linux-kernel - Re: [PATCH v4 01/15] perf tools: Add utility function to fetch executable

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Date:   Wed, 6 Mar 2019 17:53:37 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Andi Kleen <andi@...stfloor.org>
Cc:     jolsa@...nel.org, namhyung@...nel.org,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v4 01/15] perf tools: Add utility function to fetch
 executable

Em Tue, Mar 05, 2019 at 06:47:44AM -0800, Andi Kleen escreveu:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> Add a utility function to fetch executable code. Convert one
> user over to it. There are more places doing that, but they
> do significantly different actions, so they are not
> easy to fit into a single library function.
> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> ---
>  tools/perf/util/Build       |  1 +
>  tools/perf/util/fetch.c     | 28 ++++++++++++++++++++++++++++
>  tools/perf/util/fetch.h     |  7 +++++++
>  tools/perf/util/intel-bts.c | 21 +++------------------
>  4 files changed, 39 insertions(+), 18 deletions(-)
>  create mode 100644 tools/perf/util/fetch.c
>  create mode 100644 tools/perf/util/fetch.h

So I've made some changes and the end result is below, will fixup the
following patches, holler if you find any problems:

Changes:

. No need to cast around, make 'buf' be a void pointer

. Rename it to thread__memcpy() to reflect the fact it is about copying
  a chunk of memory from a thread, i.e. from its address space.

. No need to have it in a separate object file, move it to thread.[ch]

. Check the return of map__load(), the original code didn't do it, but
  since we're moving this around, check that as well, could be moved to
  a separate patch tho.

- Arnaldo

diff --git a/tools/perf/util/intel-bts.c b/tools/perf/util/intel-bts.c
index 0c0180c67574..47025bc727e1 100644
--- a/tools/perf/util/intel-bts.c
+++ b/tools/perf/util/intel-bts.c
@@ -328,35 +328,19 @@ static int intel_bts_get_next_insn(struct intel_bts_queue *btsq, u64 ip)
 {
 	struct machine *machine = btsq->bts->machine;
 	struct thread *thread;
-	struct addr_location al;
 	unsigned char buf[INTEL_PT_INSN_BUF_SZ];
 	ssize_t len;
-	int x86_64;
-	uint8_t cpumode;
+	bool x86_64;
 	int err = -1;
 
-	if (machine__kernel_ip(machine, ip))
-		cpumode = PERF_RECORD_MISC_KERNEL;
-	else
-		cpumode = PERF_RECORD_MISC_USER;
-
 	thread = machine__find_thread(machine, -1, btsq->tid);
 	if (!thread)
 		return -1;
 
-	if (!thread__find_map(thread, cpumode, ip, &al) || !al.map->dso)
-		goto out_put;
-
-	len = dso__data_read_addr(al.map->dso, al.map, machine, ip, buf,
-				  INTEL_PT_INSN_BUF_SZ);
+	len = thread__memcpy(thread, machine, buf, ip, INTEL_PT_INSN_BUF_SZ, &x86_64);
 	if (len <= 0)
 		goto out_put;
 
-	/* Load maps to ensure dso->is_64_bit has been updated */
-	map__load(al.map);
-
-	x86_64 = al.map->dso->is_64_bit;
-
 	if (intel_pt_get_insn(buf, len, x86_64, &btsq->intel_pt_insn))
 		goto out_put;
 
diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 4c179fef442d..50678d318185 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -12,6 +12,7 @@
 #include "debug.h"
 #include "namespaces.h"
 #include "comm.h"
+#include "map.h"
 #include "symbol.h"
 #include "unwind.h"
 
@@ -393,3 +394,25 @@ struct thread *thread__main_thread(struct machine *machine, struct thread *threa
 
 	return machine__find_thread(machine, thread->pid_, thread->pid_);
 }
+
+int thread__memcpy(struct thread *thread, struct machine *machine,
+		   void *buf, u64 ip, int len, bool *is64bit)
+{
+       u8 cpumode = PERF_RECORD_MISC_USER;
+       struct addr_location al;
+       long offset;
+
+       if (machine__kernel_ip(machine, ip))
+               cpumode = PERF_RECORD_MISC_KERNEL;
+
+       if (!thread__find_map(thread, cpumode, ip, &al) || !al.map->dso ||
+	   al.map->dso->data.status == DSO_DATA_STATUS_ERROR ||
+	   map__load(al.map) < 0)
+               return -1;
+
+       offset = al.map->map_ip(al.map, ip);
+       if (is64bit)
+               *is64bit = al.map->dso->is_64_bit;
+
+       return dso__data_read_offset(al.map->dso, machine, offset, buf, len);
+}
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 8276ffeec556..cf8375c017a0 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -113,6 +113,9 @@ struct symbol *thread__find_symbol_fb(struct thread *thread, u8 cpumode,
 void thread__find_cpumode_addr_location(struct thread *thread, u64 addr,
 					struct addr_location *al);
 
+int thread__memcpy(struct thread *thread, struct machine *machine,
+		   void *buf, u64 ip, int len, bool *is64bit);
+
 static inline void *thread__priv(struct thread *thread)
 {
 	return thread->priv;