Re: [PATCH] x86/kbuild: enable modversions for symbols exported from asm

From	Dodji Seketeli <dodji@seketeli.org>
Newsgroups	linux.debian.kernel, linux.kernel
Subject	Re: [PATCH] x86/kbuild: enable modversions for symbols exported from asm
Date	2016-12-14 11:20 +0100
Message-ID	<sOevU-4RP-27@gated-at.bofh.it> (permalink)
References	(7 earlier) <sMCiZ-Cg-9@gated-at.bofh.it> <sO4db-71b-3@gated-at.bofh.it> <sOdJw-4BA-25@gated-at.bofh.it> <sOdTb-4EN-7@gated-at.bofh.it> <sOecx-4L4-1@gated-at.bofh.it>
Organization	Me, myself and I

Cross-posted to 2 groups.

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Dodji Seketeli <dodji@seketeli.org> a écrit:

Grr, I did paste the wrong content of t1.c and t2.c in my last message sorry.

Here are the correct ones:

$ cat t1.c
struct s1;
struct s2 {
	int i;
};
struct s3 {
	struct s1 *ptr1;
	struct s2 *ptr2;
};

void foo(struct s3* s __attribute__((unused)))
{
}

$ cat t2.c
struct s1 {
	int j;
};
struct s2;
struct s3 {
	struct s1 *ptr1;
	struct s2 *ptr2;
};

void foo(struct s3* s __attribute__((unused)))
{
}

$ gcc -g -c t1.c
$ gcc -g -c t2.c
$ abidiff t1.o t2.o
$ 

The rest of my previous message still applies :-)

> So, as you see here, abidiff considers t1.o and t2.o has having the same
> ABI, so it considers the two foo functions to be equivalent.
>
>> The types are the same, but their visibility in the different
>> compilation units differs.
>
> I see, for genksyms, the order of declarations matters, especially when
> forward declarations are involved.
>
> Libabigail does a "whole binary" analysis of types.
>
> So, consider the point of use of the type 'struct s1*'.  Even if 'struct
> s' is just forward-declared at that point, the declaration of struct s1
> is "resolved" to its definition.  Even if the definition comes later in
> the binary.
>
> In other words, if struct s1 is defined in the binary, you'll never have
> that "struct s1 {UNKNOWN} *ptr1;" that you see in genksyms's
> representation.

Thanks.

-- 
		Dodji

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Re: [PATCH] x86/kbuild: enable modversions for symbols exported from  asm Michal Marek <mmarek@suse.com> - 2016-12-14 00:10 +0100
  Re: [PATCH] x86/kbuild: enable modversions for symbols exported from asm Dodji Seketeli <dodji@seketeli.org> - 2016-12-14 10:20 +0100
    Re: [PATCH] x86/kbuild: enable modversions for symbols exported from  asm Michal Marek <mmarek@suse.com> - 2016-12-14 10:40 +0100
      Re: [PATCH] x86/kbuild: enable modversions for symbols exported from  asm Michal Marek <mmarek@suse.com> - 2016-12-14 11:00 +0100
      Re: [PATCH] x86/kbuild: enable modversions for symbols exported from asm Dodji Seketeli <dodji@seketeli.org> - 2016-12-14 11:00 +0100
        Re: [PATCH] x86/kbuild: enable modversions for symbols exported from  asm Michal Marek <mmarek@suse.com> - 2016-12-14 11:10 +0100
          Re: [PATCH] x86/kbuild: enable modversions for symbols exported from asm Dodji Seketeli <dodji@seketeli.org> - 2016-12-14 11:20 +0100
            Re: [PATCH] x86/kbuild: enable modversions for symbols exported from  asm Michal Marek <mmarek@suse.com> - 2016-12-14 11:40 +0100
        Re: [PATCH] x86/kbuild: enable modversions for symbols exported from asm Dodji Seketeli <dodji@seketeli.org> - 2016-12-14 11:20 +0100

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