* [Qemu-devel] [PATCH v2] Use the GDB JIT debugging interface
@ 2012-03-19 19:25 Richard Henderson
2012-03-19 19:25 ` [Qemu-devel] [PATCH] tcg: " Richard Henderson
2012-03-19 20:08 ` [Qemu-devel] [PATCH v2] " Peter Maydell
0 siblings, 2 replies; 6+ messages in thread
From: Richard Henderson @ 2012-03-19 19:25 UTC (permalink / raw)
To: qemu-devel
I was reminded about this from a comment on the list, where
a new developer had gotten confused by our backtrace.
Changes from V1 to V2:
* Rebase to master.
* Do not try to allocate the ELF stuff within the code_gen_buffer.
Instead we can use a SHT_NOBITS trick to say that's out-of-line.
* Use C structures (with alignment and packing annotations) to create
the Dwarf2 unwind info. Previously I had used inline assembly.
Example:
Breakpoint 1, helper_idivl_EAX (t0=512)
at /home/rth/work/qemu/qemu/target-i386/op_helper.c:1882
1882 {
(gdb) where
#0 helper_idivl_EAX (t0=512)
at /home/rth/work/qemu/qemu/target-i386/op_helper.c:1882
#1 0x00005555557c0fdf in static_code_gen_buffer ()
#2 0x000055555559714d in cpu_x86_exec (env=0x5555577fba30)
at /home/rth/work/qemu/qemu/cpu-exec.c:564
#3 0x00005555555b3290 in cpu_loop (env=0x5555577fba30)
at /home/rth/work/qemu/qemu/linux-user/main.c:317
#4 0x00005555555b40a4 in main (argc=<optimized out>, argv=<optimized out>,
envp=<optimized out>) at /home/rth/work/qemu/qemu/linux-user/main.c:3826
r~
Richard Henderson (1):
tcg: Use the GDB JIT debugging interface.
elf.h | 1 +
exec.c | 1 +
tcg/i386/tcg-target.c | 114 ++++++++++++++++++++++++++--
tcg/tcg.c | 194 +++++++++++++++++++++++++++++++++++++++++++++++++
tcg/tcg.h | 2 +
5 files changed, 303 insertions(+), 9 deletions(-)
--
1.7.7.6
^ permalink raw reply [flat|nested] 6+ messages in thread* [Qemu-devel] [PATCH] tcg: Use the GDB JIT debugging interface. 2012-03-19 19:25 [Qemu-devel] [PATCH v2] Use the GDB JIT debugging interface Richard Henderson @ 2012-03-19 19:25 ` Richard Henderson 2012-03-24 16:11 ` Blue Swirl 2012-03-19 20:08 ` [Qemu-devel] [PATCH v2] " Peter Maydell 1 sibling, 1 reply; 6+ messages in thread From: Richard Henderson @ 2012-03-19 19:25 UTC (permalink / raw) To: qemu-devel This allows us to generate unwind info for the dynamicly generated code in the code_gen_buffer. Only i386 is converted at this point. Signed-off-by: Richard Henderson <rth@twiddle.net> --- elf.h | 1 + exec.c | 1 + tcg/i386/tcg-target.c | 114 ++++++++++++++++++++++++++-- tcg/tcg.c | 194 +++++++++++++++++++++++++++++++++++++++++++++++++ tcg/tcg.h | 2 + 5 files changed, 303 insertions(+), 9 deletions(-) diff --git a/elf.h b/elf.h index 2e05d34..310e05a 100644 --- a/elf.h +++ b/elf.h @@ -216,6 +216,7 @@ typedef int64_t Elf64_Sxword; #define ELF_ST_BIND(x) ((x) >> 4) #define ELF_ST_TYPE(x) (((unsigned int) x) & 0xf) +#define ELF_ST_INFO(bind, type) (((bind) << 4) | ((type) & 0xf)) #define ELF32_ST_BIND(x) ELF_ST_BIND(x) #define ELF32_ST_TYPE(x) ELF_ST_TYPE(x) #define ELF64_ST_BIND(x) ELF_ST_BIND(x) diff --git a/exec.c b/exec.c index be392e2..dd24939 100644 --- a/exec.c +++ b/exec.c @@ -636,6 +636,7 @@ void tcg_exec_init(unsigned long tb_size) cpu_gen_init(); code_gen_alloc(tb_size); code_gen_ptr = code_gen_buffer; + tcg_register_jit(code_gen_buffer, code_gen_buffer_size); page_init(); #if !defined(CONFIG_USER_ONLY) || !defined(CONFIG_USE_GUEST_BASE) /* There's no guest base to take into account, so go ahead and diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c index 43a51a1..871a7e7 100644 --- a/tcg/i386/tcg-target.c +++ b/tcg/i386/tcg-target.c @@ -1989,22 +1989,29 @@ static int tcg_target_callee_save_regs[] = { #endif }; +/* Compute frame size via macros, to share between tcg_target_qemu_prologue + and tcg_register_jit. */ + +#define PUSH_SIZE \ + ((1 + ARRAY_SIZE(tcg_target_callee_save_regs)) \ + * (TCG_TARGET_REG_BITS / 8)) + +#define FRAME_SIZE \ + ((PUSH_SIZE \ + + TCG_STATIC_CALL_ARGS_SIZE \ + + CPU_TEMP_BUF_NLONGS * sizeof(long) \ + + TCG_TARGET_STACK_ALIGN - 1) \ + & ~(TCG_TARGET_STACK_ALIGN - 1)) + /* Generate global QEMU prologue and epilogue code */ static void tcg_target_qemu_prologue(TCGContext *s) { - int i, frame_size, push_size, stack_addend; + int i, stack_addend; /* TB prologue */ /* Reserve some stack space, also for TCG temps. */ - push_size = 1 + ARRAY_SIZE(tcg_target_callee_save_regs); - push_size *= TCG_TARGET_REG_BITS / 8; - - frame_size = push_size + TCG_STATIC_CALL_ARGS_SIZE + - CPU_TEMP_BUF_NLONGS * sizeof(long); - frame_size = (frame_size + TCG_TARGET_STACK_ALIGN - 1) & - ~(TCG_TARGET_STACK_ALIGN - 1); - stack_addend = frame_size - push_size; + stack_addend = FRAME_SIZE - PUSH_SIZE; tcg_set_frame(s, TCG_REG_CALL_STACK, TCG_STATIC_CALL_ARGS_SIZE, CPU_TEMP_BUF_NLONGS * sizeof(long)); @@ -2070,3 +2077,92 @@ static void tcg_target_init(TCGContext *s) tcg_add_target_add_op_defs(x86_op_defs); } + +typedef