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authorIngo Molnar <mingo@kernel.org>2015-03-04 06:33:49 +0100
committerIngo Molnar <mingo@kernel.org>2015-03-04 06:36:15 +0100
commitf8e92fb4b0ffc4d62279ab39f34e798e37e90b0b (patch)
tree9caa8df664792e64ddcb4ea03fd418a8a529c82e /arch/x86/lib
parentd2c032e3dc58137a7261a7824d3acce435db1d66 (diff)
parentdfecb95cdfeaf7872d83a96bec3a606e9cd95c8d (diff)
downloadlinux-f8e92fb4b0ffc4d62279ab39f34e798e37e90b0b.tar.bz2
Merge tag 'alternatives_padding' of git://git.kernel.org/pub/scm/linux/kernel/git/bp/bp into x86/asm
Pull alternative instructions framework improvements from Borislav Petkov: "A more involved rework of the alternatives framework to be able to pad instructions and thus make using the alternatives macros more straightforward and without having to figure out old and new instruction sizes but have the toolchain figure that out for us. Furthermore, it optimizes JMPs used so that fetch and decode can be relieved with smaller versions of the JMPs, where possible. Some stats: x86_64 defconfig: Alternatives sites total: 2478 Total padding added (in Bytes): 6051 The padding is currently done for: X86_FEATURE_ALWAYS X86_FEATURE_ERMS X86_FEATURE_LFENCE_RDTSC X86_FEATURE_MFENCE_RDTSC X86_FEATURE_SMAP This is with the latest version of the patchset. Of course, on each machine the alternatives sites actually being patched are a proper subset of the total number." Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/lib')
-rw-r--r--arch/x86/lib/clear_page_64.S66
-rw-r--r--arch/x86/lib/copy_page_64.S37
-rw-r--r--arch/x86/lib/copy_user_64.S46
-rw-r--r--arch/x86/lib/memcpy_64.S68
-rw-r--r--arch/x86/lib/memmove_64.S19
-rw-r--r--arch/x86/lib/memset_64.S61
6 files changed, 96 insertions, 201 deletions
diff --git a/arch/x86/lib/clear_page_64.S b/arch/x86/lib/clear_page_64.S
index f2145cfa12a6..e67e579c93bd 100644
--- a/arch/x86/lib/clear_page_64.S
+++ b/arch/x86/lib/clear_page_64.S
@@ -1,31 +1,35 @@
#include <linux/linkage.h>
#include <asm/dwarf2.h>
+#include <asm/cpufeature.h>
#include <asm/alternative-asm.h>
/*
- * Zero a page.
- * rdi page
- */
-ENTRY(clear_page_c)
+ * Most CPUs support enhanced REP MOVSB/STOSB instructions. It is
+ * recommended to use this when possible and we do use them by default.
+ * If enhanced REP MOVSB/STOSB is not available, try to use fast string.
+ * Otherwise, use original.
+ */
+
+/*
+ * Zero a page.
+ * %rdi - page
+ */
+ENTRY(clear_page)
CFI_STARTPROC
+
+ ALTERNATIVE_2 "jmp clear_page_orig", "", X86_FEATURE_REP_GOOD, \
+ "jmp clear_page_c_e", X86_FEATURE_ERMS
+
movl $4096/8,%ecx
xorl %eax,%eax
rep stosq
ret
CFI_ENDPROC
-ENDPROC(clear_page_c)
+ENDPROC(clear_page)
-ENTRY(clear_page_c_e)
+ENTRY(clear_page_orig)
CFI_STARTPROC
- movl $4096,%ecx
- xorl %eax,%eax
- rep stosb
- ret
- CFI_ENDPROC
-ENDPROC(clear_page_c_e)
-ENTRY(clear_page)
- CFI_STARTPROC
xorl %eax,%eax
movl $4096/64,%ecx
.p2align 4
@@ -45,29 +49,13 @@ ENTRY(clear_page)
nop
ret
CFI_ENDPROC
-.Lclear_page_end:
-ENDPROC(clear_page)
-
- /*
- * Some CPUs support enhanced REP MOVSB/STOSB instructions.
