620b8f1d69
MIPS64 does not store the 'r_info' field of a relocation table entry as a 64-bit value consisting of a 32-bit symbol index in the high 32 bits and a 32-bit type in the low 32 bits as on other architectures. Instead, the 64-bit 'r_info' field is really a 32-bit symbol index followed by four individual byte type fields. For big-endian MIPS64, treating this as a 64-bit integer happens to be compatible with the layout expected by other architectures (symbol index in upper 32-bits of resulting "native" 64-bit integer). However, for little-endian MIPS64 the parsed 64-bit integer contains the symbol index in the low 32 bits and the 4 individual byte type fields in the upper 32-bits (but as if the upper 32-bits were byte-swapped). To cope, add two helper routines in gelf_getrel.c to translate between the correct native 'r_info' value and the value obtained after the normal byte-swap translation. Use these routines in gelf_getrel(), gelf_getrela(), gelf_update_rel(), and gelf_update_rela(). This fixes 'readelf -r' on little-endian MIPS64 objects which was previously decoding incorrect relocations as well as 'objcopy: invalid symbox index' warnings from objcopy when extracting debug symbols from kernel modules. Even with this fixed, objcopy was still crashing when trying to extract debug symbols from little-endian MIPS64 modules. The workaround in gelf_*rel*() depends on the current ELF object having a valid ELF header so that the 'e_machine' field can be compared against EM_MIPS. objcopy was parsing the relocation entries to possibly rewrite the 'r_info' fields in the update_relocs() function before writing the initial ELF header to the destination object file. Move the initial write of the ELF header earlier before copy_contents() so that update_relocs() uses the correct symbol index values. Note that this change should really go upstream. The binutils readelf source has a similar hack for MIPS64EL though I implemented this version from scratch using the MIPS64 ABI PDF as a reference. Discussed with: jkoshy Reviewed by: emaste, imp Approved by: re (gjb, kib) MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D15734
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