linux-kernel - Re: [PATCH V10 14/22] LoongArch: Add signal handling support

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Date:   Mon, 16 May 2022 11:51:42 +0800
From:   WANG Xuerui <kernel@...0n.name>
To:     Huacai Chen <chenhuacai@...il.com>, WANG Xuerui <kernel@...0n.name>
Cc:     Huacai Chen <chenhuacai@...ngson.cn>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Airlie <airlied@...ux.ie>,
        Jonathan Corbet <corbet@....net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Yanteng Si <siyanteng@...ngson.cn>,
        Guo Ren <guoren@...nel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Eric Biederman <ebiederm@...ssion.com>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH V10 14/22] LoongArch: Add signal handling support

Hi,

On 5/15/22 21:48, Huacai Chen wrote:
> diff --git a/arch/loongarch/include/uapi/asm/sigcontext.h b/arch/loongarch/include/uapi/asm/sigcontext.h
> new file mode 100644
> index 000000000000..efeb8b3f8236
> --- /dev/null
> +++ b/arch/loongarch/include/uapi/asm/sigcontext.h
> @@ -0,0 +1,63 @@
> +/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
> +/*
> + * Author: Hanlu Li <lihanlu@...ngson.cn>
> + *         Huacai Chen <chenhuacai@...ngson.cn>
> + *
> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
> + */
> +#ifndef _UAPI_ASM_SIGCONTEXT_H
> +#define _UAPI_ASM_SIGCONTEXT_H
> +
> +#include <linux/types.h>
> +#include <linux/posix_types.h>
> +
> +/* FP context was used */
> +#define USED_FP                      (1 << 0)
> +/* Load/Store access flags for address error */
> +#define ADRERR_RD            (1 << 30)
> +#define ADRERR_WR            (1 << 31)
>> I've searched GitHub globally, and my local glibc checkout, for usages
>> of these 3 constants, and there seems to be none; please consider
>> removing these if doable. We don't want cruft in uapi right from the
>> beginning.
> They will be used in our glibc, I promise.
Okay then. Seems simple enough, and from my quick grepping these appear 
to be original creations -- not carried over from somewhere else, so 
it's already highly likely that some of the userland tools need these 
anyway, just not released yet.
>>> +
>>> +struct sigcontext {
>>> +     __u64   sc_pc;
>>> +     __u64   sc_regs[32];
>>> +     __u32   sc_flags;
>>> +     __u64   sc_extcontext[0] __attribute__((__aligned__(16)));
>>> +};
>>> +
>>> +#define CONTEXT_INFO_ALIGN   16
>>> +struct _ctxinfo {
>>> +     __u32   magic;
>>> +     __u32   size;
>>> +     __u64   padding;        /* padding to 16 bytes */
>>> +};
>>> +
>>> +/* FPU context */
>>> +#define FPU_CTX_MAGIC                0x46505501
>>> +#define FPU_CTX_ALIGN                8
>>> +struct fpu_context {
>>> +     __u64   regs[32];
>>> +     __u64   fcc;
>>> +     __u32   fcsr;
>>> +};
>> The 3 structs above should already see usage downstream (glibc and other
>> low-level friends), so they probably shouldn't be touched by now. At
>> least I can't see problems.
>>> +
>>> +/* LSX context */
>>> +#define LSX_CTX_MAGIC                0x53580001
>>> +#define LSX_CTX_ALIGN                16
>>> +struct lsx_context {
>>> +     __u64   regs[2*32];
>>> +     __u64   fcc;
>>> +     __u32   fcsr;
>>> +     __u32   vcsr;
>>> +};
>>> +
>>> +/* LASX context */
>>> +#define LASX_CTX_MAGIC               0x41535801
>>> +#define LASX_CTX_ALIGN               32
>>> +struct lasx_context {
>>> +     __u64   regs[4*32];
>>> +     __u64   fcc;
>>> +     __u32   fcsr;
>>> +     __u32   vcsr;
>>> +};
>> Do we want to freeze the LSX/LASX layout this early, before any detail
>> of said extension are published? We'll need to update kernel later
>> anyway, so I'd recommend leaving them out for the initial bring-up.
> Yes, they are freezed.
Okay too, I remember these are the same values as in the old world, so 
it should be easy to support both worlds at least in this regard.
>>> +
>>> +#endif /* _UAPI_ASM_SIGCONTEXT_H */
Then I have no problems with this patch then ;-)