[PATCH v5 07/10] x86/kgdb: avoid redundant comparison of patched code

Nadav Amit
2018-11-13T20:26:28Z

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: Nadav Amit <namit@vmware.com>
---
arch/x86/kernel/kgdb.c | 10 ----------
1 file changed, 10 deletions(-)

diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index 8091b2e381d4..d14e1be576fd 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -751,7 +751,6 @@ 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,
@@ -772,11 +771,6 @@ int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
BREAK_INSTR_SIZE);
if (err)
return err;
- 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;
@@ -785,7 +779,6 @@ 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;
@@ -798,9 +791,6 @@ int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
err = text_poke_kgdb((void *)bpt->bpt_addr, bpt->saved_instr,
BREAK_INSTR_SIZE);
if (err)
- return err;
- 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;

--
2.17.1