Revert "um: Enable CONFIG_CONSTRUCTORS"

commit 87c9366e17259040a9118e06b6dc8de986e5d3d1 upstream.

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@vger.kernel.org [5.4+]
Fixes: 786b2384bf1c ("um: Enable CONFIG_CONSTRUCTORS")
Reported-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Anton Ivanov <anton.ivanov@cambridgegreys.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Richard Weinberger <richard@nod.at>

diff --git a/arch/um/include/asm/common.lds.S b/arch/um/include/asm/common.lds.S
index d7086b9..4049f2c 100644 (file)
--- 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 c69d69e..f500148 100644 (file)
--- 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 b4daad2..0328b53 100644 (file)
--- 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 060e8e7..3941a9c 100644 (file)
--- 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