tcg: Add debug_info to JIT ELF image.
This allows us to actually supply a function name in softmmu builds; gdb doesn't pick up the minimal symbol table otherwise. Also add a bit of documentation and statically generate more of the ELF image. Signed-off-by: Richard Henderson <rth@twiddle.net> Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
This commit is contained in:
Richard Henderson
Blue Swirl
parent
55fddd6611
commit
5872bbf24e
237
tcg/tcg.c
237
tcg/tcg.c
@ -2252,8 +2252,17 @@ void tcg_dump_info(FILE *f, fprintf_function cpu_fprintf)
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#endif
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#ifdef ELF_HOST_MACHINE
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/* The backend should define ELF_HOST_MACHINE to indicate both what value to
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put into the ELF image and to indicate support for the feature. */
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/* In order to use this feature, the backend needs to do three things:
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(1) Define ELF_HOST_MACHINE to indicate both what value to
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put into the ELF image and to indicate support for the feature.
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(2) Define tcg_register_jit. This should create a buffer containing
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the contents of a .debug_frame section that describes the post-
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prologue unwind info for the tcg machine.
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(3) Call tcg_register_jit_int, with the constructed .debug_frame.
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*/
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/* Begin GDB interface. THE FOLLOWING MUST MATCH GDB DOCS. */
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typedef enum {
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@ -2300,96 +2309,169 @@ static int find_string(const char *strtab, const char *str)
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}
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}
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static void tcg_register_jit_int(void *buf, size_t buf_size,
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static void tcg_register_jit_int(void *buf_ptr, size_t buf_size,
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void *debug_frame, size_t debug_frame_size)
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{
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static const char strings[64] =
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"\0"
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".text\0"
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".debug_frame\0"
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".symtab\0"
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".strtab\0"
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"code_gen_buffer";
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struct __attribute__((packed)) DebugInfo {
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uint32_t len;
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uint16_t version;
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uint32_t abbrev;
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uint8_t ptr_size;
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uint8_t cu_die;
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uint16_t cu_lang;
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uintptr_t cu_low_pc;
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uintptr_t cu_high_pc;
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uint8_t fn_die;
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char fn_name[16];
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uintptr_t fn_low_pc;
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uintptr_t fn_high_pc;
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uint8_t cu_eoc;
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};
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struct ElfImage {
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ElfW(Ehdr) ehdr;
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ElfW(Phdr) phdr;
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ElfW(Shdr) shdr[5];
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ElfW(Sym) sym[1];
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char str[64];
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ElfW(Shdr) shdr[7];
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ElfW(Sym) sym[2];
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struct DebugInfo di;
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uint8_t da[24];
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char str[80];
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};
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struct ElfImage *img;
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static const struct ElfImage img_template = {
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.ehdr = {
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.e_ident[EI_MAG0] = ELFMAG0,
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.e_ident[EI_MAG1] = ELFMAG1,
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.e_ident[EI_MAG2] = ELFMAG2,
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.e_ident[EI_MAG3] = ELFMAG3,
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.e_ident[EI_CLASS] = ELF_CLASS,
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.e_ident[EI_DATA] = ELF_DATA,
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.e_ident[EI_VERSION] = EV_CURRENT,
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.e_type = ET_EXEC,
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.e_machine = ELF_HOST_MACHINE,
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.e_version = EV_CURRENT,
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.e_phoff = offsetof(struct ElfImage, phdr),
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.e_shoff = offsetof(struct ElfImage, shdr),
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.e_ehsize = sizeof(ElfW(Shdr)),
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.e_phentsize = sizeof(ElfW(Phdr)),
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.e_phnum = 1,
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.e_shentsize = sizeof(ElfW(Shdr)),
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.e_shnum = ARRAY_SIZE(img->shdr),
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.e_shstrndx = ARRAY_SIZE(img->shdr) - 1,
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},
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.phdr = {
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.p_type = PT_LOAD,
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.p_flags = PF_X,
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},
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.shdr = {
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[0] = { .sh_type = SHT_NULL },
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/* Trick: The contents of code_gen_buffer are not present in
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this fake ELF file; that got allocated elsewhere. Therefore
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we mark .text as SHT_NOBITS (similar to .bss) so that readers
