On Wed, Dec 4, 2019 at 7:35 PM Anton Ivanov
<anton.ivanov@xxxxxxxxxxxxxxxxxx> wrote:
>
>
>
> On 04/12/2019 16:43, Johannes Berg wrote:
> > From: Johannes Berg <johannes.berg@xxxxxxxxx>
> >
> > This reverts commit 786b2384bf1c ("um: Enable CONFIG_CONSTRUCTORS").
> >
> > There are two issues with this commit, uncovered by Anton in tests
> > on some (Debian) systems:
> >
> > 1) I completely forgot to call any constructors if CONFIG_CONSTRUCTORS
> > isn't set. Don't recall now if it just wasn't needed on my system, or
> > if I never tested this case.
> >
> > 2) With that fixed, it works - with CONFIG_CONSTRUCTORS *unset*. If I
> > set CONFIG_CONSTRUCTORS, it fails again, which isn't totally
> > unexpected since whatever wanted to run is likely to have to run
> > before the kernel init etc. that calls the constructors in this case.
> >
> > Basically, some constructors that gcc emits (libc has?) need to run
> > very early during init; the failure mode otherwise was that the ptrace
> > fork test already failed:
> >
> > ----------------------
> > $ ./linux mem=512M
> > Core dump limits :
> > soft - 0
> > hard - NONE
> > Checking that ptrace can change system call numbers...check_ptrace : child exited with exitcode 6, while expecting 0; status 0x67f
> > Aborted
> > ----------------------
> >
> > Thinking more about this, it's clear that we simply cannot support
> > CONFIG_CONSTRUCTORS in UML. All the cases we need now (gcov, kasan)
> > involve not use of the __attribute__((constructor)), but instead
> > some constructor code/entry generated by gcc. Therefore, we cannot
> > distinguish between kernel constructors and system constructors.
> >
> > Thus, revert this commit.
> >
> > Cc: stable@xxxxxxxxxxxxxxx [5.4+]
> > Fixes: 786b2384bf1c ("um: Enable CONFIG_CONSTRUCTORS")
> > Reported-by: Anton Ivanov <anton.ivanov@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
> > ---
> > arch/um/include/asm/common.lds.S | 2 +-
> > arch/um/kernel/dyn.lds.S | 1 +
> > init/Kconfig | 1 +
> > kernel/gcov/Kconfig | 2 +-
> > 4 files changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/um/include/asm/common.lds.S b/arch/um/include/asm/common.lds.S
> > index d7086b985f27..4049f2c46387 100644
> > --- a/arch/um/include/asm/common.lds.S
> > +++ b/arch/um/include/asm/common.lds.S
> > @@ -83,8 +83,8 @@
> > __preinit_array_end = .;
> > }
> > .init_array : {
> > - /* dummy - we call this ourselves */
> > __init_array_start = .;
> > + *(.init_array)
> > __init_array_end = .;
> > }
> > .fini_array : {
> > diff --git a/arch/um/kernel/dyn.lds.S b/arch/um/kernel/dyn.lds.S
> > index c69d69ee96be..f5001481010c 100644
> > --- a/arch/um/kernel/dyn.lds.S
> > +++ b/arch/um/kernel/dyn.lds.S
> > @@ -103,6 +103,7 @@ SECTIONS
> > be empty, which isn't pretty. */
> > . = ALIGN(32 / 8);
> > .preinit_array : { *(.preinit_array) }
> > + .init_array : { *(.init_array) }
> > .fini_array : { *(.fini_array) }
> > .data : {
> > INIT_TASK_DATA(KERNEL_STACK_SIZE)
> > diff --git a/init/Kconfig b/init/Kconfig
> > index b4daad2bac23..0328b53d09ad 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -54,6 +54,7 @@ config CC_DISABLE_WARN_MAYBE_UNINITIALIZED
> >
> > config CONSTRUCTORS
> > bool
> > + depends on !UML
> >
> > config IRQ_WORK
> > bool
> > diff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig
> > index 060e8e726755..3941a9c48f83 100644
> > --- a/kernel/gcov/Kconfig
> > +++ b/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
> > + select CONSTRUCTORS if !UML
> > default n
> > ---help---
> > This option enables gcov-based code profiling (e.g. for code coverage
> >
>
> Acked-by: Anton Ivanov <anton.ivanov@xxxxxxxxxxxxxxxxxxxx>
Applied. Thanks!
--
Thanks,
//richard
