linux-kernel - Re: [PATCH 1/1] arch:hexagon/powerpc: use KSYM_NAME

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Date:   Mon, 29 May 2023 16:50:45 +0200
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     maninder1.s@...sung.com,
        "keescook@...omium.org" <keescook@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Cc:     "bcain@...cinc.com" <bcain@...cinc.com>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "npiggin@...il.com" <npiggin@...il.com>,
        "christophe.leroy@...roup.eu" <christophe.leroy@...roup.eu>,
        "nathanl@...ux.ibm.com" <nathanl@...ux.ibm.com>,
        "ustavoars@...nel.org" <ustavoars@...nel.org>,
        "alex.gaynor@...il.com" <alex.gaynor@...il.com>,
        "gary@...yguo.net" <gary@...yguo.net>,
        "ojeda@...nel.org" <ojeda@...nel.org>,
        "pmladek@...e.com" <pmladek@...e.com>,
        "linux-hexagon@...r.kernel.org" <linux-hexagon@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        Onkarnath <onkarnath.1@...sung.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>
Subject: Re: [PATCH 1/1] arch:hexagon/powerpc: use KSYM_NAME_LEN in array size

On Mon, May 29, 2023 at 1:08 PM Maninder Singh <maninder1.s@...sung.com> wrote:
>
> I Will add co-developed-by` tag.
> because this change was identified while we were working on kallsyms some time back.
> https://lore.kernel.org/lkml/YonTOL4zC4CytVrn@infradead.org/t/
>
> this patch set is pending and we will start working on that again, so i thought better
> to send bugfix first.

Sounds good to me!

(Fixed Wedson's email address)

> Yes, I think second buffer was not related to kallsyms, so I have not touched that.

Kees: what is the current stance on `[static N]` parameters? Something like:

    const char *kallsyms_lookup(unsigned long addr,
                                unsigned long *symbolsize,
                                unsigned long *offset,
    -                           char **modname, char *namebuf);
    +                           char **modname, char namebuf[static
KSYM_NAME_LEN]);

makes the compiler complain about cases like these (even if trivial):

    arch/powerpc/xmon/xmon.c:1711:10: error: array argument is too small;
        contains 128 elements, callee requires at least 512
[-Werror,-Warray-bounds]
            name = kallsyms_lookup(pc, &size, &offset, NULL, tmpstr);
                 ^                                           ~~~~~~
    ./include/linux/kallsyms.h:86:29: note: callee declares array
parameter as static here
            char **modname, char namebuf[static KSYM_NAME_LEN]);
                                 ^      ~~~~~~~~~~~~~~~~~~~~~~

But I only see 2 files in the kernel using `[static N]` (from 2020 and
2021). Should something else be used instead (e.g. `__counted_by`),
even if constexpr-sized?.

Also, I went through the other callers to `kallsyms_lookup` to see
other issues -- one I am not sure about is `fetch_store_symstring` in
`kernel/trace/trace_probe_tmpl.h`. Steven/Masami: is that "with max
length" in the function docs enough? Is it 0xffff?

Thanks!

Cheers,
Miguel