/* Set default memcmp impl based on ISA level.
> -   Copyright (C) 2022-2023 Free Software Foundation, Inc.
> +/* Message-writing for the dynamic linker.  Linux/i386 version.
> +   Copyright (C) 2013-2023 Free Software Foundation, Inc.
>      This file is part of the GNU C Library.
>   
>      The GNU C Library is free software; you can redistribute it and/or
> @@ -16,13 +16,9 @@
>      License along with the GNU C Library; if not, see
>      <https://www.gnu.org/licenses/>.  */
>   
> -#include <isa-level.h>
> -#if MINIMUM_X86_ISA_LEVEL == 1 || MINIMUM_X86_ISA_LEVEL == 2
> -# define DEFAULT_MEMCMP	__memcmp_sse2
> -#elif MINIMUM_X86_ISA_LEVEL == 3
> -# define DEFAULT_MEMCMP	__memcmp_avx2_movbe
> -#elif MINIMUM_X86_ISA_LEVEL == 4
> -# define DEFAULT_MEMCMP	__memcmp_evex_movbe
> -#else
> -# error "Unknown default memcmp implementation"
> +#if BUILD_PIE_DEFAULT
> +/* Can't use "call *%gs:SYSINFO_OFFSET" during startup in static PIE.  */
> +# define I386_USE_SYSENTER 0
>   #endif
> +
> +#include <sysdeps/unix/sysv/linux/dl-writev.h>
> diff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c
> index 0d4f328585..5697885226 100644
> --- a/sysdeps/x86/cpu-tunables.c
> +++ b/sysdeps/x86/cpu-tunables.c
> @@ -24,24 +24,11 @@
>   #include <string.h>
>   #include <cpu-features.h>
>   #include <ldsodefs.h>
> -
> -/* We can't use IFUNC memcmp nor strlen in init_cpu_features from libc.a
> -   since IFUNC must be set up by init_cpu_features.  */
> -#if defined USE_MULTIARCH && !defined SHARED
> -# ifdef __x86_64__
> -/* DEFAULT_MEMCMP by sysdeps/x86_64/memcmp-isa-default-impl.h.  */
> -#  include <sysdeps/x86_64/memcmp-isa-default-impl.h>
> -# else
> -#  define DEFAULT_MEMCMP	__memcmp_ia32
> -# endif
> -extern __typeof (memcmp) DEFAULT_MEMCMP;
> -#else
> -# define DEFAULT_MEMCMP	memcmp
> -#endif
> +#include <dl-symbol-redir-ifunc.h>
>   
>   #define CHECK_GLIBC_IFUNC_CPU_OFF(f, cpu_features, name, len)		\
>     _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);	\
> -  if (!DEFAULT_MEMCMP (f, #name, len))					\
> +  if (memcmp (f, #name, len) == 0)					\
>       {									\
>         CPU_FEATURE_UNSET (cpu_features, name)				\
>         break;								\
> @@ -51,7 +38,7 @@ extern __typeof (memcmp) DEFAULT_MEMCMP;
>      which isn't available.  */
>   #define CHECK_GLIBC_IFUNC_PREFERRED_OFF(f, cpu_features, name, len)	\
>     _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);	\
> -  if (!DEFAULT_MEMCMP (f, #name, len))					\
> +  if (memcmp (f, #name, len) == 0)					\
>       {									\
>         cpu_features->preferred[index_arch_##name]			\
>   	&= ~bit_arch_##name;						\
> @@ -62,7 +49,7 @@ extern __typeof (memcmp) DEFAULT_MEMCMP;
>   #define CHECK_GLIBC_IFUNC_PREFERRED_BOTH(f, cpu_features, name,	\
>   					  disable, len)			\
>     _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);	\
> -  if (!DEFAULT_MEMCMP (f, #name, len))					\
> +  if (memcmp (f, #name, len) == 0)					\
>       {									\
>         if (disable)							\
>   	cpu_features->preferred[index_arch_##name] &= ~bit_arch_##name;	\
> @@ -76,7 +63,7 @@ extern __typeof (memcmp) DEFAULT_MEMCMP;
>   #define CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH(f, cpu_features, name,	\
