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* [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored
@ 2021-12-08 23:51 hjl.tools at gmail dot com
2021-12-09 1:11 ` [Bug dynamic-link/28676] " hjl.tools at gmail dot com
` (11 more replies)
0 siblings, 12 replies; 13+ messages in thread
From: hjl.tools at gmail dot com @ 2021-12-08 23:51 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28676
Bug ID: 28676
Summary: p_align on PT_LOAD segment in DSO isn't honored
Product: glibc
Version: 2.35
Status: NEW
Severity: normal
Priority: P2
Component: dynamic-link
Assignee: unassigned at sourceware dot org
Reporter: hjl.tools at gmail dot com
Target Milestone: ---
Created attachment 13838
--> https://sourceware.org/bugzilla/attachment.cgi?id=13838&action=edit
A testcase
[hjl@gnu-cfl-2 aligned-1]$ make
gcc -pie -fPIE -Wl,-z,max-page-size=0x200000 -O2 -o pie main.c load.c
gcc -no-pie -Wl,-z,max-page-size=0x200000 -O2 -o pde main.c load.c
gcc -O2 -fPIC -c -o load.o load.c
gcc -shared -Wl,-z,max-page-size=0x200000 -o libload.so load.o
gcc -no-pie -Wl,-z,max-page-size=0x200000 -O2 -o dso main.c libload.so -Wl,-R,.
./pde
foo: 0xe00000
./pie
foo: 0x55ea36a00000
./dso
foo: 0x7fafe6308000
make: *** [Makefile:8: all] Aborted (core dumped)
[hjl@gnu-cfl-2 aligned-1]$
Kernel loader honors 2MB p_align in PIE. But ld.so doesn't honor 2MB p_align
in DSO.
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* [Bug dynamic-link/28676] p_align on PT_LOAD segment in DSO isn't honored
2021-12-08 23:51 [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored hjl.tools at gmail dot com
@ 2021-12-09 1:11 ` hjl.tools at gmail dot com
2021-12-10 19:45 ` hjl.tools at gmail dot com
` (10 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: hjl.tools at gmail dot com @ 2021-12-09 1:11 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28676
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://bugzilla.kernel.org
| |/show_bug.cgi?id=215275
--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
I also opened a kernel bug:
https://bugzilla.kernel.org/show_bug.cgi?id=215275
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* [Bug dynamic-link/28676] p_align on PT_LOAD segment in DSO isn't honored
2021-12-08 23:51 [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored hjl.tools at gmail dot com
2021-12-09 1:11 ` [Bug dynamic-link/28676] " hjl.tools at gmail dot com
@ 2021-12-10 19:45 ` hjl.tools at gmail dot com
2021-12-13 15:00 ` fweimer at redhat dot com
` (9 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: hjl.tools at gmail dot com @ 2021-12-10 19:45 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28676
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|NEW |RESOLVED
Target Milestone|--- |2.35
--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> ---
Fixed by
commit 718fdd87b1b98ef88e883a37d9c18867256fa5a4
Author: Rongwei Wang <rongwei.wang@linux.alibaba.com>
Date: Fri Dec 10 20:39:10 2021 +0800
elf: Properly align PT_LOAD segments [BZ #28676]
When PT_LOAD segment alignment > the page size, allocate enough space to
ensure that the segment can be properly aligned. This change helps code
segments use huge pages become simple and available.
This fixes [BZ #28676].
Signed-off-by: Xu Yu <xuyu@linux.alibaba.com>
Signed-off-by: Rongwei Wang <rongwei.wang@linux.alibaba.com>
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* [Bug dynamic-link/28676] p_align on PT_LOAD segment in DSO isn't honored
2021-12-08 23:51 [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored hjl.tools at gmail dot com
2021-12-09 1:11 ` [Bug dynamic-link/28676] " hjl.tools at gmail dot com
2021-12-10 19:45 ` hjl.tools at gmail dot com
@ 2021-12-13 15:00 ` fweimer at redhat dot com
2021-12-13 15:00 ` fweimer at redhat dot com
` (8 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: fweimer at redhat dot com @ 2021-12-13 15:00 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28676
Florian Weimer <fweimer at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://sourceware.org/bugz
| |illa/show_bug.cgi?id=28688
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* [Bug dynamic-link/28676] p_align on PT_LOAD segment in DSO isn't honored
2021-12-08 23:51 [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored hjl.tools at gmail dot com
` (2 preceding siblings ...)
2021-12-13 15:00 ` fweimer at redhat dot com
@ 2021-12-13 15:00 ` fweimer at redhat dot com
2021-12-13 15:02 ` fweimer at redhat dot com
` (7 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: fweimer at redhat dot com @ 2021-12-13 15:00 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28676
Florian Weimer <fweimer at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://sourceware.org/bugz
| |illa/show_bug.cgi?id=28689
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* [Bug dynamic-link/28676] p_align on PT_LOAD segment in DSO isn't honored
2021-12-08 23:51 [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored hjl.tools at gmail dot com
` (3 preceding siblings ...)
