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cpython/Python/perf_jit_trampoline.c

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#include "Python.h"
#include "pycore_ceval.h" // _PyPerf_Callbacks
#include "pycore_frame.h"
#include "pycore_interp.h"
#ifdef PY_HAVE_PERF_TRAMPOLINE
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h> // mmap()
#include <sys/types.h>
#include <unistd.h> // sysconf()
#include <sys/time.h> // gettimeofday()
#include <sys/syscall.h>
// ----------------------------------
// Perf jitdump API
// ----------------------------------
typedef struct {
FILE* perf_map;
PyThread_type_lock map_lock;
void* mapped_buffer;
size_t mapped_size;
int code_id;
} PerfMapJitState;
static PerfMapJitState perf_jit_map_state;
/*
Usually the binary and libraries are mapped in separate region like below:
address ->
--+---------------------+--//--+---------------------+--
| .text | .data | ... | | .text | .data | ... |
--+---------------------+--//--+---------------------+--
myprog libc.so
So it'd be easy and straight-forward to find a mapped binary or library from an
address.
But for JIT code, the code arena only cares about the code section. But the
resulting DSOs (which is generated by perf inject -j) contain ELF headers and
unwind info too. Then it'd generate following address space with synthesized
MMAP events. Let's say it has a sample between address B and C.
sample
|
address -> A B v C
---------------------------------------------------------------------------------------------------
/tmp/jitted-PID-0.so | (headers) | .text | unwind info |
/tmp/jitted-PID-1.so | (headers) | .text | unwind info |
/tmp/jitted-PID-2.so | (headers) | .text | unwind info |
...
---------------------------------------------------------------------------------------------------
If it only maps the .text section, it'd find the jitted-PID-1.so but cannot see
the unwind info. If it maps both .text section and unwind sections, the sample
could be mapped to either jitted-PID-0.so or jitted-PID-1.so and it's confusing
which one is right. So to make perf happy we have non-overlapping ranges for each
DSO:
address ->
-------------------------------------------------------------------------------------------------------
/tmp/jitted-PID-0.so | (headers) | .text | unwind info |
/tmp/jitted-PID-1.so | (headers) | .text | unwind info |
/tmp/jitted-PID-2.so | (headers) | .text | unwind info |
...
-------------------------------------------------------------------------------------------------------
As the trampolines are constant, we add a constant padding but in general the padding needs to have the
size of the unwind info rounded to 16 bytes. In general, for our trampolines this is 0x50
*/
#define PERF_JIT_CODE_PADDING 0x100
#define trampoline_api _PyRuntime.ceval.perf.trampoline_api
typedef uint64_t uword;
typedef const char* CodeComments;
#define Pd "d"
#define MB (1024 * 1024)
#define EM_386 3
#define EM_X86_64 62
#define EM_ARM 40
#define EM_AARCH64 183
#define EM_RISCV 243
#define TARGET_ARCH_IA32 0
#define TARGET_ARCH_X64 0
#define TARGET_ARCH_ARM 0
#define TARGET_ARCH_ARM64 0
#define TARGET_ARCH_RISCV32 0
#define TARGET_ARCH_RISCV64 0
#define FLAG_generate_perf_jitdump 0
#define FLAG_write_protect_code 0
#define FLAG_write_protect_vm_isolate 0
#define FLAG_code_comments 0
#define UNREACHABLE()
static uword GetElfMachineArchitecture(void) {
#if TARGET_ARCH_IA32
return EM_386;
#elif TARGET_ARCH_X64
return EM_X86_64;
#elif TARGET_ARCH_ARM
return EM_ARM;
#elif TARGET_ARCH_ARM64
return EM_AARCH64;
#elif TARGET_ARCH_RISCV32 || TARGET_ARCH_RISCV64
return EM_RISCV;
#else
UNREACHABLE();
return 0;
#endif
}
typedef struct {
uint32_t magic;
uint32_t version;
uint32_t size;
uint32_t elf_mach_target;
uint32_t reserved;
uint32_t process_id;
uint64_t time_stamp;
uint64_t flags;
} Header;
enum PerfEvent {
PerfLoad = 0,
PerfMove = 1,
PerfDebugInfo = 2,
PerfClose = 3,
PerfUnwindingInfo = 4
};
struct BaseEvent {
uint32_t event;
uint32_t size;
uint64_t time_stamp;
};
typedef struct {
struct BaseEvent base;
uint32_t process_id;
uint32_t thread_id;
uint64_t vma;
uint64_t code_address;
uint64_t code_size;
uint64_t code_id;
} CodeLoadEvent;
typedef struct {
struct BaseEvent base;
uint64_t unwind_data_size;
uint64_t eh_frame_hdr_size;
uint64_t mapped_size;
} CodeUnwindingInfoEvent;
static const intptr_t nanoseconds_per_second = 1000000000;
// Dwarf encoding constants
static const uint8_t DwarfUData4 = 0x03;
static const uint8_t DwarfSData4 = 0x0b;
static const uint8_t DwarfPcRel = 0x10;
static const uint8_t DwarfDataRel = 0x30;
// static uint8_t DwarfOmit = 0xff;
typedef struct {
unsigned char version;
unsigned char eh_frame_ptr_enc;
unsigned char fde_count_enc;
unsigned char table_enc;
int32_t eh_frame_ptr;
int32_t eh_fde_count;
int32_t from;
int32_t to;
} EhFrameHeader;
static int64_t get_current_monotonic_ticks(void) {
struct timespec ts;
if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0) {
UNREACHABLE();
return 0;
}
// Convert to nanoseconds.
