[BOLT,test] Make linker scripts less sensitive to lld's orphan placement #93763
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@llvm/pr-subscribers-bolt Author: Fangrui Song (MaskRay) ChangesThen two tests rely on .interp being the first section. For best portability, when a linker scripts specifies a SECTIONS Full diff: https://github.com/llvm/llvm-project/pull/93763.diff 2 Files Affected:
diff --git a/bolt/test/AArch64/Inputs/array_end.lld_script b/bolt/test/AArch64/Inputs/array_end.lld_script
index 182c13d370a39..bf77c0493a095 100644
--- a/bolt/test/AArch64/Inputs/array_end.lld_script
+++ b/bolt/test/AArch64/Inputs/array_end.lld_script
@@ -1,4 +1,7 @@
SECTIONS {
+ .interp : { *(.interp) }
+
+ . = ALIGN(CONSTANT(MAXPAGESIZE));
.fini_array :
{
PROVIDE_HIDDEN (__fini_array_start = .);
diff --git a/bolt/test/Inputs/lsda.ldscript b/bolt/test/Inputs/lsda.ldscript
index aa608ecd97e8c..011e0c6ac8a0f 100644
--- a/bolt/test/Inputs/lsda.ldscript
+++ b/bolt/test/Inputs/lsda.ldscript
@@ -1,5 +1,8 @@
SECTIONS {
+ .interp : { *(.interp) }
+ . = ALIGN(CONSTANT(MAXPAGESIZE));
.text : { *(.text*) }
+ . = ALIGN(CONSTANT(MAXPAGESIZE));
.gcc_except_table.main : { *(.gcc_except_table*) }
. = 0x20000;
.eh_frame : { *(.eh_frame) }
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ayermolo
approved these changes
May 30, 2024
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thanks! |
MaskRay
added a commit
that referenced
this pull request
May 30, 2024
Follow-up to a previous simplification 2473b1a. The xor difference between a SHT_NOTE and a read-only SHT_PROGBITS (previously >=NOT_SPECIAL) should be smaller than RF_EXEC. Otherwise, for the following section layout, `findOrphanPos` would place .text before note. ``` // simplified from linkerscript/custom-section-type.s non orphans: progbits 0x8060c00 NOT_SPECIAL note 0x8040003 orphan: .text 0x8061000 NOT_SPECIAL ``` rw-text.lds in orphan.s (added by 73e07e9) demonstrates a similar case. The new behavior is more similar to GNU ld. #93763 fixed BOLT's brittle reliance on the previous .interp behavior.
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Then two tests rely on .interp being the first section.
llvm-bolt would crash if lld places .interp after .got
(f639b57).
For best portability, when a linker scripts specifies a SECTIONS
command, the first section for each PT_LOAD segment should be specified
with a MAXPAGESIZE alignment. Otherwise, linkers have freedom to decide
how to place orphan sections, which might break intention.