>   					       need, disable, len)	\
>     _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);	\
> -  if (!DEFAULT_MEMCMP (f, #name, len))					\
> +  if (memcmp (f, #name, len) == 0)					\
>       {									\
>         if (disable)							\
>   	cpu_features->preferred[index_arch_##name] &= ~bit_arch_##name;	\
> @@ -177,7 +164,7 @@ TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
>   	      CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, POPCNT, 6);
>   	      CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_1, 6);
>   	      CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_2, 6);
> -	      if (!DEFAULT_MEMCMP (n, "XSAVEC", 6))
> +	      if (memcmp (n, "XSAVEC", 6) == 0)
>   		{
>   		  /* Update xsave_state_size to XSAVE state size.  */
>   		  cpu_features->xsave_state_size
> @@ -290,12 +277,11 @@ attribute_hidden
>   void
>   TUNABLE_CALLBACK (set_x86_ibt) (tunable_val_t *valp)
>   {
> -  if (DEFAULT_MEMCMP (valp->strval, "on", sizeof ("on")) == 0)
> +  if (memcmp (valp->strval, "on", sizeof ("on")) == 0)
>       GL(dl_x86_feature_control).ibt = cet_always_on;
> -  else if (DEFAULT_MEMCMP (valp->strval, "off", sizeof ("off")) == 0)
> +  else if (memcmp (valp->strval, "off", sizeof ("off")) == 0)
>       GL(dl_x86_feature_control).ibt = cet_always_off;
> -  else if (DEFAULT_MEMCMP (valp->strval, "permissive",
> -			   sizeof ("permissive")) == 0)
> +  else if (memcmp (valp->strval, "permissive", sizeof ("permissive")) == 0)
>       GL(dl_x86_feature_control).ibt = cet_permissive;
>   }
>   
> @@ -303,12 +289,11 @@ attribute_hidden
>   void
>   TUNABLE_CALLBACK (set_x86_shstk) (tunable_val_t *valp)
>   {
> -  if (DEFAULT_MEMCMP (valp->strval, "on", sizeof ("on")) == 0)
> +  if (memcmp (valp->strval, "on", sizeof ("on")) == 0)
>       GL(dl_x86_feature_control).shstk = cet_always_on;
> -  else if (DEFAULT_MEMCMP (valp->strval, "off", sizeof ("off")) == 0)
> +  else if (memcmp (valp->strval, "off", sizeof ("off")) == 0)
>       GL(dl_x86_feature_control).shstk = cet_always_off;
> -  else if (DEFAULT_MEMCMP (valp->strval, "permissive",
> -			   sizeof ("permissive")) == 0)
> +  else if (memcmp (valp->strval, "permissive", sizeof ("permissive")) == 0)
>       GL(dl_x86_feature_control).shstk = cet_permissive;
>   }
>   #endif
> diff --git a/sysdeps/x86_64/multiarch/dl-symbol-redir-ifunc.h b/sysdeps/x86_64/multiarch/dl-symbol-redir-ifunc.h
> index 3fe73ca1c3..c7d8961bb6 100644
> --- a/sysdeps/x86_64/multiarch/dl-symbol-redir-ifunc.h
> +++ b/sysdeps/x86_64/multiarch/dl-symbol-redir-ifunc.h
> @@ -19,6 +19,8 @@
>   #ifndef _DL_IFUNC_GENERIC_H
>   #define _DL_IFUNC_GENERIC_H
>   
> +#ifndef SHARED
> +
>   #include <isa-level.h>
>   
>   #if MINIMUM_X86_ISA_LEVEL >= 4
> @@ -31,4 +33,17 @@
>   
>   asm ("memset = " HAVE_MEMSET_IFUNC_GENERIC);
>   
> +
> +#if MINIMUM_X86_ISA_LEVEL >= 4
> +# define HAVE_MEMCMP_IFUNC_GENERIC "__memcmp_evex_movbe"
> +#elif MINIMUM_X86_ISA_LEVEL == 3
> +# define HAVE_MEMCMP_IFUNC_GENERIC "__memcmp_avx2_movbe"
> +#else
> +# define HAVE_MEMCMP_IFUNC_GENERIC "__memcmp_sse2"
> +#endif
> +
> +asm ("memcmp = " HAVE_MEMCMP_IFUNC_GENERIC);
> +
> +#endif /* SHARED */
> +
>   #endif
diff mbox series

