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Commit 86a22057 authored by Nadav Amit's avatar Nadav Amit Committed by Ingo Molnar
Browse files

x86/kgdb: Avoid redundant comparison of patched code 



text_poke() already ensures that the written value is the correct one
and fails if that is not the case. There is no need for an additional
comparison. Remove it.

Signed-off-by: default avatarNadav Amit <namit@vmware.com>
Signed-off-by: default avatarRick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
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@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190426001143.4983-9-namit@vmware.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent b3fd8e83

arch/x86/kernel/kgdb.c

+1 −13
Original line number Diff line number Diff line
@@ -747,7 +747,6 @@ void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip) 
int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)

{

	int err;

	char opc[BREAK_INSTR_SIZE];



	bpt->type = BP_BREAKPOINT;

	err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
@@ -766,11 +765,6 @@ int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt) 
		return -EBUSY;

	text_poke_kgdb((void *)bpt->bpt_addr, arch_kgdb_ops.gdb_bpt_instr,

		       BREAK_INSTR_SIZE);

	err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE);

	if (err)

		return err;

	if (memcmp(opc, arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE))

		return -EINVAL;

	bpt->type = BP_POKE_BREAKPOINT;



	return err;
@@ -778,9 +772,6 @@ int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt) 


int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)

{

	int err;

	char opc[BREAK_INSTR_SIZE];



	if (bpt->type != BP_POKE_BREAKPOINT)

		goto knl_write;

	/*
@@ -791,10 +782,7 @@ int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt) 
		goto knl_write;

	text_poke_kgdb((void *)bpt->bpt_addr, bpt->saved_instr,

		       BREAK_INSTR_SIZE);

	err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE);

	if (err || memcmp(opc, bpt->saved_instr, BREAK_INSTR_SIZE))

		goto knl_write;

	return err;

	return 0;



knl_write:

	return probe_kernel_write((char *)bpt->bpt_addr,