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will not look for contents. We can record any address. */
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[1] = { /* .text */
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.sh_type = SHT_NOBITS,
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.sh_flags = SHF_EXECINSTR | SHF_ALLOC,
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},
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[2] = { /* .debug_info */
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.sh_type = SHT_PROGBITS,
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.sh_offset = offsetof(struct ElfImage, di),
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.sh_size = sizeof(struct DebugInfo),
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},
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[3] = { /* .debug_abbrev */
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.sh_type = SHT_PROGBITS,
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.sh_offset = offsetof(struct ElfImage, da),
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.sh_size = sizeof(img->da),
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},
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[4] = { /* .debug_frame */
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.sh_type = SHT_PROGBITS,
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.sh_offset = sizeof(struct ElfImage),
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},
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[5] = { /* .symtab */
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.sh_type = SHT_SYMTAB,
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.sh_offset = offsetof(struct ElfImage, sym),
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.sh_size = sizeof(img->sym),
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.sh_info = 1,
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.sh_link = ARRAY_SIZE(img->shdr) - 1,
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.sh_entsize = sizeof(ElfW(Sym)),
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},
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[6] = { /* .strtab */
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.sh_type = SHT_STRTAB,
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.sh_offset = offsetof(struct ElfImage, str),
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.sh_size = sizeof(img->str),
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}
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},
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.sym = {
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[1] = { /* code_gen_buffer */
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.st_info = ELF_ST_INFO(STB_GLOBAL, STT_FUNC),
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.st_shndx = 1,
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}
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},
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.di = {
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.len = sizeof(struct DebugInfo) - 4,
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.version = 2,
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.ptr_size = sizeof(void *),
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.cu_die = 1,
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.cu_lang = 0x8001, /* DW_LANG_Mips_Assembler */
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.fn_die = 2,
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.fn_name = "code_gen_buffer"
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},
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.da = {
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1, /* abbrev number (the cu) */
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0x11, 1, /* DW_TAG_compile_unit, has children */
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0x13, 0x5, /* DW_AT_language, DW_FORM_data2 */
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0x11, 0x1, /* DW_AT_low_pc, DW_FORM_addr */
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0x12, 0x1, /* DW_AT_high_pc, DW_FORM_addr */
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0, 0, /* end of abbrev */
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2, /* abbrev number (the fn) */
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0x2e, 0, /* DW_TAG_subprogram, no children */
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0x3, 0x8, /* DW_AT_name, DW_FORM_string */
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0x11, 0x1, /* DW_AT_low_pc, DW_FORM_addr */
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0x12, 0x1, /* DW_AT_high_pc, DW_FORM_addr */
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0, 0, /* end of abbrev */
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0 /* no more abbrev */
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},
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.str = "\0" ".text\0" ".debug_info\0" ".debug_abbrev\0"
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".debug_frame\0" ".symtab\0" ".strtab\0" "code_gen_buffer",
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};
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/* We only need a single jit entry; statically allocate it. */
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static struct jit_code_entry one_entry;
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uintptr_t buf = (uintptr_t)buf_ptr;
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size_t img_size = sizeof(struct ElfImage) + debug_frame_size;
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struct ElfImage *img = g_malloc0(img_size);
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img->ehdr.e_ident[EI_MAG0] = ELFMAG0;
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img->ehdr.e_ident[EI_MAG1] = ELFMAG1;
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img->ehdr.e_ident[EI_MAG2] = ELFMAG2;
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img->ehdr.e_ident[EI_MAG3] = ELFMAG3;
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img->ehdr.e_ident[EI_CLASS] = ELF_CLASS;
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img->ehdr.e_ident[EI_DATA] = ELF_DATA;
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img->ehdr.e_ident[EI_VERSION] = EV_CURRENT;
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img->ehdr.e_type = ET_EXEC;
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img->ehdr.e_machine = ELF_HOST_MACHINE;
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img->ehdr.e_version = EV_CURRENT;
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img->ehdr.e_phoff = offsetof(struct ElfImage, phdr);
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img->ehdr.e_shoff = offsetof(struct ElfImage, shdr);
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img->ehdr.e_ehsize = sizeof(ElfW(Shdr));
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img->ehdr.e_phentsize = sizeof(ElfW(Phdr));
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img->ehdr.e_phnum = 1;
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img->ehdr.e_shentsize = sizeof(img->shdr[0]);
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img->ehdr.e_shnum = ARRAY_SIZE(img->shdr);
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img->ehdr.e_shstrndx = ARRAY_SIZE(img->shdr) - 1;
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img->phdr.p_type = PT_LOAD;
