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authorRichard Henderson <rth@twiddle.net>2012-03-24 10:47:36 -0700
committerBlue Swirl <blauwirbel@gmail.com>2012-03-24 19:57:12 +0000
commit5872bbf24e524899d002dc4fc9a8544b8334137a (patch)
tree18c8e414485724feb01305590b36b967781da7b4
parent55fddd661187bd321343776e2d460cc4e67d225b (diff)
downloadqemu-arm-5872bbf24e524899d002dc4fc9a8544b8334137a.tar.gz
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>
-rw-r--r--tcg/tcg.c233
1 files changed, 158 insertions, 75 deletions
diff --git a/tcg/tcg.c b/tcg/tcg.c
index eb595ce6fd..df4edc08f3 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -2252,8 +2252,17 @@ void tcg_dump_info(FILE *f, fprintf_function cpu_fprintf)
#endif
#ifdef ELF_HOST_MACHINE
-/* The backend should define ELF_HOST_MACHINE to indicate both what value to
- put into the ELF image and to indicate support for the feature. */
+/* In order to use this feature, the backend needs to do three things:
+
+ (1) Define ELF_HOST_MACHINE to indicate both what value to
+ put into the ELF image and to indicate support for the feature.
+
+ (2) Define tcg_register_jit. This should create a buffer containing
+ the contents of a .debug_frame section that describes the post-
+ prologue unwind info for the tcg machine.
+
+ (3) Call tcg_register_jit_int, with the constructed .debug_frame.
+*/
/* Begin GDB interface. THE FOLLOWING MUST MATCH GDB DOCS. */
typedef enum {
@@ -2300,96 +2309,169 @@ static int find_string(const char *strtab, const char *str)
}
}
-static void tcg_register_jit_int(void *buf, size_t buf_size,
+static void tcg_register_jit_int(void *buf_ptr, size_t buf_size,
void *debug_frame, size_t debug_frame_size)
{
- static const char strings[64] =
- "\0"
- ".text\0"
- ".debug_frame\0"
- ".symtab\0"
- ".strtab\0"
- "code_gen_buffer";
+ struct __attribute__((packed)) DebugInfo {
+ uint32_t len;
+ uint16_t version;
+ uint32_t abbrev;
+ uint8_t ptr_size;
+ uint8_t cu_die;
+ uint16_t cu_lang;
+ uintptr_t cu_low_pc;
+ uintptr_t cu_high_pc;
+ uint8_t fn_die;
+ char fn_name[16];
+ uintptr_t fn_low_pc;
+ uintptr_t fn_high_pc;
+ uint8_t cu_eoc;
+ };
struct ElfImage {
ElfW(Ehdr) ehdr;
ElfW(Phdr) phdr;
- ElfW(Shdr) shdr[5];
- ElfW(Sym) sym[1];
- char str[64];
+ ElfW(Shdr) shdr[7];
+ ElfW(Sym) sym[2];
+ struct DebugInfo di;
+ uint8_t da[24];
+ char str[80];
+ };
+
+ struct ElfImage *img;
+
+ static const struct ElfImage img_template = {
+ .ehdr = {
+ .e_ident[EI_MAG0] = ELFMAG0,
+ .e_ident[EI_MAG1] = ELFMAG1,
+ .e_ident[EI_MAG2] = ELFMAG2,
+ .e_ident[EI_MAG3] = ELFMAG3,
+ .e_ident[EI_CLASS] = ELF_CLASS,
+ .e_ident[EI_DATA] = ELF_DATA,
+ .e_ident[EI_VERSION] = EV_CURRENT,
+ .e_type = ET_EXEC,
+ .e_machine = ELF_HOST_MACHINE,
+ .e_version = EV_CURRENT,
+ .e_phoff = offsetof(struct ElfImage, phdr),
+ .e_shoff = offsetof(struct ElfImage, shdr),
+ .e_ehsize = sizeof(ElfW(Shdr)),
+ .e_phentsize = sizeof(ElfW(Phdr)),
+ .e_phnum = 1,
+ .e_shentsize = sizeof(ElfW(Shdr)),
+ .e_shnum = ARRAY_SIZE(img->shdr),
+ .e_shstrndx = ARRAY_SIZE(img->shdr) - 1,
+ },
+ .phdr = {
+ .p_type = PT_LOAD,
+ .p_flags = PF_X,
+ },
+ .shdr = {
+ [0] = { .sh_type = SHT_NULL },
+ /* Trick: The contents of code_gen_buffer are not present in
+ this fake ELF file; that got allocated elsewhere. Therefore
