diff mbox series

[v5,14/21] modpost: remove is_shndx_special() check from section_rel(a)

Message ID 20230514152739.962109-15-masahiroy@kernel.org
State New
Headers
Series Unify <linux/export.h> and <asm/export.h>, remove EXPORT_DATA_SYMBOL(), faster TRIM_UNUSED_KSYMS |

Commit Message

Masahiro Yamada May 14, 2023, 3:27 p.m. UTC 
  This check is unneeded. Without it, sec_name() will returns the null
string "", then section_mismatch() will return immediately.

Anyway, special section indices do not appear quite often in these
loops.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 scripts/mod/modpost.c | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

Comments

Nick Desaulniers May 17, 2023, 9:23 p.m. UTC | #1 
On Sun, May 14, 2023 at 8:28 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> This check is unneeded. Without it, sec_name() will returns the null
> string "", then section_mismatch() will return immediately.
>
> Anyway, special section indices do not appear quite often in these
> loops.
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Could almost eliminate is_shndx_special after this. I think there's
only one callsite after this? (I should check with the series applied;
this patch fails to apply on mainline if that's relevant for potential
merge conflicts).

Does doing that additional work speed things up though?

> ---
>
>  scripts/mod/modpost.c | 16 ++++------------
>  1 file changed, 4 insertions(+), 12 deletions(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 0ef9d6964b6a..28db215ecc71 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -1370,7 +1370,6 @@ static int addend_mips_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
>  static void section_rela(const char *modname, struct elf_info *elf,
>                          Elf_Shdr *sechdr)
>  {
> -       Elf_Sym  *sym;
>         Elf_Rela *rela;
>         Elf_Rela r;
>         unsigned int r_sym;
> @@ -1413,11 +1412,8 @@ static void section_rela(const char *modname, struct elf_info *elf,
>                                 continue;
>                         break;
>                 }
> -               sym = elf->symtab_start + r_sym;
> -               /* Skip special sections */
> -               if (is_shndx_special(sym->st_shndx))
> -                       continue;
> -               check_section_mismatch(modname, elf, sym,
> +
> +               check_section_mismatch(modname, elf, elf->symtab_start + r_sym,
>                                        fsecndx, fromsec, r.r_offset, r.r_addend);
>         }
>  }
> @@ -1425,7 +1421,6 @@ static void section_rela(const char *modname, struct elf_info *elf,
>  static void section_rel(const char *modname, struct elf_info *elf,
>                         Elf_Shdr *sechdr)
>  {
> -       Elf_Sym *sym;
>         Elf_Rel *rel;
>         Elf_Rela r;
>         unsigned int r_sym;
> @@ -1472,11 +1467,8 @@ static void section_rel(const char *modname, struct elf_info *elf,
>                 default:
>                         fatal("Please add code to calculate addend for this architecture\n");
>                 }
> -               sym = elf->symtab_start + r_sym;
> -               /* Skip special sections */
> -               if (is_shndx_special(sym->st_shndx))
> -                       continue;
> -               check_section_mismatch(modname, elf, sym,
> +
> +               check_section_mismatch(modname, elf, elf->symtab_start + r_sym,
>                                        fsecndx, fromsec, r.r_offset, r.r_addend);
>         }
>  }
> --
> 2.39.2
>
Nick Desaulniers May 17, 2023, 9:24 p.m. UTC | #2 
On Wed, May 17, 2023 at 2:23 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Sun, May 14, 2023 at 8:28 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > This check is unneeded. Without it, sec_name() will returns the null
> > string "", then section_mismatch() will return immediately.
> >
> > Anyway, special section indices do not appear quite often in these
> > loops.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
>
> Could almost eliminate is_shndx_special after this. I think there's
> only one callsite after this? (I should check with the series applied;
> this patch fails to apply on mainline if that's relevant for potential
> merge conflicts).
>
> Does doing that additional work speed things up though?

Either way,
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

>
> > ---
> >
> >  scripts/mod/modpost.c | 16 ++++------------
> >  1 file changed, 4 insertions(+), 12 deletions(-)
> >
> > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > index 0ef9d6964b6a..28db215ecc71 100644
> > --- a/scripts/mod/modpost.c
> > +++ b/scripts/mod/modpost.c
> > @@ -1370,7 +1370,6 @@ static int addend_mips_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
> >  static void section_rela(const char *modname, struct elf_info *elf,
> >                          Elf_Shdr *sechdr)
> >  {
> > -       Elf_Sym  *sym;
> >         Elf_Rela *rela;
> >         Elf_Rela r;
> >         unsigned int r_sym;
> > @@ -1413,11 +1412,8 @@ static void section_rela(const char *modname, struct elf_info *elf,
> >                                 continue;
> >                         break;
> >                 }
> > -               sym = elf->symtab_start + r_sym;
> > -               /* Skip special sections */
> > -               if (is_shndx_special(sym->st_shndx))
> > -                       continue;
> > -               check_section_mismatch(modname, elf, sym,
> > +
> > +               check_section_mismatch(modname, elf, elf->symtab_start + r_sym,
> >                                        fsecndx, fromsec, r.r_offset, r.r_addend);
> >         }
> >  }
> > @@ -1425,7 +1421,6 @@ static void section_rela(const char *modname, struct elf_info *elf,
> >  static void section_rel(const char *modname, struct elf_info *elf,
> >                         Elf_Shdr *sechdr)
> >  {
> > -       Elf_Sym *sym;
> >         Elf_Rel *rel;
> >         Elf_Rela r;
> >         unsigned int r_sym;
> > @@ -1472,11 +1467,8 @@ static void section_rel(const char *modname, struct elf_info *elf,
> >                 default:
> >                         fatal("Please add code to calculate addend for this architecture\n");
> >                 }
> > -               sym = elf->symtab_start + r_sym;
> > -               /* Skip special sections */
> > -               if (is_shndx_special(sym->st_shndx))
> > -                       continue;
> > -               check_section_mismatch(modname, elf, sym,
> > +
> > +               check_section_mismatch(modname, elf, elf->symtab_start + r_sym,
> >                                        fsecndx, fromsec, r.r_offset, r.r_addend);
> >         }
> >  }
> > --
> > 2.39.2
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
Masahiro Yamada May 20, 2023, 1:45 p.m. UTC | #3 
On Thu, May 18, 2023 at 6:23 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Sun, May 14, 2023 at 8:28 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > This check is unneeded. Without it, sec_name() will returns the null
> > string "", then section_mismatch() will return immediately.
> >
> > Anyway, special section indices do not appear quite often in these
> > loops.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
>
> Could almost eliminate is_shndx_special after this. I think there's
> only one callsite after this?

