* [rfc, v2] Fix ELF synthetic symbol size bug (affects PPC64)
[not found] <200711052014.lA5KEiTm019854@d12av02.megacenter.de.ibm.com>
@ 2007-11-06 21:33 ` Ulrich Weigand
2007-11-06 21:44 ` Daniel Jacobowitz
0 siblings, 1 reply; 6+ messages in thread
From: Ulrich Weigand @ 2007-11-06 21:33 UTC (permalink / raw)
To: gdb-patches, binutils, amodra
Hello,
in http://sourceware.org/ml/gdb-patches/2007-11/msg00080.html I wrote:
> This is particularly problematic because on PPC64, the "regular"
> symbol for a function points to the function descriptor, and the
> actual code of the function is only identified by a synthetic
> symbol. This means we basically do not get any size information
> for functions at all.
>
> Interestingly enough, BFD seems to actually have the size of the
> function code available; it's just not possible right now to pass
> that information through the "synthetic symbol" interface ...
Alan suggested a way to pass that information: have the udata.p
member of the synthetic symbol point back to the full ELF symbol
structure of the original symbol used to derive the synthetic
symbol from. The patch below implements this.
Tested (GDB) on powerpc64-linux, fixes another 12 FAILs on top
of the ones already fixed by the original patch.
Is the bfd part OK?
Bye,
Ulrich
bfd/ChangeLog:
* elf.c (_bfd_elf_get_synthetic_symtab): Set udata.p of synthetic
symbol to point back to the ELF symbol it was derived from.
* elf64-ppc.c (ppc64_elf_get_synthetic_symtab): Likewise.
gdb/ChangeLog:
* elfread.c (ST_REGULAR, ST_DYNAMIC, ST_SYNTHETIC): New defines.
(elf_symtab_read): Rename DYNAMIC argument to TYPE. Do not access
ELF-private symbol data when processing synthetic symbols.
(elf_symfile_read): Pass TYPE argument to elf_symtab_read.
diff -urNp gdb-orig/bfd/elf64-ppc.c gdb-head/bfd/elf64-ppc.c
--- gdb-orig/bfd/elf64-ppc.c 2007-11-06 20:31:59.661739207 +0100
+++ gdb-head/bfd/elf64-ppc.c 2007-11-06 20:17:17.399685878 +0100
@@ -2959,6 +2959,9 @@ ppc64_elf_get_synthetic_symtab (bfd *abf
len = strlen (syms[i]->name);
memcpy (names, syms[i]->name, len + 1);
names += len + 1;
+ /* Have udata.p point back to the original symbol this
+ synthetic symbol was derived from. */
+ s->udata.p = syms[i];
s++;
}
}
@@ -3046,6 +3049,9 @@ ppc64_elf_get_synthetic_symtab (bfd *abf
len = strlen (syms[i]->name);
memcpy (names, syms[i]->name, len + 1);
names += len + 1;
+ /* Have udata.p point back to the original symbol this
+ synthetic symbol was derived from. */
+ s->udata.p = syms[i];
s++;
}
}
diff -urNp gdb-orig/bfd/elf.c gdb-head/bfd/elf.c
--- gdb-orig/bfd/elf.c 2007-11-06 20:31:59.687735465 +0100
+++ gdb-head/bfd/elf.c 2007-11-06 20:17:56.179085383 +0100
@@ -8700,6 +8700,9 @@ _bfd_elf_get_synthetic_symtab (bfd *abfd
names += len;
memcpy (names, "@plt", sizeof ("@plt"));
names += sizeof ("@plt");
+ /* Have udata.p point back to the original symbol this
+ synthetic symbol was derived from. */
+ s->udata.p = *p->sym_ptr_ptr;
++n;
}
diff -urNp gdb-orig/gdb/elfread.c gdb-head/gdb/elfread.c
--- gdb-orig/gdb/elfread.c 2007-11-06 21:10:11.292646086 +0100
+++ gdb-head/gdb/elfread.c 2007-11-06 20:37:46.532472318 +0100
@@ -180,14 +180,14 @@ record_minimal_symbol (char *name, CORE_
SYNOPSIS
- void elf_symtab_read (struct objfile *objfile, int dynamic,
+ void elf_symtab_read (struct objfile *objfile, int type,
long number_of_symbols, asymbol **symbol_table)
DESCRIPTION
Given an objfile, a symbol table, and a flag indicating whether the
- symbol table contains dynamic symbols, add all the global function
- and data symbols to the minimal symbol table.
