Revert "um: Enable CONFIG_CONSTRUCTORS"

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: Richard Weinberger <richard@nod.at>

diff --git a/arch/um/include/asm/common.lds.S b/arch/um/include/asm/common.lds.S
index 7145ce6999822613f7923ae936b9d70a85044de4..eca6c452a41bd16d14a4631a3e61e65cc3467ada 100644 (file)
--- a/arch/um/include/asm/common.lds.S
+++ b/arch/um/include/asm/common.lds.S
@@ -82,8 +82,8 @@
        __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 c69d69ee96bebae0c8125dbd2cd9b468398e2710..f5001481010c0a5cb80a60b1d8ab5ad0e9c4ce5d 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 a34064a031a5ed785eb4c7bab830408f1fb2608a..47d40f39900053eeaad547a1adb7ce5e6a60f014 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 060e8e726755f02ddd18572f6e1279678d184510..3941a9c48f833b3c9de3ee594a9ff5051d69fc5b 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