struct { + uint32_t len __attribute__((aligned((sizeof(void *))))); + uint32_t id; + uint8_t version; + char augmentation[1]; + uint8_t code_align; + uint8_t data_align; + uint8_t return_column; +} DebugFrameCIE; + +typedef struct { + uint32_t len __attribute__((aligned((sizeof(void *))))); + uint32_t cie_offset; + tcg_target_long func_start __attribute__((packed)); + tcg_target_long func_len __attribute__((packed)); + uint8_t def_cfa[4]; + uint8_t reg_ofs[14]; +} DebugFrameFDE; + +typedef struct { + DebugFrameCIE cie; + DebugFrameFDE fde; +} DebugFrame; + +#if TCG_TARGET_REG_BITS == 64 +#define ELF_HOST_MACHINE EM_X86_64 +static DebugFrame debug_frame = { + .cie.len = sizeof(DebugFrameCIE)-4, /* length after .len member */ + .cie.id = -1, + .cie.version = 1, + .cie.code_align = 1, + .cie.data_align = 0x78, /* sleb128 -8 */ + .cie.return_column = 16, + + .fde.len = sizeof(DebugFrameFDE)-4, /* length after .len member */ + .fde.def_cfa = { + 12, 7, /* DW_CFA_def_cfa %rsp, ... */ + (FRAME_SIZE & 0x7f) | 0x80, /* ... uleb128 FRAME_SIZE */ + (FRAME_SIZE >> 7) + }, + .fde.reg_ofs = { + 0x90, 1, /* DW_CFA_offset, %rip, -8 */ + /* The following ordering must match tcg_target_callee_save_regs. */ + 0x86, 2, /* DW_CFA_offset, %rbp, -16 */ + 0x83, 3, /* DW_CFA_offset, %rbx, -24 */ + 0x8c, 4, /* DW_CFA_offset, %r12, -32 */ + 0x8d, 5, /* DW_CFA_offset, %r13, -40 */ + 0x8e, 6, /* DW_CFA_offset, %r14, -48 */ + 0x8f, 7, /* DW_CFA_offset, %r15, -56 */ + } +}; +#else +#define ELF_HOST_MACHINE EM_386 +static DebugFrame debug_frame = { + .cie.len = sizeof(DebugFrameCIE)-4, /* length after .len member */ + .cie.id = -1, + .cie.version = 1, + .cie.code_align = 1, + .cie.data_align = 0x7c, /* sleb128 -4 */ + .cie.return_column = 8, + + .fde.len = sizeof(DebugFrameFDE)-4, /* length after .len member */ + .fde.def_cfa = { + 12, 4, /* DW_CFA_def_cfa %esp, ... */ + (FRAME_SIZE & 0x7f) | 0x80, /* ... uleb128 FRAME_SIZE */ + (FRAME_SIZE >> 7) + }, + .fde.reg_ofs = { + 0x88, 1, /* DW_CFA_offset, %eip, -4 */ + /* The following ordering must match tcg_target_callee_save_regs. */ + 0x85, 2, /* DW_CFA_offset, %ebp, -8 */ + 0x83, 3, /* DW_CFA_offset, %ebx, -12 */ + 0x86, 4, /* DW_CFA_offset, %esi, -16 */ + 0x87, 5, /* DW_CFA_offset, %edi, -20 */ + } +}; +#endif + +void tcg_register_jit(void *buf, size_t buf_size) +{ + /* We're expecting a 2 byte uleb128 encoded value. */ + assert(FRAME_SIZE >> 14 == 0); + + debug_frame.fde.func_start = (tcg_target_long) buf; + debug_frame.fde.func_len = buf_size; + + tcg_register_jit_int(buf, buf_size, &debug_frame, sizeof(debug_frame)); +} diff --git a/tcg/tcg.c b/tcg/tcg.c index ccfcd1a..eb595ce 100644 --- a/tcg/tcg.c +++ b/tcg/tcg.c @@ -28,6 +28,9 @@ #include "config.h" +/* Define to jump the ELF file used to communicate with GDB. */ +#undef DEBUG_JIT + #if !defined(CONFIG_DEBUG_TCG) && !defined(NDEBUG) /* define it to suppress various consistency checks (faster) */ #define NDEBUG @@ -45,6 +48,18 @@ #include "cpu.h" #include "tcg-op.h" + +#if TCG_TARGET_REG_BITS == 64 +# define ELF_CLASS ELFCLASS64 +#else +# define ELF_CLASS ELFCLASS32 +#endif +#ifdef HOST_WORDS_BIGENDIAN +# define ELF_DATA ELFDATA2MSB +#else +# define ELF_DATA ELFDATA2LSB +#endif + #include "elf.h" #if defined(CONFIG_USE_GUEST_BASE) && !defined(TCG_TARGET_HAS_GUEST_BASE) @@ -57,6 +72,10 @@ static void tcg_target_qemu_prologue(TCGContext *s); static void patch_reloc(uint8_t *code_ptr, int type, tcg_target_long value, tcg_target_long addend); +static void tcg_register_jit_int(void *buf, size_t size, + void *debug_frame, size_t debug_frame_size) + __attribute__((unused)); + /* Forward declarations for functions declared and used in tcg-target.c. */ static int target_parse_constraint(TCGArgConstraint *ct, const char **pct_str); static void tcg_out_ld(TCGContext *s, TCGType type, TCGReg ret, TCGReg arg1, @@ -2231,3 +2250,178 @@ void tcg_dump_info(FILE *f, fprintf_function cpu_fprintf) cpu_fprintf(f, "[TCG profiler not compiled]\n"); } #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. */ + +/* Begin GDB interface. THE FOLLOWING MUST MATCH GDB DOCS. */ +typedef enum { + JIT_NOACTION = 0, + JIT_REGISTER_FN, + JIT_UNREGISTER_FN +} jit_actions_t; + +struct jit_code_entry { + struct jit_code_entry *next_entry; + struct jit_code_entry *prev_entry; + const void *symfile_addr; + uint64_t symfile_size; +}; + +struct jit_descriptor { + uint32_t version; + uint32_t action_flag; + struct jit_code_entry *relevant_entry; + struct jit_code_entry *first_entry; +}; + +void __jit_debug_register_code(void) __attribute__((noinline)); +void __jit_debug_register_code(void) +{ + asm(""); +} + +/* Must statically initialize the version, because GDB may check + the version before we can set it. */ +struct jit_descriptor __jit_debug_descriptor = { 1, 0, 0, 0 }; + +/* End GDB interface. */ + +static int find_string(const char *strtab, const char *str) +{ + const char *p = strtab + 1; + + while (1) { + if (strcmp(p, str) == 0) { + return p - strtab; + } + p += strlen(p) + 1; + } +} + +static void tcg_register_jit_int(void *buf, 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 ElfImage { + ElfW(Ehdr) ehdr; + ElfW(Phdr) phdr; + ElfW(Shdr) shdr[5]; + ElfW(Sym) sym[1]; + char str[64]; + }; + + /* We only need a single jit entry; statically allocate it. */ + static struct jit_code_entry one_entry; + + 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->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, 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_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[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; + +#ifdef DEBUG_JIT + /* Enable this block to be able to debug the ELF image file creation. + One can use readelf, objdump, or other inspection utilities. */ + { + FILE *f = fopen("/tmp/qemu.jit", "w+b"); + if (f) { + if (fwrite(img, img_size, 1, f) != buf_size) { + /* Avoid stupid unused return value warning for fwrite. */ + } + fclose(f); + } + } +#endif + + one_entry.symfile_addr = img; + one_entry.symfile_size = img_size; + + __jit_debug_descriptor.action_flag = JIT_REGISTER_FN; + __jit_debug_descriptor.relevant_entry = &one_entry; + __jit_debug_descriptor.first_entry = &one_entry; + __jit_debug_register_code(); +} +#else +/* No support for the feature. Provide the entry point expected by exec.c. */ + +static void tcg_register_jit_int(void *buf, size_t size, + void *debug_frame, size_t debug_frame_size) +{ +} + +void tcg_register_jit(void *buf, size_t buf_size) +{ +} +#endif /* ELF_HOST_MACHINE */ diff --git a/tcg/tcg.h b/tcg/tcg.h index 5f6c647..a83bddd 100644 --- a/tcg/tcg.h +++ b/tcg/tcg.h @@ -586,3 +586,5 @@ extern uint8_t code_gen_prologue[]; # define tcg_qemu_tb_exec(env, tb_ptr) \ ((tcg_target_ulong (*)(void *, void *))code_gen_prologue)(env, tb_ptr) #endif + +void tcg_register_jit(void *buf, size_t buf_size); -- 1.7.7.6 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH] tcg: Use the GDB JIT debugging interface. 2012-03-19 19:25 ` [Qemu-devel] [PATCH] tcg: " Richard Henderson @ 2012-03-24 16:11 ` Blue Swirl 2012-03-24 17:04 ` Peter Maydell 0 siblings, 1 reply; 6+ messages in thread From: Blue Swirl @ 2012-03-24 16:11 UTC (permalink / raw) To: Richard Henderson; +Cc: qemu-devel Thanks, applied. On Mon, Mar 19, 2012 at 19:25, Richard Henderson <rth@twiddle.net> wrote: > This allows us to generate unwind info for the dynamicly generated > code in the code_gen_buffer. Only i386 is converted at this point. > > Signed-off-by: Richard Henderson <rth@twiddle.net> > --- > elf.h | 1 + > exec.c | 1 + > tcg/i386/tcg-target.c | 114 ++++++++++++++++++++++++++-- > tcg/tcg.c | 194 +++++++++++++++++++++++++++++++++++++++++++++++++ > tcg/tcg.h | 2 + > 5 files changed, 303 insertions(+), 9 deletions(-) > > diff --git a/elf.h b/elf.h > index 2e05d34..310e05a 100644 > --- a/elf.h > +++ b/elf.h > @@ -216,6 +216,7 @@ typedef int64_t Elf64_Sxword; > > #define ELF_ST_BIND(x) ((x) >> 4) > #define ELF_ST_TYPE(x) (((unsigned int) x) & 0xf) > +#define ELF_ST_INFO(bind, type) (((bind) << 4) | ((type) & 0xf)) > #define ELF32_ST_BIND(x) ELF_ST_BIND(x) > #define ELF32_ST_TYPE(x) ELF_ST_TYPE(x) > #define ELF64_ST_BIND(x) ELF_ST_BIND(x) > diff --git a/exec.c b/exec.c > index be392e2..dd24939 100644 > --- a/exec.c > +++ b/exec.c > @@ -636,6 +636,7 @@ void tcg_exec_init(unsigned long tb_size) > cpu_gen_init(); > code_gen_alloc(tb_size); > code_gen_ptr = code_gen_buffer; > + tcg_register_jit(code_gen_buffer, code_gen_buffer_size); > page_init(); > #if !defined(CONFIG_USER_ONLY) || !defined(CONFIG_USE_GUEST_BASE) > /* There's no guest base to take into account, so go ahead and > diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c > index 43a51a1..871a7e7 100644 > --- a/tcg/i386/tcg-target.c > +++ b/tcg/i386/tcg-target.c > @@ -1989,22 +1989,29 @@ static int tcg_target_callee_save_regs[] = { > #endif > }; > > +/* Compute frame size via macros, to share between tcg_target_qemu_prologue > + and tcg_register_jit. */ > + > +#define PUSH_SIZE \ > + ((1 + ARRAY_SIZE(tcg_target_callee_save_regs)) \ > + * (TCG_TARGET_REG_BITS / 8)) > + > +#define FRAME_SIZE \ > + ((PUSH_SIZE \ > + + TCG_STATIC_CALL_ARGS_SIZE \ > + + CPU_TEMP_BUF_NLONGS * sizeof(long) \ > + + TCG_TARGET_STACK_ALIGN - 1) \ > + & ~(TCG_TARGET_STACK_ALIGN - 1)) > + > /* Generate global QEMU prologue and epilogue code */ > static void tcg_target_qemu_prologue(TCGContext *s) > { > - int i, frame_size, push_size, stack_addend; > + int i, stack_addend; > > /* TB prologue */ > > /* Reserve some stack space, also for TCG temps. */ > - push_size = 1 + ARRAY_SIZE(tcg_target_callee_save_regs); > - push_size *= TCG_TARGET_REG_BITS / 8; > - > - frame_size = push_size + TCG_STATIC_CALL_ARGS_SIZE + > - CPU_TEMP_BUF_NLONGS * sizeof(long); > - frame_size = (frame_size + TCG_TARGET_STACK_ALIGN - 1) & > - ~(TCG_TARGET_STACK_ALIGN - 1); > - stack_addend = frame_size - push_size; > + stack_addend = FRAME_SIZE - PUSH_SIZE; > tcg_set_frame(s, TCG_REG_CALL_STACK, TCG_STATIC_CALL_ARGS_SIZE, > CPU_TEMP_BUF_NLONGS * sizeof(long)); > > @@ -2070,3 +2077,92 @@ static void tcg_target_init(TCGContext *s) > > tcg_add_target_add_op_defs(x86_op_defs); > } > + > +typedef struct { > + uint32_t len __attribute__((aligned((sizeof(void *))))); > + uint32_t id; > + uint8_t version; > + char augmentation[1]; > + uint8_t code_align; > + uint8_t data_align; > + uint8_t return_column; > +} DebugFrameCIE; > + > +typedef struct { > + uint32_t len __attribute__((aligned((sizeof(void *))))); > + uint32_t cie_offset; > + tcg_target_long func_start __attribute__((packed)); > + tcg_target_long func_len __attribute__((packed)); > + uint8_t def_cfa[4]; > + uint8_t reg_ofs[14]; > +} DebugFrameFDE; > + > +typedef struct { > + DebugFrameCIE cie; > + DebugFrameFDE fde; > +} DebugFrame; > + > +#if TCG_TARGET_REG_BITS == 64 > +#define ELF_HOST_MACHINE EM_X86_64 > +static DebugFrame debug_frame = { > + .cie.len = sizeof(DebugFrameCIE)-4, /* length after .len member */ > + .cie.id = -1, > + .cie.version = 1, > + .cie.code_align = 1, > + .cie.data_align = 0x78, /* sleb128 -8 */ > + .cie.return_column = 16, > + > + .fde.len = sizeof(DebugFrameFDE)-4, /* length after .len member */ > + .fde.def_cfa = { > + 12, 7, /* DW_CFA_def_cfa %rsp, ... */ > + (FRAME_SIZE & 0x7f) | 0x80, /* ... uleb128 FRAME_SIZE */ > + (FRAME_SIZE >> 7) > + }, > + .fde.reg_ofs = { > + 0x90, 1, /* DW_CFA_offset, %rip, -8 */ > + /* The following ordering must match tcg_target_callee_save_regs. */ > + 0x86, 2, /* DW_CFA_offset, %rbp, -16 */ > + 0x83, 3, /* DW_CFA_offset, %rbx, -24 */ > + 0x8c, 4, /* DW_CFA_offset, %r12, -32 */ > + 0x8d, 5, /* DW_CFA_offset, %r13, -40 */ > + 0x8e, 6, /* DW_CFA_offset, %r14, -48 */ > + 0x8f, 7, /* DW_CFA_offset, %r15, -56 */ > + } > +}; > +#else > +#define ELF_HOST_MACHINE EM_386 > +static DebugFrame debug_frame = { > + .cie.len = sizeof(DebugFrameCIE)-4, /* length after .len member */ > + .cie.id = -1, > + .cie.version = 1, > + .cie.code_align = 1, > + .cie.data_align = 0x7c, /* sleb128 -4 */ > + .cie.return_column = 8, > + > + .fde.len = sizeof(DebugFrameFDE)-4, /* length after .len member */ > + .fde.def_cfa = { > + 12, 4, /* DW_CFA_def_cfa %esp, ... */ > + (FRAME_SIZE & 0x7f) | 0x80, /* ... uleb128 FRAME_SIZE */ > + (FRAME_SIZE >> 7) > + }, > + .fde.reg_ofs = { > + 0x88, 1, /* DW_CFA_offset, %eip, -4 */ > + /* The following ordering must match tcg_target_callee_save_regs. */ > + 0x85, 2, /* DW_CFA_offset, %ebp, -8 */ > + 0x83, 3, /* DW_CFA_offset, %ebx, -12 */ > + 0x86, 4, /* DW_CFA_offset, %esi, -16 */ > + 0x87, 5, /* DW_CFA_offset, %edi, -20 */ > + } > +}; > +#endif > + > +void tcg_register_jit(void *buf, size_t buf_size) > +{ > + /* We're expecting a 2 byte uleb128 encoded value. */ > + assert(FRAME_SIZE >> 14 == 0); > + > + debug_frame.fde.func_start = (tcg_target_long) buf; > + debug_frame.fde.func_len = buf_size; > + > + tcg_register_jit_int(buf, buf_size, &debug_frame, sizeof(debug_frame)); > +} > diff --git a/tcg/tcg.c b/tcg/tcg.c > index ccfcd1a..eb595ce 100644 > --- a/tcg/tcg.c > +++ b/tcg/tcg.c > @@ -28,6 +28,9 @@ > > #include "config.h" > > +/* Define to jump the ELF file used to communicate with GDB. */ > +#undef DEBUG_JIT > + > #if !defined(CONFIG_DEBUG_TCG) && !defined(NDEBUG) > /* define it to suppress various consistency checks (faster) */ > #define NDEBUG > @@ -45,6 +48,18 @@ > #include "cpu.h" > > #include "tcg-op.h" > + > +#if TCG_TARGET_REG_BITS == 64 > +# define ELF_CLASS ELFCLASS64 > +#else > +# define ELF_CLASS ELFCLASS32 > +#endif > +#ifdef HOST_WORDS_BIGENDIAN > +# define ELF_DATA ELFDATA2MSB > +#else > +# define ELF_DATA ELFDATA2LSB > +#endif > + > #include "elf.h" > > #if defined(CONFIG_USE_GUEST_BASE) && !defined(TCG_TARGET_HAS_GUEST_BASE) > @@ -57,6 +72,10 @@ static void tcg_target_qemu_prologue(TCGContext *s); > static void patch_reloc(uint8_t *code_ptr, int type, > tcg_target_long value, tcg_target_long addend); > > +static void tcg_register_jit_int(void *buf, size_t size, > + void *debug_frame, size_t debug_frame_size) > + __attribute__((unused)); > + > /* Forward declarations for functions declared and used in tcg-target.c. */ > static int target_parse_constraint(TCGArgConstraint *ct, const char **pct_str); > static void tcg_out_ld(TCGContext *s, TCGType type, TCGReg ret, TCGReg arg1, > @@ -2231,3 +2250,178 @@ void tcg_dump_info(FILE *f, fprintf_function cpu_fprintf) > cpu_fprintf(f, "[TCG profiler not compiled]\n"); > } > #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. */ > + > +/* Begin GDB interface. THE FOLLOWING MUST MATCH GDB DOCS. */ > +typedef enum { > + JIT_NOACTION = 0, > + JIT_REGISTER_FN, > + JIT_UNREGISTER_FN > +} jit_actions_t; > + > +struct jit_code_entry { > + struct jit_code_entry *next_entry; > + struct jit_code_entry *prev_entry; > + const void *symfile_addr; > + uint64_t symfile_size; > +}; > + > +struct jit_descriptor { > + uint32_t version; > + uint32_t action_flag; > + struct jit_code_entry *relevant_entry; > + struct jit_code_entry *first_entry; > +}; > + > +void __jit_debug_register_code(void) __attribute__((noinline)); > +void __jit_debug_register_code(void) > +{ > + asm(""); > +} > + > +/* Must statically initialize the version, because GDB may check > + the version before we can set it. */ > +struct jit_descriptor __jit_debug_descriptor = { 1, 0, 0, 0 }; > + > +/* End GDB interface. */ > + > +static int find_string(const char *strtab, const char *str) > +{ > + const char *p = strtab + 1; > + > + while (1) { > + if (strcmp(p, str) == 0) { > + return p - strtab; > + } > + p += strlen(p) + 1; > + } > +} > + > +static void tcg_register_jit_int(void *buf, 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 ElfImage { > + ElfW(Ehdr) ehdr; > + ElfW(Phdr) phdr; > + ElfW(Shdr) shdr[5]; > + ElfW(Sym) sym[1]; > + char str[64]; > + }; > + > + /* We only need a single jit entry; statically allocate it. */ > + static struct jit_code_entry one_entry; > + > + 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->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, 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_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[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; > + > +#ifdef DEBUG_JIT > + /* Enable this block to be able to debug the ELF image file creation. > + One can use readelf, objdump, or other inspection utilities. */ > + { > + FILE *f = fopen("/tmp/qemu.jit", "w+b"); > + if (f) { > + if (fwrite(img, img_size, 1, f) != buf_size) { > + /* Avoid stupid unused return value warning for fwrite. */ > + } > + fclose(f); > + } > + } > +#endif > + > + one_entry.symfile_addr = img; > + one_entry.symfile_size = img_size; > + > + __jit_debug_descriptor.action_flag = JIT_REGISTER_FN; > + __jit_debug_descriptor.relevant_entry = &one_entry; > + __jit_debug_descriptor.first_entry = &one_entry; > + __jit_debug_register_code(); > +} > +#else > +/* No support for the feature. Provide the entry point expected by exec.c. */ > + > +static void tcg_register_jit_int(void *buf, size_t size, > + void *debug_frame, size_t debug_frame_size) > +{ > +} > + > +void tcg_register_jit(void *buf, size_t buf_size) > +{ > +} > +#endif /* ELF_HOST_MACHINE */ > diff --git a/tcg/tcg.h b/tcg/tcg.h > index 5f6c647..a83bddd 100644 > --- a/tcg/tcg.h > +++ b/tcg/tcg.h > @@ -586,3 +586,5 @@ extern uint8_t code_gen_prologue[]; > # define tcg_qemu_tb_exec(env, tb_ptr) \ > ((tcg_target_ulong (*)(void *, void *))code_gen_prologue)(env, tb_ptr) > #endif > + > +void tcg_register_jit(void *buf, size_t buf_size); > -- > 1.7.7.6 > > ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH] tcg: Use the GDB JIT debugging interface. 2012-03-24 16:11 ` Blue Swirl @ 2012-03-24 17:04 ` Peter Maydell 0 siblings, 0 replies; 6+ messages in thread From: Peter Maydell @ 2012-03-24 17:04 UTC (permalink / raw) To: Blue Swirl; +Cc: qemu-devel, Richard Henderson Er, this is the v2 patch, which Richard updated based on review comments, can you apply the later v3 one instead? thanks -- PMM On 24 March 2012 16:11, Blue Swirl <blauwirbel@gmail.com> wrote: > Thanks, applied. > > On Mon, Mar 19, 2012 at 19:25, Richard Henderson <rth@twiddle.net> wrote: >> This allows us to generate unwind info for the dynamicly generated >> code in the code_gen_buffer. Only i386 is converted at this point. >> >> Signed-off-by: Richard Henderson <rth@twiddle.net> >> --- >> elf.h | 1 + >> exec.c | 1 + >> tcg/i386/tcg-target.c | 114 ++++++++++++++++++++++++++-- >> tcg/tcg.c | 194 +++++++++++++++++++++++++++++++++++++++++++++++++ >> tcg/tcg.h | 2 + >> 5 files changed, 303 insertions(+), 9 deletions(-) >> >> diff --git a/elf.h b/elf.h >> index 2e05d34..310e05a 100644 >> --- a/elf.h >> +++ b/elf.h >> @@ -216,6 +216,7 @@ typedef int64_t Elf64_Sxword; >> >> #define ELF_ST_BIND(x) ((x) >> 4) >> #define ELF_ST_TYPE(x) (((unsigned int) x) & 0xf) >> +#define ELF_ST_INFO(bind, type) (((bind) << 4) | ((type) & 0xf)) >> #define ELF32_ST_BIND(x) ELF_ST_BIND(x) >> #define ELF32_ST_TYPE(x) ELF_ST_TYPE(x) >> #define ELF64_ST_BIND(x) ELF_ST_BIND(x) >> diff --git a/exec.c b/exec.c >> index be392e2..dd24939 100644 >> --- a/exec.c >> +++ b/exec.c >> @@ -636,6 +636,7 @@ void tcg_exec_init(unsigned