ba08abca66
Commitab234a260b("x86/pv: Rework arch_local_irq_restore() to not use popf") replaced "push %reg; popf" with something like: "test $0x200, %reg; jz 1f; sti; 1:", which breaks the pushf/popf symmetry that commitea24213d80("objtool: Add UACCESS validation") relies on. The result is: drivers/gpu/drm/amd/amdgpu/si.o: warning: objtool: si_common_hw_init()+0xf36: PUSHF stack exhausted Meanwhile, commitc9c324dc22("objtool: Support stack layout changes in alternatives") makes that we can actually use stack-ops in alternatives, which means we can revert1ff865e343("x86,smap: Fix smap_{save,restore}() alternatives"). That in turn means we can limit the PUSHF/POPF handling ofea24213d80to those instructions that are in alternatives. Fixes:ab234a260b("x86/pv: Rework arch_local_irq_restore() to not use popf") Reported-by: Borislav Petkov <bp@alien8.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lkml.kernel.org/r/YEY4rIbQYa5fnnEp@hirez.programming.kicks-ass.net
98 lines
2.0 KiB
C
98 lines
2.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Supervisor Mode Access Prevention support
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*
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* Copyright (C) 2012 Intel Corporation
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* Author: H. Peter Anvin <hpa@linux.intel.com>
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*/
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#ifndef _ASM_X86_SMAP_H
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#define _ASM_X86_SMAP_H
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#include <asm/nops.h>
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#include <asm/cpufeatures.h>
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/* "Raw" instruction opcodes */
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#define __ASM_CLAC ".byte 0x0f,0x01,0xca"
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#define __ASM_STAC ".byte 0x0f,0x01,0xcb"
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#ifdef __ASSEMBLY__
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#include <asm/alternative-asm.h>
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#ifdef CONFIG_X86_SMAP
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#define ASM_CLAC \
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ALTERNATIVE "", __ASM_CLAC, X86_FEATURE_SMAP
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#define ASM_STAC \
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ALTERNATIVE "", __ASM_STAC, X86_FEATURE_SMAP
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#else /* CONFIG_X86_SMAP */
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#define ASM_CLAC
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#define ASM_STAC
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#endif /* CONFIG_X86_SMAP */
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#else /* __ASSEMBLY__ */
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#include <asm/alternative.h>
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#ifdef CONFIG_X86_SMAP
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static __always_inline void clac(void)
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{
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/* Note: a barrier is implicit in alternative() */
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alternative("", __ASM_CLAC, X86_FEATURE_SMAP);
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}
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static __always_inline void stac(void)
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{
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/* Note: a barrier is implicit in alternative() */
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alternative("", __ASM_STAC, X86_FEATURE_SMAP);
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}
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static __always_inline unsigned long smap_save(void)
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{
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unsigned long flags;
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asm volatile ("# smap_save\n\t"
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ALTERNATIVE("", "pushf; pop %0; " __ASM_CLAC "\n\t",
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X86_FEATURE_SMAP)
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: "=rm" (flags) : : "memory", "cc");
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return flags;
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}
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static __always_inline void smap_restore(unsigned long flags)
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{
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asm volatile ("# smap_restore\n\t"
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ALTERNATIVE("", "push %0; popf\n\t",
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X86_FEATURE_SMAP)
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: : "g" (flags) : "memory", "cc");
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}
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/* These macros can be used in asm() statements */
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#define ASM_CLAC \
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ALTERNATIVE("", __ASM_CLAC, X86_FEATURE_SMAP)
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#define ASM_STAC \
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ALTERNATIVE("", __ASM_STAC, X86_FEATURE_SMAP)
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#else /* CONFIG_X86_SMAP */
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static inline void clac(void) { }
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static inline void stac(void) { }
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static inline unsigned long smap_save(void) { return 0; }
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static inline void smap_restore(unsigned long flags) { }
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#define ASM_CLAC
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#define ASM_STAC
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#endif /* CONFIG_X86_SMAP */
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_X86_SMAP_H */
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