linux.git/arch/um/kernel/skas/Makefile, branch master

um: fix stub exe build with CONFIG_GCOV

2024-10-26T14:06:10+00:00

CONFIG_GCOV is special and only in UML since it builds the
kernel with a "userspace" option. This is fine, but the stub
is even more special and not really a full userspace process,
so it then fails to link as reported.

Remove the GCOV options from the stub build.

For good measure, also remove the GPROF options, even though
they don't seem to cause build failures now.

To be able to do this, export the specific options (GCOV_OPT
and GPROF_OPT) but rename them so there's less chance of any
conflicts.

Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202410242238.SXhs2kQ4-lkp@intel.com/
Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Link: https://patch.msgid.link/20241025102700.9fbb9c34473f.I7f1537fe075638f8da64beb52ef6c9e5adc51bc3@changeid
Signed-off-by: Johannes Berg

um: Disable auto variable initialization for stub_exe.c

2024-10-17T08:33:31+00:00

When automatic variable initialization is enabled via
CONFIG_INIT_STACK_ALL_{PATTERN,ZERO}, clang will insert a call to
memset() to initialize an object created with __builtin_alloca(). This
ultimately breaks the build when linking stub_exe because it is a
standalone executable that does not include or link against memset().

  ld: arch/um/kernel/skas/stub_exe.o: in function `_start':
  arch/um/kernel/skas/stub_exe.c:83:(.ltext+0x15): undefined reference to `memset'

Disable automatic variable initialization for stub_exe.c by passing the
default value of 'uninitialized' to '-ftrivial-auto-var-init', which
avoids generating the call to memset(). This code is small and runs
quickly as it is just designed to set up an environment, so stack
variable initialization is unnecessary overhead for little gain.

Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Signed-off-by: Nathan Chancellor 
Link: https://patch.msgid.link/20241016-uml-fix-stub_exe-clang-v1-2-3d6381dc5a78@kernel.org
Signed-off-by: Johannes Berg

um: Fix passing '-n' to linker for stub_exe

2024-10-17T08:33:31+00:00

When building stub_exe with clang, there is an error because '-n' is not
a recognized flag by the clang driver (which is being used to invoke the
linker):

  clang: error: unknown argument: '-n'

'-n' should be passed along to the linker, as it is the short flag for
'--nmagic', so prefix it with '-Wl,'.

Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Signed-off-by: Nathan Chancellor 
Link: https://patch.msgid.link/20241016-uml-fix-stub_exe-clang-v1-1-3d6381dc5a78@kernel.org
Signed-off-by: Johannes Berg

um: use execveat to create userspace MMs

2024-10-10T11:37:16+00:00

Using clone will not undo features that have been enabled by libc. An
example of this already happening is rseq, which could cause the kernel
to read/write memory of the userspace process. In the future the
standard library might also use mseal by default to protect itself,
which would also thwart our attempts at unmapping everything.

Solve all this by taking a step back and doing an execve into a tiny
static binary that sets up the minimal environment required for the
stub without using any standard library. That way we have a clean
execution environment that is fully under the control of UML.

Note that this changes things a bit as the FDs are not anymore shared
with the kernel. Instead, we explicitly share the FDs for the physical
memory and all existing iomem regions. Doing this is fine, as iomem
regions cannot be added at runtime.

Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20240919124511.282088-3-benjamin@sipsolutions.net
[use pipe() instead of pipe2(), remove unneeded close() calls]
Signed-off-by: Johannes Berg

um: remove copy_context_skas0

2024-07-03T15:09:49+00:00

The kernel flushes the memory ranges anyway for CoW and does not assume
that the userspace process has anything set up already. So, start with a
fresh process for the new mm context.

Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20240703134536.1161108-8-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg

um: Rework syscall handling

2024-07-03T15:09:49+00:00

Rework syscall handling to be platform independent. Also create a clean
split between queueing of syscalls and flushing them out, removing the
need to keep state in the code that triggers the syscalls.

The code adds syscall_data_len to the global mm_id structure. This will
be used later to allow surrounding code to track whether syscalls still
need to run and if errors occurred.

Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20240703134536.1161108-5-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg

kbuild: remove --include-dir MAKEFLAG from top Makefile

2023-02-05T09:51:22+00:00

I added $(srctree)/ to some included Makefiles in the following commits:

 - 3204a7fb98a3 ("kbuild: prefix $(srctree)/ to some included Makefiles")
 - d82856395505 ("kbuild: do not require sub-make for separate output tree builds")

They were a preparation for removing --include-dir flag.

I have never thought --include-dir useful. Rather, it _is_ harmful.

For example, run the following commands:

  $ make -s ARCH=x86 mrproper defconfig
  $ make ARCH=arm O=foo dtbs
  make[1]: Entering directory '/tmp/linux/foo'
    HOSTCC  scripts/basic/fixdep
  Error: kernelrelease not valid - run 'make prepare' to update it
    UPD     include/config/kernel.release
  make[1]: Leaving directory '/tmp/linux/foo'

The first command configures the source tree for x86. The next command
tries to build ARM device trees in the separate foo/ directory - this
must stop because the directory foo/ has not been configured yet.

However, due to --include-dir=$(abs_srctree), the top Makefile includes
the wrong include/config/auto.conf from the source tree and continues
building. Kbuild traverses the directory tree, but of course it does
not work correctly. The Error message is also pointless - 'make prepare'
does not help at all for fixing the issue.

This commit fixes more arch Makefile, and finally removes --include-dir
from the top Makefile.

There are more breakages under drivers/, but I do not volunteer to fix
them all. I just moved --include-dir to drivers/Makefile.

With this commit, the second command will stop with a sensible message.

  $ make -s ARCH=x86 mrproper defconfig
  $ make ARCH=arm O=foo dtbs
  make[1]: Entering directory '/tmp/linux/foo'
    SYNC    include/config/auto.conf.cmd
  ***
  *** The source tree is not clean, please run 'make ARCH=arm mrproper'
  *** in /tmp/linux
  ***
  make[2]: *** [../Makefile:646: outputmakefile] Error 1
  /tmp/linux/Makefile:770: include/config/auto.conf.cmd: No such file or directory
  make[1]: *** [/tmp/linux/Makefile:793: include/config/auto.conf.cmd] Error 2
  make[1]: Leaving directory '/tmp/linux/foo'
  make: *** [Makefile:226: __sub-make] Error 2

Signed-off-by: Masahiro Yamada

um: Add SPDX headers to files in arch/um/kernel/

2019-09-15T19:37:17+00:00

Convert files to use SPDX header. All files are licensed under the
GPLv2.

Signed-off-by: Alex Dewar 
Signed-off-by: Richard Weinberger

um: Fix kcov crash during startup

2019-07-02T21:27:42+00:00

Kcov fails to start when compiled with kcov. Disable KCOV on
arch/uml/kernel/skas.

  $ gdb -q -ex r ./vmlinux
  Program received signal SIGSEGV, Segmentation fault.
  check_kcov_mode (t=<>, needed_mode=<>) at kernel/kcov.c:70
  70		mode = READ_ONCE(t->kcov_mode);

Signed-off-by: Marek Majkowski 
Signed-off-by: Richard Weinberger

uml: style fixes pass 3

2007-10-16T16:43:05+00:00

Formatting changes in the files which have been changed in the course
of folding foo_skas functions into their callers.  These include:
	copyright updates
	header file trimming
	style fixes
	adding severity to printks

These changes should be entirely non-functional.

Signed-off-by: Jeff Dike 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds