jitsrc.py

import gdb
import re

patterns = [("__memmove_avx_unaligned_erms", 1, "js::jit::X86Encoding::BaseAssembler::executableCopy", "src", "dst"),
            ("__memcpy_avx_unaligned", 1, "js::jit::X86Encoding::BaseAssembler::executableCopy", "src", "dst"),
            ("__memmove_avx_unaligned_erms", 1, "arena_t::RallocSmallOrLarge", "aPtr", "ret"),
            ("__memcpy_avx_unaligned", 1, "arena_t::RallocSmallOrLarge", "aPtr", "ret"),
            ("mozilla::detail::VectorImpl<.*>::new_<.*>", 3, "mozilla::Vector<.*>::convertToHeapStorage", "beginNoCheck()", "newBuf"),
            ("__memmove_avx_unaligned_erms", 1, "js::jit::AssemblerBufferWithConstantPools", "&cur->instructions[0]", "dest"),
            ("__memcpy_sse2_unaligned", 1, "js::jit::AssemblerBufferWithConstantPools", "&cur->instructions[0]", "dest"),
            ("__memcpy_sse2_unaligned", 2, "js::jit::AssemblerX86Shared::executableCopy", "masm.m_formatter.m_buffer.m_buffer.mBegin", "buffer"),
            ("__memcpy_sse2_unaligned", 1, "arena_t::RallocSmallOrLarge", "aPtr", "ret")]

class JitSource(gdb.Command):
    def __init__(self):
        super(JitSource, self).__init__("jitsrc", gdb.COMMAND_RUNNING)
        self.dont_repeat()

    def disable_breakpoints(self):
        self.disabled_breakpoints = [b for b in gdb.breakpoints() if b.enabled]
        for b in self.disabled_breakpoints:
            b.enabled = False

    def enable_breakpoints(self):
        for b in self.disabled_breakpoints:
            b.enabled = True

    def search_stack(self, base_name, hops, name, src, dst, address):
        if not re.match(base_name, gdb.newest_frame().name()):
            return None
        f = gdb.newest_frame()
        for _ in range(hops):
            f = f.older()
        if not re.match(name, f.name()):
            return None
        f.select()
        src_val = gdb.parse_and_eval(src)
        dst_val = gdb.parse_and_eval(dst)
        return hex(src_val + int(address, 16) - dst_val)

    def next_address(self, old):
        for pattern in patterns:
            found = self.search_stack(*pattern, old)
            if found:
                return found
        return None

    def runback(self, address):
        b = gdb.Breakpoint("*" + address,
                           type=gdb.BP_WATCHPOINT,
                           wp_class=gdb.WP_WRITE,
                           internal=True, temporary=True)
        while b.hit_count == 0:
            gdb.execute('rc', to_string=True)
        b.delete()

    def invoke(self, arg, from_tty):
        args = gdb.string_to_argv(arg)
        address = args[0]
        self.disable_breakpoints()
        while address:
            self.runback(address)
            address = self.next_address(address)
        self.enable_breakpoints()


# Register to the gdb runtime
JitSource()