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* [Bug target/63373] New: ELF symbol sizes for variable-length objects are too small
@ 2014-09-25 17:26 srk31 at srcf dot ucam.org
2014-09-26 8:22 ` [Bug middle-end/63373] " rguenth at gcc dot gnu.org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: srk31 at srcf dot ucam.org @ 2014-09-25 17:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63373
Bug ID: 63373
Summary: ELF symbol sizes for variable-length objects are too
small
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: srk31 at srcf dot ucam.org
Created attachment 33569
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33569&action=edit
Source files used in the bug description
Suppose I have an object file containing a data object of some variable-length
type.
$ cat section-size-test.c
struct blah
{
float foo;
int i[];
};
struct blah b = { 42.0, { 1, 2, 3, 4, 0 } };
$ cc -c -o section-size-test.o section-size-test.c
Now I have an object of size 24 bytes. From ELF's point of view, we have a
section of size 24 but a symbol of size only 4.
$ readelf -Ss section-size-test.o
There are 9 section headers, starting at offset 0xc8:
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .text PROGBITS 0000000000000000 00000040
0000000000000000 0000000000000000 AX 0 0 1
[ 2] .data PROGBITS 0000000000000000 00000040
0000000000000018 0000000000000000 WA 0 0 4
[ 3] .bss NOBITS 0000000000000000 00000058
0000000000000000 0000000000000000 WA 0 0 1
[ 4] .comment PROGBITS 0000000000000000 00000058
0000000000000024 0000000000000001 MS 0 0 1
[ 5] .note.GNU-stack PROGBITS 0000000000000000 0000007c
0000000000000000 0000000000000000 0 0 1
[ 6] .shstrtab STRTAB 0000000000000000 0000007c
0000000000000045 0000000000000000 0 0 1
[ 7] .symtab SYMTAB 0000000000000000 00000308
00000000000000c0 0000000000000018 8 7 8
[ 8] .strtab STRTAB 0000000000000000 000003c8
0000000000000017 0000000000000000 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), l (large)
I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
O (extra OS processing required) o (OS specific), p (processor specific)
Symbol table '.symtab' contains 8 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 FILE LOCAL DEFAULT ABS section-size-test.c
2: 0000000000000000 0 SECTION LOCAL DEFAULT 1
3: 0000000000000000 0 SECTION LOCAL DEFAULT 2
4: 0000000000000000 0 SECTION LOCAL DEFAULT 3
5: 0000000000000000 0 SECTION LOCAL DEFAULT 5
6: 0000000000000000 0 SECTION LOCAL DEFAULT 4
7: 0000000000000000 4 OBJECT GLOBAL DEFAULT 2 b
The bug is that when copy relocations are used, the variable-length part of the
object will get thrown away. I think the symbol size should also be 24 (hence
filing a gcc bug not a binutils bug).
Continuing: I create a shared library out of this object file, and an
executable that depends on my object.
$ cat exe.c
struct blah
{
float foo;
int i[];
};
extern struct blah b;
int main(void)
{
return (unsigned long long) &b % 32;
}
$ cc -shared -o section-size-test.so section-size-test.o
$ cc -o exe exe.c section-size-test.so
Now the executable is using a copy reloc to address my variable-length object.
$ objdump -RT exe
exe: file format elf64-x86-64
DYNAMIC SYMBOL TABLE:
0000000000000000 w D *UND* 0000000000000000
_ITM_deregisterTMCloneTable
0000000000000000 DF *UND* 0000000000000000 GLIBC_2.2.5 __libc_start_main
0000000000000000 w D *UND* 0000000000000000 __gmon_start__
0000000000000000 w D *UND* 0000000000000000
_Jv_RegisterClasses
0000000000000000 w D *UND* 0000000000000000
_ITM_registerTMCloneTable
0000000000601038 g D .data 0000000000000000 Base _edata
0000000000601040 g D .bss 0000000000000000 Base _end
0000000000601038 g D .bss 0000000000000000 Base __bss_start
0000000000400550 g DF .init 0000000000000000 Base _init
0000000000601038 g DO .bss 0000000000000004 b
0000000000400724 g DF .fini 0000000000000000 Base _fini
DYNAMIC RELOCATION RECORDS
OFFSET TYPE VALUE
0000000000600ff8 R_X86_64_GLOB_DAT __gmon_start__
0000000000601038 R_X86_64_COPY b
0000000000601018 R_X86_64_JUMP_SLOT __libc_start_main
0000000000601020 R_X86_64_JUMP_SLOT __gmon_start__
We can see that b has size 4, and the object has been truncated, since _end is
at b+8. The variable-length part of the object has not been copy-relocated.
