[tip:x86/fpu] x86: Add a static_cpu_has_safe variant
Commit-ID: 4a90a99c4f8002edaa6be11bd756872ebf3f3d97
Gitweb: http://git.kernel.org/tip/4a90a99c4f8002edaa6be11bd756872ebf3f3d97
Author: Borislav Petkov
AuthorDate: Sun, 9 Jun 2013 12:07:33 +0200
Committer: H. Peter Anvin
CommitDate: Thu, 20 Jun 2013 17:38:14 -0700
x86: Add a static_cpu_has_safe variant
We want to use this in early code where alternatives might not have run
yet and for that case we fall back to the dynamic boot_cpu_has.
For that, force a 5-byte jump since the compiler could be generating
differently sized jumps for each label.
Signed-off-by: Borislav Petkov
Link: http://lkml.kernel.org/r/1370772454-6106-5-git-send-email...@alien8.de
Signed-off-by: H. Peter Anvin
---
arch/x86/include/asm/cpufeature.h | 86 ++-
arch/x86/kernel/cpu/common.c | 6 +++
2 files changed, 91 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/cpufeature.h
b/arch/x86/include/asm/cpufeature.h
index 252b28f..47538a6 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -357,6 +357,7 @@ extern const char * const x86_power_flags[32];
#if __GNUC__ >= 4
extern void warn_pre_alternatives(void);
+extern bool __static_cpu_has_safe(u16 bit);
/*
* Static testing of CPU features. Used the same as boot_cpu_has().
@@ -437,11 +438,94 @@ static __always_inline __pure bool __static_cpu_has(u16
bit)
__static_cpu_has(bit) : \
boot_cpu_has(bit) \
)
+
+static __always_inline __pure bool _static_cpu_has_safe(u16 bit)
+{
+#if __GNUC__ > 4 || __GNUC_MINOR__ >= 5
+/*
+ * We need to spell the jumps to the compiler because, depending on the offset,
+ * the replacement jump can be bigger than the original jump, and this we
cannot
+ * have. Thus, we force the jump to the widest, 4-byte, signed relative
+ * offset even though the last would often fit in less bytes.
+ */
+ asm goto("1: .byte 0xe9\n .long %l[t_dynamic] - 2f\n"
+"2:\n"
+".section .altinstructions,\"a\"\n"
+" .long 1b - .\n" /* src offset */
+" .long 3f - .\n" /* repl offset */
+" .word %P1\n" /* always replace */
+" .byte 2b - 1b\n" /* src len */
+" .byte 4f - 3f\n" /* repl len */
+".previous\n"
+".section .altinstr_replacement,\"ax\"\n"
+"3: .byte 0xe9\n .long %l[t_no] - 2b\n"
+"4:\n"
+".previous\n"
+".section .altinstructions,\"a\"\n"
+" .long 1b - .\n" /* src offset */
+" .long 0\n" /* no replacement */
+" .word %P0\n" /* feature bit */
+" .byte 2b - 1b\n" /* src len */
+" .byte 0\n" /* repl len */
+".previous\n"
+: : "i" (bit), "i" (X86_FEATURE_ALWAYS)
+: : t_dynamic, t_no);
+ return true;
+ t_no:
+ return false;
+ t_dynamic:
+ return __static_cpu_has_safe(bit);
+#else /* GCC_VERSION >= 40500 */
+ u8 flag;
+ /* Open-coded due to __stringify() in ALTERNATIVE() */
+ asm volatile("1: movb $2,%0\n"
+"2:\n"
+".section .altinstructions,\"a\"\n"
+" .long 1b - .\n" /* src offset */
+" .long 3f - .\n" /* repl offset */
+" .word %P2\n" /* always replace */
+" .byte 2b - 1b\n" /* source len */
+" .byte 4f - 3f\n" /* replacement len */
+".previous\n"
+".section .discard,\"aw\",@progbits\n"
+" .byte 0xff + (4f-3f) - (2b-1b)\n" /* size check
*/
+".previous\n"
+".section .altinstr_replacement,\"ax\"\n"
+"3: movb $0,%0\n"
+"4:\n"
+".previous\n"
+".section .altinstructions,\"a\"\n"
+" .long 1b - .\n" /* src offset */
+" .long 5f - .\n" /* repl offset */
+" .word %P1\n" /* feature bit */
+" .byte 4b - 3b\n" /* src len */
+" .byte 6f - 5f\n" /* repl len */
+
[tip:x86/fpu] x86: Add a static_cpu_has_safe variant
Commit-ID: 4a90a99c4f8002edaa6be11bd756872ebf3f3d97
Gitweb: http://git.kernel.org/tip/4a90a99c4f8002edaa6be11bd756872ebf3f3d97
Author: Borislav Petkov b...@suse.de
AuthorDate: Sun, 9 Jun 2013 12:07:33 +0200
Committer: H. Peter Anvin h...@linux.intel.com
CommitDate: Thu, 20 Jun 2013 17:38:14 -0700
x86: Add a static_cpu_has_safe variant
We want to use this in early code where alternatives might not have run
yet and for that case we fall back to the dynamic boot_cpu_has.
