[PATCH] x86/kgdb: return 0 from kgdb_arch_set_breakpoint

[PATCH] x86/kgdb: return 0 from kgdb_arch_set_breakpoint

[Matt Mullins]

err must be nonzero in order to reach text_poke(), which caused kgdb to
fail to set breakpoints:

	(gdb) break __x64_sys_sync
	Breakpoint 1 at 0xffffffff81288910: file ../fs/sync.c, line 124.
	(gdb) c
	Continuing.
	Warning:
	Cannot insert breakpoint 1.
	Cannot access memory at address 0xffffffff81288910

	Command aborted.

Fixes: 86a22057127d ("x86/kgdb: Avoid redundant comparison of patched code")
Signed-off-by: Matt Mullins <mmullins@fb.com>
---
 arch/x86/kernel/kgdb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index 9a8c1648fc9a..6690c5652aeb 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -758,7 +758,7 @@ int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
 		       BREAK_INSTR_SIZE);
 	bpt->type = BP_POKE_BREAKPOINT;
 
-	return err;
+	return 0;
 }
 
 int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
-- 
2.17.1

Re: [PATCH] x86/kgdb: return 0 from kgdb_arch_set_breakpoint

[Nadav Amit]

> On May 31, 2019, at 12:47 PM, Matt Mullins <mmullins@fb.com> wrote:
> 
> err must be nonzero in order to reach text_poke(), which caused kgdb to
> fail to set breakpoints:
> 
> 	(gdb) break __x64_sys_sync
> 	Breakpoint 1 at 0xffffffff81288910: file ../fs/sync.c, line 124.
> 	(gdb) c
> 	Continuing.
> 	Warning:
> 	Cannot insert breakpoint 1.
> 	Cannot access memory at address 0xffffffff81288910
> 
> 	Command aborted.
> 
> Fixes: 86a22057127d ("x86/kgdb: Avoid redundant comparison of patched code")
> Signed-off-by: Matt Mullins <mmullins@fb.com>
> ---
> arch/x86/kernel/kgdb.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
> index 9a8c1648fc9a..6690c5652aeb 100644
> --- a/arch/x86/kernel/kgdb.c
> +++ b/arch/x86/kernel/kgdb.c
> @@ -758,7 +758,7 @@ int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
> 		       BREAK_INSTR_SIZE);
> 	bpt->type = BP_POKE_BREAKPOINT;
> 
> -	return err;
> +	return 0;
> }
> 
> int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
> -- 
> 2.17.1

My bad. Thanks for fixing it.

Reviewed-by: Nadav Amit <namit@vmware.com>

[tip:x86/urgent] x86/kgdb: Return 0 from kgdb_arch_set_breakpoint()

[tip-bot for Matt Mullins]

Commit-ID:  71ab8323cc357c68985a2d6fc6cfc22b1dbbc1c3
Gitweb:     https://git.kernel.org/tip/71ab8323cc357c68985a2d6fc6cfc22b1dbbc1c3
Author:     Matt Mullins <mmullins@fb.com>
AuthorDate: Fri, 31 May 2019 12:47:54 -0700
Committer:  Borislav Petkov <bp@suse.de>
CommitDate: Wed, 12 Jun 2019 18:52:44 +0200

x86/kgdb: Return 0 from kgdb_arch_set_breakpoint()

err must be nonzero in order to reach text_poke(), which caused kgdb to
fail to set breakpoints:

  (gdb) break __x64_sys_sync
  Breakpoint 1 at 0xffffffff81288910: file ../fs/sync.c, line 124.
  (gdb) c
  Continuing.
  Warning:
  Cannot insert breakpoint 1.
  Cannot access memory at address 0xffffffff81288910

  Command aborted.

Fixes: 86a22057127d ("x86/kgdb: Avoid redundant comparison of patched code")
Signed-off-by: Matt Mullins <mmullins@fb.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Nadav Amit <namit@vmware.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190531194755.6320-1-mmullins@fb.com
---
 arch/x86/kernel/kgdb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index 9a8c1648fc9a..6690c5652aeb 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -758,7 +758,7 @@ int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
 		       BREAK_INSTR_SIZE);
 	bpt->type = BP_POKE_BREAKPOINT;
 
-	return err;
+	return 0;
 }
 
 int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)