+ we mark .text as SHT_NOBITS (similar to .bss) so that readers
+ will not look for contents. We can record any address. */
+ [1] = { /* .text */
+ .sh_type = SHT_NOBITS,
+ .sh_flags = SHF_EXECINSTR | SHF_ALLOC,
+ },
+ [2] = { /* .debug_info */
+ .sh_type = SHT_PROGBITS,
+ .sh_offset = offsetof(struct ElfImage, di),
+ .sh_size = sizeof(struct DebugInfo),
+ },
+ [3] = { /* .debug_abbrev */
+ .sh_type = SHT_PROGBITS,
+ .sh_offset = offsetof(struct ElfImage, da),
+ .sh_size = sizeof(img->da),
+ },
+ [4] = { /* .debug_frame */
+ .sh_type = SHT_PROGBITS,
+ .sh_offset = sizeof(struct ElfImage),
+ },
+ [5] = { /* .symtab */
+ .sh_type = SHT_SYMTAB,
+ .sh_offset = offsetof(struct ElfImage, sym),
+ .sh_size = sizeof(img->sym),
+ .sh_info = 1,
+ .sh_link = ARRAY_SIZE(img->shdr) - 1,
+ .sh_entsize = sizeof(ElfW(Sym)),
+ },
+ [6] = { /* .strtab */
+ .sh_type = SHT_STRTAB,
+ .sh_offset = offsetof(struct ElfImage, str),
+ .sh_size = sizeof(img->str),
+ }
+ },
+ .sym = {
+ [1] = { /* code_gen_buffer */
+ .st_info = ELF_ST_INFO(STB_GLOBAL, STT_FUNC),
+ .st_shndx = 1,
+ }
+ },
+ .di = {
+ .len = sizeof(struct DebugInfo) - 4,
+ .version = 2,
+ .ptr_size = sizeof(void *),
+ .cu_die = 1,
+ .cu_lang = 0x8001, /* DW_LANG_Mips_Assembler */
+ .fn_die = 2,
+ .fn_name = "code_gen_buffer"
+ },
+ .da = {
+ 1, /* abbrev number (the cu) */
+ 0x11, 1, /* DW_TAG_compile_unit, has children */
+ 0x13, 0x5, /* DW_AT_language, DW_FORM_data2 */
+ 0x11, 0x1, /* DW_AT_low_pc, DW_FORM_addr */
+ 0x12, 0x1, /* DW_AT_high_pc, DW_FORM_addr */
+ 0, 0, /* end of abbrev */
+ 2, /* abbrev number (the fn) */
+ 0x2e, 0, /* DW_TAG_subprogram, no children */
+ 0x3, 0x8, /* DW_AT_name, DW_FORM_string */
+ 0x11, 0x1, /* DW_AT_low_pc, DW_FORM_addr */
+ 0x12, 0x1, /* DW_AT_high_pc, DW_FORM_addr */
+ 0, 0, /* end of abbrev */
+ 0 /* no more abbrev */
+ },
+ .str = "\0" ".text\0" ".debug_info\0" ".debug_abbrev\0"
+ ".debug_frame\0" ".symtab\0" ".strtab\0" "code_gen_buffer",
};
/* We only need a single jit entry; statically allocate it. */
static struct jit_code_entry one_entry;
+ uintptr_t buf = (uintptr_t)buf_ptr;
size_t img_size = sizeof(struct ElfImage) + debug_frame_size;
- struct ElfImage *img = g_malloc0(img_size);
-
- img->ehdr.e_ident[EI_MAG0] = ELFMAG0;
- img->ehdr.e_ident[EI_MAG1] = ELFMAG1;
- img->ehdr.e_ident[EI_MAG2] = ELFMAG2;
- img->ehdr.e_ident[EI_MAG3] = ELFMAG3;
- img->ehdr.e_ident[EI_CLASS] = ELF_CLASS;
- img->ehdr.e_ident[EI_DATA] = ELF_DATA;
- img->ehdr.e_ident[EI_VERSION] = EV_CURRENT;
- img->ehdr.e_type = ET_EXEC;
- img->ehdr.e_machine = ELF_HOST_MACHINE;
- img->ehdr.e_version = EV_CURRENT;
- img->ehdr.e_phoff = offsetof(struct ElfImage, phdr);
- img->ehdr.e_shoff = offsetof(struct ElfImage, shdr);
- img->ehdr.e_ehsize = sizeof(ElfW(Shdr));
- img->ehdr.e_phentsize = sizeof(ElfW(Phdr));
- img->ehdr.e_phnum = 1;
- img->ehdr.e_shentsize = sizeof(img->shdr[0]);
- img->ehdr.e_shnum = ARRAY_SIZE(img->shdr);
- img->ehdr.e_shstrndx = ARRAY_SIZE(img->shdr) - 1;
-
- img->phdr.p_type = PT_LOAD;
- img->phdr.p_offset = (char *)buf - (char *)img;
- img->phdr.p_vaddr = (ElfW(Addr))buf;
- img->phdr.p_paddr = img->phdr.p_vaddr;
- img->phdr.p_filesz = 0;
- img->phdr.p_memsz = buf_size;
- img->phdr.p_flags = PF_X;
