2020-08-12 17:59:30

by Kristen Carlson Accardi

Subject: [PATCH] objtool: support symtab_shndx during dump

When getting the symbol index number, make sure to use the
extended symbol table information in order to support symbol
index's greater than 64K.

Signed-off-by: Kristen Carlson Accardi <[email protected]>
---
tools/objtool/orc_dump.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/tools/objtool/orc_dump.c b/tools/objtool/orc_dump.c
index fca46e006fc2..cf835069724a 100644
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -74,7 +74,8 @@ int orc_dump(const char *_objname)
GElf_Rela rela;
GElf_Sym sym;
Elf_Data *data, *symtab = NULL, *rela_orc_ip = NULL;
-
+ Elf_Data *xsymtab = NULL;
+ Elf32_Word shndx;

objname = _objname;

@@ -138,6 +139,8 @@ int orc_dump(const char *_objname)
orc_ip_addr = sh.sh_addr;
} else if (!strcmp(name, ".rela.orc_unwind_ip")) {
rela_orc_ip = data;
+ } else if (!strcmp(name, ".symtab_shndx")) {
+ xsymtab = data;
}
}

@@ -157,13 +160,22 @@ int orc_dump(const char *_objname)
return -1;
}

- if (!gelf_getsym(symtab, GELF_R_SYM(rela.r_info), &sym)) {
- WARN_ELF("gelf_getsym");
+ if (!gelf_getsymshndx(symtab, xsymtab,
+ GELF_R_SYM(rela.r_info),
+ &sym, &shndx)) {
+ WARN_ELF("gelf_getsymshndx");
return -1;
}

if (GELF_ST_TYPE(sym.st_info) == STT_SECTION) {
- scn = elf_getscn(elf, sym.st_shndx);
+ if ((sym.st_shndx > SHN_UNDEF &&
+ sym.st_shndx < SHN_LORESERVE) ||
+ (xsymtab && sym.st_shndx == SHN_XINDEX)) {
+ if (sym.st_shndx != SHN_XINDEX)
+ shndx = sym.st_shndx;
+ }
+
+ scn = elf_getscn(elf, shndx);
if (!scn) {
WARN_ELF("elf_getscn");
return -1;
--
2.20.1

2020-09-03 15:15:24

by Miroslav Benes

Subject: Re: [PATCH] objtool: support symtab_shndx during dump

On Wed, 12 Aug 2020, Kristen Carlson Accardi wrote:

> When getting the symbol index number, make sure to use the
> extended symbol table information in order to support symbol
> index's greater than 64K.
>
> Signed-off-by: Kristen Carlson Accardi <[email protected]>

Reviewed-by: Miroslav Benes <[email protected]>

M

2020-09-03 15:36:55

by Josh Poimboeuf

Subject: Re: [PATCH] objtool: support symtab_shndx during dump

On Wed, Aug 12, 2020 at 10:57:11AM -0700, Kristen Carlson Accardi wrote:
> When getting the symbol index number, make sure to use the
> extended symbol table information in order to support symbol
> index's greater than 64K.

"indexes"

> if (GELF_ST_TYPE(sym.st_info) == STT_SECTION) {
> - scn = elf_getscn(elf, sym.st_shndx);
> + if ((sym.st_shndx > SHN_UNDEF &&
> + sym.st_shndx < SHN_LORESERVE) ||
> + (xsymtab && sym.st_shndx == SHN_XINDEX)) {
> + if (sym.st_shndx != SHN_XINDEX)
> + shndx = sym.st_shndx;

The sym.st_shndx checks are redundant, if 'sym.st_shndx == SHN_XINDEX'
then 'sym.st_shndx != SHN_XINDEX' can't be true.

Actually I think this can be even further simplified to something like

if (!shndx)
shndx = sym.st_shndx;

--
Josh

2020-09-04 07:57:56

by Miroslav Benes

Subject: Re: [PATCH] objtool: support symtab_shndx during dump

On Thu, 3 Sep 2020, Josh Poimboeuf wrote:

> On Wed, Aug 12, 2020 at 10:57:11AM -0700, Kristen Carlson Accardi wrote:
>
> > if (GELF_ST_TYPE(sym.st_info) == STT_SECTION) {
> > - scn = elf_getscn(elf, sym.st_shndx);
> > + if ((sym.st_shndx > SHN_UNDEF &&
> > + sym.st_shndx < SHN_LORESERVE) ||
> > + (xsymtab && sym.st_shndx == SHN_XINDEX)) {
> > + if (sym.st_shndx != SHN_XINDEX)
> > + shndx = sym.st_shndx;
>
> The sym.st_shndx checks are redundant, if 'sym.st_shndx == SHN_XINDEX'
> then 'sym.st_shndx != SHN_XINDEX' can't be true.

It is probably a copy-paste from read_symbols() in elf.c, where the logic
is different.

> Actually I think this can be even further simplified to something like
>
> if (!shndx)
> shndx = sym.st_shndx;

This relies on the fact that gelf_getsymshndx() always initializes shndx,
no? I think it would be better to initialize it in orc_dump() too. Safer
and easier to read. It applies to Kristen's patch as well. I missed that.

Miroslav

2020-09-04 14:21:21

by Josh Poimboeuf

Subject: Re: [PATCH] objtool: support symtab_shndx during dump

On Fri, Sep 04, 2020 at 09:54:29AM +0200, Miroslav Benes wrote:
> On Thu, 3 Sep 2020, Josh Poimboeuf wrote:
>
> > On Wed, Aug 12, 2020 at 10:57:11AM -0700, Kristen Carlson Accardi wrote:
> >
> > > if (GELF_ST_TYPE(sym.st_info) == STT_SECTION) {
> > > - scn = elf_getscn(elf, sym.st_shndx);
> > > + if ((sym.st_shndx > SHN_UNDEF &&
> > > + sym.st_shndx < SHN_LORESERVE) ||
> > > + (xsymtab && sym.st_shndx == SHN_XINDEX)) {
> > > + if (sym.st_shndx != SHN_XINDEX)
> > > + shndx = sym.st_shndx;
> >
> > The sym.st_shndx checks are redundant, if 'sym.st_shndx == SHN_XINDEX'
> > then 'sym.st_shndx != SHN_XINDEX' can't be true.
>
> It is probably a copy-paste from read_symbols() in elf.c, where the logic
> is different.

Yeah.

> > Actually I think this can be even further simplified to something like
> >
> > if (!shndx)
> > shndx = sym.st_shndx;
>
> This relies on the fact that gelf_getsymshndx() always initializes shndx,
> no? I think it would be better to initialize it in orc_dump() too. Safer
> and easier to read. It applies to Kristen's patch as well. I missed that.

Agreed.

--
Josh