+ symbol table contains regular, dynamic, or synthetic symbols, add all
+ the global function and data symbols to the minimal symbol table.
In stabs-in-ELF, as implemented by Sun, there are some local symbols
defined in the ELF symbol table, which can be used to locate
@@ -197,8 +197,12 @@ record_minimal_symbol (char *name, CORE_
*/
+#define ST_REGULAR 0
+#define ST_DYNAMIC 1
+#define ST_SYNTHETIC 2
+
static void
-elf_symtab_read (struct objfile *objfile, int dynamic,
+elf_symtab_read (struct objfile *objfile, int type,
long number_of_symbols, asymbol **symbol_table)
{
long storage_needed;
@@ -235,7 +239,7 @@ elf_symtab_read (struct objfile *objfile
continue;
offset = ANOFFSET (objfile->section_offsets, sym->section->index);
- if (dynamic
+ if (type == ST_DYNAMIC
&& sym->section == &bfd_und_section
&& (sym->flags & BSF_FUNCTION))
{
@@ -284,7 +288,7 @@ elf_symtab_read (struct objfile *objfile
/* If it is a nonstripped executable, do not enter dynamic
symbols, as the dynamic symbol table is usually a subset
of the main symbol table. */
- if (dynamic && !stripped)
+ if (type == ST_DYNAMIC && !stripped)
continue;
if (sym->flags & BSF_FILE)
{
@@ -324,8 +328,11 @@ elf_symtab_read (struct objfile *objfile
{
/* This is a hack to get the minimal symbol type
right for Irix 5, which has absolute addresses
- with special section indices for dynamic symbols. */
- unsigned short shndx =
+ with special section indices for dynamic symbols.
+
+ NOTE: uweigand/20071105: Synthetic symbols do not
+ have an ELF-private part, so do not touch those. */
+ unsigned short shndx = type == ST_SYNTHETIC ? 0 :
((elf_symbol_type *) sym)->internal_elf_sym.st_shndx;
switch (shndx)
@@ -484,11 +491,22 @@ elf_symtab_read (struct objfile *objfile
msym = record_minimal_symbol
((char *) sym->name, symaddr,
ms_type, sym->section, objfile);
+
if (msym)
{
/* Pass symbol size field in via BFD. FIXME!!! */
- unsigned long size = ((elf_symbol_type *) sym)->internal_elf_sym.st_size;
- MSYMBOL_SIZE(msym) = size;
+ elf_symbol_type *elf_sym;
+
+ /* NOTE: uweigand/20071105: A synthetic symbol does not have an
+ ELF-private part. However, its udata.p entry points back to
+ the original ELF symbol it was derived from. Get the size
+ from that symbol. */
+ if (type != ST_SYNTHETIC)
+ elf_sym = (elf_symbol_type *) sym;
+ else
+ elf_sym = (elf_symbol_type *) sym->udata.p;
+
+ MSYMBOL_SIZE(msym) = elf_sym->internal_elf_sym.st_size;
}
if (msym != NULL)
msym->filename = filesymname;
@@ -569,7 +587,7 @@ elf_symfile_read (struct objfile *objfil
error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile->obfd),
bfd_errmsg (bfd_get_error ()));
- elf_symtab_read (objfile, 0, symcount, symbol_table);
+ elf_symtab_read (objfile, ST_REGULAR, symcount, symbol_table);
}
/* Add the dynamic symbols. */
@@ -587,7 +605,7 @@ elf_symfile_read (struct objfile *objfil
error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile->obfd),
bfd_errmsg (bfd_get_error ()));
- elf_symtab_read (objfile, 1, dynsymcount, dyn_symbol_table);
+ elf_symtab_read (objfile, ST_DYNAMIC, dynsymcount, dyn_symbol_table);
}
/* Add synthetic symbols - for instance, names for any PLT entries. */
@@ -605,7 +623,7 @@ elf_symfile_read (struct objfile *objfil
for (i = 0; i < synthcount; i++)
synth_symbol_table[i] = synthsyms + i;
make_cleanup (xfree, synth_symbol_table);
- elf_symtab_read (objfile, 0, synthcount, synth_symbol_table);
+ elf_symtab_read (objfile, ST_SYNTHETIC, synthcount, synth_symbol_table);
}
/* Install any minimal symbols that have been collected as the current
--
Dr. Ulrich Weigand
GNU Toolchain for Linux on System z and Cell BE
Ulrich.Weigand@de.ibm.com
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [rfc, v2] Fix ELF synthetic symbol size bug (affects PPC64)
2007-11-06 21:33 ` [rfc, v2] Fix ELF synthetic symbol size bug (affects PPC64) Ulrich Weigand
@ 2007-11-06 21:44 ` Daniel Jacobowitz
2007-11-12 3:29 ` Alan Modra
0 siblings, 1 reply; 6+ messages in thread
From: Daniel Jacobowitz @ 2007-11-06 21:44 UTC (permalink / raw)
To: Ulrich Weigand; +Cc: gdb-patches, binutils, amodra
On Tue, Nov 06, 2007 at 10:33:04PM +0100, Ulrich Weigand wrote:
> Alan suggested a way to pass that information: have the udata.p
> member of the synthetic symbol point back to the full ELF symbol
> structure of the original symbol used to derive the synthetic
> symbol from. The patch below implements this.
>
> Tested (GDB) on powerpc64-linux, fixes another 12 FAILs on top
> of the ones already fixed by the original patch.
>
> Is the bfd part OK?
The elf.c part of this does not make sense to me. Why should we have
the same size as that symbol? The @plt entry is only a couple of
instructions. To figure out its size you need to ask the backend
plt_sym_val routine.
--
Daniel Jacobowitz
CodeSourcery
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [rfc, v2] Fix ELF synthetic symbol size bug (affects PPC64)
2007-11-06 21:44 ` Daniel Jacobowitz
@ 2007-11-12 3:29 ` Alan Modra
2007-11-12 15:37 ` [rfc, v3] " Ulrich Weigand
0 siblings, 1 reply; 6+ messages in thread
From: Alan Modra @ 2007-11-12 3:29 UTC (permalink / raw)
To: Ulrich Weigand, binutils
On Tue, Nov 06, 2007 at 04:44:02PM -0500, Daniel Jacobowitz wrote:
> > Is the bfd part OK?
>
> The elf.c part of this does not make sense to me. Why should we have
> the same size as that symbol? The @plt entry is only a couple of
> instructions. To figure out its size you need to ask the backend
> plt_sym_val routine.
Agreed. The ppc64 part is OK. I'm committing the following to fix
a bug I noticed in the elf.c get_synthetic_symtab function. I also
set udata.p to NULL as this may be all that's needed with a modified
version of Ulrich's patch.
* elf.c (_bfd_elf_get_synthetic_symtab): Only bump the symbol
pointer when we have a valid symbol. Init udata.p to NULL.
Index: bfd/elf.c
===================================================================
RCS file: /cvs/src/src/bfd/elf.c,v
retrieving revision 1.422
diff -u -p -r1.422 elf.c
--- bfd/elf.c 25 Oct 2007 00:40:34 -0000 1.422
+++ bfd/elf.c 12 Nov 2007 03:21:58 -0000
@@ -8678,7 +8678,7 @@ _bfd_elf_get_synthetic_symtab (bfd *abfd
names = (char *) (s + count);
p = relplt->relocation;
n = 0;
- for (i = 0; i < count; i++, s++, p++)
+ for (i = 0; i < count; i++, p++)
{
size_t len;
bfd_vma addr;
@@ -8695,12 +8695,13 @@ _bfd_elf_get_synthetic_symtab (bfd *abfd
s->section = plt;
s->value = addr - plt->vma;
s->name = names;
+ s->udata.p = NULL;
len = strlen ((*p->sym_ptr_ptr)->name);
memcpy (names, (*p->sym_ptr_ptr)->name, len);
names += len;
memcpy (names, "@plt", sizeof ("@plt"));
names += sizeof ("@plt");
- ++n;
+ ++s, ++n;
}
return n;
--
Alan Modra
Australia Development Lab, IBM
^ permalink raw reply [flat|nested] 6+ messages in thread
* [rfc, v3] Fix ELF synthetic symbol size bug (affects PPC64)
2007-11-12 3:29 ` Alan Modra
@ 2007-11-12 15:37 ` Ulrich Weigand
2007-11-12 15:45 ` Daniel Jacobowitz
2007-11-15 23:49 ` Ulrich Weigand
0 siblings, 2 replies; 6+ messages in thread
From: Ulrich Weigand @ 2007-11-12 15:37 UTC (permalink / raw)
To: Alan Modra, binutils, gdb-patches; +Cc: drow
Alan Modra wrote:
> On Tue, Nov 06, 2007 at 04:44:02PM -0500, Daniel Jacobowitz wrote:
> > > Is the bfd part OK?
> >
> > The elf.c part of this does not make sense to me. Why should we have
> > the same size as that symbol? The @plt entry is only a couple of
> > instructions. To figure out its size you need to ask the backend
> > plt_sym_val routine.
>
> Agreed. The ppc64 part is OK. I'm committing the following to fix
> a bug I noticed in the elf.c get_synthetic_symtab function. I also
> set udata.p to NULL as this may be all that's needed with a modified
> version of Ulrich's patch.
Thanks, Alan. The following version of the patch has only the ppc64
binutils part, and uses the udata.p setting in GDB only if it is not
NULL. This fixes the ppc64 problem as well (and has no regressions
on ppc32 either).
This still will not give us size information for PLT stubs, but I
guess that could still be added at some later time ...
Any additional comments on this approach?
Thanks,
Ulrich
bfd/ChangeLog:
* elf64-ppc.c (ppc64_elf_get_synthetic_symtab): Set udata.p of
synthetic symbol to point to the ELF symbol it was derived from.
gdb/ChangeLog:
* elfread.c (ST_REGULAR, ST_DYNAMIC, ST_SYNTHETIC): New defines.
(elf_symtab_read): Rename DYNAMIC argument to TYPE. Do not access
ELF-private symbol data when processing synthetic symbols. Use
udata.p to get at the size of ppc64 synthetic 'dot' symbols.
(elf_symfile_read): Pass TYPE argument to elf_symtab_read.
diff -urNp gdb-orig/bfd/elf64-ppc.c gdb-head/bfd/elf64-ppc.c
--- gdb-orig/bfd/elf64-ppc.c 2007-11-12 14:58:24.116239234 +0100
+++ gdb-head/bfd/elf64-ppc.c 2007-11-12 14:54:46.277454025 +0100
@@ -2959,6 +2959,9 @@ ppc64_elf_get_synthetic_symtab (bfd *abf
len = strlen (syms[i]->name);
memcpy (names, syms[i]->name, len + 1);
names += len + 1;
+ /* Have udata.p point back to the original symbol this
+ synthetic symbol was derived from. */
+ s->udata.p = syms[i];
s++;
}
}
@@ -3046,6 +3049,9 @@ ppc64_elf_get_synthetic_symtab (bfd *abf
len = strlen (syms[i]->name);
memcpy (names, syms[i]->name, len + 1);
names += len + 1;
+ /* Have udata.p point back to the original symbol this
+ synthetic symbol was derived from. */
+ s->udata.p = syms[i];
s++;
}
}
diff -urNp gdb-orig/gdb/elfread.c gdb-head/gdb/elfread.c
--- gdb-orig/gdb/elfread.c 2007-11-12 14:58:24.126237797 +0100
+++ gdb-head/gdb/elfread.c 2007-11-12 14:56:11.781191611 +0100
@@ -180,14 +180,14 @@ record_minimal_symbol (char *name, CORE_
SYNOPSIS
- void elf_symtab_read (struct objfile *objfile, int dynamic,
+ void elf_symtab_read (struct objfile *objfile, int type,
long number_of_symbols, asymbol **symbol_table)
DESCRIPTION
Given an objfile, a symbol table, and a flag indicating whether the
- symbol table contains dynamic symbols, add all the global function
- and data symbols to the minimal symbol table.
+ symbol table contains regular, dynamic, or synthetic symbols, add all
+ the global function and data symbols to the minimal symbol table.
In stabs-in-ELF, as implemented by Sun, there are some local symbols
defined in the ELF symbol table, which can be used to locate
@@ -197,8 +197,12 @@ record_minimal_symbol (char *name, CORE_
*/
+#define ST_REGULAR 0
+#define ST_DYNAMIC 1
+#define ST_SYNTHETIC 2
+
static void
-elf_symtab_read (struct objfile *objfile, int dynamic,
+elf_symtab_read (struct objfile *objfile, int type,
long number_of_symbols, asymbol **symbol_table)
{
long storage_needed;
@@ -235,7 +239,7 @@ elf_symtab_read (struct objfile *objfile
continue;
offset = ANOFFSET (objfile->section_offsets, sym->section->index);
- if (dynamic
+ if (type == ST_DYNAMIC
&& sym->section == &bfd_und_section
&& (sym->flags & BSF_FUNCTION))
{
@@ -284,7 +288,7 @@ elf_symtab_read (struct objfile *objfile
/* If it is a nonstripped executable, do not enter dynamic
symbols, as the dynamic symbol table is usually a subset
of the main symbol table. */
- if (dynamic && !stripped)
+ if (type == ST_DYNAMIC && !stripped)
continue;
if (sym->flags & BSF_FILE)
{
@@ -324,8 +328,11 @@ elf_symtab_read (struct objfile *objfile
{
/* This is a hack to get the minimal symbol type
right for Irix 5, which has absolute addresses
- with special section indices for dynamic symbols. */
- unsigned short shndx =
+ with special section indices for dynamic symbols.
+
+ NOTE: uweigand-20071112: Synthetic symbols do not
+ have an ELF-private part, so do not touch those. */
+ unsigned short shndx = type == ST_SYNTHETIC ? 0 :
((elf_symbol_type *) sym)->internal_elf_sym.st_shndx;
switch (shndx)
@@ -484,11 +491,24 @@ elf_symtab_read (struct objfile *objfile
msym = record_minimal_symbol
((char *) sym->name, symaddr,
ms_type, sym->section, objfile);
+
if (msym)
{
/* Pass symbol size field in via BFD. FIXME!!! */
- unsigned long size = ((elf_symbol_type *) sym)->internal_elf_sym.st_size;
- MSYMBOL_SIZE(msym) = size;
+ elf_symbol_type *elf_sym;
+
+ /* NOTE: uweigand-20071112: A synthetic symbol does not have an
+ ELF-private part. However, in some cases (e.g. synthetic
+ 'dot' symbols on ppc64) the udata.p entry is set to point back
+ to the original ELF symbol it was derived from. Get the size
+ from that symbol. */
+ if (type != ST_SYNTHETIC)
+ elf_sym = (elf_symbol_type *) sym;
+ else
+ elf_sym = (elf_symbol_type *) sym->udata.p;
+
+ if (elf_sym)
+ MSYMBOL_SIZE(msym) = elf_sym->internal_elf_sym.st_size;
}
if (msym != NULL)
msym->filename = filesymname;
@@ -569,7 +589,7 @@ elf_symfile_read (struct objfile *objfil
error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile->obfd),
bfd_errmsg (bfd_get_error ()));
- elf_symtab_read (objfile, 0, symcount, symbol_table);
+ elf_symtab_read (objfile, ST_REGULAR, symcount, symbol_table);
}
/* Add the dynamic symbols. */
@@ -587,7 +607,7 @@ elf_symfile_read (struct objfile *objfil
error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile->obfd),
bfd_errmsg (bfd_get_error ()));
- elf_symtab_read (objfile, 1, dynsymcount, dyn_symbol_table);
+ elf_symtab_read (objfile, ST_DYNAMIC, dynsymcount, dyn_symbol_table);
}
/* Add synthetic symbols - for instance, names for any PLT entries. */
@@ -605,7 +625,7 @@ elf_symfile_read (struct objfile *objfil
for (i = 0; i < synthcount; i++)
synth_symbol_table[i] = synthsyms + i;
make_cleanup (xfree, synth_symbol_table);
- elf_symtab_read (objfile, 0, synthcount, synth_symbol_table);
+ elf_symtab_read (objfile, ST_SYNTHETIC, synthcount, synth_symbol_table);
}
/* Install any minimal symbols that have been collected as the current
--
Dr. Ulrich Weigand
GNU Toolchain for Linux on System z and Cell BE
Ulrich.Weigand@de.ibm.com
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [rfc, v3] Fix ELF synthetic symbol size bug (affects PPC64)
2007-11-12 15:37 ` [rfc, v3] " Ulrich Weigand
@ 2007-11-12 15:45 ` Daniel Jacobowitz
2007-11-15 23:49 ` Ulrich Weigand
1 sibling, 0 replies; 6+ messages in thread
From: Daniel Jacobowitz @ 2007-11-12 15:45 UTC (permalink / raw)
To: Ulrich Weigand; +Cc: Alan Modra, binutils, gdb-patches
On Mon, Nov 12, 2007 at 04:37:29PM +0100, Ulrich Weigand wrote:
> Thanks, Alan. The following version of the patch has only the ppc64
> binutils part, and uses the udata.p setting in GDB only if it is not
> NULL. This fixes the ppc64 problem as well (and has no regressions
> on ppc32 either).
>
> This still will not give us size information for PLT stubs, but I
> guess that could still be added at some later time ...
>
> Any additional comments on this approach?
Not from me; it seems fine.
--
Daniel Jacobowitz
CodeSourcery
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [rfc, v3] Fix ELF synthetic symbol size bug (affects PPC64)
2007-11-12 15:37 ` [rfc, v3] " Ulrich Weigand
2007-11-12 15:45 ` Daniel Jacobowitz
@ 2007-11-15 23:49 ` Ulrich Weigand
1 sibling, 0 replies; 6+ messages in thread
From: Ulrich Weigand @ 2007-11-15 23:49 UTC (permalink / raw)
To: binutils, gdb-patches
> bfd/ChangeLog:
>
> * elf64-ppc.c (ppc64_elf_get_synthetic_symtab): Set udata.p of
> synthetic symbol to point to the ELF symbol it was derived from.
>
> gdb/ChangeLog:
>
> * elfread.c (ST_REGULAR, ST_DYNAMIC, ST_SYNTHETIC): New defines.
> (elf_symtab_read): Rename DYNAMIC argument to TYPE. Do not access
> ELF-private symbol data when processing synthetic symbols. Use
> udata.p to get at the size of ppc64 synthetic 'dot' symbols.
> (elf_symfile_read): Pass TYPE argument to elf_symtab_read.
I've checked this in now.
Thanks,
Ulrich
--
Dr. Ulrich Weigand
GNU Toolchain for Linux on System z and Cell BE
Ulrich.Weigand@de.ibm.com
^ permalink raw reply [flat|nested] 6+ messages in thread
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[not found] <200711052014.lA5KEiTm019854@d12av02.megacenter.de.ibm.com>
2007-11-06 21:33 ` [rfc, v2] Fix ELF synthetic symbol size bug (affects PPC64) Ulrich Weigand
2007-11-06 21:44 ` Daniel Jacobowitz
2007-11-12 3:29 ` Alan Modra
2007-11-12 15:37 ` [rfc, v3] " Ulrich Weigand
2007-11-12 15:45 ` Daniel Jacobowitz
2007-11-15 23:49 ` Ulrich Weigand
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