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elf: Fix localplt.awk for DT_RELR-enabled builds (BZ 31978)
For each input readelf output, localplt.awk parses each 'Relocation section' entry, checks its offset against the dynamic section entry, and saves each DT_JMPREL, DT_RELA, and DT_REL offset value it finds. After all lines are read, the script checks if any segment offset differed from 0, meaning at least one 'Relocation section' was matched. However, if the shared object was built with RELR support and the static linker could place all the relocation on DT_RELR, there would be no DT_JMPREL, DT_RELA, and DT_REL entries; only a DT_RELR. For the current three ABIs that support (aarch64, x86, and powerpc64), the powerpc64 ld.so shows the behavior above. Both x86_64 and aarch64 show extra relocations on '.rela.dyn', which makes the script check to succeed. This patch fixes by handling DT_RELR, where the offset is checked against the dynamic section entries and if the shared object contains an entry it means that there are no extra PLT entries (since all relocations are relative). It fixes the elf/check-localplt failure on powerpc. Checked with a build/check for aarch64-linux-gnu, x86_64-linux-gnu, i686-linux-gnu, arm-linux-gnueabihf, s390x-linux-gnu, powerpc-linux-gnu, powerpc64-linux-gnu, and powerpc64le-linux-gnu. Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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@ -10,7 +10,8 @@ BEGIN {
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}
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FILENAME != lastfile {
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if (lastfile && jmprel_offset == 0 && rela_offset == 0 && rel_offset == 0) {
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if (lastfile && jmprel_offset == 0 && rela_offset == 0 && rel_offset == 0 \
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&& relr_offset == 0) {
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print FILENAME ": *** failed to find expected output (readelf -WSdr)";
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result = 2;
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}
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@ -22,6 +23,7 @@ FILENAME != lastfile {
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jmprel_offset = 0;
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rela_offset = 0;
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rel_offset = 0;
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relr_offset = 0;
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pltrelsz = -1;
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delete section_offset_by_address;
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}
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@ -77,6 +79,8 @@ in_relocs && relocs_offset == rel_offset && NF >= 5 {
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}
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}
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# No need to handle DT_RELR (all packed relocations are relative).
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in_relocs { next }
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$1 == "Relocation" && $2 == "section" && $5 == "offset" {
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@ -121,4 +125,14 @@ $2 == "(REL)" {
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}
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next
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}
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$2 == "(RELR)" {
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relr_addr = strtonum($3);
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if (relr_addr in section_offset_by_address) {
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relr_offset = section_offset_by_address[relr_addr];
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} else {
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print FILENAME ": *** DT_RELR does not match any section's address";
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result = 2;
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}
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}
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END { exit(result) }
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