2021-12-13 15:00 ` fweimer at redhat dot com
@ 2021-12-13 15:02 ` fweimer at redhat dot com
2021-12-13 23:36 ` sam at gentoo dot org
` (6 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: fweimer at redhat dot com @ 2021-12-13 15:02 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28676
Florian Weimer <fweimer at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |fweimer at redhat dot com
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* [Bug dynamic-link/28676] p_align on PT_LOAD segment in DSO isn't honored
2021-12-08 23:51 [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored hjl.tools at gmail dot com
` (4 preceding siblings ...)
2021-12-13 15:02 ` fweimer at redhat dot com
@ 2021-12-13 23:36 ` sam at gentoo dot org
2021-12-14 5:31 ` i at maskray dot me
` (5 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: sam at gentoo dot org @ 2021-12-13 23:36 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28676
Sam James <sam at gentoo dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |sam at gentoo dot org
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* [Bug dynamic-link/28676] p_align on PT_LOAD segment in DSO isn't honored
2021-12-08 23:51 [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored hjl.tools at gmail dot com
` (5 preceding siblings ...)
2021-12-13 23:36 ` sam at gentoo dot org
@ 2021-12-14 5:31 ` i at maskray dot me
2021-12-15 22:25 ` hjl.tools at gmail dot com
` (4 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: i at maskray dot me @ 2021-12-14 5:31 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28676
Fangrui Song <i at maskray dot me> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |i at maskray dot me
--- Comment #3 from Fangrui Song <i at maskray dot me> ---
This is not a bug per se. My reasoning is at
https://sourceware.org/pipermail/libc-alpha/2021-December/134121.html
`__attribute__((aligned(0x200000))) = 1;` does not necessarily mean the large
alignment needs to be satisfied on a system with a smaller page size.
Now "elf: Properly align PT_LOAD segments [BZ #28676]" overaligns memory
mappings to p_align to make the use case work. It's a new feature, not a
bugfix.
The 2020 kernel commit
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ce81bb256a224259ab686742a6284930cbe4f1fa
has no waste, so it is more justifiable.
The emulation in ld.so, however, would incur significant overhead, so it needs
more thoughts.
At the very least, the max-page-size=0x200000 for -z noseparate-code on x86-64
may be problematic.
It looks like we need more thoughts how tools like objcopy and ld can make the
cost small, or whether such changes are justifiable.
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* [Bug dynamic-link/28676] p_align on PT_LOAD segment in DSO isn't honored
2021-12-08 23:51 [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored hjl.tools at gmail dot com
` (6 preceding siblings ...)
2021-12-14 5:31 ` i at maskray dot me
@ 2021-12-15 22:25 ` hjl.tools at gmail dot com
2022-01-05 13:32 ` hjl.tools at gmail dot com
` (3 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: hjl.tools at gmail dot com @ 2021-12-15 22:25 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28676
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Resolution|FIXED |---
--- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> ---
Linker may set p_align of a PT_LOAD segment larger than p_align of the
first PT_LOAD segment to satisfy a section alignment:
Elf file type is DYN (Shared object file)
Entry point 0x0
There are 10 program headers, starting at offset 64
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000834 0x0000000000000834 R E 0x1000
LOAD 0x0000000000000e00 0x0000000000001e00 0x0000000000001e00
0x0000000000000230 0x0000000000000230 RW 0x1000
LOAD 0x0000000000400000 0x0000000000400000 0x0000000000400000
0x0000000000000004 0x0000000000000008 RW 0x400000
...
Section to Segment mapping:
Segment Sections...
00 .note.gnu.property .note.gnu.build-id .gnu.hash .dynsym .dynstr
.gnu.v
ersion .gnu.version_r .rela.dyn .rela.plt .init .plt .plt.got .text .fini
.rodat
a .eh_frame_hdr .eh_frame
01 .init_array .fini_array .data.rel.ro .dynamic .got .got.plt
02 .data .bss
We should align the first PT_LOAD segment to the maximum p_align of all
PT_LOAD segments, similar to the kernel commit:
commit ce81bb256a224259ab686742a6284930cbe4f1fa
Author: Chris Kennelly <ckennelly@google.com>
Date: Thu Oct 15 20:12:32 2020 -0700
fs/binfmt_elf: use PT_LOAD p_align values for suitable start address
A patch with a testcase is posted at
https://sourceware.org/pipermail/libc-alpha/2021-December/134219.html
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* [Bug dynamic-link/28676] p_align on PT_LOAD segment in DSO isn't honored
2021-12-08 23:51 [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored hjl.tools at gmail dot com
` (7 preceding siblings ...)