- * It is recommended to use this when possible.
- * If enhanced REP MOVSB/STOSB is not available, try to use fast string.
- * Otherwise, use original function.
- *
- */
+ENDPROC(clear_page_orig)
-#include <asm/cpufeature.h>
-
- .section .altinstr_replacement,"ax"
-1: .byte 0xeb /* jmp <disp8> */
- .byte (clear_page_c - clear_page) - (2f - 1b) /* offset */
-2: .byte 0xeb /* jmp <disp8> */
- .byte (clear_page_c_e - clear_page) - (3f - 2b) /* offset */
-3:
- .previous
- .section .altinstructions,"a"
- altinstruction_entry clear_page,1b,X86_FEATURE_REP_GOOD,\
- .Lclear_page_end-clear_page, 2b-1b
- altinstruction_entry clear_page,2b,X86_FEATURE_ERMS, \
- .Lclear_page_end-clear_page,3b-2b
- .previous
+ENTRY(clear_page_c_e)
+ CFI_STARTPROC
+ movl $4096,%ecx
+ xorl %eax,%eax
+ rep stosb
+ ret
+ CFI_ENDPROC
+ENDPROC(clear_page_c_e)
diff --git a/arch/x86/lib/copy_page_64.S b/arch/x86/lib/copy_page_64.S
index 176cca67212b..8239dbcbf984 100644
--- a/arch/x86/lib/copy_page_64.S
+++ b/arch/x86/lib/copy_page_64.S
@@ -2,23 +2,26 @@
#include <linux/linkage.h>
#include <asm/dwarf2.h>
+#include <asm/cpufeature.h>
#include <asm/alternative-asm.h>
+/*
+ * Some CPUs run faster using the string copy instructions (sane microcode).
+ * It is also a lot simpler. Use this when possible. But, don't use streaming
+ * copy unless the CPU indicates X86_FEATURE_REP_GOOD. Could vary the
+ * prefetch distance based on SMP/UP.
+ */
ALIGN
-copy_page_rep:
+ENTRY(copy_page)
CFI_STARTPROC
+ ALTERNATIVE "jmp copy_page_regs", "", X86_FEATURE_REP_GOOD
movl $4096/8, %ecx
rep movsq
ret
CFI_ENDPROC
-ENDPROC(copy_page_rep)
-
-/*
- * Don't use streaming copy unless the CPU indicates X86_FEATURE_REP_GOOD.
- * Could vary the prefetch distance based on SMP/UP.
-*/
+ENDPROC(copy_page)
-ENTRY(copy_page)
+ENTRY(copy_page_regs)
CFI_STARTPROC
subq $2*8, %rsp
CFI_ADJUST_CFA_OFFSET 2*8
@@ -90,21 +93,5 @@ ENTRY(copy_page)
addq $2*8, %rsp
CFI_ADJUST_CFA_OFFSET -2*8
ret
-.Lcopy_page_end:
CFI_ENDPROC
-ENDPROC(copy_page)
-
- /* Some CPUs run faster using the string copy instructions.
- It is also a lot simpler. Use this when possible */
-
-#include <asm/cpufeature.h>
-
- .section .altinstr_replacement,"ax"
-1: .byte 0xeb /* jmp <disp8> */
- .byte (copy_page_rep - copy_page) - (2f - 1b) /* offset */
-2:
- .previous
- .section .altinstructions,"a"
- altinstruction_entry copy_page, 1b, X86_FEATURE_REP_GOOD, \
- .Lcopy_page_end-copy_page, 2b-1b
- .previous
+ENDPROC(copy_page_regs)
diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index dee945d55594..fa997dfaef24 100644
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -8,9 +8,6 @@
#include <linux/linkage.h>
#include <asm/dwarf2.h>
-
-#define FIX_ALIGNMENT 1
-
#include <asm/current.h>
#include <asm/asm-offsets.h>
#include <asm/thread_info.h>
@@ -19,33 +16,7 @@
#include <asm/asm.h>
#include <asm/smap.h>
-/*
- * By placing feature2 after feature1 in altinstructions section, we logically
- * implement:
- * If CPU has feature2, jmp to alt2 is used
- * else if CPU has feature1, jmp to alt1 is used
- * else jmp to orig is used.
