Re: [PATCH 4.4.y-cip] signal/m68k: Use force_sigsegv(SIGSEGV) in fpsp040_die

[Ulrich Hecht <uli@fpond.eu>]

Sorry, I saw these five minutes too late. Applied for the next release.

CU
Uli

> On 02/13/2025 8:22 AM CET Finn Thain <fthain@linux-m68k.org> wrote:
> 
>  
> From: "Eric W. Biederman" <ebiederm@xmission.com>
> 
> [ Upstream commit a3616a3c02722d1edb95acc7fceade242f6553ba ]
> 
> In the fpsp040 code when copyin or copyout fails call
> force_sigsegv(SIGSEGV) instead of do_exit(SIGSEGV).
> 
> This solves a couple of problems.  Because do_exit embeds the ptrace
> stop PTRACE_EVENT_EXIT a complete stack frame needs to be present for
> that to work correctly.  There is always the information needed for a
> ptrace stop where get_signal is called.  So exiting with a signal
> solves the ptrace issue.
> 
> Further exiting with a signal ensures that all of the threads in a
> process are killed not just the thread that malfunctioned.  Which
> avoids confusing userspace.
> 
> To make force_sigsegv(SIGSEGV) work in fpsp040_die modify the code to
> save all of the registers and jump to ret_from_exception (which
> ultimately calls get_signal) after fpsp040_die returns.
> 
> v2: Updated the branches to use gas's pseudo ops that automatically
>     calculate the best branch instruction to use for the purpose.
> 
> v1: https://lkml.kernel.org/r/87a6m8kgtx.fsf_-_@disp2133
> Link: https://lkml.kernel.org/r/87tukghjfs.fsf_-_@disp2133
> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
> [ Pass 'current' to force_sigsegv() as was done prior to v5.3 ]
> Signed-off-by: Finn Thain <fthain@linux-m68k.org>
> ---
>  arch/m68k/fpsp040/skeleton.S | 3 ++-
>  arch/m68k/kernel/traps.c     | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/m68k/fpsp040/skeleton.S b/arch/m68k/fpsp040/skeleton.S
> index 31a9c634c81e..081922c72daa 100644
> --- a/arch/m68k/fpsp040/skeleton.S
> +++ b/arch/m68k/fpsp040/skeleton.S
> @@ -502,7 +502,8 @@ in_ea:
>  	.section .fixup,"ax"
>  	.even
>  1:
> -	jbra	fpsp040_die
> +	jbsr	fpsp040_die
> +	jbra	.Lnotkern
>  
>  	.section __ex_table,"a"
>  	.align	4
> diff --git a/arch/m68k/kernel/traps.c b/arch/m68k/kernel/traps.c
> index 35f706d836c5..c6f18dc5884b 100644
> --- a/arch/m68k/kernel/traps.c
> +++ b/arch/m68k/kernel/traps.c
> @@ -1155,7 +1155,7 @@ asmlinkage void set_esp0(unsigned long ssp)
>   */
>  asmlinkage void fpsp040_die(void)
>  {
> -	do_exit(SIGSEGV);
> +	force_sigsegv(SIGSEGV, current);
>  }
>  
>  #ifdef CONFIG_M68KFPU_EMU