int64_t result = ts.tv_sec;
result *= nanoseconds_per_second;
result += ts.tv_nsec;
return result;
}
static int64_t get_current_time_microseconds(void) {
// gettimeofday has microsecond resolution.
struct timeval tv;
if (gettimeofday(&tv, NULL) < 0) {
UNREACHABLE();
return 0;
}
return ((int64_t)(tv.tv_sec) * 1000000) + tv.tv_usec;
}
static size_t round_up(int64_t value, int64_t multiple) {
if (multiple == 0) {
// Avoid division by zero
return value;
}
int64_t remainder = value % multiple;
if (remainder == 0) {
// Value is already a multiple of 'multiple'
return value;
}
// Calculate the difference to the next multiple
int64_t difference = multiple - remainder;
// Add the difference to the value
int64_t rounded_up_value = value + difference;
return rounded_up_value;
}
static void perf_map_jit_write_fully(const void* buffer, size_t size) {
FILE* out_file = perf_jit_map_state.perf_map;
const char* ptr = (const char*)(buffer);
while (size > 0) {
const size_t written = fwrite(ptr, 1, size, out_file);
if (written == 0) {
UNREACHABLE();
break;
}
size -= written;
ptr += written;
}
}
static void perf_map_jit_write_header(int pid, FILE* out_file) {
Header header;
header.magic = 0x4A695444;
header.version = 1;
header.size = sizeof(Header);
header.elf_mach_target = GetElfMachineArchitecture();
header.process_id = pid;
header.time_stamp = get_current_time_microseconds();
header.flags = 0;
perf_map_jit_write_fully(&header, sizeof(header));
}
static void* perf_map_jit_init(void) {
char filename[100];
int pid = getpid();
snprintf(filename, sizeof(filename) - 1, "/tmp/jit-%d.dump", pid);
const int fd = open(filename, O_CREAT | O_TRUNC | O_RDWR, 0666);
if (fd == -1) {
return NULL;
}
const long page_size = sysconf(_SC_PAGESIZE); // NOLINT(runtime/int)
if (page_size == -1) {
close(fd);
return NULL;
}
// The perf jit interface forces us to map the first page of the file
// to signal that we are using the interface.
