linux-kernel - Re: [PATCH v4 03/19] gendwarfksyms: Add address matching

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Message-ID: <CABCJKue0rb_7V5bpuC3Zvwnv4n29=s+9J_hW5Z+6i6VPRQs9Nw@mail.gmail.com>
Date: Thu, 17 Oct 2024 10:16:37 -0700
From: Sami Tolvanen <samitolvanen@...gle.com>
To: Petr Pavlu <petr.pavlu@...e.com>
Cc: Masahiro Yamada <masahiroy@...nel.org>, Luis Chamberlain <mcgrof@...nel.org>, 
	Miguel Ojeda <ojeda@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Matthew Maurer <mmaurer@...gle.com>, Alex Gaynor <alex.gaynor@...il.com>, Gary Guo <gary@...yguo.net>, 
	Daniel Gomez <da.gomez@...sung.com>, Neal Gompa <neal@...pa.dev>, Hector Martin <marcan@...can.st>, 
	Janne Grunau <j@...nau.net>, Miroslav Benes <mbenes@...e.cz>, Asahi Linux <asahi@...ts.linux.dev>, 
	Sedat Dilek <sedat.dilek@...il.com>, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-modules@...r.kernel.org, 
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v4 03/19] gendwarfksyms: Add address matching

Hi,

On Thu, Oct 17, 2024 at 7:08 AM Petr Pavlu <petr.pavlu@...e.com> wrote:
>
> > @@ -22,9 +53,13 @@ static unsigned int for_each(const char *name, symbol_callback_t func,
> >               if (strcmp(match->name, name))
> >                       continue;
> >
> > +             /* Call func for the match, and all address matches */
> >               if (func)
> >                       func(match, data);
> >
> > +             if (match->addr.section != SHN_UNDEF)
> > +                     return __for_each_addr(match, func, data) + 1;
> > +
> >               return 1;
> >       }
>
> This change means that symbol_get() doesn't return the first matching
> symbol but the last one matched by an address.
>
> For instance:
> void foo(int a1) {}
> void bar(int a1) __attribute__((alias("foo")));
>
> The compiler produces the debug information only for foo() but
> gendwarfksyms would instead report that it processed bar() when reading
> this data, which is misleading. On the other hand, I don't immediately
> see that it would result in an incorrect CRC or symtypes output, because
> the symbols with the same address are effectively treated as one group,
> so I'm not sure if this is important or not.

Hmm, I suppose we could print out all the symbol names that matched,
but no, this doesn't affect versions or type output. I'll think about
it.

Sami