For that, force a 5-byte jump since the compiler could be generating
differently sized jumps for each label.
Signed-off-by: Borislav Petkov b...@suse.de
Link: http://lkml.kernel.org/r/1370772454-6106-5-git-send-email...@alien8.de
Signed-off-by: H. Peter Anvin h...@linux.intel.com
---
arch/x86/include/asm/cpufeature.h | 86 ++-
arch/x86/kernel/cpu/common.c | 6 +++
2 files changed, 91 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/cpufeature.h
b/arch/x86/include/asm/cpufeature.h
index 252b28f..47538a6 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -357,6 +357,7 @@ extern const char * const x86_power_flags[32];
#if __GNUC__ = 4
extern void warn_pre_alternatives(void);
+extern bool __static_cpu_has_safe(u16 bit);
/*
* Static testing of CPU features. Used the same as boot_cpu_has().
@@ -437,11 +438,94 @@ static __always_inline __pure bool __static_cpu_has(u16
bit)
__static_cpu_has(bit) : \
boot_cpu_has(bit) \
)
+
+static __always_inline __pure bool _static_cpu_has_safe(u16 bit)
+{
+#if __GNUC__ 4 || __GNUC_MINOR__ = 5
+/*
+ * We need to spell the jumps to the compiler because, depending on the offset,
+ * the replacement jump can be bigger than the original jump, and this we
cannot
+ * have. Thus, we force the jump to the widest, 4-byte, signed relative
+ * offset even though the last would often fit in less bytes.
+ */
+ asm goto(1: .byte 0xe9\n .long %l[t_dynamic] - 2f\n
+2:\n
+.section .altinstructions,\a\\n
+ .long 1b - .\n /* src offset */
+ .long 3f - .\n /* repl offset */
+ .word %P1\n /* always replace */
+ .byte 2b - 1b\n /* src len */
+ .byte 4f - 3f\n /* repl len */
+.previous\n
+.section .altinstr_replacement,\ax\\n
+3: .byte 0xe9\n .long %l[t_no] - 2b\n
+4:\n
+.previous\n
+.section .altinstructions,\a\\n
+ .long 1b - .\n /* src offset */
+ .long 0\n /* no replacement */
+ .word %P0\n /* feature bit */
+ .byte 2b - 1b\n /* src len */
+ .byte 0\n /* repl len */
+.previous\n
+: : i (bit), i (X86_FEATURE_ALWAYS)
+: : t_dynamic, t_no);
+ return true;
+ t_no:
+ return false;
+ t_dynamic:
+ return __static_cpu_has_safe(bit);
+#else /* GCC_VERSION = 40500 */
+ u8 flag;
+ /* Open-coded due to __stringify() in ALTERNATIVE() */
+ asm volatile(1: movb $2,%0\n
+2:\n
+.section .altinstructions,\a\\n
+ .long 1b - .\n /* src offset */
+ .long 3f - .\n /* repl offset */
+ .word %P2\n /* always replace */
+ .byte 2b - 1b\n /* source len */
+ .byte 4f - 3f\n /* replacement len */
+.previous\n
+.section .discard,\aw\,@progbits\n
+ .byte 0xff + (4f-3f) - (2b-1b)\n /* size check
*/
+.previous\n
+.section .altinstr_replacement,\ax\\n
+3: movb $0,%0\n
+4:\n
+.previous\n
+.section .altinstructions,\a\\n
+ .long 1b - .\n /* src offset */
+ .long 5f - .\n /* repl offset */
+ .word %P1\n /* feature bit */
+ .byte 4b - 3b\n /* src len */
+ .byte 6f - 5f\n /* repl len */
+.previous\n
+
