linux-kernel - Re: [PATCH] x86/kgdb: return 0 from kgdb_arch_set

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Date:   Fri, 31 May 2019 19:51:44 +0000
From:   Nadav Amit <namit@...are.com>
To:     Matt Mullins <mmullins@...com>
CC:     Borislav Petkov <bp@...en8.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "luto@...nel.org" <luto@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Douglas Anderson <dianders@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/kgdb: return 0 from kgdb_arch_set_breakpoint

> On May 31, 2019, at 12:47 PM, Matt Mullins <mmullins@...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@...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@...are.com>