linux-kernel - Re: [patches] [PATCH 1/9] RISC-V: Init and Halt Code

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Date:   Fri, 7 Jul 2017 14:58:55 +0200
From:   Jonathan Neuschäfer <j.neuschaefer@....net>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     j.neuschaefer@....net, patches@...ups.riscv.org,
        peterz@...radead.org, mingo@...hat.com, mcgrof@...nel.org,
        viro@...iv.linux.org.uk, sfr@...b.auug.org.au,
        nicolas.dichtel@...nd.com, rmk+kernel@...linux.org.uk,
        msalter@...hat.com, tklauser@...tanz.ch, will.deacon@....com,
        james.hogan@...tec.com, paul.gortmaker@...driver.com,
        linux@...ck-us.net, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, albert@...ive.com
Subject: Re: [patches] [PATCH 1/9] RISC-V: Init and Halt Code

On Thu, Jul 06, 2017 at 03:34:39PM -0700, Palmer Dabbelt wrote:
> On Tue, 04 Jul 2017 14:54:01 PDT (-0700), j.neuschaefer@....net wrote:
[...]
> >> +#define DO_ERROR_INFO(name, signo, code, str)				\
> >> +asmlinkage void name(struct pt_regs *regs)				\
> >> +{									\
> >> +	do_trap_error(regs, signo, code, regs->sepc, "Oops - " str);	\
> >> +}
> >> +
> >> +DO_ERROR_INFO(do_trap_unknown,
> >> +	SIGILL, ILL_ILLTRP, "unknown exception");
> >> +DO_ERROR_INFO(do_trap_insn_misaligned,
> >> +	SIGBUS, BUS_ADRALN, "instruction address misaligned");
> >> +DO_ERROR_INFO(do_trap_insn_fault,
> >> +	SIGBUS, BUS_ADRALN, "instruction access fault");
> >
> > For a general instruction access fault, BUS_ADRALN seems wrong. A
> > variant of SIGSEGV seems more appropriate, IMHO.
> 
> How does this look?
> 
>   diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
>   index 4c693b5b9980..3ce9ac6e736e 100644
>   --- a/arch/riscv/kernel/traps.c
>   +++ b/arch/riscv/kernel/traps.c
>   @@ -112,7 +112,7 @@ DO_ERROR_INFO(do_trap_unknown,
>    DO_ERROR_INFO(do_trap_insn_misaligned,
>           SIGBUS, BUS_ADRALN, "instruction address misaligned");
>    DO_ERROR_INFO(do_trap_insn_fault,
>   -       SIGBUS, BUS_ADRALN, "instruction access fault");
>   +       SIGBUS, SEGV_ACCERR, "instruction access fault");
>    DO_ERROR_INFO(do_trap_insn_illegal,
>           SIGILL, ILL_ILLOPC, "illegal instruction");
>    DO_ERROR_INFO(do_trap_load_misaligned,

I'm not familiar with the trap handling infrastructure, but looking at
include/uapi/asm-generic/siginfo.h, SEGV_ACCERR would alias to
BUS_ADRERR (both are defined as (__SI_FAULT|2)). So if you use SEGV_*,
you need to use SIGSEGV, too.

With DO_ERROR_INFO(..., SIGSEGV, SEGV_ACCERR, ...); it looks good to me.


Jonathan Neuschäfer

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