Messages in this thread | | | From | Christophe Leroy <> | Subject | Re: [RFC PATCH v1] objtool: Use target file endianness instead of a compiled constant | Date | Thu, 31 Mar 2022 08:10:29 +0000 |
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Le 31/03/2022 à 10:08, Peter Zijlstra a écrit : > On Thu, Mar 31, 2022 at 09:52:07AM +0200, Christophe Leroy wrote: >> Some architectures like powerpc support both endianness, it's >> therefore not possible to fix the endianness via arch/endianness.h >> because there is no easy way to get the target endianness at >> build time. >> >> Use the endianness recorded in the file objtool is working on. >> > >> +#include <objtool/elf.h> >> >> /* >> - * Does a byte swap if target endianness doesn't match the host, i.e. cross >> + * Does a byte swap if target file endianness doesn't match the host, i.e. cross >> * compilation for little endian on big endian and vice versa. >> * To be used for multi-byte values conversion, which are read from / about >> * to be written to a target native endianness ELF file. >> */ >> -#define bswap_if_needed(val) \ >> +static inline bool need_bswap(GElf_Ehdr *ehdr) >> +{ >> + return (__BYTE_ORDER == __LITTLE_ENDIAN) ^ >> + (ehdr->e_ident[EI_DATA] == ELFDATA2LSB); >> +} >> + >> +#define bswap_if_needed(ehdr, val) \ >> ({ \ >> __typeof__(val) __ret; \ >> + bool __need_bswap = need_bswap(ehdr); \ >> switch (sizeof(val)) { \ >> - case 8: __ret = __NEED_BSWAP ? bswap_64(val) : (val); break; \ >> - case 4: __ret = __NEED_BSWAP ? bswap_32(val) : (val); break; \ >> - case 2: __ret = __NEED_BSWAP ? bswap_16(val) : (val); break; \ >> + case 8: __ret = __need_bswap ? bswap_64(val) : (val); break; \ >> + case 4: __ret = __need_bswap ? bswap_32(val) : (val); break; \ >> + case 2: __ret = __need_bswap ? bswap_16(val) : (val); break; \ >> default: \ >> BUILD_BUG(); break; \ >> } \ > > Far less painfull that I imagined it would be,.. but I think I prefer > passing in elf, as opposed to elf->ehdr, would that work?
That's what I wanted to do in the beginning, but we don't have it in orc_dump()
Christophe
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