[PATCH 6.6 175/393] perf machine: Dont ignore _etext when not a text symbol

[PATCH 6.6 175/393] perf machine: Dont ignore _etext when not a text symbol

[Greg Kroah-Hartman]

6.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christophe Leroy <christophe.leroy@csgroup.eu>

[ Upstream commit 7a93786c306296f15e728b1dbd949a319e4e3d19 ]

Depending on how vmlinux.lds is written, _etext might be the very first
data symbol instead of the very last text symbol.

Don't require it to be a text symbol, accept any symbol type.

Comitter notes:

See the first Link for further discussion, but it all boils down to
this:

 ---
  # grep -e _stext -e _etext -e _edata /proc/kallsyms
  c0000000 T _stext
  c08b8000 D _etext

  So there is no _edata and _etext is not text

  $ ppc-linux-objdump -x vmlinux | grep -e _stext -e _etext -e _edata
  c0000000 g       .head.text	00000000 _stext
  c08b8000 g       .rodata	00000000 _etext
  c1378000 g       .sbss	00000000 _edata
 ---

Fixes: ed9adb2035b5be58 ("perf machine: Read also the end of the kernel")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/r/b3ee1994d95257cb7f2de037c5030ba7d1bed404.1736327613.git.christophe.leroy@csgroup.eu
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 tools/perf/util/machine.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 7c6874804660e..e2a6facd1c4e2 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1217,7 +1217,7 @@ static int machine__get_running_kernel_start(struct machine *machine,
 
 	err = kallsyms__get_symbol_start(filename, "_edata", &addr);
 	if (err)
-		err = kallsyms__get_function_start(filename, "_etext", &addr);
+		err = kallsyms__get_symbol_start(filename, "_etext", &addr);
 	if (!err)
 		*end = addr;
 
-- 
2.39.5

[PATCH 6.6 309/393] module: Extend the preempt disabled section in dereference_symbol_descriptor().

[Greg Kroah-Hartman]

6.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

[ Upstream commit a145c848d69f9c6f32008d8319edaa133360dd74 ]

dereference_symbol_descriptor() needs to obtain the module pointer
belonging to pointer in order to resolve that pointer.
The returned mod pointer is obtained under RCU-sched/ preempt_disable()
guarantees and needs to be used within this section to ensure that the
module is not removed in the meantime.

Extend the preempt_disable() section to also cover
dereference_module_function_descriptor().

Fixes: 04b8eb7a4ccd9 ("symbol lookup: introduce dereference_symbol_descriptor()")
Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Helge Deller <deller@gmx.de>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Naveen N Rao <naveen@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20250108090457.512198-2-bigeasy@linutronix.de
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/kallsyms.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index c3f075e8f60cb..1c6a6c1704d8d 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -57,10 +57,10 @@ static inline void *dereference_symbol_descriptor(void *ptr)
 
 	preempt_disable();
 	mod = __module_address((unsigned long)ptr);
-	preempt_enable();
 
 	if (mod)
 		ptr = dereference_module_function_descriptor(mod, ptr);
+	preempt_enable();
 #endif
 	return ptr;
 }
-- 
2.39.5