Given the simplest program:
int main()
{
}
and a simple linker script (not a real world example):
SECTIONS
{
.text :
{
*(.text .stub .text.* .gnu.linkonce.t.*)
} =0
.post_text_reserve :
{
/* Reserve some space so we can drop something in here later */
. += 0x160;
}
}
compiled with:
sh-elf-gcc test.c -T link2.ld -nostdlib
I get a file with the following properties:
sh-elf-objdump -h a.out
a.out: file format elf32-shl
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 0000000c 00000000 00000000 00000080 2**1
CONTENTS, ALLOC, LOAD, READONLY, CODE
1 .post_text_reserve 00000160 0000000c 0000000c 0000008c 2**0
ALLOC
2 .comment 00000043 00000000 00000000 0000008c 2**0
CONTENTS, READONLY
sh-elf-readelf -S a.out
There are 7 section headers, starting at offset 0x10c:
Section Headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf
Al
[ 0] NULL 00000000 000000 000000 00 0 0 0
[ 1] .text PROGBITS 00000000 000080 00000c 00 AX 0 0
2
[ 2] .post_text_reserv NOBITS 0000000c 00008c 000160 00 WA 0 0
1
[ 3] .comment PROGBITS 00000000 00008c 000043 00 0 0 1
[ 4] .shstrtab STRTAB 00000000 0000cf 00003d 00 0 0 1
[ 5] .symtab SYMTAB 00000000 000224 0000b0 10 6 8 4
[ 6] .strtab STRTAB 00000000 0002d4 00001c 00 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings)
I (info), L (link order), G (group), x (unknown)
O (extra OS processing required) o (OS specific), p (processor specific)
All is good so far.
Now I want to add the missing flags to the .post_test_reserve (the next step
would be to actually add some data).
So I do the following:
sh-elf-objcopy --set-section-flags
.post_text_reserve=contents,alloc,load,readonly,code a.out a2.out
Now I get:
sh-elf-objdump -h a2.out
a2.out: file format elf32-shl
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 0000000c 00000000 00000000 00000080 2**1
CONTENTS, ALLOC, LOAD, READONLY, CODE
1 .post_text_reserve 00000160 0000000c 0000000c 0000008c 2**0
ALLOC, READONLY, CODE
2 .comment 00000043 00000000 00000000 000001ec 2**0
CONTENTS, READONLY
sh-elf-readelf -S a2.out
There are 7 section headers, starting at offset 0x26c:
Section Headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf
Al
[ 0] NULL 00000000 000000 000000 00 0 0 0
[ 1] .text PROGBITS 00000000 000080 00000c 00 AX 0 0
2
[ 2] .post_text_reserv NOBITS 0000000c 00008c 000160 00 AX 0 0
1
[ 3] .comment PROGBITS 00000000 0001ec 000043 00 0 0 1
[ 4] .shstrtab STRTAB 00000000 00022f 00003d 00 0 0 1
[ 5] .symtab SYMTAB 00000000 000384 0000b0 10 6 8 4
[ 6] .strtab STRTAB 00000000 000434 00001c 00 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings)
I (info), L (link order), G (group), x (unknown)
O (extra OS processing required) o (OS specific), p (processor specific)
The READONLY and CODE flags have been added, but the CONTENTS and LOAD flags
remain absent. Also, the ELF section type remains NOBITS, where it ought to be
PROGBITS.
After some examination of the source code and the ELF format I find that the
CONTENTS and LOAD flags are in fact implicit in the PROGBITS section type, so
all the above problems come down to the same issue.
AFAICT, the section type is set in elf_fake_sections(), but only if there is no
existing type (sh_type != SHT_NULL). In this case the section already has a type
- presumably loaded from the input file - and therefore does not have its type
set. Thus the change to the CONTENTS and LOAD flags is ignored.
The documentation says:
`--set-section-flags SECTION=FLAGS'
Set the flags for the named section. The FLAGS argument is a
comma separated string of flag names. The recognized names are
`alloc', `contents', `load', `noload', `readonly', `code', `data',
`rom', `share', and `debug'. You can set the `contents' flag for
a section which does not have contents, but it is not meaningful
to clear the `contents' flag of a section which does have
contents-just remove the section instead. Not all flags are
meaningful for all object file formats.
What I want to do - set the contents flag - is explicitly described.
This used to work in 2.15.94.0.1 from kernel.org, but it does not work in
2.16.91.0.5, also from kernel.org. Nor does it work in CVS HEAD.
I have tested it with sh-elf, but the bug probably also occurs with other
targets.
--
Summary: Cannot set the CONTENTS or LOAD flags
Product: binutils
Version: 2.18 (HEAD)
Status: NEW
Severity: normal
Priority: P2
Component: binutils
AssignedTo: unassigned at sources dot redhat dot com
ReportedBy: andrew dot stubbs at st dot com
CC: bug-binutils at gnu dot org
GCC target triplet: sh-elf
http://sourceware.org/bugzilla/show_bug.cgi?id=2593
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