Clang's integrated assembler supports multiple section with the same
name:
.section .text,"ax",@progbits,unique,1
nop
.section .text,"ax",@progbits,unique,2
nop
"unique,N" assigns the number, N, as the section ID, to a section. The
valid values of the section ID are between 0 and 4294967295. It can be
used to distinguish different sections with the same section name.
This is useful with -fno-unique-section-names -ffunction-sections.
-ffunction-sections by default generates .text.foo, .text.bar, etc.
Using the same string can save lots of space in .strtab.
This patch adds section_id to bfd_section and reuses the linker
internal bit in BFD section flags, SEC_LINKER_CREATED, for assmebler
internal use to mark valid section_id. It also updates objdump to
compare section pointers if 2 sections comes from the same file since
2 different sections can have the same section name.
bfd/
PR gas/25380
* bfd-in2.h: Regenerated.
* ecoff.c (bfd_debug_section): Add section_id.
* section.c (bfd_section): Add section_id.
(SEC_ASSEMBLER_SECTION_ID): New.
(BFD_FAKE_SECTION): Add section_id.
binutils/
PR gas/25380
* objdump.c (sym_ok): Return FALSE if 2 sections are in the
same file with different section pointers.
gas/
PR gas/25380
* config/obj-elf.c (section_match): Removed.
(get_section): Also match SEC_ASSEMBLER_SECTION_ID and
section_id.
(obj_elf_change_section): Replace info and group_name arguments
with match_p. Also update the section ID and flags from match_p.
(obj_elf_section): Handle "unique,N". Update call to
obj_elf_change_section.
* config/obj-elf.h (elf_section_match): New.
(obj_elf_change_section): Updated.
* config/tc-arm.c (start_unwind_section): Update call to
obj_elf_change_section.
* config/tc-ia64.c (obj_elf_vms_common): Likewise.
* config/tc-microblaze.c (microblaze_s_data): Likewise.
(microblaze_s_sdata): Likewise.
(microblaze_s_rdata): Likewise.
(microblaze_s_bss): Likewise.
* config/tc-mips.c (s_change_section): Likewise.
* config/tc-msp430.c (msp430_profiler): Likewise.
* config/tc-rx.c (parse_rx_section): Likewise.
* config/tc-tic6x.c (tic6x_start_unwind_section): Likewise.
* doc/as.texi: Document "unique,N" in .section directive.
* testsuite/gas/elf/elf.exp: Run "unique,N" tests.
* testsuite/gas/elf/section15.d: New file.
* testsuite/gas/elf/section15.s: Likewise.
* testsuite/gas/elf/section16.s: Likewise.
* testsuite/gas/elf/section16a.d: Likewise.
* testsuite/gas/elf/section16b.d: Likewise.
* testsuite/gas/elf/section17.d: Likewise.
* testsuite/gas/elf/section17.l: Likewise.
* testsuite/gas/elf/section17.s: Likewise.
* testsuite/gas/i386/unique.d: Likewise.
* testsuite/gas/i386/unique.s: Likewise.
* testsuite/gas/i386/x86-64-unique.d: Likewise.
* testsuite/gas/i386/i386.exp: Run unique and x86-64-unique.
ld/
PR gas/25380
* testsuite/ld-i386/pr22001-1c.S: Use "unique,N" in .section
directives.
* testsuite/ld-i386/tls-gd1.S: Likewise.
* testsuite/ld-x86-64/pr21481b.S: Likewise.
We can generate i386 TLS code sequences for general and local dynamic
models without PLT, which uses indirect call via GOT:
call *___tls_get_addr@GOT(%reg)
where EBX register isn't required as GOT base, instead of direct call:
call ___tls_get_addr[@PLT]
which requires EBX register as GOT base.
Since direct call is 4-byte long and indirect call, is 5-byte long, the
extra one byte must be handled properly.
For general dynamic model, 7-byte lea instruction before call instruction
is replaced by 6-byte one to make room for indirect call. For local
dynamic model, we simply use 5-byte indirect call.
TLS linker optimization is updated to recognize new instruction patterns.
For local dynamic model to local exec model transition, we generate
a 6-byte lea instruction as nop, instead of a 1-byte nop plus a 4-byte
lea instruction. Since linker may convert
call ___tls_get_addr[@PLT]
to
addr32 call ____tls_get_addr
when producing static executable, both patterns are recognized.
bfd/
* elf64-i386.c (elf_i386_link_hash_entry): Add tls_get_addr.
(elf_i386_link_hash_newfunc): Initialize tls_get_addr to 2.
(elf_i386_check_tls_transition): Check indirect call and direct
call with the addr32 prefix for general and local dynamic models.
Set the tls_get_addr feild.
(elf_i386_convert_load_reloc): Always use addr32 prefix for
indirect ___tls_get_addr call via GOT.
(elf_i386_relocate_section): Handle GD->LE, GD->IE and LD->LE
transitions with indirect call and direct call with the addr32
prefix.
ld/
* testsuite/ld-i386/i386.exp: Run libtlspic2.so, tlsbin2,
tlsgd3, tlsld2, tlsgd4, tlspie3a, tlspie3b and tlspie3c.
* testsuite/ld-i386/pass.out: New file.
* testsuite/ld-i386/tls-def1.c: Likewise.
* testsuite/ld-i386/tls-gd1.S: Likewise.
* testsuite/ld-i386/tls-ld1.S: Likewise.
* testsuite/ld-i386/tls-main1.c: Likewise.
* testsuite/ld-i386/tls.exp: Likewise.
* testsuite/ld-i386/tlsbin2-nacl.rd: Likewise.
* testsuite/ld-i386/tlsbin2.dd: Likewise.
* testsuite/ld-i386/tlsbin2.rd: Likewise.
* testsuite/ld-i386/tlsbin2.sd: Likewise.
* testsuite/ld-i386/tlsbin2.td: Likewise.
* testsuite/ld-i386/tlsbinpic2.s: Likewise.
* testsuite/ld-i386/tlsgd3.dd: Likewise.
* testsuite/ld-i386/tlsgd3.s: Likewise.
* testsuite/ld-i386/tlsgd4.d: Likewise.
* testsuite/ld-i386/tlsgd4.s: Likewise.
* testsuite/ld-i386/tlsld2.s: Likewise.
* testsuite/ld-i386/tlspic2-nacl.rd: Likewise.
* testsuite/ld-i386/tlspic2.dd: Likewise.
* testsuite/ld-i386/tlspic2.rd: Likewise.
* testsuite/ld-i386/tlspic2.sd: Likewise.
* testsuite/ld-i386/tlspic2.td: Likewise.
* testsuite/ld-i386/tlspic3.s: Likewise.
* testsuite/ld-i386/tlspie3.s: Likewise.
* testsuite/ld-i386/tlspie3a.d: Likewise.
* testsuite/ld-i386/tlspie3b.d: Likewise.
* testsuite/ld-i386/tlspie3c.d: Likewise.
H.J. Lu