perf_jit_map_state.mapped_buffer = mmap(NULL, page_size, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0);
if (perf_jit_map_state.mapped_buffer == NULL) {
close(fd);
return NULL;
}
perf_jit_map_state.mapped_size = page_size;
perf_jit_map_state.perf_map = fdopen(fd, "w+");
if (perf_jit_map_state.perf_map == NULL) {
close(fd);
return NULL;
}
setvbuf(perf_jit_map_state.perf_map, NULL, _IOFBF, 2 * MB);
perf_map_jit_write_header(pid, perf_jit_map_state.perf_map);
perf_jit_map_state.map_lock = PyThread_allocate_lock();
if (perf_jit_map_state.map_lock == NULL) {
fclose(perf_jit_map_state.perf_map);
return NULL;
}
perf_jit_map_state.code_id = 0;
trampoline_api.code_padding = PERF_JIT_CODE_PADDING;
return &perf_jit_map_state;
}
/* DWARF definitions. */
#define DWRF_CIE_VERSION 1
enum {
DWRF_CFA_nop = 0x0,
DWRF_CFA_offset_extended = 0x5,
DWRF_CFA_def_cfa = 0xc,
DWRF_CFA_def_cfa_offset = 0xe,
DWRF_CFA_offset_extended_sf = 0x11,
DWRF_CFA_advance_loc = 0x40,
DWRF_CFA_offset = 0x80
};
enum
{
DWRF_EH_PE_absptr = 0x00,
DWRF_EH_PE_omit = 0xff,
/* FDE data encoding. */
DWRF_EH_PE_uleb128 = 0x01,
DWRF_EH_PE_udata2 = 0x02,
DWRF_EH_PE_udata4 = 0x03,
DWRF_EH_PE_udata8 = 0x04,
DWRF_EH_PE_sleb128 = 0x09,
DWRF_EH_PE_sdata2 = 0x0a,
DWRF_EH_PE_sdata4 = 0x0b,
DWRF_EH_PE_sdata8 = 0x0c,
DWRF_EH_PE_signed = 0x08,
/* FDE flags. */
DWRF_EH_PE_pcrel = 0x10,
DWRF_EH_PE_textrel = 0x20,
DWRF_EH_PE_datarel = 0x30,
DWRF_EH_PE_funcrel = 0x40,
DWRF_EH_PE_aligned = 0x50,
DWRF_EH_PE_indirect = 0x80
};
enum { DWRF_TAG_compile_unit = 0x11 };
enum { DWRF_children_no = 0, DWRF_children_yes = 1 };
enum { DWRF_AT_name = 0x03, DWRF_AT_stmt_list = 0x10, DWRF_AT_low_pc = 0x11, DWRF_AT_high_pc = 0x12 };
enum { DWRF_FORM_addr = 0x01, DWRF_FORM_data4 = 0x06, DWRF_FORM_string = 0x08 };
enum { DWRF_LNS_extended_op = 0, DWRF_LNS_copy = 1, DWRF_LNS_advance_pc = 2, DWRF_LNS_advance_line = 3 };
enum { DWRF_LNE_end_sequence = 1, DWRF_LNE_set_address = 2 };
enum {
#ifdef __x86_64__
/* Yes, the order is strange, but correct. */
DWRF_REG_AX,
DWRF_REG_DX,
DWRF_REG_CX,
DWRF_REG_BX,
DWRF_REG_SI,
DWRF_REG_DI,
DWRF_REG_BP,
DWRF_REG_SP,
DWRF_REG_8,
DWRF_REG_9,
DWRF_REG_10,
DWRF_REG_11,
DWRF_REG_12,
DWRF_REG_13,
DWRF_REG_14,
DWRF_REG_15,
DWRF_REG_RA,
#elif defined(__aarch64__) && defined(__AARCH64EL__) && !defined(__ILP32__)
DWRF_REG_SP = 31,
DWRF_REG_RA = 30,
#else
# error "Unsupported target architecture"
#endif
};
typedef struct ELFObjectContext
{
uint8_t* p; /* Pointer to next address in obj.space. */
uint8_t* startp; /* Pointer to start address in obj.space. */
uint8_t* eh_frame_p; /* Pointer to start address in obj.space. */
uint32_t code_size; /* Size of machine code. */
} ELFObjectContext;
/* Append a null-terminated string. */
static uint32_t
elfctx_append_string(ELFObjectContext* ctx, const char* str)
{
uint8_t* p = ctx->p;
uint32_t ofs = (uint32_t)(p - ctx->startp);
do {
*p++ = (uint8_t)*str;
} while (*str++);
ctx->p = p;
return ofs;
}
/* Append a SLEB128 value. */
static void
elfctx_append_sleb128(ELFObjectContext* ctx, int32_t v)
{
uint8_t* p = ctx->p;
for (; (uint32_t)(v + 0x40) >= 0x80; v >>= 7) {
*p++ = (uint8_t)((v & 0x7f) | 0x80);
}
*p++ = (uint8_t)(v & 0x7f);
ctx->p = p;
}
/* Append a ULEB128 to buffer. */
static void
elfctx_append_uleb128(ELFObjectContext* ctx, uint32_t v)
{
uint8_t* p = ctx->p;
for (; v >= 0x80; v >>= 7) {
*p++ = (char)((v & 0x7f) | 0x80);
