perf inject jit: Add namespaces support

This patch fixes "perf inject --jit" to properly operate on
namespaced/containerized processes:

* jitdump files are generated by the process, thus they should be
looked up in its mount NS.

* DSOs of injected MMAP events will later be looked up in the process
mount NS, so write them into its NS.

* PIDs & TIDs from jitdump events need to be translated to the PID as
seen by "perf record" before written into MMAP events.

For a process in a different PID NS, the TID & PID given in the jitdump
event are actually ignored; I use the TID & PID of the thread which
mmap()ed the jitdump file. This is simplified and won't do for forks of
the initial process, if they continue using the same jitdump file.
Future patches might improve it.

This was tested by recording a NodeJS process running with
"--perf-prof", inside a Docker container, and by recording another
NodeJS process running in the same namespaces as perf itself, to make
sure it's not broken for non-containerized processes.

Signed-off-by: Yonatan Goldschmidt <[e-mail]>
Acked-by: Jiri Olsa <[e-mail]>
Acked-by: Namhyung Kim <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-inject.c

···
 	 * if jit marker, then inject jit mmaps and generate ELF images
 	 */
 	ret = jit_process(inject->session, &inject->output, machine,
-			  event->mmap.filename, event->mmap.pid, &n);
+			  event->mmap.filename, event->mmap.pid, event->mmap.tid, &n);
 	if (ret < 0)
 		return ret;
 	if (ret) {
···
 	 * if jit marker, then inject jit mmaps and generate ELF images
 	 */
 	ret = jit_process(inject->session, &inject->output, machine,
-			  event->mmap2.filename, event->mmap2.pid, &n);
+			  event->mmap2.filename, event->mmap2.pid, event->mmap2.tid, &n);
 	if (ret < 0)
 		return ret;
 	if (ret) {

tools/perf/util/jit.h

···
 #include <data.h>
 
 int jit_process(struct perf_session *session, struct perf_data *output,
-		struct machine *machine, char *filename, pid_t pid, u64 *nbytes);
+		struct machine *machine, char *filename, pid_t pid, pid_t tid, u64 *nbytes);
 
 int jit_inject_record(const char *filename);
 

tools/perf/util/jitdump.c

···
 #include "event.h"
 #include "debug.h"
 #include "evlist.h"
+#include "namespaces.h"
 #include "symbol.h"
 #include <elf.h>
 
···
 	struct perf_data *output;
 	struct perf_session *session;
 	struct machine *machine;
+	struct nsinfo  *nsi;
 	union jr_entry   *entry;
 	void             *buf;
 	uint64_t	 sample_type;
···
 #define get_jit_tool(t) (container_of(tool, struct jit_tool, tool))
 
 static int
-jit_emit_elf(char *filename,
+jit_emit_elf(struct jit_buf_desc *jd,
+	     char *filename,
 	     const char *sym,
 	     uint64_t code_addr,
 	     const void *code,
···
 	     uint32_t unwinding_header_size,
 	     uint32_t unwinding_size)
 {
-	int ret, fd;
+	int ret, fd, saved_errno;
+	struct nscookie nsc;
 
 	if (verbose > 0)
 		fprintf(stderr, "write ELF image %s\n", filename);
 
+	nsinfo__mountns_enter(jd->nsi, &nsc);
 	fd = open(filename, O_CREAT|O_TRUNC|O_WRONLY, 0644);
+	saved_errno = errno;
+	nsinfo__mountns_exit(&nsc);
 	if (fd == -1) {
-		pr_warning("cannot create jit ELF %s: %s\n", filename, strerror(errno));
+		pr_warning("cannot create jit ELF %s: %s\n", filename, strerror(saved_errno));
 		return -1;
 	}
 
···
 
         close(fd);
 
-        if (ret)
-                unlink(filename);
+	if (ret) {
+		nsinfo__mountns_enter(jd->nsi, &nsc);
+		unlink(filename);
+		nsinfo__mountns_exit(&nsc);
+	}
 
 	return ret;
 }
···
 jit_open(struct jit_buf_desc *jd, const char *name)
 {
 	struct jitheader header;
+	struct nscookie nsc;
 	struct jr_prefix *prefix;
 	ssize_t bs, bsz = 0;
 	void *n, *buf = NULL;
 	int ret, retval = -1;
 
+	nsinfo__mountns_enter(jd->nsi, &nsc);
 	jd->in = fopen(name, "r");
+	nsinfo__mountns_exit(&nsc);
 	if (!jd->in)
 		return -1;
 
···
 	return 0;
 }
 
+static pid_t jr_entry_pid(struct jit_buf_desc *jd, union jr_entry *jr)
+{
+	if (jd->nsi && jd->nsi->in_pidns)
+		return jd->nsi->tgid;
+	return jr->load.pid;
+}
+
+static pid_t jr_entry_tid(struct jit_buf_desc *jd, union jr_entry *jr)
+{
+	if (jd->nsi && jd->nsi->in_pidns)
+		return jd->nsi->pid;
+	return jr->load.tid;
+}
+
 static uint64_t convert_timestamp(struct jit_buf_desc *jd, uint64_t timestamp)
 {
 	struct perf_tsc_conversion tc;
···
 	const char *sym;
 	uint64_t count;
 	int ret, csize, usize;
-	pid_t pid, tid;
+	pid_t nspid, pid, tid;
 	struct {
 		u32 pid, tid;
 		u64 time;
 	} *id;
 