There will be no callsite of is_shndx_special().
I will remove the definition as well.



 (I should check with the series applied;
> this patch fails to apply on mainline if that's relevant for potential
> merge conflicts).
>
> Does doing that additional work speed things up though?


I do not know.

As I wrote in the comment, special indices rarely appear in
the relocation.
I do not believe "let's bail out earlier" does not buy us.



>
> > ---
> >
> >  scripts/mod/modpost.c | 16 ++++------------
> >  1 file changed, 4 insertions(+), 12 deletions(-)
> >
> > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > index 0ef9d6964b6a..28db215ecc71 100644
> > --- a/scripts/mod/modpost.c
> > +++ b/scripts/mod/modpost.c
> > @@ -1370,7 +1370,6 @@ static int addend_mips_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
> >  static void section_rela(const char *modname, struct elf_info *elf,
> >                          Elf_Shdr *sechdr)
> >  {
> > -       Elf_Sym  *sym;
> >         Elf_Rela *rela;
> >         Elf_Rela r;
> >         unsigned int r_sym;
> > @@ -1413,11 +1412,8 @@ static void section_rela(const char *modname, struct elf_info *elf,
> >                                 continue;
> >                         break;
> >                 }
> > -               sym = elf->symtab_start + r_sym;
> > -               /* Skip special sections */
> > -               if (is_shndx_special(sym->st_shndx))
> > -                       continue;
> > -               check_section_mismatch(modname, elf, sym,
> > +
> > +               check_section_mismatch(modname, elf, elf->symtab_start + r_sym,
> >                                        fsecndx, fromsec, r.r_offset, r.r_addend);
> >         }
> >  }
> > @@ -1425,7 +1421,6 @@ static void section_rela(const char *modname, struct elf_info *elf,
> >  static void section_rel(const char *modname, struct elf_info *elf,
> >                         Elf_Shdr *sechdr)
> >  {
> > -       Elf_Sym *sym;
> >         Elf_Rel *rel;
> >         Elf_Rela r;
> >         unsigned int r_sym;
> > @@ -1472,11 +1467,8 @@ static void section_rel(const char *modname, struct elf_info *elf,
> >                 default:
> >                         fatal("Please add code to calculate addend for this architecture\n");
> >                 }
> > -               sym = elf->symtab_start + r_sym;
> > -               /* Skip special sections */
> > -               if (is_shndx_special(sym->st_shndx))
> > -                       continue;
> > -               check_section_mismatch(modname, elf, sym,
> > +
> > +               check_section_mismatch(modname, elf, elf->symtab_start + r_sym,
> >                                        fsecndx, fromsec, r.r_offset, r.r_addend);
> >         }
> >  }
> > --
> > 2.39.2
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
diff mbox series

Patch

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 0ef9d6964b6a..28db215ecc71 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1370,7 +1370,6 @@  static int addend_mips_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
 static void section_rela(const char *modname, struct elf_info *elf,
 			 Elf_Shdr *sechdr)
 {
-	Elf_Sym  *sym;
 	Elf_Rela *rela;
 	Elf_Rela r;
 	unsigned int r_sym;
@@ -1413,11 +1412,8 @@  static void section_rela(const char *modname, struct elf_info *elf,
 				continue;
 			break;
 		}
-		sym = elf->symtab_start + r_sym;
-		/* Skip special sections */
-		if (is_shndx_special(sym->st_shndx))
-			continue;
-		check_section_mismatch(modname, elf, sym,
+
+		check_section_mismatch(modname, elf, elf->symtab_start + r_sym,
 				       fsecndx, fromsec, r.r_offset, r.r_addend);
 	}
 }
@@ -1425,7 +1421,6 @@  static void section_rela(const char *modname, struct elf_info *elf,
 static void section_rel(const char *modname, struct elf_info *elf,
 			Elf_Shdr *sechdr)
 {
-	Elf_Sym *sym;
 	Elf_Rel *rel;
 	Elf_Rela r;
 	unsigned int r_sym;
@@ -1472,11 +1467,8 @@  static void section_rel(const char *modname, struct elf_info *elf,
 		default:
 			fatal("Please add code to calculate addend for this architecture\n");
 		}
-		sym = elf->symtab_start + r_sym;
-		/* Skip special sections */
-		if (is_shndx_special(sym->st_shndx))
-			continue;
-		check_section_mismatch(modname, elf, sym,
+
+		check_section_mismatch(modname, elf, elf->symtab_start + r_sym,
 				       fsecndx, fromsec, r.r_offset, r.r_addend);
 	}
 }