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e836673c9b
text_mutex is currently expected to be held before text_poke() is
called, but kgdb does not take the mutex, and instead *supposedly*
ensures the lock is not taken and will not be acquired by any other core
while text_poke() is running.
The reason for the "supposedly" comment is that it is not entirely clear
that this would be the case if gdb_do_roundup is zero.
Create two wrapper functions, text_poke() and text_poke_kgdb(), which do
or do not run the lockdep assertion respectively.
While we are at it, change the return code of text_poke() to something
meaningful. One day, callers might actually respect it and the existing
BUG_ON() when patching fails could be removed. For kgdb, the return
value can actually be used.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Cc: <akpm@linux-foundation.org>
Cc: <ard.biesheuvel@linaro.org>
Cc: <deneen.t.dock@intel.com>
Cc: <kernel-hardening@lists.openwall.com>
Cc: <kristen@linux.intel.com>
Cc: <linux_dti@icloud.com>
Cc: <will.deacon@arm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 9222f60650 ("x86/alternatives: Lockdep-enforce text_mutex in text_poke*()")
Link: https://lkml.kernel.org/r/20190426001143.4983-2-namit@vmware.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
44 lines
1.6 KiB
C
44 lines
1.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_TEXT_PATCHING_H
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#define _ASM_X86_TEXT_PATCHING_H
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#include <linux/types.h>
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#include <linux/stddef.h>
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#include <asm/ptrace.h>
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struct paravirt_patch_site;
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#ifdef CONFIG_PARAVIRT
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void apply_paravirt(struct paravirt_patch_site *start,
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struct paravirt_patch_site *end);
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#else
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static inline void apply_paravirt(struct paravirt_patch_site *start,
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struct paravirt_patch_site *end)
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{}
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#define __parainstructions NULL
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#define __parainstructions_end NULL
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#endif
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extern void *text_poke_early(void *addr, const void *opcode, size_t len);
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/*
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* Clear and restore the kernel write-protection flag on the local CPU.
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* Allows the kernel to edit read-only pages.
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* Side-effect: any interrupt handler running between save and restore will have
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* the ability to write to read-only pages.
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*
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* Warning:
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* Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
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* no thread can be preempted in the instructions being modified (no iret to an
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* invalid instruction possible) or if the instructions are changed from a
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* consistent state to another consistent state atomically.
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* On the local CPU you need to be protected again NMI or MCE handlers seeing an
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* inconsistent instruction while you patch.
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*/
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extern void *text_poke(void *addr, const void *opcode, size_t len);
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extern void *text_poke_kgdb(void *addr, const void *opcode, size_t len);
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extern int poke_int3_handler(struct pt_regs *regs);
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extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler);
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extern int after_bootmem;
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#endif /* _ASM_X86_TEXT_PATCHING_H */
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