From d5a581d84ae6b8a4a740464b80d8d9cf1e7947b2 Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Fri, 5 Oct 2018 13:27:17 -0700 Subject: [PATCH] x86/cpufeature: Macrofy inline assembly code to work around GCC inlining bugs As described in: 77b0bf55bc67: ("kbuild/Makefile: Prepare for using macros in inline assembly code to work around asm() related GCC inlining bugs") GCC's inlining heuristics are broken with common asm() patterns used in kernel code, resulting in the effective disabling of inlining. The workaround is to set an assembly macro and call it from the inline assembly block - which is pretty pointless indirection in the static_cpu_has() case, but is worth it to improve overall inlining quality. The patch slightly increases the kernel size: text data bss dec hex filename 18162879 10226256 2957312 31346447 1de4f0f ./vmlinux before 18163528 10226300 2957312 31347140 1de51c4 ./vmlinux after (+693) And enables the inlining of function such as free_ldt_pgtables(). Tested-by: Kees Cook Signed-off-by: Nadav Amit Acked-by: Peter Zijlstra (Intel) Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20181005202718.229565-3-namit@vmware.com Link: https://lore.kernel.org/lkml/20181003213100.189959-10-namit@vmware.com/T/#u Signed-off-by: Ingo Molnar --- arch/x86/include/asm/cpufeature.h | 82 ++++++++++++++++++++++----------------- arch/x86/kernel/macros.S | 1 + 2 files changed, 48 insertions(+), 35 deletions(-) diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index aced6c9..7d44272 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -2,10 +2,10 @@ #ifndef _ASM_X86_CPUFEATURE_H #define _ASM_X86_CPUFEATURE_H -#include - -#if defined(__KERNEL__) && !defined(__ASSEMBLY__) +#ifdef __KERNEL__ +#ifndef __ASSEMBLY__ +#include #include #include @@ -161,37 +161,10 @@ extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit); */ static __always_inline __pure bool _static_cpu_has(u16 bit) { - asm_volatile_goto("1: jmp 6f\n" - "2:\n" - ".skip -(((5f-4f) - (2b-1b)) > 0) * " - "((5f-4f) - (2b-1b)),0x90\n" - "3:\n" - ".section .altinstructions,\"a\"\n" - " .long 1b - .\n" /* src offset */ - " .long 4f - .\n" /* repl offset */ - " .word %P[always]\n" /* always replace */ - " .byte 3b - 1b\n" /* src len */ - " .byte 5f - 4f\n" /* repl len */ - " .byte 3b - 2b\n" /* pad len */ - ".previous\n" - ".section .altinstr_replacement,\"ax\"\n" - "4: jmp %l[t_no]\n" - "5:\n" - ".previous\n" - ".section .altinstructions,\"a\"\n" - " .long 1b - .\n" /* src offset */ - " .long 0\n" /* no replacement */ - " .word %P[feature]\n" /* feature bit */ - " .byte 3b - 1b\n" /* src len */ - " .byte 0\n" /* repl len */ - " .byte 0\n" /* pad len */ - ".previous\n" - ".section .altinstr_aux,\"ax\"\n" - "6:\n" - " testb %[bitnum],%[cap_byte]\n" - " jnz %l[t_yes]\n" - " jmp %l[t_no]\n" - ".previous\n" + asm_volatile_goto("STATIC_CPU_HAS bitnum=%[bitnum] " + "cap_byte=\"%[cap_byte]\" " + "feature=%P[feature] t_yes=%l[t_yes] " + "t_no=%l[t_no] always=%P[always]" : : [feature] "i" (bit), [always] "i" (X86_FEATURE_ALWAYS), [bitnum] "i" (1 << (bit & 7)), @@ -226,5 +199,44 @@ t_no: #define CPU_FEATURE_TYPEVAL boot_cpu_data.x86_vendor, boot_cpu_data.x86, \ boot_cpu_data.x86_model -#endif /* defined(__KERNEL__) && !defined(__ASSEMBLY__) */ +#else /* __ASSEMBLY__ */ + +.macro STATIC_CPU_HAS bitnum:req cap_byte:req feature:req t_yes:req t_no:req always:req +1: + jmp 6f +2: + .skip -(((5f-4f) - (2b-1b)) > 0) * ((5f-4f) - (2b-1b)),0x90 +3: + .section .altinstructions,"a" + .long 1b - . /* src offset */ + .long 4f - . /* repl offset */ + .word \always /* always replace */ + .byte 3b - 1b /* src len */ + .byte 5f - 4f /* repl len */ + .byte 3b - 2b /* pad len */ + .previous + .section .altinstr_replacement,"ax" +4: + jmp \t_no +5: + .previous + .section .altinstructions,"a" + .long 1b - . /* src offset */ + .long 0 /* no replacement */ + .word \feature /* feature bit */ + .byte 3b - 1b /* src len */ + .byte 0 /* repl len */ + .byte 0 /* pad len */ + .previous + .section .altinstr_aux,"ax" +6: + testb \bitnum,\cap_byte + jnz \t_yes + jmp \t_no + .previous +.endm + +#endif /* __ASSEMBLY__ */ + +#endif /* __KERNEL__ */ #endif /* _ASM_X86_CPUFEATURE_H */ diff --git a/arch/x86/kernel/macros.S b/arch/x86/kernel/macros.S index 7baa40d..bf8b9c9 100644 --- a/arch/x86/kernel/macros.S +++ b/arch/x86/kernel/macros.S @@ -12,3 +12,4 @@ #include #include #include +#include -- 2.7.4