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Message-Id: <20190426232303.28381-10-nadav.amit@gmail.com>
Date: Fri, 26 Apr 2019 16:22:48 -0700
From: nadav.amit@...il.com
To: Peter Zijlstra <peterz@...radead.org>,
Borislav Petkov <bp@...en8.de>,
Andy Lutomirski <luto@...nel.org>,
Ingo Molnar <mingo@...hat.com>
Cc: linux-kernel@...r.kernel.org,
x86@...nel.org,
hpa@...or.com,
Thomas Gleixner <tglx@...utronix.de>,
Nadav Amit <nadav.amit@...il.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
linux_dti@...oud.com,
linux-integrity@...r.kernel.org,
linux-security-module@...r.kernel.org,
akpm@...ux-foundation.org,
kernel-hardening@...ts.openwall.com,
linux-mm@...ck.org,
will.deacon@....com,
ard.biesheuvel@...aro.org,
kristen@...ux.intel.com,
deneen.t.dock@...el.com,
Rick Edgecombe <rick.p.edgecombe@...el.com>,
Nadav Amit <namit@...are.com>
Subject: [PATCH v6 09/24] x86/kgdb: Avoid redundant comparison of patched code
From: Nadav Amit <namit@...are.com>
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.
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Nadav Amit <namit@...are.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
---
arch/x86/kernel/kgdb.c | 14 +-------------
1 file changed, 1 insertion(+), 13 deletions(-)
diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index 2b203ee5b879..13b13311b792 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -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,
--
2.17.1
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