Stefan Hajnoczi <stefa...@gmail.com> writes:
> On Fri, Aug 30, 2019 at 09:19:02AM -0300, vandersonmr wrote: >> This commit adds support to Linux Perf in order >> to be able to analyze qemu jitted code and >> also to able to see the TBs PC in it. >> >> When using "-perf" qemu creates a jitdump file in >> the current working directory. The file format >> specification can be found in: >> https://github.com/torvalds/linux/blob/master/tools/perf/Documentation/jitdump-specification.tx > > Oops, the link is broken: .txt > >> +struct jr_code_close { >> + struct jr_prefix p; >> +}; > > Unused? > >> + >> +struct jr_code_move { > > Unused? > >> +static uint32_t get_e_machine(void) >> +{ >> + uint32_t e_machine = EM_NONE; >> + Elf64_Ehdr elf_header; >> + FILE *exe = fopen("/proc/self/exe", "r"); >> + >> + if (exe == NULL) { >> + return e_machine; >> + } >> + >> + if (fread(&elf_header, sizeof(Elf64_Ehdr), 1, exe) != 1) { > > What if this is a 32-bit binary because QEMU was built for a 32-bit > host? > >> + goto end; >> + } >> + >> + e_machine = elf_header.e_machine; >> + >> +end: >> + fclose(exe); >> + return e_machine; >> +} >> + >> +void start_jitdump_file(void) >> +{ >> + gchar *dumpfile_name = g_strdup_printf("./jit-%d.dump", getpid()); > > You can now use g_autofree: > > g_autofree gchar *dumpfile_name = g_strdup_printf(...); > > and then the explicit g_free() isn't necessary anymore (and the memory > leak in the mmap error case is also solved). > >> +void append_load_in_jitdump_file(TranslationBlock *tb) >> +{ >> + gchar *func_name = g_strdup_printf("TB virt:0x"TARGET_FMT_lx, tb->pc); >> + >> + struct jr_code_load load_event; >> + load_event.p.id = JIT_CODE_LOAD; >> + load_event.p.total_size = >> + sizeof(struct jr_code_load) + strlen(func_name) + 1 + tb->tc.size; >> + load_event.p.timestamp = get_timestamp(); >> + load_event.pid = getpid(); >> + load_event.tid = syscall(SYS_gettid); >> + load_event.vma = tb->pc; >> + load_event.code_addr = (uint64_t) tb->tc.ptr; >> + load_event.code_size = tb->tc.size; >> + load_event.code_index = tb->pc; >> + >> + fwrite(&load_event, sizeof(struct jr_code_load), 1, dumpfile); >> + fwrite(func_name, strlen(func_name) + 1, 1, dumpfile); >> + fwrite(tb->tc.ptr, tb->tc.size, 1, dumpfile); >> + >> + g_free(func_name); >> + fflush(dumpfile); >> +} > > I didn't see a reply to my question on the previous patch series: > > "append_load_in_jitdump_file() calls fwrite() multiple times. What > guarantees they will not be interleaved when multiple threads call > this function?" Ahh that was exactly the problem I was debugging. Fixed with a lock now. > Does TCG ever throw away TBs and is it necessary to record this in the > file so perf knows about it? Yes - I suspect that's what the currently unused headers are for. -- Alex Bennée