Patch

diff --git a/sysdeps/i386/i686/multiarch/dl-symbol-redir-ifunc.h b/sysdeps/i386/i686/multiarch/dl-symbol-redir-ifunc.h
index dee69d19db..220c586bd2 100644
--- a/sysdeps/i386/i686/multiarch/dl-symbol-redir-ifunc.h
+++ b/sysdeps/i386/i686/multiarch/dl-symbol-redir-ifunc.h
@@ -19,6 +19,11 @@ 
 #ifndef _DL_IFUNC_GENERIC_H
 #define _DL_IFUNC_GENERIC_H
 
+#ifndef SHARED
+
 asm ("memset = __memset_ia32");
+asm ("memcmp = __memcmp_ia32");
+
+#endif /* SHARED */
 
 #endif
diff --git a/sysdeps/x86_64/memcmp-isa-default-impl.h b/sysdeps/unix/sysv/linux/i386/dl-writev.h
similarity index 62%
rename from sysdeps/x86_64/memcmp-isa-default-impl.h
rename to sysdeps/unix/sysv/linux/i386/dl-writev.h
index 0962e83c3d..624d0e46b0 100644
--- a/sysdeps/x86_64/memcmp-isa-default-impl.h
+++ b/sysdeps/unix/sysv/linux/i386/dl-writev.h
@@ -1,5 +1,5 @@ 
-/* Set default memcmp impl based on ISA level.
-   Copyright (C) 2022-2023 Free Software Foundation, Inc.
+/* Message-writing for the dynamic linker.  Linux/i386 version.
+   Copyright (C) 2013-2023 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -16,13 +16,9 @@ 
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <isa-level.h>
-#if MINIMUM_X86_ISA_LEVEL == 1 || MINIMUM_X86_ISA_LEVEL == 2
-# define DEFAULT_MEMCMP	__memcmp_sse2
-#elif MINIMUM_X86_ISA_LEVEL == 3
-# define DEFAULT_MEMCMP	__memcmp_avx2_movbe
-#elif MINIMUM_X86_ISA_LEVEL == 4
-# define DEFAULT_MEMCMP	__memcmp_evex_movbe
-#else
-# error "Unknown default memcmp implementation"
+#if BUILD_PIE_DEFAULT
+/* Can't use "call *%gs:SYSINFO_OFFSET" during startup in static PIE.  */
+# define I386_USE_SYSENTER 0
 #endif
+
+#include <sysdeps/unix/sysv/linux/dl-writev.h>
diff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c
index 0d4f328585..5697885226 100644
--- a/sysdeps/x86/cpu-tunables.c
+++ b/sysdeps/x86/cpu-tunables.c
@@ -24,24 +24,11 @@ 
 #include <string.h>
 #include <cpu-features.h>
 #include <ldsodefs.h>
-
-/* We can't use IFUNC memcmp nor strlen in init_cpu_features from libc.a
-   since IFUNC must be set up by init_cpu_features.  */
-#if defined USE_MULTIARCH && !defined SHARED
-# ifdef __x86_64__
-/* DEFAULT_MEMCMP by sysdeps/x86_64/memcmp-isa-default-impl.h.  */
-#  include <sysdeps/x86_64/memcmp-isa-default-impl.h>
-# else
-#  define DEFAULT_MEMCMP	__memcmp_ia32
-# endif
-extern __typeof (memcmp) DEFAULT_MEMCMP;
-#else
-# define DEFAULT_MEMCMP	memcmp
-#endif
+#include <dl-symbol-redir-ifunc.h>
 
