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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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ab3257042c
Now that objtool is able to rewrite jump_label instructions, have the compiler emit a JMP, such that it can decide on the optimal encoding, and set jump_entry::key bit1 to indicate that objtool should rewrite the instruction to a matching NOP. For x86_64-allyesconfig this gives: jl\ NOP JMP short: 22997 124 long: 30874 90 IOW, we save (22997+124) * 3 bytes of kernel text in hotpaths. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20210506194158.216763632@infradead.org
69 lines
1.4 KiB
C
69 lines
1.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_JUMP_LABEL_H
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#define _ASM_X86_JUMP_LABEL_H
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#define HAVE_JUMP_LABEL_BATCH
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#include <asm/asm.h>
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#include <asm/nops.h>
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#ifndef __ASSEMBLY__
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#include <linux/stringify.h>
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#include <linux/types.h>
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#define JUMP_TABLE_ENTRY \
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".pushsection __jump_table, \"aw\" \n\t" \
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_ASM_ALIGN "\n\t" \
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".long 1b - . \n\t" \
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".long %l[l_yes] - . \n\t" \
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_ASM_PTR "%c0 + %c1 - .\n\t" \
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".popsection \n\t"
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#ifdef CONFIG_STACK_VALIDATION
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static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
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{
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asm_volatile_goto("1:"
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"jmp %l[l_yes] # objtool NOPs this \n\t"
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JUMP_TABLE_ENTRY
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: : "i" (key), "i" (2 | branch) : : l_yes);
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return false;
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l_yes:
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return true;
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}
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#else
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static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch)
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{
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asm_volatile_goto("1:"
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".byte " __stringify(BYTES_NOP5) "\n\t"
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JUMP_TABLE_ENTRY
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: : "i" (key), "i" (branch) : : l_yes);
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return false;
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l_yes:
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return true;
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}
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#endif /* STACK_VALIDATION */
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static __always_inline bool arch_static_branch_jump(struct static_key * const key, const bool branch)
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{
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asm_volatile_goto("1:"
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"jmp %l[l_yes]\n\t"
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JUMP_TABLE_ENTRY
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: : "i" (key), "i" (branch) : : l_yes);
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return false;
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l_yes:
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return true;
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}
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extern int arch_jump_entry_size(struct jump_entry *entry);
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#endif /* __ASSEMBLY__ */
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#endif
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