-	pid   = jr->load.pid;
-	tid   = jr->load.tid;
+	nspid = jr->load.pid;
+	pid   = jr_entry_pid(jd, jr);
+	tid   = jr_entry_tid(jd, jr);
 	csize = jr->load.code_size;
 	usize = jd->unwinding_mapped_size;
 	addr  = jr->load.code_addr;
···
 	filename = event->mmap2.filename;
 	size = snprintf(filename, PATH_MAX, "%s/jitted-%d-%" PRIu64 ".so",
 			jd->dir,
-			pid,
+			nspid,
 			count);
 
 	size++; /* for \0 */
 
 	size = PERF_ALIGN(size, sizeof(u64));
 	uaddr = (uintptr_t)code;
-	ret = jit_emit_elf(filename, sym, addr, (const void *)uaddr, csize, jd->debug_data, jd->nr_debug_entries,
+	ret = jit_emit_elf(jd, filename, sym, addr, (const void *)uaddr, csize, jd->debug_data, jd->nr_debug_entries,
 			   jd->unwinding_data, jd->eh_frame_hdr_size, jd->unwinding_size);
 
 	if (jd->debug_data && jd->nr_debug_entries) {
···
 		free(event);
 		return -1;
 	}
-	if (stat(filename, &st))
+	if (nsinfo__stat(filename, &st, jd->nsi))
 		memset(&st, 0, sizeof(st));
 
 	event->mmap2.header.type = PERF_RECORD_MMAP2;
···
 	int usize;
 	u16 idr_size;
 	int ret;
-	pid_t pid, tid;
+	pid_t nspid, pid, tid;
 	struct {
 		u32 pid, tid;
 		u64 time;
 	} *id;
 
-	pid = jr->move.pid;
-	tid =  jr->move.tid;
+	nspid = jr->load.pid;
+	pid   = jr_entry_pid(jd, jr);
+	tid   = jr_entry_tid(jd, jr);
 	usize = jd->unwinding_mapped_size;
 	idr_size = jd->machine->id_hdr_size;
 
···
 	filename = event->mmap2.filename;
 	size = snprintf(filename, PATH_MAX, "%s/jitted-%d-%" PRIu64 ".so",
 	         jd->dir,
-	         pid,
+		 nspid,
 		 jr->move.code_index);
 
 	size++; /* for \0 */
 
-	if (stat(filename, &st))
+	if (nsinfo__stat(filename, &st, jd->nsi))
 		memset(&st, 0, sizeof(st));
 
 	size = PERF_ALIGN(size, sizeof(u64));
···
  * as captured in the RECORD_MMAP record
  */
 static int
-jit_detect(char *mmap_name, pid_t pid)
+jit_detect(char *mmap_name, pid_t pid, struct nsinfo *nsi)
  {
 	char *p;
 	char *end = NULL;
···
 	 * pid does not match mmap pid
 	 * pid==0 in system-wide mode (synthesized)
 	 */
-	if (pid && pid2 != pid)
+	if (pid && pid2 != nsi->nstgid)
 		return -1;
 	/*
 	 * validate suffix
···
 	    struct machine *machine,
 	    char *filename,
 	    pid_t pid,
+	    pid_t tid,
 	    u64 *nbytes)
 {
+	struct thread *thread;
+	struct nsinfo *nsi;
 	struct evsel *first;
 	struct jit_buf_desc jd;
 	int ret;
 
+	thread = machine__findnew_thread(machine, pid, tid);
+	if (thread == NULL) {
+		pr_err("problem processing JIT mmap event, skipping it.\n");
+		return 0;
+	}
+
+	nsi = nsinfo__get(thread->nsinfo);
+	thread__put(thread);
+
 	/*
 	 * first, detect marker mmap (i.e., the jitdump mmap)
 	 */
-	if (jit_detect(filename, pid)) {
+	if (jit_detect(filename, pid, nsi)) {
+		nsinfo__put(nsi);
+
 		// Strip //anon* mmaps if we processed a jitdump for this pid
 		if (jit_has_pid(machine, pid) && (strncmp(filename, "//anon", 6) == 0))
 			return 1;
···
 	jd.session = session;
 	jd.output  = output;
 	jd.machine = machine;
+	jd.nsi = nsi;
 
 	/*
 	 * track sample_type to compute id_all layout
···
 		*nbytes = jd.bytes_written;
 		ret = 1;
 	}
+
+	nsinfo__put(jd.nsi);
 
 	return ret;
 }

tools/perf/util/namespaces.c

···
 
 	return rpath;
 }
+
+int nsinfo__stat(const char *filename, struct stat *st, struct nsinfo *nsi)
+{
+	int ret;
+	struct nscookie nsc;
+
+	nsinfo__mountns_enter(nsi, &nsc);
+	ret = stat(filename, st);
+	nsinfo__mountns_exit(&nsc);
+
+	return ret;
+}

tools/perf/util/namespaces.h

···
 #define __PERF_NAMESPACES_H
 
 #include <sys/types.h>
+#include <sys/stat.h>
 #include <linux/stddef.h>
 #include <linux/perf_event.h>
 #include <linux/refcount.h>
···
 void nsinfo__mountns_exit(struct nscookie *nc);
 
 char *nsinfo__realpath(const char *path, struct nsinfo *nsi);
+int nsinfo__stat(const char *filename, struct stat *st, struct nsinfo *nsi);
 
 static inline void __nsinfo__zput(struct nsinfo **nsip)
 {