 #define CHECK_GLIBC_IFUNC_CPU_OFF(f, cpu_features, name, len)		\
   _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);	\
-  if (!DEFAULT_MEMCMP (f, #name, len))					\
+  if (memcmp (f, #name, len) == 0)					\
     {									\
       CPU_FEATURE_UNSET (cpu_features, name)				\
       break;								\
@@ -51,7 +38,7 @@  extern __typeof (memcmp) DEFAULT_MEMCMP;
    which isn't available.  */
 #define CHECK_GLIBC_IFUNC_PREFERRED_OFF(f, cpu_features, name, len)	\
   _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);	\
-  if (!DEFAULT_MEMCMP (f, #name, len))					\
+  if (memcmp (f, #name, len) == 0)					\
     {									\
       cpu_features->preferred[index_arch_##name]			\
 	&= ~bit_arch_##name;						\
@@ -62,7 +49,7 @@  extern __typeof (memcmp) DEFAULT_MEMCMP;
 #define CHECK_GLIBC_IFUNC_PREFERRED_BOTH(f, cpu_features, name,	\
 					  disable, len)			\
   _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);	\
-  if (!DEFAULT_MEMCMP (f, #name, len))					\
+  if (memcmp (f, #name, len) == 0)					\
     {									\
       if (disable)							\
 	cpu_features->preferred[index_arch_##name] &= ~bit_arch_##name;	\
@@ -76,7 +63,7 @@  extern __typeof (memcmp) DEFAULT_MEMCMP;
 #define CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH(f, cpu_features, name,	\
 					       need, disable, len)	\
   _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);	\
-  if (!DEFAULT_MEMCMP (f, #name, len))					\
+  if (memcmp (f, #name, len) == 0)					\
     {									\
       if (disable)							\
 	cpu_features->preferred[index_arch_##name] &= ~bit_arch_##name;	\
@@ -177,7 +164,7 @@  TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
 	      CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, POPCNT, 6);
 	      CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_1, 6);
 	      CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_2, 6);
-	      if (!DEFAULT_MEMCMP (n, "XSAVEC", 6))
+	      if (memcmp (n, "XSAVEC", 6) == 0)
 		{
 		  /* Update xsave_state_size to XSAVE state size.  */
 		  cpu_features->xsave_state_size
@@ -290,12 +277,11 @@  attribute_hidden
 void
 TUNABLE_CALLBACK (set_x86_ibt) (tunable_val_t *valp)
 {
-  if (DEFAULT_MEMCMP (valp->strval, "on", sizeof ("on")) == 0)
+  if (memcmp (valp->strval, "on", sizeof ("on")) == 0)
     GL(dl_x86_feature_control).ibt = cet_always_on;
-  else if (DEFAULT_MEMCMP (valp->strval, "off", sizeof ("off")) == 0)
+  else if (memcmp (valp->strval, "off", sizeof ("off")) == 0)
     GL(dl_x86_feature_control).ibt = cet_always_off;
-  else if (DEFAULT_MEMCMP (valp->strval, "permissive",
-			   sizeof ("permissive")) == 0)
+  else if (memcmp (valp->strval, "permissive", sizeof ("permissive")) == 0)
     GL(dl_x86_feature_control).ibt = cet_permissive;
 }
 
@@ -303,12 +289,11 @@  attribute_hidden
 void
 TUNABLE_CALLBACK (set_x86_shstk) (tunable_val_t *valp)
 {
-  if (DEFAULT_MEMCMP (valp->strval, "on", sizeof ("on")) == 0)
+  if (memcmp (valp->strval, "on", sizeof ("on")) == 0)
     GL(dl_x86_feature_control).shstk = cet_always_on;
-  else if (DEFAULT_MEMCMP (valp->strval, "off", sizeof ("off")) == 0)
+  else if (memcmp (valp->strval, "off", sizeof ("off")) == 0)
     GL(dl_x86_feature_control).shstk = cet_always_off;
-  else if (DEFAULT_MEMCMP (valp->strval, "permissive",
-			   sizeof ("permissive")) == 0)
+  else if (memcmp (valp->strval, "permissive", sizeof ("permissive")) == 0)
     GL(dl_x86_feature_control).shstk = cet_permissive;
 }
 #endif
diff --git a/sysdeps/x86_64/multiarch/dl-symbol-redir-ifunc.h b/sysdeps/x86_64/multiarch/dl-symbol-redir-ifunc.h
index 3fe73ca1c3..c7d8961bb6 100644
--- a/sysdeps/x86_64/multiarch/dl-symbol-redir-ifunc.h
+++ b/sysdeps/x86_64/multiarch/dl-symbol-redir-ifunc.h
@@ -19,6 +19,8 @@ 
 #ifndef _DL_IFUNC_GENERIC_H
 #define _DL_IFUNC_GENERIC_H
 
+#ifndef SHARED
+
 #include <isa-level.h>
 
 #if MINIMUM_X86_ISA_LEVEL >= 4
@@ -31,4 +33,17 @@ 
 
 asm ("memset = " HAVE_MEMSET_IFUNC_GENERIC);
 
+
+#if MINIMUM_X86_ISA_LEVEL >= 4
+# define HAVE_MEMCMP_IFUNC_GENERIC "__memcmp_evex_movbe"
+#elif MINIMUM_X86_ISA_LEVEL == 3
+# define HAVE_MEMCMP_IFUNC_GENERIC "__memcmp_avx2_movbe"
+#else
+# define HAVE_MEMCMP_IFUNC_GENERIC "__memcmp_sse2"
+#endif
+
+asm ("memcmp = " HAVE_MEMCMP_IFUNC_GENERIC);
+
+#endif /* SHARED */
+
 #endif