- memcpy(img->str, strings, sizeof(img->str));
+ img = g_malloc(img_size);
+ *img = img_template;
+ memcpy(img + 1, debug_frame, debug_frame_size);
- img->shdr[0].sh_type = SHT_NULL;
+ img->phdr.p_vaddr = buf;
+ img->phdr.p_paddr = buf;
+ img->phdr.p_memsz = buf_size;
- /* Trick: The contents of code_gen_buffer are not present in this fake
- ELF file; that got allocated elsewhere, discontiguously. Therefore
- we mark .text as SHT_NOBITS (similar to .bss) so that readers will
- not look for contents. We can record any address at will. */
img->shdr[1].sh_name = find_string(img->str, ".text");
- img->shdr[1].sh_type = SHT_NOBITS;
- img->shdr[1].sh_flags = SHF_EXECINSTR | SHF_ALLOC;
- img->shdr[1].sh_addr = (ElfW(Addr))buf;
+ img->shdr[1].sh_addr = buf;
img->shdr[1].sh_size = buf_size;
- img->shdr[2].sh_name = find_string(img->str, ".debug_frame");
- img->shdr[2].sh_type = SHT_PROGBITS;
- img->shdr[2].sh_offset = sizeof(*img);
- img->shdr[2].sh_size = debug_frame_size;
- memcpy(img + 1, debug_frame, debug_frame_size);
+ img->shdr[2].sh_name = find_string(img->str, ".debug_info");
+ img->shdr[3].sh_name = find_string(img->str, ".debug_abbrev");
+
+ img->shdr[4].sh_name = find_string(img->str, ".debug_frame");
+ img->shdr[4].sh_size = debug_frame_size;
+
+ img->shdr[5].sh_name = find_string(img->str, ".symtab");
+ img->shdr[6].sh_name = find_string(img->str, ".strtab");
+
+ img->sym[1].st_name = find_string(img->str, "code_gen_buffer");
+ img->sym[1].st_value = buf;
+ img->sym[1].st_size = buf_size;
- img->shdr[3].sh_name = find_string(img->str, ".symtab");
- img->shdr[3].sh_type = SHT_SYMTAB;
- img->shdr[3].sh_offset = offsetof(struct ElfImage, sym);
- img->shdr[3].sh_size = sizeof(img->sym);
- img->shdr[3].sh_info = ARRAY_SIZE(img->sym);
- img->shdr[3].sh_link = img->ehdr.e_shstrndx;
- img->shdr[3].sh_entsize = sizeof(ElfW(Sym));
-
- img->shdr[4].sh_name = find_string(img->str, ".strtab");
- img->shdr[4].sh_type = SHT_STRTAB;
- img->shdr[4].sh_offset = offsetof(struct ElfImage, str);
- img->shdr[4].sh_size = sizeof(img->str);
-
- img->sym[0].st_name = find_string(img->str, "code_gen_buffer");
- img->sym[0].st_info = ELF_ST_INFO(STB_GLOBAL, STT_FUNC);
- img->sym[0].st_shndx = 1;
- img->sym[0].st_value = (ElfW(Addr))buf;
- img->sym[0].st_size = buf_size;
+ img->di.cu_low_pc = buf;
+ img->di.cu_high_pc = buf_size;
+ img->di.fn_low_pc = buf;
+ img->di.fn_high_pc = buf_size;
#ifdef DEBUG_JIT
/* Enable this block to be able to debug the ELF image file creation.
@@ -2397,7 +2479,7 @@ static void tcg_register_jit_int(void *buf, size_t buf_size,
{
FILE *f = fopen("/tmp/qemu.jit", "w+b");
if (f) {
- if (fwrite(img, img_size, 1, f) != buf_size) {
+ if (fwrite(img, img_size, 1, f) != img_size) {
/* Avoid stupid unused return value warning for fwrite. */
}
fclose(f);
@@ -2414,7 +2496,8 @@ static void tcg_register_jit_int(void *buf, size_t buf_size,
__jit_debug_register_code();
}
#else
-/* No support for the feature. Provide the entry point expected by exec.c. */
+/* No support for the feature. Provide the entry point expected by exec.c,
+ and implement the internal function we declared earlier. */
static void tcg_register_jit_int(void *buf, size_t size,
void *debug_frame, size_t debug_frame_size)