Linkers (ld.bfd/gold/lld) place the section header table at the very
end. This allows tools to strip it, which is optional in executable/shared objects.
In addition, if we add or section, the size of the section header table
will change. Placing the section header table in the end keeps section
offsets unchanged.
yaml2obj currently places the section header table immediately after the
program header. Follow what linkers do to make offset updating easier.
Reviewed By: grimar
Differential Revision: https://reviews.llvm.org/D67221
llvm-svn: 371074
We have a few sections that can be added implicitly to the output:
".dynsym", ".dynstr", ".symtab", ".strtab" and ".shstrtab".
Problem appears when such section is listed explicitly in YAML.
In that case it's content is written twice:
first time during writing of regular sections listed in the document
and second time during special handling.
Because of that their file offsets can become unexpectedly broken:
(yaml file for sample below lists .dynsym explicitly before .text.foo)
Before patch:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .dynsym DYNSYM 0000000000000100 00000250
0000000000000030 0000000000000018 A 6 0 8
[ 2] .text.foo PROGBITS 0000000000000200 00000200
0000000000000000 0000000000000000 AX 0 0 0
After patch:
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .dynsym DYNSYM 0000000000000100 00000200
0000000000000030 0000000000000018 A 6 0 8
[ 2] .text.foo PROGBITS 0000000000000200 00000230
0000000000000000 0000000000000000 AX 0 0 0
This patch reorganizes our code and fixes the issue described.
Differential revision: https://reviews.llvm.org/D62809
llvm-svn: 362602
