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086f9f3d78
When the jit_buf_desc contains unwinding information, it is emitted as eh_frame unwinding sections in the DSOs generated by perf inject. The unwinding information is required to unwind of JITed code which do not maintain the frame pointer register during function calls. It can be emitted by V8 / Chromium when the --perf_prof_unwinding_info is passed to V8. The eh_frame and eh_frame_hdr sections are emitted immediately after the .text. The .eh_frame is aligned at a 8-byte boundary, and .eh_frame_hdr at a 4-byte one. Since size of the .eh_frame is required to be a multiple of the word size, which means there will never be additional padding between it and the .eh_frame_hdr on machines where the word size is 4 or 8 bytes. However, additional padding might be inserted between .text and .eh_frame to reach the correct alignment, which will always be 8 bytes, also on 32bit machines. The reasoning behind this choice is that 4 extra bytes of padding worst case are not a large cost for the advantage of removing word-size dependent offset calculations when emitting the jitdump. Signed-off-by: Stefano Sanfilippo <ssanfilippo@chromium.org> Signed-off-by: Ross McIlroy <rmcilroy@chromium.org> Reviewed-by: Stephane Eranian <eranian@google.com> Cc: Anton Blanchard <anton@ozlabs.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1476356383-30100-8-git-send-email-eranian@google.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
64 lines
1.8 KiB
C
64 lines
1.8 KiB
C
#ifndef __GENELF_H__
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#define __GENELF_H__
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/* genelf.c */
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int jit_write_elf(int fd, uint64_t code_addr, const char *sym,
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const void *code, int csize, void *debug, int nr_debug_entries,
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void *unwinding, uint64_t unwinding_header_size, uint64_t unwinding_size);
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#ifdef HAVE_DWARF_SUPPORT
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/* genelf_debug.c */
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int jit_add_debug_info(Elf *e, uint64_t code_addr, void *debug, int nr_debug_entries);
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#endif
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#if defined(__arm__)
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#define GEN_ELF_ARCH EM_ARM
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#define GEN_ELF_CLASS ELFCLASS32
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#elif defined(__aarch64__)
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#define GEN_ELF_ARCH EM_AARCH64
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#define GEN_ELF_CLASS ELFCLASS64
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#elif defined(__x86_64__)
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#define GEN_ELF_ARCH EM_X86_64
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#define GEN_ELF_CLASS ELFCLASS64
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#elif defined(__i386__)
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#define GEN_ELF_ARCH EM_386
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#define GEN_ELF_CLASS ELFCLASS32
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#elif defined(__powerpc64__)
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#define GEN_ELF_ARCH EM_PPC64
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#define GEN_ELF_CLASS ELFCLASS64
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#elif defined(__powerpc__)
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#define GEN_ELF_ARCH EM_PPC
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#define GEN_ELF_CLASS ELFCLASS32
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#else
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#error "unsupported architecture"
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#endif
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#if __BYTE_ORDER == __BIG_ENDIAN
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#define GEN_ELF_ENDIAN ELFDATA2MSB
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#else
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#define GEN_ELF_ENDIAN ELFDATA2LSB
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#endif
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#if GEN_ELF_CLASS == ELFCLASS64
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#define elf_newehdr elf64_newehdr
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#define elf_getshdr elf64_getshdr
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#define Elf_Ehdr Elf64_Ehdr
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#define Elf_Shdr Elf64_Shdr
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#define Elf_Sym Elf64_Sym
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#define ELF_ST_TYPE(a) ELF64_ST_TYPE(a)
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#define ELF_ST_BIND(a) ELF64_ST_BIND(a)
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#define ELF_ST_VIS(a) ELF64_ST_VISIBILITY(a)
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#else
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#define elf_newehdr elf32_newehdr
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#define elf_getshdr elf32_getshdr
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#define Elf_Ehdr Elf32_Ehdr
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#define Elf_Shdr Elf32_Shdr
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#define Elf_Sym Elf32_Sym
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#define ELF_ST_TYPE(a) ELF32_ST_TYPE(a)
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#define ELF_ST_BIND(a) ELF32_ST_BIND(a)
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#define ELF_ST_VIS(a) ELF32_ST_VISIBILITY(a)
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#endif
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/* The .text section is directly after the ELF header */
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#define GEN_ELF_TEXT_OFFSET sizeof(Elf_Ehdr)
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#endif
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