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b1b0586dc2
The bloom filter of the GNU_HASH section of binaries is made of words (bitmasks) that are either 32-bits for ELFCLASS32 binaries or 64-bits for ELFCLASS64 binaries. By using the GElf_Word type to hold the content of each bitmask we assume the bitmask to be of a size of at most 'sizeof(Elf64_Word)'. Unfortunately, the name Elf64_Word is a bit misleading because it's a 32-bits wide type (uint32_t). That type is thus too short to hold an entire bitmask for 64-bits binaries. I won't give too many details here about how the bloom filter works as it's described in details in the documentation for the GNU_HASH section at http://www.linker-aliens.org/blogs/ali/entry/gnu_hash_elf_sections/. Suffice it to say that in practise, we were comparing the least significant bytes of a 64-bits bloom bitmask to a 32-bits value. Depending on if we read those least significant bytes on a big or little endian, we obviously don't get the same result. Hence the recent buid breakage at https://builder.wildebeest.org/buildbot/#builders/14/builds/352 where the runtestlookupsyms test fails. This patch thus changes the code of lookup_symbol_from_gnu_hash_tab to use a 64-bits type to hold the value of the bloom bitmask. That way, we never have any information loss. The function bloom_word_at is also changed to read the bloom bitmask as a 64-bits value when looking at an ELFCLASS64 binary and to always return a 64-bits value. It also adds a test to access the bloom filter of an ELFCLASS32 binary. * src/abg-dwarf-reader.cc (bloom_word_at): Properly read an element from the bloom bitmasks array of 32-bits values as a 64-bits value in a portable way. Always return a 64 bits value. (lookup_symbol_from_gnu_hash_tab): Use a 64-bits value to store the bloom bitmask. * tests/data/test-lookup-syms/test1-32bits.so: New test input, compiled as a 32bits binary to test for ELFCLASS32 binaries. * tests/data/test-lookup-syms/test1.c.compiling.txt: Documentation about how to compile the test1[-21bits].so files. * tests/data/Makefile.am: Add the new test material above to source distribution. * tests/test-lookup-syms.cc (in_out_specs): Add the test1-32bits.so test case to this test harness. Signed-off-by: Dodji Seketeli <dodji@redhat.com> |
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| .. | ||
| test0-report.txt | ||
| test0.cc | ||
| test0.o | ||
| test1-1-report.txt | ||
| test1-2-report.txt | ||
| test1-3-report.txt | ||
| test1-32bits.so | ||
| test1.c | ||
| test1.c.compiling.txt | ||
| test1.so | ||
| test1.version-script | ||
| test01-report.txt | ||
| test02-report.txt | ||