+ init-gcov-allow-config_constructors-on-uml-to-fix-module-gcov.patch added to -mm tree

+ init-gcov-allow-config_constructors-on-uml-to-fix-module-gcov.patch added to -mm tree

[akpm]

The patch titled
     Subject: init/gcov: allow CONFIG_CONSTRUCTORS on UML to fix module gcov
has been added to the -mm tree.  Its filename is
     init-gcov-allow-config_constructors-on-uml-to-fix-module-gcov.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/init-gcov-allow-config_constructors-on-uml-to-fix-module-gcov.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/init-gcov-allow-config_constructors-on-uml-to-fix-module-gcov.patch

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------------------------------------------------------
From: Johannes Berg <johannes.berg@intel.com>
Subject: init/gcov: allow CONFIG_CONSTRUCTORS on UML to fix module gcov

On ARCH=um, loading a module doesn't result in its constructors getting
called, which breaks module gcov since the debugfs files are never
registered.  On the other hand, in-kernel constructors have already been
called by the dynamic linker, so we can't call them again.

Get out of this conundrum by allowing CONFIG_CONSTRUCTORS to be selected,
but avoiding the in-kernel constructor calls.

Also remove the "if !UML" from GCOV selecting CONSTRUCTORS now, since we
really do want CONSTRUCTORS, just not kernel binary ones.

Link: https://lkml.kernel.org/r/20210120172041.c246a2cac2fb.I1358f584b76f1898373adfed77f4462c8705b736@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 init/Kconfig        |    1 -
 init/main.c         |    8 +++++++-
 kernel/gcov/Kconfig |    2 +-
 3 files changed, 8 insertions(+), 3 deletions(-)

--- a/init/Kconfig~init-gcov-allow-config_constructors-on-uml-to-fix-module-gcov
+++ a/init/Kconfig
@@ -76,7 +76,6 @@ config CC_HAS_ASM_INLINE
 
 config CONSTRUCTORS
 	bool
-	depends on !UML
 
 config IRQ_WORK
 	bool
--- a/init/main.c~init-gcov-allow-config_constructors-on-uml-to-fix-module-gcov
+++ a/init/main.c
@@ -1066,7 +1066,13 @@ asmlinkage __visible void __init __no_sa
 /* Call all constructor functions linked into the kernel. */
 static void __init do_ctors(void)
 {
-#ifdef CONFIG_CONSTRUCTORS
+/*
+ * For UML, the constructors have already been called by the
+ * normal setup code as it's just a normal ELF binary, so we
+ * cannot do it again - but we do need CONFIG_CONSTRUCTORS
+ * even on UML for modules.
+ */
+#if defined(CONFIG_CONSTRUCTORS) && !defined(CONFIG_UML)
 	ctor_fn_t *fn = (ctor_fn_t *) __ctors_start;
 
 	for (; fn < (ctor_fn_t *) __ctors_end; fn++)
--- a/kernel/gcov/Kconfig~init-gcov-allow-config_constructors-on-uml-to-fix-module-gcov
+++ a/kernel/gcov/Kconfig
@@ -4,7 +4,7 @@ menu "GCOV-based kernel profiling"
 config GCOV_KERNEL
 	bool "Enable gcov-based kernel profiling"
 	depends on DEBUG_FS
-	select CONSTRUCTORS if !UML
+	select CONSTRUCTORS
 	default n
 	help
 	This option enables gcov-based code profiling (e.g. for code coverage
_

Patches currently in -mm which might be from johannes.berg@intel.com are

init-gcov-allow-config_constructors-on-uml-to-fix-module-gcov.patch
mm-slub-disable-user-tracing-for-kmemleak-caches-by-default.patch