[PATCH 0/6] ld: Add "-z textonly" option to ELF linker
H.J. Lu
hjl.tools@gmail.com
Tue Nov 21 22:28:00 GMT 2017
Text-only LOAD segment has the same requirement for segment alignment
and page sizes as GNU_RELRO segment. But for GNU_RELRO segment, the
segment may not end at the same address of the end of data segment. But
for text-only LOAD segment, it is exactly the same as text LOAD segment.
The new "-z textonly" option will turn on both text-only LOAD segment and
GNU_RELRO segment. The new "-z notextonly" option will turn off only
text-only LOAD segment. "-z relro" is updated not to turn off text-only
LOAD segment. "-z norelro" is updated to turn off both GNU_RELRO segment
and text-only LOAD segment.
When there is a text-only LOAD segment, create a new LOAD segment if the
previous section contains text and the current section doesn't or vice
versa:
Elf file type is DYN (Shared object file)
Entry point 0x200ff0
There are 7 program headers, starting at offset 52
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
LOAD 0x000000 0x00000000 0x00000000 0x00200 0x00200 R 0x200000
LOAD 0x000fd0 0x00200fd0 0x00200fd0 0x0002b 0x0002b R E 0x200000
LOAD 0x001000 0x00201000 0x00201000 0x00058 0x00058 R 0x200000
LOAD 0x200f80 0x00400f80 0x00400f80 0x000a0 0x000a0 RW 0x200000
DYNAMIC 0x200f80 0x00400f80 0x00400f80 0x00080 0x00080 RW 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x10
GNU_RELRO 0x200f80 0x00400f80 0x00400f80 0x00080 0x00080 R 0x1
Section to Segment mapping:
Segment Sections...
00 .hash .gnu.hash .dynsym .dynstr .rela.plt
01 .plt .text
02 .rodata .eh_frame
03 .dynamic .got.plt
04 .dynamic
05
06 .dynamic
This is to prevent executing data in read-only sections as instructions.
Also don't put a writable section in a read-only segment if there is a
RELRO segment.
Since there are more than 2 LOAD segments, the minimum file size is
bigger than the maximum page size which is 2MB (0x200000):
-rwxr-xr-x 1 hjl hjl 2104892 Nov 12 11:53 libfoo.so
"-z max-page-size=0x1000" can be used to reduce the maximum page size to
4KB (0x1000):
-rwxr-xr-x 1 hjl hjl 11836 Nov 12 13:22 libfoo.so
Elf file type is DYN (Shared object file)
Entry point 0x1ff0
There are 7 program headers, starting at offset 52
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
LOAD 0x000000 0x00000000 0x00000000 0x00200 0x00200 R 0x1000
LOAD 0x000fd0 0x00001fd0 0x00001fd0 0x0002b 0x0002b R E 0x1000
LOAD 0x001000 0x00002000 0x00002000 0x00058 0x00058 R 0x1000
LOAD 0x001f80 0x00002f80 0x00002f80 0x000a0 0x000a0 RW 0x1000
DYNAMIC 0x001f80 0x00002f80 0x00002f80 0x00080 0x00080 RW 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x10
GNU_RELRO 0x001f80 0x00002f80 0x00002f80 0x00080 0x00080 R 0x1
Section to Segment mapping:
Segment Sections...
00 .hash .gnu.hash .dynsym .dynstr .rela.plt
01 .plt .text
02 .rodata .eh_frame
03 .dynamic .got.plt
04 .dynamic
05
06 .dynamic
This is the set of updated patches. Tested on x86-64, x32 and i686.
Any comments or suggestions?
H.J. Lu (6):
ld: Add "-z textonly" option to ELF linker
ld: Add TEXT_SEGMENT_ALIGN/TEXT_SEGMENT_{RELRO_}END
ld: Create a new LOAD segment for text-only LOAD segment
ld/ppc/spu: Also set expld.textseg.phase to exp_seg_none
ld: Add tests for -z textonly and -z notextonly
x86-64: Add tests for -z textonly -z max-page-size=0x1000
bfd/elf.c | 32 +++++++---
include/bfdlink.h | 9 ++-
ld/NEWS | 2 +
ld/emultempl/elf32.em | 104 +++++++++++++++++++++++++++++----
ld/emultempl/ppc32elf.em | 1 +
ld/emultempl/ppc64elf.em | 1 +
ld/emultempl/spuelf.em | 1 +
ld/genscripts.sh | 76 +++++++++++++++++++++---
ld/ld.texinfo | 10 +++-
ld/ldexp.c | 18 +++++-
ld/ldexp.h | 3 +
ld/ldgram.y | 7 +++
ld/ldlang.c | 109 ++++++++++++++++++++++++++---------
ld/ldlex.l | 3 +
ld/lexsup.c | 8 ++-
ld/scripttempl/elf.sc | 21 +++++++
ld/testsuite/ld-elf/pr16322.d | 2 +-
ld/testsuite/ld-elf/pr22393-1.s | 21 +++++++
ld/testsuite/ld-elf/pr22393-1a.d | 9 +++
ld/testsuite/ld-elf/pr22393-1b.d | 9 +++
ld/testsuite/ld-elf/pr22393-1c.d | 9 +++
ld/testsuite/ld-elf/pr22393-1d.d | 9 +++
ld/testsuite/ld-elf/pr22393-1e.d | 9 +++
ld/testsuite/ld-elf/pr22393-1f.d | 9 +++
ld/testsuite/ld-elf/pr22393-2a.c | 7 +++
ld/testsuite/ld-elf/pr22393-2a.rd | 9 +++
ld/testsuite/ld-elf/pr22393-2b.c | 7 +++
ld/testsuite/ld-elf/pr22393-2b.rd | 9 +++
ld/testsuite/ld-elf/shared.exp | 71 +++++++++++++++++++++++
ld/testsuite/ld-x86-64/pr22393-3a.c | 7 +++
ld/testsuite/ld-x86-64/pr22393-3a.rd | 9 +++
ld/testsuite/ld-x86-64/pr22393-3b.c | 7 +++
ld/testsuite/ld-x86-64/pr22393-3b.rd | 9 +++
ld/testsuite/ld-x86-64/x86-64.exp | 71 +++++++++++++++++++++++
34 files changed, 627 insertions(+), 61 deletions(-)
create mode 100644 ld/testsuite/ld-elf/pr22393-1.s
create mode 100644 ld/testsuite/ld-elf/pr22393-1a.d
create mode 100644 ld/testsuite/ld-elf/pr22393-1b.d
create mode 100644 ld/testsuite/ld-elf/pr22393-1c.d
create mode 100644 ld/testsuite/ld-elf/pr22393-1d.d
create mode 100644 ld/testsuite/ld-elf/pr22393-1e.d
create mode 100644 ld/testsuite/ld-elf/pr22393-1f.d
create mode 100644 ld/testsuite/ld-elf/pr22393-2a.c
create mode 100644 ld/testsuite/ld-elf/pr22393-2a.rd
create mode 100644 ld/testsuite/ld-elf/pr22393-2b.c
create mode 100644 ld/testsuite/ld-elf/pr22393-2b.rd
create mode 100644 ld/testsuite/ld-x86-64/pr22393-3a.c
create mode 100644 ld/testsuite/ld-x86-64/pr22393-3a.rd
create mode 100644 ld/testsuite/ld-x86-64/pr22393-3b.c
create mode 100644 ld/testsuite/ld-x86-64/pr22393-3b.rd
--
2.14.3
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