- */
- .macro ALTERNATIVE_JUMP feature1,feature2,orig,alt1,alt2
-0:
- .byte 0xe9 /* 32bit jump */
- .long \orig-1f /* by default jump to orig */
-1:
- .section .altinstr_replacement,"ax"
-2: .byte 0xe9 /* near jump with 32bit immediate */
- .long \alt1-1b /* offset */ /* or alternatively to alt1 */
-3: .byte 0xe9 /* near jump with 32bit immediate */
- .long \alt2-1b /* offset */ /* or alternatively to alt2 */
- .previous
-
- .section .altinstructions,"a"
- altinstruction_entry 0b,2b,\feature1,5,5
- altinstruction_entry 0b,3b,\feature2,5,5
- .previous
- .endm
-
.macro ALIGN_DESTINATION
-#ifdef FIX_ALIGNMENT
/* check for bad alignment of destination */
movl %edi,%ecx
andl $7,%ecx
@@ -67,7 +38,6 @@
_ASM_EXTABLE(100b,103b)
_ASM_EXTABLE(101b,103b)
-#endif
.endm
/* Standard copy_to_user with segment limit checking */
@@ -79,9 +49,11 @@ ENTRY(_copy_to_user)
jc bad_to_user
cmpq TI_addr_limit(%rax),%rcx
ja bad_to_user
- ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,X86_FEATURE_ERMS, \
- copy_user_generic_unrolled,copy_user_generic_string, \
- copy_user_enhanced_fast_string
+ ALTERNATIVE_2 "jmp copy_user_generic_unrolled", \
+ "jmp copy_user_generic_string", \
+ X86_FEATURE_REP_GOOD, \
+ "jmp copy_user_enhanced_fast_string", \
+ X86_FEATURE_ERMS
CFI_ENDPROC
ENDPROC(_copy_to_user)
@@ -94,9 +66,11 @@ ENTRY(_copy_from_user)
jc bad_from_user
cmpq TI_addr_limit(%rax),%rcx
ja bad_from_user
- ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,X86_FEATURE_ERMS, \
- copy_user_generic_unrolled,copy_user_generic_string, \
- copy_user_enhanced_fast_string
+ ALTERNATIVE_2 "jmp copy_user_generic_unrolled", \
+ "jmp copy_user_generic_string", \
+ X86_FEATURE_REP_GOOD, \
+ "jmp copy_user_enhanced_fast_string", \
+ X86_FEATURE_ERMS
CFI_ENDPROC
ENDPROC(_copy_from_user)
diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S
index 89b53c9968e7..b046664f5a1c 100644
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -1,12 +1,20 @@
/* Copyright 2002 Andi Kleen */
#include <linux/linkage.h>
-
#include <asm/cpufeature.h>
#include <asm/dwarf2.h>
#include <asm/alternative-asm.h>
/*
+ * We build a jump to memcpy_orig by default which gets NOPped out on
+ * the majority of x86 CPUs which set REP_GOOD. In addition, CPUs which
+ * have the enhanced REP MOVSB/STOSB feature (ERMS), change those NOPs
+ * to a jmp to memcpy_erms which does the REP; MOVSB mem copy.
+ */
+
+.weak memcpy
+
+/*
* memcpy - Copy a memory block.
