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commit 87c9366e17259040a9118e06b6dc8de986e5d3d1 upstream. This reverts commit786b2384bf("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:786b2384bf("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>
79 lines
2.0 KiB
Plaintext
79 lines
2.0 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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menu "GCOV-based kernel profiling"
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config GCOV_KERNEL
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bool "Enable gcov-based kernel profiling"
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depends on DEBUG_FS
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select CONSTRUCTORS if !UML
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default n
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---help---
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This option enables gcov-based code profiling (e.g. for code coverage
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measurements).
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If unsure, say N.
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Additionally specify CONFIG_GCOV_PROFILE_ALL=y to get profiling data
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for the entire kernel. To enable profiling for specific files or
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directories, add a line similar to the following to the respective
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Makefile:
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For a single file (e.g. main.o):
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GCOV_PROFILE_main.o := y
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For all files in one directory:
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GCOV_PROFILE := y
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To exclude files from being profiled even when CONFIG_GCOV_PROFILE_ALL
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is specified, use:
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GCOV_PROFILE_main.o := n
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and:
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GCOV_PROFILE := n
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Note that the debugfs filesystem has to be mounted to access
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profiling data.
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config ARCH_HAS_GCOV_PROFILE_ALL
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def_bool n
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config GCOV_PROFILE_ALL
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bool "Profile entire Kernel"
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depends on !COMPILE_TEST
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depends on GCOV_KERNEL
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depends on ARCH_HAS_GCOV_PROFILE_ALL
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default n
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---help---
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This options activates profiling for the entire kernel.
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If unsure, say N.
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Note that a kernel compiled with profiling flags will be significantly
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larger and run slower. Also be sure to exclude files from profiling
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which are not linked to the kernel image to prevent linker errors.
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choice
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prompt "Specify GCOV format"
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depends on GCOV_KERNEL
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depends on CC_IS_GCC
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---help---
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The gcov format is usually determined by the GCC version, and the
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default is chosen according to your GCC version. However, there are
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exceptions where format changes are integrated in lower-version GCCs.
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In such a case, change this option to adjust the format used in the
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kernel accordingly.
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config GCOV_FORMAT_3_4
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bool "GCC 3.4 format"
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depends on GCC_VERSION < 40700
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---help---
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Select this option to use the format defined by GCC 3.4.
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config GCOV_FORMAT_4_7
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bool "GCC 4.7 format"
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---help---
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Select this option to use the format defined by GCC 4.7.
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endchoice
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endmenu
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