long tb_size) >> cpu_gen_init(); >> code_gen_alloc(tb_size); >> code_gen_ptr = code_gen_buffer; >> + tcg_register_jit(code_gen_buffer, code_gen_buffer_size); >> page_init(); >> #if !defined(CONFIG_USER_ONLY) || !defined(CONFIG_USE_GUEST_BASE) >> /* There's no guest base to take into account, so go ahead and >> diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c >> index 43a51a1..871a7e7 100644 >> --- a/tcg/i386/tcg-target.c >> +++ b/tcg/i386/tcg-target.c >> @@ -1989,22 +1989,29 @@ static int tcg_target_callee_save_regs[] = { >> #endif >> }; >> >> +/* Compute frame size via macros, to share between tcg_target_qemu_prologue >> + and tcg_register_jit. */ >> + >> +#define PUSH_SIZE \ >> + ((1 + ARRAY_SIZE(tcg_target_callee_save_regs)) \ >> + * (TCG_TARGET_REG_BITS / 8)) >> + >> +#define FRAME_SIZE \ >> + ((PUSH_SIZE \ >> + + TCG_STATIC_CALL_ARGS_SIZE \ >> + + CPU_TEMP_BUF_NLONGS * sizeof(long) \ >> + + TCG_TARGET_STACK_ALIGN - 1) \ >> + & ~(TCG_TARGET_STACK_ALIGN - 1)) >> + >> /* Generate global QEMU prologue and epilogue code */ >> static void tcg_target_qemu_prologue(TCGContext *s) >> { >> - int i, frame_size, push_size, stack_addend; >> + int i, stack_addend; >> >> /* TB prologue */ >> >> /* Reserve some stack space, also for TCG temps. */ >> - push_size = 1 + ARRAY_SIZE(tcg_target_callee_save_regs); >> - push_size *= TCG_TARGET_REG_BITS / 8; >> - >> - frame_size = push_size + TCG_STATIC_CALL_ARGS_SIZE + >> - CPU_TEMP_BUF_NLONGS * sizeof(long); >> - frame_size = (frame_size + TCG_TARGET_STACK_ALIGN - 1) & >> - ~(TCG_TARGET_STACK_ALIGN - 1); >> - stack_addend = frame_size - push_size; >> + stack_addend = FRAME_SIZE - PUSH_SIZE; >> tcg_set_frame(s, TCG_REG_CALL_STACK, TCG_STATIC_CALL_ARGS_SIZE, >> CPU_TEMP_BUF_NLONGS * sizeof(long)); >> >> @@ -2070,3 +2077,92 @@ static void tcg_target_init(TCGContext *s) >> >> tcg_add_target_add_op_defs(x86_op_defs); >> } >> + >> +typedef struct { >> + uint32_t len __attribute__((aligned((sizeof(void *))))); >> + uint32_t id; >> + uint8_t version; >> + char augmentation[1]; >> + uint8_t code_align; >> + uint8_t data_align; >> + uint8_t return_column; >> +} DebugFrameCIE; >> + >> +typedef struct { >> + uint32_t len __attribute__((aligned((sizeof(void *))))); >> + uint32_t cie_offset; >> + tcg_target_long func_start __attribute__((packed)); >> + tcg_target_long func_len __attribute__((packed)); >> + uint8_t def_cfa[4]; >> + uint8_t reg_ofs[14]; >> +} DebugFrameFDE; >> + >> +typedef struct { >> + DebugFrameCIE cie; >> + DebugFrameFDE fde; >> +} DebugFrame; >> + >> +#if TCG_TARGET_REG_BITS == 64 >> +#define ELF_HOST_MACHINE EM_X86_64 >> +static DebugFrame debug_frame = { >> + .cie.len = sizeof(DebugFrameCIE)-4, /* length after .len member */ >> + .cie.id = -1, >> + .cie.version = 1, >> + .cie.code_align = 1, >> + .cie.data_align = 0x78, /* sleb128 -8 */ >> + .cie.return_column = 16, >> + >> + .fde.len = sizeof(DebugFrameFDE)-4, /* length after .len member */ >> + .fde.def_cfa = { >> + 12, 7, /* DW_CFA_def_cfa %rsp, ... */ >> + (FRAME_SIZE & 0x7f) | 0x80, /* ... uleb128 FRAME_SIZE */ >> + (FRAME_SIZE >> 7) >> + }, >> + .fde.reg_ofs = { >> + 0x90, 1, /* DW_CFA_offset, %rip, -8 */ >> + /* The following ordering must match tcg_target_callee_save_regs. */ >> + 0x86, 2, /* DW_CFA_offset, %rbp, -16 */ >> + 0x83, 3, /* DW_CFA_offset, %rbx, -24 */ >> + 0x8c, 4, /* DW_CFA_offset, %r12, -32 */ >> + 0x8d, 5, /* DW_CFA_offset, %r13, -40 */ >> + 0x8e, 6, /* DW_CFA_offset, %r14, -48 */ >> + 0x8f, 7, /* DW_CFA_offset, %r15, -56 */ >> + } >> +}; >> +#else >> +#define ELF_HOST_MACHINE EM_386 >> +static DebugFrame debug_frame = { >> + .cie.len = sizeof(DebugFrameCIE)-4, /* length after .len member */ >> + .cie.id = -1, >> + .cie.version = 1, >> + .cie.code_align = 1, >> + .cie.data_align = 0x7c, /* sleb128 -4 */ >> + .cie.return_column = 8, >> + >> + .fde.len = sizeof(DebugFrameFDE)-4, /* length after .len member */ >> + .fde.def_cfa = { >> + 12, 4, /* DW_CFA_def_cfa %esp, ... */ >> + (FRAME_SIZE & 0x7f) | 0x80, /* ... uleb128 FRAME_SIZE */ >> + (FRAME_SIZE >> 7) >> + }, >> + .fde.reg_ofs = { >> + 0x88, 1, /* DW_CFA_offset, %eip, -4 */ >> + /* The following ordering must match tcg_target_callee_save_regs. */ >> + 0x85, 2, /* DW_CFA_offset, %ebp, -8 */ >> + 0x83, 3, /* DW_CFA_offset, %ebx, -12 */ >> + 0x86, 4, /* DW_CFA_offset, %esi, -16 */ >> + 0x87, 5, /* DW_CFA_offset, %edi, -20 */ >> + } >> +}; >> +#endif >> + >> +void tcg_register_jit(void *buf, size_t buf_size) >> +{ >> + /* We're expecting a 2 byte uleb128 encoded value. */ >> + assert(FRAME_SIZE >> 14 == 0); >> + >> + debug_frame.fde.func_start = (tcg_target_long) buf; >> + debug_frame.fde.func_len = buf_size; >> + >> + tcg_register_jit_int(buf, buf_size, &debug_frame, sizeof(debug_frame)); >> +} >> diff --git a/tcg/tcg.c b/tcg/tcg.c >> index ccfcd1a..eb595ce 100644 >> --- a/tcg/tcg.c >> +++ b/tcg/tcg.c >> @@ -28,6 +28,9 @@ >> >> #include "config.h" >> >> +/* Define to jump the ELF file used to communicate with GDB. */ >> +#undef DEBUG_JIT >> + >> #if !defined(CONFIG_DEBUG_TCG) && !defined(NDEBUG) >> /* define it to suppress various consistency checks (faster) */ >> #define NDEBUG >> @@ -45,6 +48,18 @@ >> #include "cpu.h" >> >> #include "tcg-op.h" >> + >> +#if TCG_TARGET_REG_BITS == 64 >> +# define ELF_CLASS ELFCLASS64 >> +#else >> +# define ELF_CLASS ELFCLASS32 >> +#endif >> +#ifdef HOST_WORDS_BIGENDIAN >> +# define ELF_DATA ELFDATA2MSB >> +#else >> +# define ELF_DATA ELFDATA2LSB >> +#endif >> + >> #include "elf.h" >> >> #if defined(CONFIG_USE_GUEST_BASE) && !defined(TCG_TARGET_HAS_GUEST_BASE) >> @@ -57,6 +72,10 @@ static void tcg_target_qemu_prologue(TCGContext *s); >> static void patch_reloc(uint8_t *code_ptr, int type, >> tcg_target_long value, tcg_target_long addend); >> >> +static void tcg_register_jit_int(void *buf, size_t size, >> + void *debug_frame, size_t debug_frame_size) >> + __attribute__((unused)); >> + >> /* Forward declarations for functions declared and used in tcg-target.c. */ >> static int target_parse_constraint(TCGArgConstraint *ct, const char **pct_str); >> static void tcg_out_ld(TCGContext *s, TCGType type, TCGReg ret, TCGReg arg1, >> @@ -2231,3 +2250,178 @@ void tcg_dump_info(FILE *f, fprintf_function cpu_fprintf) >> cpu_fprintf(f, "[TCG profiler not compiled]\n"); >> } >> #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. */ >> + >> +/* Begin GDB interface. THE FOLLOWING MUST MATCH GDB DOCS. */ >> +typedef enum { >> + JIT_NOACTION = 0, >> + JIT_REGISTER_FN, >> + JIT_UNREGISTER_FN >> +} jit_actions_t; >> + >> +struct jit_code_entry { >> + struct jit_code_entry *next_entry; >> + struct jit_code_entry *prev_entry; >> + const void *symfile_addr; >> + uint64_t symfile_size; >> +}; >> + >> +struct jit_descriptor { >> + uint32_t version; >> + uint32_t action_flag; >> + struct jit_code_entry *relevant_entry; >> + struct jit_code_entry *first_entry; >> +}; >> + >> +void __jit_debug_register_code(void) __attribute__((noinline)); >> +void __jit_debug_register_code(void) >> +{ >> + asm(""); >> +} >> + >> +/* Must statically initialize the version, because GDB may check >> + the version before we can set it. */ >> +struct jit_descriptor __jit_debug_descriptor = { 1, 0, 0, 0 }; >> + >> +/* End GDB interface. */ >> + >> +static int find_string(const char *strtab, const char *str) >> +{ >> + const char *p = strtab + 1; >> + >> + while (1) { >> + if (strcmp(p, str) == 0) { >> + return p - strtab; >> + } >> + p += strlen(p) + 1; >> + } >> +} >> + >> +static void tcg_register_jit_int(void *buf, 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 ElfImage { >> + ElfW(Ehdr) ehdr; >> + ElfW(Phdr) phdr; >> + ElfW(Shdr) shdr[5]; >> + ElfW(Sym) sym[1]; >> + char str[64]; >> + }; >> + >> + /* We only need a single jit entry; statically allocate it. */ >> + static struct jit_code_entry one_entry; >> + >> + 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->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, 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_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[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; >> + >> +#ifdef DEBUG_JIT >> + /* Enable this block to be able to debug the ELF image file creation. >> + One can use readelf, objdump, or other inspection utilities. */ >> + { >> + FILE *f = fopen("/tmp/qemu.jit", "w+b"); >> + if (f) { >> + if (fwrite(img, img_size, 1, f) != buf_size) { >> + /* Avoid stupid unused return value warning for fwrite. */ >> + } >> + fclose(f); >> + } >> + } >> +#endif >> + >> + one_entry.symfile_addr = img; >> + one_entry.symfile_size = img_size; >> + >> + __jit_debug_descriptor.action_flag = JIT_REGISTER_FN; >> + __jit_debug_descriptor.relevant_entry = &one_entry; >> + __jit_debug_descriptor.first_entry = &one_entry; >> + __jit_debug_register_code(); >> +} >> +#else >> +/* No support for the feature. Provide the entry point expected by exec.c. */ >> + >> +static void tcg_register_jit_int(void *buf, size_t size, >> + void *debug_frame, size_t debug_frame_size) >> +{ >> +} >> + >> +void tcg_register_jit(void *buf, size_t buf_size) >> +{ >> +} >> +#endif /* ELF_HOST_MACHINE */ >> diff --git a/tcg/tcg.h b/tcg/tcg.h >> index 5f6c647..a83bddd 100644 >> --- a/tcg/tcg.h >> +++ b/tcg/tcg.h >> @@ -586,3 +586,5 @@ extern uint8_t code_gen_prologue[]; >> # define tcg_qemu_tb_exec(env, tb_ptr) \ >> ((tcg_target_ulong (*)(void *, void *))code_gen_prologue)(env, tb_ptr) >> #endif >> + >> +void tcg_register_jit(void *buf, size_t buf_size); >> -- >> 1.7.7.6 >> >> > -- 12345678901234567890123456789012345678901234567890123456789012345678901234567890 