*
* Input:
@@ -17,15 +25,11 @@
* Output:
* rax original destination
*/
+ENTRY(__memcpy)
+ENTRY(memcpy)
+ ALTERNATIVE_2 "jmp memcpy_orig", "", X86_FEATURE_REP_GOOD, \
+ "jmp memcpy_erms", X86_FEATURE_ERMS
-/*
- * memcpy_c() - fast string ops (REP MOVSQ) based variant.
- *
- * This gets patched over the unrolled variant (below) via the
- * alternative instructions framework:
- */
- .section .altinstr_replacement, "ax", @progbits
-.Lmemcpy_c:
movq %rdi, %rax
movq %rdx, %rcx
shrq $3, %rcx
@@ -34,29 +38,21 @@
movl %edx, %ecx
rep movsb
ret
-.Lmemcpy_e:
- .previous
+ENDPROC(memcpy)
+ENDPROC(__memcpy)
/*
- * memcpy_c_e() - enhanced fast string memcpy. This is faster and simpler than
- * memcpy_c. Use memcpy_c_e when possible.
- *
- * This gets patched over the unrolled variant (below) via the
- * alternative instructions framework:
+ * memcpy_erms() - enhanced fast string memcpy. This is faster and
+ * simpler than memcpy. Use memcpy_erms when possible.
*/
- .section .altinstr_replacement, "ax", @progbits
-.Lmemcpy_c_e:
+ENTRY(memcpy_erms)
movq %rdi, %rax
movq %rdx, %rcx
rep movsb
ret
-.Lmemcpy_e_e:
- .previous
-
-.weak memcpy
+ENDPROC(memcpy_erms)
-ENTRY(__memcpy)
-ENTRY(memcpy)
+ENTRY(memcpy_orig)
CFI_STARTPROC
movq %rdi, %rax
@@ -183,26 +179,4 @@ ENTRY(memcpy)
.Lend:
retq
CFI_ENDPROC
-ENDPROC(memcpy)
-ENDPROC(__memcpy)
-
- /*
- * Some CPUs are adding enhanced REP MOVSB/STOSB feature
- * If the feature is supported, memcpy_c_e() is the first choice.
- * If enhanced rep movsb copy is not available, use fast string copy
- * memcpy_c() when possible. This is faster and code is simpler than
- * original memcpy().
- * Otherwise, original memcpy() is used.
- * In .altinstructions section, ERMS feature is placed after REG_GOOD
- * feature to implement the right patch order.
- *
- * Replace only beginning, memcpy is used to apply alternatives,
- * so it is silly to overwrite itself with nops - reboot is the
- * only outcome...
- */
- .section .altinstructions, "a"
- altinstruction_entry __memcpy,.Lmemcpy_c,X86_FEATURE_REP_GOOD,\
- .Lmemcpy_e-.Lmemcpy_c,.Lmemcpy_e-.Lmemcpy_c
- altinstruction_entry __memcpy,.Lmemcpy_c_e,X86_FEATURE_ERMS, \
- .Lmemcpy_e_e-.Lmemcpy_c_e,.Lmemcpy_e_e-.Lmemcpy_c_e
- .previous
+ENDPROC(memcpy_orig)
diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S
index 9c4b530575da..0f8a0d0331b9 100644
--- a/arch/x86/lib/memmove_64.S
+++ b/arch/x86/lib/memmove_64.S
@@ -5,7 +5,6 @@
* This assembly file is re-written from memmove_64.c file.
* - Copyright 2011 Fenghua Yu <fenghua.yu@intel.com>
*/
-#define _STRING_C
#include <linux/linkage.h>
#include <asm/dwarf2.h>
#include <asm/cpufeature.h>
@@ -44,6 +43,8 @@ ENTRY(__memmove)
jg 2f
.Lmemmove_begin_forward:
+ ALTERNATIVE "", "movq %rdx, %rcx; rep movsb; retq", X86_FEATURE_ERMS
+
/*
* movsq instruction have many startup latency
* so we handle small size by general register.
