linux-kernel - Re: [PATCH] riscv: elf: add .riscv.attributes parsing

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Message-ID: <Y73g/nkDe7Sfp9ps@spud>
Date:   Tue, 10 Jan 2023 22:04:46 +0000
From:   Conor Dooley <conor@...nel.org>
To:     Vineet Gupta <vineetg@...osinc.com>
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        palmer@...osinc.com, Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Eric Biederman <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>, Guo Ren <guoren@...nel.org>,
        Greentime Hu <greentime.hu@...ive.com>,
        Conor Dooley <conor.dooley@...rochip.com>, linux@...osinc.com,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] riscv: elf: add .riscv.attributes parsing

Hey Vineet,

While you're at it with Jess' concerns, couple nitpicks for you.
May as well say them now rather than while a v2 comes around.

On Tue, Jan 10, 2023 at 12:18:41PM -0800, Vineet Gupta wrote:

> Reported-by: kernel test robot <lkp@...el.com>  # code under CONFIG_COMPAT

You can drop this, even if it reported against a private branch AFAIU,
just like its complaints about patches. As Greg would say, LKP didn't
report a feature!

> diff --git a/arch/riscv/kernel/elf-attr.c b/arch/riscv/kernel/elf-attr.c
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2023-24 Rivos Inc.

s/-24//


> +static u64
> +decode_uleb128(unsigned char **dpp)

Surely that fits inside 80?

> +static int rv_parse_elf_attributes(struct file *f, const struct elf_phdr *phdr,
> +				   struct arch_elf_state *state)
> +{
> +	unsigned char buf[RV_ATTR_SEC_SZ];
> +	unsigned char *p;
> +	ssize_t n;
> +	int ret = 0;
> +	loff_t pos;
> +
> +	pr_debug("Section .riscv.attributes found\n");
> +
> +	/* Assume a reasonable size for now */
> +	if (phdr->p_filesz > sizeof(buf))
> +		return -ENOEXEC;
> +
> +	memset(buf, 0, RV_ATTR_SEC_SZ);
> +	pos = phdr->p_offset;
> +	n = kernel_read(f, &buf, phdr->p_filesz, &pos);
> +
> +	if (n < 0)
> +		return -EIO;
> +
> +	p = buf;
> +	p++;				/* format-version (1B) */
> +
> +	while ((p - buf) < n) {
> +

While I'm already passing through, checkpatch isn't the biggest fan of
your whitespace after open braces:

https://gist.github.com/conor-pwbot/a572e395763916c7716cab9c870df4f3

> +		unsigned char *vendor_start;
> +		u32 len;
> +
> +		/*
> +		 * Organized as "vendor" sub-section(s).
> +		 * Current only 1 specified "riscv"

Is it worth having a comment like this that may rapidly go out of date?

Cheers,
Conor.


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