2019-05-31 19:50:28

by Matt Mullins

Subject: [PATCH] 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 <[email protected]>
---
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

2019-05-31 19:53:05

by Nadav Amit

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

> On May 31, 2019, at 12:47 PM, Matt Mullins <[email protected]> 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 <[email protected]>
> ---
> 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 <[email protected]>

2019-06-12 18:08:04

by tip-bot for Vasyl Gomonovych

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

Commit-ID: 71ab8323cc357c68985a2d6fc6cfc22b1dbbc1c3
Gitweb: https://git.kernel.org/tip/71ab8323cc357c68985a2d6fc6cfc22b1dbbc1c3
Author: Matt Mullins <[email protected]>
AuthorDate: Fri, 31 May 2019 12:47:54 -0700
Committer: Borislav Petkov <[email protected]>
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 <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Nadav Amit <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Christophe Leroy <[email protected]>
Cc: Daniel Thompson <[email protected]>
Cc: Douglas Anderson <[email protected]>
Cc: "Gustavo A. R. Silva" <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "Peter Zijlstra (Intel)" <[email protected]>
Cc: Rick Edgecombe <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
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)