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Avoid padding in _init and _fini. [BZ #31042]

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The linker just concatenates the .init and .fini sections which
results in the complete _init and _fini functions. If needed the
linker adds padding bytes due to an alignment. GNU ld is adding
NOPs, which is fine.  But e.g. mold is adding traps which results
in broken _init and _fini functions.

Thus this patch removes the alignment in .init and .fini sections
in crtn.S files.

We keep the 4 byte function alignment in crti.S files. As the
assembler now also outputs the start of _init and _fini functions
as multiples of 4 byte, it perhaps has to fill it. Although GNU as
is using NOPs here, to be sure, we just keep the alignment with
0x07 (=NOPs) at the end of crti.S.

In order to avoid an obvious NOP slide in _fini, this patch also
uses an lg instead of lgr instruction. Then the emitted instructions
needs a multiple of 4 bytes.
This commit is contained in:
Stefan Liebler 2023-11-21 13:33:03 +01:00
parent 7b12776584
commit 807849965b
2 changed files with 1 additions and 3 deletions
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2
sysdeps/s390/s390-64/crti.S
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@ -85,7 +85,7 @@ _init:
.type _fini,@function
_fini:
stmg %r6,%r15,48(%r15)
lgr %r1,%r15
lg %r1,120(%r15)
aghi %r15,-160
stg %r1,0(%r15)
larl %r12,_GLOBAL_OFFSET_TABLE_

2
sysdeps/s390/s390-64/crtn.S
View File

@ -37,13 +37,11 @@
corresponding to the prologues in crti.S. */
.section .init
.align 4
lg %r4,272(%r15)
lmg %r6,%r15,208(%r15)
br %r4
.section .fini
.align 4
lg %r4,272(%r15)
lmg %r6,%r15,208(%r15)
br %r4