2021-12-15 22:25 ` hjl.tools at gmail dot com
@ 2022-01-05 13:32 ` hjl.tools at gmail dot com
2022-01-05 13:32 ` hjl.tools at gmail dot com
` (2 subsequent siblings)
11 siblings, 0 replies; 13+ messages in thread
From: hjl.tools at gmail dot com @ 2022-01-05 13:32 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28676
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://sourceware.org/bugz
| |illa/show_bug.cgi?id=28695
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* [Bug dynamic-link/28676] p_align on PT_LOAD segment in DSO isn't honored
2021-12-08 23:51 [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored hjl.tools at gmail dot com
` (8 preceding siblings ...)
2022-01-05 13:32 ` hjl.tools at gmail dot com
@ 2022-01-05 13:32 ` hjl.tools at gmail dot com
2022-01-21 19:43 ` cvs-commit at gcc dot gnu.org
2022-01-24 14:52 ` hjl.tools at gmail dot com
11 siblings, 0 replies; 13+ messages in thread
From: hjl.tools at gmail dot com @ 2022-01-05 13:32 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28676
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|REOPENED |NEW
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* [Bug dynamic-link/28676] p_align on PT_LOAD segment in DSO isn't honored
2021-12-08 23:51 [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored hjl.tools at gmail dot com
` (9 preceding siblings ...)
2022-01-05 13:32 ` hjl.tools at gmail dot com
@ 2022-01-21 19:43 ` cvs-commit at gcc dot gnu.org
2022-01-24 14:52 ` hjl.tools at gmail dot com
11 siblings, 0 replies; 13+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2022-01-21 19:43 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28676
--- Comment #5 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by H.J. Lu <hjl@sourceware.org>:
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e22a4557eb39d7cba9a74d70f4582c13f1a7a83a
commit e22a4557eb39d7cba9a74d70f4582c13f1a7a83a
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Wed Dec 15 13:58:33 2021 -0800
elf: Properly align all PT_LOAD segments [BZ #28676]
Linker may set p_align of a PT_LOAD segment larger than p_align of the
first PT_LOAD segment to satisfy a section alignment:
Elf file type is DYN (Shared object file)
Entry point 0x0
There are 10 program headers, starting at offset 64
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000834 0x0000000000000834 R E 0x1000
LOAD 0x0000000000000e00 0x0000000000001e00 0x0000000000001e00
0x0000000000000230 0x0000000000000230 RW 0x1000
LOAD 0x0000000000400000 0x0000000000400000 0x0000000000400000
0x0000000000000004 0x0000000000000008 RW 0x400000
...
Section to Segment mapping:
Segment Sections...
00 .note.gnu.property .note.gnu.build-id .gnu.hash .dynsym .dynstr
.gnu.version .gnu.version_r .rela.dyn .rela.plt .init .plt .plt.got .text .fini
.rodata .eh_frame_hdr .eh_frame
01 .init_array .fini_array .data.rel.ro .dynamic .got .got.plt
02 .data .bss
We should align the first PT_LOAD segment to the maximum p_align of all
PT_LOAD segments, similar to the kernel commit:
commit ce81bb256a224259ab686742a6284930cbe4f1fa
Author: Chris Kennelly <ckennelly@google.com>
Date: Thu Oct 15 20:12:32 2020 -0700
fs/binfmt_elf: use PT_LOAD p_align values for suitable start address
This fixes BZ #28676.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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* [Bug dynamic-link/28676] p_align on PT_LOAD segment in DSO isn't honored
2021-12-08 23:51 [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored hjl.tools at gmail dot com
` (10 preceding siblings ...)
2022-01-21 19:43 ` cvs-commit at gcc dot gnu.org
@ 2022-01-24 14:52 ` hjl.tools at gmail dot com
11 siblings, 0 replies; 13+ messages in thread
From: hjl.tools at gmail dot com @ 2022-01-24 14:52 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28676
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|NEW |RESOLVED
--- Comment #6 from H.J. Lu <hjl.tools at gmail dot com> ---
Fixed.
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2021-12-08 23:51 [Bug dynamic-link/28676] New: p_align on PT_LOAD segment in DSO isn't honored hjl.tools at gmail dot com
2021-12-09 1:11 ` [Bug dynamic-link/28676] " hjl.tools at gmail dot com
2021-12-10 19:45 ` hjl.tools at gmail dot com
2021-12-13 15:00 ` fweimer at redhat dot com
2021-12-13 15:00 ` fweimer at redhat dot com
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2021-12-15 22:25 ` hjl.tools at gmail dot com
2022-01-05 13:32 ` hjl.tools at gmail dot com
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