https://sourceware.org/bugzilla/show_bug.cgi?id=29259
Bug ID: 29259
Summary: ld -r may create reloc sections with unordered relocs
again
Product: binutils
Version: 2.39 (HEAD)
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: ld
Assignee: unassigned at sourceware dot org
Reporter: kawada at kmckk dot co.jp
Target Milestone: ---
Created attachment 14149
--> https://sourceware.org/bugzilla/attachment.cgi?id=14149&action=edit
Proposed patch
The optimization to the relocation entry sorting algorithm introduced in
commit bca6d0e31 can lead to incorrect (unsorted) outputs in rare
circumstances.
The symptoms include a link warning about `.eh_frame_hdr` not being created
(similar to bug #16345) and a C++ exception causing abort instead of being
caught by an exception handler.
Reproducer:
#!/bin/sh
cat > test.ld <<EOF
SECTIONS {
.text : {
KEEP(*(.text.1));
KEEP(*(.text.4));
KEEP(*(.text.3));
KEEP(*(.text.2));
}
}
EOF
${AS:-as} -o test.o <<EOF
.text
.L1:
.word 0
.section ".text.1", "ax", %progbits
.L2:
.dc.a .L1
.section ".text.2", "ax", %progbits
.dc.a .L1
.section ".text.3", "ax", %progbits
.dc.a .L1
.section ".text.4", "ax", %progbits
.dc.a .L1
EOF
${LD:-ld} -o test2.o test.o -r -q -T test.ld
${READELF:-readelf} -r test2.o
The above script outputs reloc entries out-of-order:
Relocation section '.rela.text' at offset 0x118 contains 4 entries:
Offset Info Type Sym. Value Sym. Name +
Addend
000000000000 000100000001 R_X86_64_64 0000000000000000 .text + 20
000000000010 000100000001 R_X86_64_64 0000000000000000 .text + 20
000000000008 000100000001 R_X86_64_64 0000000000000000 .text + 20
000000000018 000100000001 R_X86_64_64 0000000000000000 .text + 20
The problem is that the current algorithm incorrectly assembles "runs" from
unsorted entries and inserted them to an already-sorted prefix, breaking the
loop invariants of insertion sort. The attached patch fixes the problem by
adding a check to ensure that only sorted entries are included in the runs.
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