[tip:x86/asm] x86-64: Modify copy_user_generic() alternatives mechanism
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From: tip-bot for Jan Beulich on 30 Dec 2009 07:30 Commit-ID: 1b1d9258181bae199dc940f4bd0298126b9a73d9 Gitweb: http://git.kernel.org/tip/1b1d9258181bae199dc940f4bd0298126b9a73d9 Author: Jan Beulich <JBeulich(a)novell.com> AuthorDate: Fri, 18 Dec 2009 16:12:56 +0000 Committer: Ingo Molnar <mingo(a)elte.hu> CommitDate: Wed, 30 Dec 2009 11:57:31 +0100 x86-64: Modify copy_user_generic() alternatives mechanism In order to avoid unnecessary chains of branches, rather than implementing copy_user_generic() as a function consisting of just a single (possibly patched) branch, instead properly deal with patching call instructions in the alternative instructions framework, and move the patching into the callers. As a follow-on, one could also introduce something like __EXPORT_SYMBOL_ALT() to avoid patching call sites in modules. Signed-off-by: Jan Beulich <jbeulich(a)novell.com> Cc: Nick Piggin <npiggin(a)suse.de> Cc: Linus Torvalds <torvalds(a)linux-foundation.org> Cc: Andrew Morton <akpm(a)linux-foundation.org> LKML-Reference: <4B2BB8180200007800026AE7(a)vpn.id2.novell.com> Signed-off-by: Ingo Molnar <mingo(a)elte.hu> --- arch/x86/include/asm/alternative.h | 7 ++++++- arch/x86/include/asm/uaccess_64.h | 21 ++++++++++++++++++++- arch/x86/kernel/alternative.c | 4 +++- arch/x86/kernel/x8664_ksyms_64.c | 3 ++- arch/x86/lib/copy_user_64.S | 6 ------ 5 files changed, 31 insertions(+), 10 deletions(-) diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index 69b74a7..3b5b828 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -125,11 +125,16 @@ static inline void alternatives_smp_switch(int smp) {} asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ : output : "i" (0), ## input) +/* Like alternative_io, but for replacing a direct call with another one. */ +#define alternative_call(oldfunc, newfunc, feature, output, input...) \ + asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ + : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) + /* * use this macro(s) if you need more than one output parameter * in alternative_io */ -#define ASM_OUTPUT2(a, b) a, b +#define ASM_OUTPUT2(a...) a struct paravirt_patch_site; #ifdef CONFIG_PARAVIRT diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h index 46324c6..a78c403 100644 --- a/arch/x86/include/asm/uaccess_64.h +++ b/arch/x86/include/asm/uaccess_64.h @@ -8,6 +8,8 @@ #include <linux/errno.h> #include <linux/prefetch.h> #include <linux/lockdep.h> +#include <asm/alternative.h> +#include <asm/cpufeature.h> #include <asm/page.h> /* @@ -16,7 +18,24 @@ /* Handles exceptions in both to and from, but doesn't do access_ok */ __must_check unsigned long -copy_user_generic(void *to, const void *from, unsigned len); +copy_user_generic_string(void *to, const void *from, unsigned len); +__must_check unsigned long +copy_user_generic_unrolled(void *to, const void *from, unsigned len); + +static __always_inline __must_check unsigned long +copy_user_generic(void *to, const void *from, unsigned len) +{ + unsigned ret; + + alternative_call(copy_user_generic_unrolled, + copy_user_generic_string, + X86_FEATURE_REP_GOOD, + ASM_OUTPUT2("=a" (ret), "=D" (to), "=S" (from), + "=d" (len)), + "1" (to), "2" (from), "3" (len) + : "memory", "rcx", "r8", "r9", "r10", "r11"); + return ret; +} __must_check unsigned long _copy_to_user(void __user *to, const void *from, unsigned len); diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index de7353c..2589ea4 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -205,7 +205,7 @@ void __init_or_module apply_alternatives(struct alt_instr *start, struct alt_instr *end) { struct alt_instr *a; - char insnbuf[MAX_PATCH_LEN]; + u8 insnbuf[MAX_PATCH_LEN]; DPRINTK("%s: alt table %p -> %p\n", __func__, start, end); for (a = start; a < end; a++) { @@ -223,6 +223,8 @@ void __init_or_module apply_alternatives(struct alt_instr *start, } #endif memcpy(insnbuf, a->replacement, a->replacementlen); + if (*insnbuf == 0xe8 && a->replacementlen == 5) + *(s32 *)(insnbuf + 1) += a->replacement - a->instr; add_nops(insnbuf + a->replacementlen, a->instrlen - a->replacementlen); text_poke_early(instr, insnbuf, a->instrlen); diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c index 619f7f8..693920b 100644 --- a/arch/x86/kernel/x8664_ksyms_64.c +++ b/arch/x86/kernel/x8664_ksyms_64.c @@ -26,7 +26,8 @@ EXPORT_SYMBOL(__put_user_2); EXPORT_SYMBOL(__put_user_4); EXPORT_SYMBOL(__put_user_8); -EXPORT_SYMBOL(copy_user_generic); +EXPORT_SYMBOL(copy_user_generic_string); +EXPORT_SYMBOL(copy_user_generic_unrolled); EXPORT_SYMBOL(__copy_user_nocache); EXPORT_SYMBOL(_copy_from_user); EXPORT_SYMBOL(_copy_to_user); diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S index cf889d4..71100c9 100644 --- a/arch/x86/lib/copy_user_64.S +++ b/arch/x86/lib/copy_user_64.S @@ -90,12 +90,6 @@ ENTRY(_copy_from_user) CFI_ENDPROC ENDPROC(_copy_from_user) -ENTRY(copy_user_generic) - CFI_STARTPROC - ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string - CFI_ENDPROC -ENDPROC(copy_user_generic) - .section .fixup,"ax" /* must zero dest */ ENTRY(bad_from_user) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |