On 03.04.2007 [09:01:34 -0500], Adam Litke wrote:
> On Mon, 2007-04-02 at 18:27 -0700, Nishanth Aravamudan wrote:
> > ppc: rework plt detection
> >
> > We currently emit LONG(0) into the .plt section of relinked ppc binaries
> > to make it appear in the filesz (on-disk) portion of the data/bss
> > segment. This is a problem, however, for powerpc64, where the ABI
> > specifies that the .plt section is NOBITS (x86 and x86_64 mark the .plt
> > PROGBITS). Given that the program is being relinked to begin with,
> > however, it seems logical to simply add a tag, similar to
> > __executable_start, to make finding the "libhuge" filesz easy to find.
> > Do exactly this, via __libhuge_filesz, and skip the extracopy detection
> > if this symbol is defined. Tested on powerpc64.
>
> Looks good to me...
>
> What do you think about adding some comments into the linker scripts
> here so it will be easy to remember what this is for later?
Updated patch below:
ppc: rework plt detection
We currently emit LONG(0) into the .plt section to make it appear in the
filesz (on-disk) portion of the data/bss segment. This is a problem,
however, for powerpc64, where the ABI specifies that the .plt section is
NOBITS (x86 and x86_64 mark the .plt PROGBITS). Given that the program
is being relinked to begin with, however, it seems logical to simply add
a tag, similar to __executable_start, to make finding the "libhuge"
filesz easy to find. Do exactly this, via __libhuge_filesz, and skip the
extracopy detection if this symbol is defined. Tested on powerpc64.
Signed-off-by: Nishanth Aravamudan <[EMAIL PROTECTED]>
diff --git a/elflink.c b/elflink.c
index 5058248..00b403a 100644
--- a/elflink.c
+++ b/elflink.c
@@ -414,6 +414,7 @@ static void get_extracopy(struct seg_info *seg, Elf_Phdr
*phdr, int phnum)
int ret, numsyms, found_sym = 0;
void *start, *end, *start_orig, *end_orig;
void *sym_start, *sym_end;
+ extern void __libhuge_filesz __attribute__((weak));
end_orig = seg->vaddr + seg->memsz;
start_orig = seg->vaddr + seg->filesz;
@@ -422,6 +423,13 @@ static void get_extracopy(struct seg_info *seg, Elf_Phdr
*phdr, int phnum)
if (!minimal_copy)
goto bail2;
+ if (&__libhuge_filesz) {
+ found_sym = 1;
+ start = start_orig;
+ end = &__libhuge_filesz;
+ goto found;
+ }
+
/* Find dynamic program header */
ret = find_dynamic(&dyntab, phdr, phnum);
if (ret < 0)
@@ -462,6 +470,7 @@ static void get_extracopy(struct seg_info *seg, Elf_Phdr
*phdr, int phnum)
if (__debug)
check_bss(end, end_orig);
+found:
if (found_sym) {
/* Return the copy window */
seg->extra_vaddr = start;
diff --git a/ldscripts/elf32ppclinux.xBDT b/ldscripts/elf32ppclinux.xBDT
index f30bd3b..109d556 100644
--- a/ldscripts/elf32ppclinux.xBDT
+++ b/ldscripts/elf32ppclinux.xBDT
@@ -161,9 +161,11 @@ SECTIONS
.dynamic : { *(.dynamic) } :dynamic :hdata
.got : { *(.got.plt .got) } :hdata
/* . = DATA_SEGMENT_RELRO_END (0, .); */
- /* Ensure the plt appears in the on-disk portion of the binary so it
- * will be copied during hugetlb remapping */
- .plt : { *(.plt) LONG(0) } :hdata
+ .plt : { *(.plt) } :hdata
+ /* Rather than emit LONG(0) in the .plt section, use a symbol to mark
+ * the end of the need-to-copy data so that it will be copied during
+ * hugetlb remapping */
+ __libhuge_filesz = .;
.data :
{
*(.data .data.* .gnu.linkonce.d.*)
diff --git a/ldscripts/elf64ppc.xBDT b/ldscripts/elf64ppc.xBDT
index 68abf09..548b707 100644
--- a/ldscripts/elf64ppc.xBDT
+++ b/ldscripts/elf64ppc.xBDT
@@ -179,9 +179,11 @@ SECTIONS
*(.sbss .sbss.* .gnu.linkonce.sb.*)
*(.scommon)
} :hdata
- /* Ensure the plt appears in the on-disk portion of the binary so it
- * will be copied during hugetlb remapping */
- .plt : { LONG(0) *(.plt) } :hdata
+ .plt : { *(.plt) } :hdata
+ /* Rather than emit LONG(0) in the .plt section, use a symbol to mark
+ * the end of the need-to-copy data so that it will be copied during
+ * hugetlb remapping */
+ __libhuge_filesz = .;
.bss :
{
*(.dynbss)
--
Nishanth Aravamudan <[EMAIL PROTECTED]>
IBM Linux Technology Center
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