1 2 3 4 5 6 7 8 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH v2] Use the GDB JIT debugging interface 2012-03-19 19:25 [Qemu-devel] [PATCH v2] Use the GDB JIT debugging interface Richard Henderson 2012-03-19 19:25 ` [Qemu-devel] [PATCH] tcg: " Richard Henderson @ 2012-03-19 20:08 ` Peter Maydell 2012-03-19 20:48 ` Richard Henderson 1 sibling, 1 reply; 6+ messages in thread From: Peter Maydell @ 2012-03-19 20:08 UTC (permalink / raw) To: Richard Henderson; +Cc: qemu-devel On 19 March 2012 19:25, Richard Henderson <rth@twiddle.net> wrote: > I was reminded about this from a comment on the list, where > a new developer had gotten confused by our backtrace. This is neat. > Example: > > Breakpoint 1, helper_idivl_EAX (t0=512) > at /home/rth/work/qemu/qemu/target-i386/op_helper.c:1882 > 1882 { > (gdb) where > #0 helper_idivl_EAX (t0=512) > at /home/rth/work/qemu/qemu/target-i386/op_helper.c:1882 > #1 0x00005555557c0fdf in static_code_gen_buffer () > #2 0x000055555559714d in cpu_x86_exec (env=0x5555577fba30) > at /home/rth/work/qemu/qemu/cpu-exec.c:564 > #3 0x00005555555b3290 in cpu_loop (env=0x5555577fba30) > at /home/rth/work/qemu/qemu/linux-user/main.c:317 > #4 0x00005555555b40a4 in main (argc=<optimized out>, argv=<optimized out>, > envp=<optimized out>) at /home/rth/work/qemu/qemu/linux-user/main.c:3826 In system mode I get a backtrace like this: (gdb) bt #0 helper_set_cp15 (env=0x80b41500, insn=3993505559, val=0) at /home/pm215/src/qemu/qemu/target-arm/helper.c:1455 #1 0x0101983d in ?? () #2 0x8020bec3 in cpu_arm_exec (env=0x80b41500) at /home/pm215/src/qemu/qemu/cpu-exec.c:564 #3 0x8020e978 in tcg_cpu_exec (env=0x80b41500) at /home/pm215/src/qemu/qemu/cpus.c:1022 #4 0x8020eab8 in tcg_exec_all () at /home/pm215/src/qemu/qemu/cpus.c:1054 #5 0x8020df8f in qemu_tcg_cpu_thread_fn (arg=0x80b41500) at /home/pm215/src/qemu/qemu/cpus.c:772 #6 0x003bcd31 in start_thread (arg=0xaeecdb70) at pthread_create.c:304 #7 0x0089d46e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130 Backtrace stopped: Not enough registers or memory available to unwind further ...is it possible to put in a useful string to replace that '??' in line #1? Any chance of some comments describing (a) what the limited debug info does and what this does/doesn't support? [for instance it doesn't seem to support doing a gdb backtrace while you're inside the code_gen_prologue code] and (b) what the cpu-specific tcg backend code needs to do/provide to support this? thanks -- PMM ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH v2] Use the GDB JIT debugging interface 2012-03-19 20:08 ` [Qemu-devel] [PATCH v2] " Peter Maydell @ 2012-03-19 20:48 ` Richard Henderson 0 siblings, 0 replies; 6+ messages in thread From: Richard Henderson @ 2012-03-19 20:48 UTC (permalink / raw) To: Peter Maydell; +Cc: qemu-devel On 03/19/12 13:08, Peter Maydell wrote: > In system mode I get a backtrace like this: > > (gdb) bt > #0 helper_set_cp15 (env=0x80b41500, insn=3993505559, val=0) at > /home/pm215/src/qemu/qemu/target-arm/helper.c:1455 > #1 0x0101983d in ?? () > > ...is it possible to put in a useful string to replace that '??' > in line #1? I'm not sure. Maybe, with some more effort. GDB seems to be ignoring the elf-level symbol table, but reading the dwarf info. So it would be possible to add a minimal debug_info section as well. "Minimal" is irritatingly large though... > Any chance of some comments describing (a) what the limited debug > info does and what this does/doesn't support? [for instance it > doesn't seem to support doing a gdb backtrace while you're inside > the code_gen_prologue code] and (b) what the cpu-specific tcg backend > code needs to do/provide to support this? Putting this in tcg.c, perhaps? Sure. You're right that I don't try to handle code_gen_prologue. Getting that right is more difficult. Of course, I doubt we need to auto-generate the prologue code *at all*. Some statically generated assembler would do just as well, at which point we *could* add .cfi directives to handle that code. All the cpu-specific tcg backend needs to do is provide the contents of a .debug_frame section that describes the steady- state frame established by the prologue. Since the entire code_gen_buffer uses this same frame, the unwind is fixed for the entire buffer. r~ ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2012-03-24 17:04 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2012-03-19 19:25 [Qemu-devel] [PATCH v2] Use the GDB JIT debugging interface Richard Henderson 2012-03-19 19:25 ` [Qemu-devel] [PATCH] tcg: " Richard Henderson 2012-03-24 16:11 ` Blue Swirl 2012-03-24 17:04 ` Peter Maydell 2012-03-19 20:08 ` [Qemu-devel] [PATCH v2] " Peter Maydell 2012-03-19 20:48 ` Richard Henderson
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