@@ -207,21 +208,5 @@ ENTRY(__memmove)
13:
retq
CFI_ENDPROC
-
- .section .altinstr_replacement,"ax"
-.Lmemmove_begin_forward_efs:
- /* Forward moving data. */
- movq %rdx, %rcx
- rep movsb
- retq
-.Lmemmove_end_forward_efs:
- .previous
-
- .section .altinstructions,"a"
- altinstruction_entry .Lmemmove_begin_forward, \
- .Lmemmove_begin_forward_efs,X86_FEATURE_ERMS, \
- .Lmemmove_end_forward-.Lmemmove_begin_forward, \
- .Lmemmove_end_forward_efs-.Lmemmove_begin_forward_efs
- .previous
ENDPROC(__memmove)
ENDPROC(memmove)
diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S
index 6f44935c6a60..93118fb23976 100644
--- a/arch/x86/lib/memset_64.S
+++ b/arch/x86/lib/memset_64.S
@@ -5,19 +5,30 @@
#include <asm/cpufeature.h>
#include <asm/alternative-asm.h>
+.weak memset
+
/*
* ISO C memset - set a memory block to a byte value. This function uses fast
* string to get better performance than the original function. The code is
* simpler and shorter than the orignal function as well.
- *
+ *
* rdi destination
- * rsi value (char)
- * rdx count (bytes)
- *
+ * rsi value (char)
+ * rdx count (bytes)
+ *
* rax original destination
- */
- .section .altinstr_replacement, "ax", @progbits
-.Lmemset_c:
+ */
+ENTRY(memset)
+ENTRY(__memset)
+ /*
+ * Some CPUs support enhanced REP MOVSB/STOSB feature. It is recommended
+ * to use it when possible. If not available, use fast string instructions.
+ *
+ * Otherwise, use original memset function.
+ */
+ ALTERNATIVE_2 "jmp memset_orig", "", X86_FEATURE_REP_GOOD, \
+ "jmp memset_erms", X86_FEATURE_ERMS
+
movq %rdi,%r9
movq %rdx,%rcx
andl $7,%edx
@@ -31,8 +42,8 @@
rep stosb
movq %r9,%rax
ret
-.Lmemset_e:
- .previous
+ENDPROC(memset)
+ENDPROC(__memset)
/*
* ISO C memset - set a memory block to a byte value. This function uses
@@ -45,21 +56,16 @@
*
* rax original destination
*/
- .section .altinstr_replacement, "ax", @progbits
-.Lmemset_c_e:
+ENTRY(memset_erms)
movq %rdi,%r9
movb %sil,%al
movq %rdx,%rcx
rep stosb
movq %r9,%rax
ret
-.Lmemset_e_e:
- .previous
-
-.weak memset
+ENDPROC(memset_erms)
-ENTRY(memset)
-ENTRY(__memset)
+ENTRY(memset_orig)
CFI_STARTPROC
movq %rdi,%r10
@@ -134,23 +140,4 @@ ENTRY(__memset)
jmp .Lafter_bad_alignment
.Lfinal:
CFI_ENDPROC
-ENDPROC(memset)
-ENDPROC(__memset)
-
- /* Some CPUs support enhanced REP MOVSB/STOSB feature.
- * It is recommended to use this when possible.
- *
- * If enhanced REP MOVSB/STOSB feature is not available, use fast string
- * instructions.
- *
- * Otherwise, use original memset function.
- *
- * In .altinstructions section, ERMS feature is placed after REG_GOOD
- * feature to implement the right patch order.
- */
- .section .altinstructions,"a"
- altinstruction_entry __memset,.Lmemset_c,X86_FEATURE_REP_GOOD,\
- .Lfinal-__memset,.Lmemset_e-.Lmemset_c
- altinstruction_entry __memset,.Lmemset_c_e,X86_FEATURE_ERMS, \
- .Lfinal-__memset,.Lmemset_e_e-.Lmemset_c_e
- .previous
+ENDPROC(memset_orig)