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Date: Fri, 9 Oct 2015 16:17:22 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Stephane Eranian <eranian@...gle.com>, linux-kernel@...r.kernel.org
Cc: acme@...hat.com, peterz@...radead.org, mingo@...e.hu,
ak@...ux.intel.com, jolsa@...hat.com, namhyung@...nel.org,
cel@...ibm.com, dsahern@...il.com, johnmccutchan@...gle.com,
brendan.d.gregg@...il.com
Subject: Re: [PATCH v7 3/5] perf inject: add jitdump mmap injection support
On 01/10/15 09:45, Stephane Eranian wrote:
> This patch adds a --jit option to perf inject.
>
> This options injects MMAP records into the perf.data
> file to cover the jitted code mmaps. It also emits
> ELF images for each function in the jidump file.
> Those images are created where the jitdump file is.
> The MMAP records point to that location as well.
>
> Typical flow:
> $ perf record -k mono -- java -agentpath:libpjvmti.so java_class
> $ perf inject --jit -i perf.data -o perf.data.jitted
> $ perf report -i perf.data.jitted
>
> Note that jitdump.h support is not limited to Java, it works with
> any jitted environment modified to emit the jitdump file format,
> include those where code can be jitted multiple times and moved
> around.
>
> The jitdump.h format is adapted from the Oprofile project.
>
> The genelf.c (ELF binary generation) depends on MD5 hash
> encoding for the buildid. To enable this, libssl-dev must
> be installed. If not, then genelf.c defaults to using
> urandom to generate the buildid, which is not ideal.
> The Makefile auto-detects the presence on libssl-dev.
>
> This version mmaps the jitdump file to create a marker
> MMAP record in the perf.data file. The marker is used to detect
> jitdump and cause perf inject to inject the jitted mmaps and
> generate ELF images for jitted functions.
>
> Signed-off-by: Stephane Eranian <eranian@...gle.com>
> ---
<SNIP>
> +static int jit_repipe_code_load(struct jit_buf_desc *jd, union jr_entry *jr)
> +{
> + struct perf_sample sample;
> + union perf_event *event;
> + struct perf_tool *tool = jd->session->tool;
> + uint64_t code, addr;
> + char *filename;
> + struct stat st;
> + size_t size;
> + u16 idr_size;
> + const char *sym;
> + uint32_t count;
> + int ret, csize;
> + pid_t pid, tid;
> + struct {
> + u32 pid, tid;
> + u64 time;
> + } *id;
> +
> + pid = jr->load.pid;
> + tid = jr->load.tid;
> + csize = jr->load.code_size;
> + addr = jr->load.code_addr;
> + sym = (void *)((unsigned long)jr + sizeof(jr->load));
> + code = (unsigned long)jr + jr->load.p.total_size - csize;
> + count = jr->load.code_index;
> + idr_size = jd->machine->id_hdr_size;
> + /*
> + * +16 to account for sample_id_all (hack)
> + */
> + event = calloc(1, sizeof(*event) + idr_size);
> + if (!event)
> + return -1;
> +
> + filename = event->mmap2.filename;
> + size = snprintf(filename, PATH_MAX, "%s/jitted-%d-%u.so",
> + jd->dir,
> + pid,
> + count);
> +
> + size++; /* for \0 */
> +
> + size = PERF_ALIGN(size, sizeof(u64));
> +
> + ret = jit_emit_elf(filename, sym, addr, (const void *)code, csize);
> +
> + if (jd->debug_data && jd->nr_debug_entries) {
> + free(jd->debug_data);
> + jd->debug_data = NULL;
> + jd->nr_debug_entries = 0;
> + }
> +
> + if (ret) {
> + free(event);
> + return -1;
> + }
> + if (stat(filename, &st))
> + memset(&st, 0, sizeof(stat));
> +
> + event->mmap2.header.type = PERF_RECORD_MMAP2;
> + event->mmap2.header.misc = PERF_RECORD_MISC_USER;
> + event->mmap2.header.size = (sizeof(event->mmap2) -
> + (sizeof(event->mmap2.filename) - size) + idr_size);
> +
> + event->mmap2.pgoff = 0;
I was testing this with Intel PT but getting decoding errors.
I think the problem is here, as described below, but I will look at it more
next week.
event->mmap2.pgoff = 0 says that the code running at 'addr' can be found at
offset 0 in the elf file, which is not correct. The MMAP event has to
inform where in the file the code is.
> + event->mmap2.start = addr;
> + event->mmap2.len = csize;
> + event->mmap2.pid = pid;
> + event->mmap2.tid = tid;
> + event->mmap2.ino = st.st_ino;
> + event->mmap2.maj = major(st.st_dev);
> + event->mmap2.min = minor(st.st_dev);
> + event->mmap2.prot = st.st_mode;
> + event->mmap2.flags = MAP_SHARED;
> + event->mmap2.ino_generation = 1;
> +
> + id = (void *)((unsigned long)event + event->mmap.header.size - idr_size);
> + if (jd->sample_type & PERF_SAMPLE_TID) {
> + id->pid = pid;
> + id->tid = tid;
> + }
> + if (jd->sample_type & PERF_SAMPLE_TIME)
> + id->time = jr->load.p.timestamp;
> +
> + /*
> + * create pseudo sample to induce dso hit increment
> + * use first address as sample address
> + */
> + memset(&sample, 0, sizeof(sample));
> + sample.pid = pid;
> + sample.tid = tid;
> + sample.time = id->time;
> + sample.ip = addr;
> +
> + ret = perf_event__process_mmap2(tool, event, &sample, jd->machine, jd->session);
> + if (ret)
> + return ret;
> +
> + ret = jit_inject_event(jd, event);
> + /*
> + * mark dso as use to generate buildid in the header
> + */
> + if (!ret)
> + build_id__mark_dso_hit(tool, event, &sample, NULL, jd->machine);
> +
> + return ret;
--
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