[PATCH] MIPS: VDSO: Avoid including .got in dynamic segment
From: Nathan Chancellor
Date: Tue Jun 09 2026 - 21:31:54 EST
After commit 2db1ec80dfd5 ("MIPS: VDSO: Fold MIPS_DISABLE_VDSO into
MIPS_GENERIC_GETTIMEOFDAY"), building ARCH=mips allnoconfig with LLVM=1
shows some warnings from llvm-readelf while checking the VDSO for
dynamic relocations:
llvm-readelf: warning: 'arch/mips/vdso/vdso.so.dbg.raw': invalid PT_DYNAMIC size (0xa4)
llvm-readelf: warning: 'arch/mips/vdso/vdso.so.dbg.raw': PT_DYNAMIC dynamic table is invalid: SHT_DYNAMIC will be used
The blamed commit alters the link order of objects into vdso.so.raw,
placing vgettimeofday.o after sigreturn.o. This ultimately results in
the .text section shrinking slightly in size, which in turn changes the
offset of the .dynamic section.
- [ 9] .text PROGBITS 000002f0 0002f0 000930 00 AX 0 0 16
- [10] .dynamic DYNAMIC 00000c20 000c20 000090 08 A 5 0 4
+ [ 9] .text PROGBITS 000002f0 0002f0 000924 00 AX 0 0 16
+ [10] .dynamic DYNAMIC 00000c14 000c14 000090 08 A 5 0 4
Changing the offset of the .dynamic section causes the dynamic segment
size to grow by the same amount, which triggers a warning in
llvm-readelf because PT_DYNAMIC's p_filesz (0xa4) is no longer a
multiple of its sh_entsize (8):
- DYNAMIC 0x000c20 0x00000c20 0x00000c20 0x00098 0x00098 R 0x10
+ DYNAMIC 0x000c14 0x00000c14 0x00000c14 0x000a4 0x000a4 R 0x10
The size of the dynamic segment was already incorrect before the blamed
comment, as it should be 0x90 like the .dynamic section above (18
entries at 8 bytes per entry); it just so happens that 0x98 % 8 is 0,
whereas 0xa4 % 8 is 4, so there was no warning.
Looking at the section to segment mapping of the dynamic segment reveals
that it includes the .got section, as it is implicitly placed after
.dynamic by ld.lld's orphan section heuristics and inherits its segments
from the linker script.
[ 9] .text PROGBITS 000002f0 0002f0 000924 00 AX 0 0 16
[10] .dynamic DYNAMIC 00000c14 000c14 000090 08 A 5 0 4
[11] .got PROGBITS 00000cb0 000cb0 000008 00 WAp 0 0 16
Section to Segment mapping:
Segment Sections...
00 .mips_abiflags
01 .reginfo
02 .mips_abiflags .reginfo .hash .dynsym .dynstr .gnu.version .gnu.version_d .note .text .dynamic .got
03 .dynamic .got
04 .note
Explicitly describe the .got section in the MIPS VDSO linker script
after .rodata, which switches back to the default text segment,
resulting in a dynamic segment that is the exact size of the .dynamic
section as expected with no other layout changes.
- DYNAMIC 0x000c14 0x00000c14 0x00000c14 0x000a4 0x000a4 R 0x10
+ DYNAMIC 0x000c14 0x00000c14 0x00000c14 0x00090 0x00090 R 0x4
- 03 .dynamic .got
+ 03 .dynamic
Closes: https://github.com/ClangBuiltLinux/linux/issues/2166
Fixes: 2db1ec80dfd5 ("MIPS: VDSO: Fold MIPS_DISABLE_VDSO into MIPS_GENERIC_GETTIMEOFDAY")
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
---
The fixes tag feels a little strong since it seems like it has just been
luck up until this point that there has been no warning but I decided to
be conservative and include it regardless. Feel free to remove it if you
see fit.
I think this should go via timers/vdso with the blamed commit. I plan to
send a follow up series for 7.3 to add '--orphan-handling' to the MIPS
VDSO to avoid issues like this in the future but that can go via the
MIPS tree, as it is not really a fix and I will need to properly test
it.
---
arch/mips/vdso/vdso.lds.S | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/mips/vdso/vdso.lds.S b/arch/mips/vdso/vdso.lds.S
index 05badf3ae0ff..278ab6444e98 100644
--- a/arch/mips/vdso/vdso.lds.S
+++ b/arch/mips/vdso/vdso.lds.S
@@ -56,6 +56,7 @@ SECTIONS
.dynamic : { *(.dynamic) } :text :dynamic
.rodata : { *(.rodata*) } :text
+ .got : { *(.got) }
_end = .;
PROVIDE(end = .);
---
base-commit: 13f6218e6fe79dc64aed76d738b765b45f62492b
change-id: 20260608-mips-vdso-fix-section-layout-262bc18d0c29
Best regards,
--
Cheers,
Nathan