}
*p++ = (char)v;
ctx->p = p;
}
/* Shortcuts to generate DWARF structures. */
#define DWRF_U8(x) (*p++ = (x))
#define DWRF_I8(x) (*(int8_t*)p = (x), p++)
#define DWRF_U16(x) (*(uint16_t*)p = (x), p += 2)
#define DWRF_U32(x) (*(uint32_t*)p = (x), p += 4)
#define DWRF_ADDR(x) (*(uintptr_t*)p = (x), p += sizeof(uintptr_t))
#define DWRF_UV(x) (ctx->p = p, elfctx_append_uleb128(ctx, (x)), p = ctx->p)
#define DWRF_SV(x) (ctx->p = p, elfctx_append_sleb128(ctx, (x)), p = ctx->p)
#define DWRF_STR(str) (ctx->p = p, elfctx_append_string(ctx, (str)), p = ctx->p)
#define DWRF_ALIGNNOP(s) \
while ((uintptr_t)p & ((s)-1)) { \
*p++ = DWRF_CFA_nop; \
}
#define DWRF_SECTION(name, stmt) \
{ \
uint32_t* szp_##name = (uint32_t*)p; \
p += 4; \
stmt; \
*szp_##name = (uint32_t)((p - (uint8_t*)szp_##name) - 4); \
}
/* Initialize .eh_frame section. */
static void
elf_init_ehframe(ELFObjectContext* ctx)
{
uint8_t* p = ctx->p;
uint8_t* framep = p;
/* Emit DWARF EH CIE. */
DWRF_SECTION(CIE, DWRF_U32(0); /* Offset to CIE itself. */
DWRF_U8(DWRF_CIE_VERSION);
DWRF_STR("zR"); /* Augmentation. */
DWRF_UV(1); /* Code alignment factor. */
DWRF_SV(-(int64_t)sizeof(uintptr_t)); /* Data alignment factor. */
DWRF_U8(DWRF_REG_RA); /* Return address register. */
DWRF_UV(1);
DWRF_U8(DWRF_EH_PE_pcrel | DWRF_EH_PE_sdata4); /* Augmentation data. */
DWRF_U8(DWRF_CFA_def_cfa); DWRF_UV(DWRF_REG_SP); DWRF_UV(sizeof(uintptr_t));
DWRF_U8(DWRF_CFA_offset|DWRF_REG_RA); DWRF_UV(1);
DWRF_ALIGNNOP(sizeof(uintptr_t));
)
ctx->eh_frame_p = p;
/* Emit DWARF EH FDE. */
DWRF_SECTION(FDE, DWRF_U32((uint32_t)(p - framep)); /* Offset to CIE. */
DWRF_U32(-0x30); /* Machine code offset relative to .text. */
DWRF_U32(ctx->code_size); /* Machine code length. */
DWRF_U8(0); /* Augmentation data. */
/* Registers saved in CFRAME. */
#ifdef __x86_64__
DWRF_U8(DWRF_CFA_advance_loc | 4);
DWRF_U8(DWRF_CFA_def_cfa_offset); DWRF_UV(16);
DWRF_U8(DWRF_CFA_advance_loc | 6);
DWRF_U8(DWRF_CFA_def_cfa_offset); DWRF_UV(8);
/* Extra registers saved for JIT-compiled code. */
#elif defined(__aarch64__) && defined(__AARCH64EL__) && !defined(__ILP32__)
DWRF_U8(DWRF_CFA_advance_loc | 1);
DWRF_U8(DWRF_CFA_def_cfa_offset); DWRF_UV(16);
DWRF_U8(DWRF_CFA_offset | 29); DWRF_UV(2);
DWRF_U8(DWRF_CFA_offset | 30); DWRF_UV(1);
DWRF_U8(DWRF_CFA_advance_loc | 3);
DWRF_U8(DWRF_CFA_offset | -(64 - 29));
DWRF_U8(DWRF_CFA_offset | -(64 - 30));
DWRF_U8(DWRF_CFA_def_cfa_offset);
DWRF_UV(0);
#else
# error "Unsupported target architecture"
#endif
DWRF_ALIGNNOP(sizeof(uintptr_t));)
ctx->p = p;
}
static void perf_map_jit_write_entry(void *state, const void *code_addr,
unsigned int code_size, PyCodeObject *co)
{
if (perf_jit_map_state.perf_map == NULL) {
void* ret = perf_map_jit_init();
if(ret == NULL){
return;
}
}
const char *entry = "";
if (co->co_qualname != NULL) {
entry = PyUnicode_AsUTF8(co->co_qualname);
}
const char *filename = "";
if (co->co_filename != NULL) {
filename = PyUnicode_AsUTF8(co->co_filename);
}
size_t perf_map_entry_size = snprintf(NULL, 0, "py::%s:%s", entry, filename) + 1;
char* perf_map_entry = (char*) PyMem_RawMalloc(perf_map_entry_size);
if (perf_map_entry == NULL) {
return;
}
snprintf(perf_map_entry, perf_map_entry_size, "py::%s:%s", entry, filename);
const size_t name_length = strlen(perf_map_entry);
uword base = (uword)code_addr;
uword size = code_size;
// Write the code unwinding info event.