I would guess that the right behaviour is to emit the symbol as having the
"full" size of the object, which is clearly known at compile time. Then the
linker will (I hope?) create a big enough copy reloc.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/63373] ELF symbol sizes for variable-length objects are too small
2014-09-25 17:26 [Bug target/63373] New: ELF symbol sizes for variable-length objects are too small srk31 at srcf dot ucam.org
@ 2014-09-26 8:22 ` rguenth at gcc dot gnu.org
2014-09-26 20:04 ` mikpelinux at gmail dot com
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2014-09-26 8:22 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63373
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jsm28 at gcc dot gnu.org
Component|target |middle-end
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
This is also a question if it is valid (GNU) C. The types in both units are
definitely not the same.
Joseph?
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/63373] ELF symbol sizes for variable-length objects are too small
2014-09-25 17:26 [Bug target/63373] New: ELF symbol sizes for variable-length objects are too small srk31 at srcf dot ucam.org
2014-09-26 8:22 ` [Bug middle-end/63373] " rguenth at gcc dot gnu.org
@ 2014-09-26 20:04 ` mikpelinux at gmail dot com
2014-09-26 21:21 ` joseph at codesourcery dot com
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: mikpelinux at gmail dot com @ 2014-09-26 20:04 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63373
--- Comment #2 from Mikael Pettersson <mikpelinux at gmail dot com> ---
Related to PR57180?
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/63373] ELF symbol sizes for variable-length objects are too small
2014-09-25 17:26 [Bug target/63373] New: ELF symbol sizes for variable-length objects are too small srk31 at srcf dot ucam.org
2014-09-26 8:22 ` [Bug middle-end/63373] " rguenth at gcc dot gnu.org
2014-09-26 20:04 ` mikpelinux at gmail dot com
@ 2014-09-26 21:21 ` joseph at codesourcery dot com
2015-03-01 22:03 ` steve at sk2 dot org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: joseph at codesourcery dot com @ 2014-09-26 21:21 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63373
--- Comment #3 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
I agree with the analysis in bug 28865 that .size should reflect the
presence of the initializer. That bug was marked FIXED, but I'm not clear
if the issue described in its summary - "Structures with a flexible arrray
member have wrong .size" - did in fact get fixed for some configurations
(but not all? or became unfixed?) or only some related issue that was
sufficient for the testcases added to pass.
I think this code should be considered valid GNU C.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/63373] ELF symbol sizes for variable-length objects are too small
2014-09-25 17:26 [Bug target/63373] New: ELF symbol sizes for variable-length objects are too small srk31 at srcf dot ucam.org
` (2 preceding siblings ...)
2014-09-26 21:21 ` joseph at codesourcery dot com
@ 2015-03-01 22:03 ` steve at sk2 dot org
2015-03-01 22:04 ` steve at sk2 dot org
2021-09-12 23:02 ` [Bug target/63373] " pinskia at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: steve at sk2 dot org @ 2015-03-01 22:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63373
Stephen Kitt <steve at sk2 dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |steve at sk2 dot org
--- Comment #4 from Stephen Kitt <steve at sk2 dot org> ---
Created attachment 34912
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34912&action=edit
Pre-processed source reproducing the bug
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/63373] ELF symbol sizes for variable-length objects are too small
2014-09-25 17:26 [Bug target/63373] New: ELF symbol sizes for variable-length objects are too small srk31 at srcf dot ucam.org
` (3 preceding siblings ...)
2015-03-01 22:03 ` steve at sk2 dot org
@ 2015-03-01 22:04 ` steve at sk2 dot org
2021-09-12 23:02 ` [Bug target/63373] " pinskia at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: steve at sk2 dot org @ 2015-03-01 22:04 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63373
--- Comment #5 from Stephen Kitt <steve at sk2 dot org> ---
Oops sorry, wrong bug...
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug target/63373] ELF symbol sizes for variable-length objects are too small
2014-09-25 17:26 [Bug target/63373] New: ELF symbol sizes for variable-length objects are too small srk31 at srcf dot ucam.org
` (4 preceding siblings ...)
2015-03-01 22:04 ` steve at sk2 dot org
@ 2021-09-12 23:02 ` pinskia at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-09-12 23:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63373
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|UNCONFIRMED |RESOLVED
Component|c |target
--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
all (majority of) elf targets was fixed with r5-2566 will file bugs about the
other targets. I already filed a bug about the C++ front-end not updating
DECL_SIZE (PR 102295).
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2021-09-12 23:02 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2014-09-25 17:26 [Bug target/63373] New: ELF symbol sizes for variable-length objects are too small srk31 at srcf dot ucam.org
2014-09-26 8:22 ` [Bug middle-end/63373] " rguenth at gcc dot gnu.org
2014-09-26 20:04 ` mikpelinux at gmail dot com
2014-09-26 21:21 ` joseph at codesourcery dot com
2015-03-01 22:03 ` steve at sk2 dot org
2015-03-01 22:04 ` steve at sk2 dot org
2021-09-12 23:02 ` [Bug target/63373] " pinskia at gcc dot gnu.org
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