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init/gcov: allow CONFIG_CONSTRUCTORS on UML to fix module gcov

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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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Berg 2021-02-04 18:32:28 -08:00 committed by Linus Torvalds
parent 4f6ec86023
commit 55b6f763d8
3 changed files with 8 additions and 3 deletions
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1
init/Kconfig
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@ -76,7 +76,6 @@ config CC_HAS_ASM_INLINE
config CONSTRUCTORS
bool
depends on !UML
config IRQ_WORK
bool

8
init/main.c
View file

@ -1066,7 +1066,13 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
/* 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++)

2
kernel/gcov/Kconfig
View file

@ -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