// Create unwinding information (eh frame)
ELFObjectContext ctx;
char buffer[1024];
ctx.code_size = code_size;
ctx.startp = ctx.p = (uint8_t*)buffer;
elf_init_ehframe(&ctx);
int eh_frame_size = ctx.p - ctx.startp;
// Populate the unwind info event for perf
CodeUnwindingInfoEvent ev2;
ev2.base.event = PerfUnwindingInfo;
ev2.base.time_stamp = get_current_monotonic_ticks();
ev2.unwind_data_size = sizeof(EhFrameHeader) + eh_frame_size;
// Ensure we have enough space between DSOs when perf maps them
assert(ev2.unwind_data_size <= PERF_JIT_CODE_PADDING);
ev2.eh_frame_hdr_size = sizeof(EhFrameHeader);
ev2.mapped_size = round_up(ev2.unwind_data_size, 16);
int content_size = sizeof(ev2) + sizeof(EhFrameHeader) + eh_frame_size;
int padding_size = round_up(content_size, 8) - content_size;
ev2.base.size = content_size + padding_size;
perf_map_jit_write_fully(&ev2, sizeof(ev2));
// Populate the eh Frame header
EhFrameHeader f;
f.version = 1;
f.eh_frame_ptr_enc = DwarfSData4 | DwarfPcRel;
f.fde_count_enc = DwarfUData4;
f.table_enc = DwarfSData4 | DwarfDataRel;
f.eh_frame_ptr = -(eh_frame_size + 4 * sizeof(unsigned char));
f.eh_fde_count = 1;
f.from = -(round_up(code_size, 8) + eh_frame_size);
int cie_size = ctx.eh_frame_p - ctx.startp;
f.to = -(eh_frame_size - cie_size);
perf_map_jit_write_fully(ctx.startp, eh_frame_size);
perf_map_jit_write_fully(&f, sizeof(f));
char padding_bytes[] = "\0\0\0\0\0\0\0\0";
perf_map_jit_write_fully(&padding_bytes, padding_size);
// Write the code load event.
CodeLoadEvent ev;
ev.base.event = PerfLoad;
ev.base.size = sizeof(ev) + (name_length+1) + size;
ev.base.time_stamp = get_current_monotonic_ticks();
ev.process_id = getpid();
ev.thread_id = syscall(SYS_gettid);
ev.vma = base;
ev.code_address = base;
ev.code_size = size;
perf_jit_map_state.code_id += 1;
ev.code_id = perf_jit_map_state.code_id;
perf_map_jit_write_fully(&ev, sizeof(ev));
perf_map_jit_write_fully(perf_map_entry, name_length+1);
perf_map_jit_write_fully((void*)(base), size);
return;
}
static int perf_map_jit_fini(void* state) {
if (perf_jit_map_state.perf_map != NULL) {
// close the file
PyThread_acquire_lock(perf_jit_map_state.map_lock, 1);
fclose(perf_jit_map_state.perf_map);
PyThread_release_lock(perf_jit_map_state.map_lock);
// clean up the lock and state
PyThread_free_lock(perf_jit_map_state.map_lock);
perf_jit_map_state.perf_map = NULL;
}
if (perf_jit_map_state.mapped_buffer != NULL) {
munmap(perf_jit_map_state.mapped_buffer, perf_jit_map_state.mapped_size);
}
trampoline_api.state = NULL;
return 0;
}
_PyPerf_Callbacks _Py_perfmap_jit_callbacks = {
&perf_map_jit_init,
&perf_map_jit_write_entry,
&perf_map_jit_fini,
};
#endif
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