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img->phdr.p_offset = (char *)buf - (char *)img;
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img->phdr.p_vaddr = (ElfW(Addr))buf;
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img->phdr.p_paddr = img->phdr.p_vaddr;
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img->phdr.p_filesz = 0;
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img->phdr.p_memsz = buf_size;
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img->phdr.p_flags = PF_X;
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memcpy(img->str, strings, sizeof(img->str));
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img->shdr[0].sh_type = SHT_NULL;
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/* Trick: The contents of code_gen_buffer are not present in this fake
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ELF file; that got allocated elsewhere, discontiguously. Therefore
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we mark .text as SHT_NOBITS (similar to .bss) so that readers will
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not look for contents. We can record any address at will. */
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img->shdr[1].sh_name = find_string(img->str, ".text");
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img->shdr[1].sh_type = SHT_NOBITS;
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img->shdr[1].sh_flags = SHF_EXECINSTR | SHF_ALLOC;
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img->shdr[1].sh_addr = (ElfW(Addr))buf;
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img->shdr[1].sh_size = buf_size;
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img->shdr[2].sh_name = find_string(img->str, ".debug_frame");
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img->shdr[2].sh_type = SHT_PROGBITS;
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img->shdr[2].sh_offset = sizeof(*img);
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img->shdr[2].sh_size = debug_frame_size;
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img = g_malloc(img_size);
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*img = img_template;
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memcpy(img + 1, debug_frame, debug_frame_size);
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img->shdr[3].sh_name = find_string(img->str, ".symtab");
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img->shdr[3].sh_type = SHT_SYMTAB;
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img->shdr[3].sh_offset = offsetof(struct ElfImage, sym);
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img->shdr[3].sh_size = sizeof(img->sym);
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img->shdr[3].sh_info = ARRAY_SIZE(img->sym);
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img->shdr[3].sh_link = img->ehdr.e_shstrndx;
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img->shdr[3].sh_entsize = sizeof(ElfW(Sym));
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img->phdr.p_vaddr = buf;
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img->phdr.p_paddr = buf;
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img->phdr.p_memsz = buf_size;
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img->shdr[4].sh_name = find_string(img->str, ".strtab");
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img->shdr[4].sh_type = SHT_STRTAB;
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img->shdr[4].sh_offset = offsetof(struct ElfImage, str);
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img->shdr[4].sh_size = sizeof(img->str);
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img->shdr[1].sh_name = find_string(img->str, ".text");
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img->shdr[1].sh_addr = buf;
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img->shdr[1].sh_size = buf_size;
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img->sym[0].st_name = find_string(img->str, "code_gen_buffer");
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img->sym[0].st_info = ELF_ST_INFO(STB_GLOBAL, STT_FUNC);
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img->sym[0].st_shndx = 1;
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img->sym[0].st_value = (ElfW(Addr))buf;
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img->sym[0].st_size = buf_size;
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img->shdr[2].sh_name = find_string(img->str, ".debug_info");
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img->shdr[3].sh_name = find_string(img->str, ".debug_abbrev");
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img->shdr[4].sh_name = find_string(img->str, ".debug_frame");
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img->shdr[4].sh_size = debug_frame_size;
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img->shdr[5].sh_name = find_string(img->str, ".symtab");
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img->shdr[6].sh_name = find_string(img->str, ".strtab");
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img->sym[1].st_name = find_string(img->str, "code_gen_buffer");
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img->sym[1].st_value = buf;
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img->sym[1].st_size = buf_size;
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img->di.cu_low_pc = buf;
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img->di.cu_high_pc = buf_size;
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img->di.fn_low_pc = buf;
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img->di.fn_high_pc = buf_size;
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#ifdef DEBUG_JIT
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/* Enable this block to be able to debug the ELF image file creation.
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@ -2397,7 +2479,7 @@ static void tcg_register_jit_int(void *buf, size_t buf_size,
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{
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FILE *f = fopen("/tmp/qemu.jit", "w+b");
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if (f) {
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if (fwrite(img, img_size, 1, f) != buf_size) {
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if (fwrite(img, img_size, 1, f) != img_size) {
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/* Avoid stupid unused return value warning for fwrite. */
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}
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fclose(f);
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@ -2414,7 +2496,8 @@ static void tcg_register_jit_int(void *buf, size_t buf_size,
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__jit_debug_register_code();
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}
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#else
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/* No support for the feature. Provide the entry point expected by exec.c. */
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/* No support for the feature. Provide the entry point expected by exec.c,
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and implement the internal function we declared earlier. */
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static void tcg_register_jit_int(void *buf, size_t size,
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void *debug_frame, size_t debug_frame_size)
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