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authorJohannes Berg <johannes.berg@intel.com>2019-12-04 17:43:46 +0100
committerRichard Weinberger <richard@nod.at>2020-01-19 22:42:06 +0100
commit87c9366e17259040a9118e06b6dc8de986e5d3d1 (patch)
tree7f9096f5abebc90807bb620d3876e4638c69cf97 /kernel/gcov
parent40814b98a57089463eb4be09c72205f551481f39 (diff)
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>
Diffstat (limited to 'kernel/gcov')
-rw-r--r--kernel/gcov/Kconfig2
1 files changed, 1 insertions, 1 deletions
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