On Thu, Feb 28, 2019 at 10:02 AM Stephen Boyd <sboyd(a)kernel.org> wrote:
>
> Quoting Brendan Higgins (2019-02-28 01:03:24)
> > On Tue, Feb 26, 2019 at 12:35 PM Stephen Boyd <sboyd(a)kernel.org> wrote:
> > >
> > > when they need to abort and then the test runner would detect that error
> > > via the return value from the 'run test' function. That would be a more
> > > direct approach, but also more verbose than a single KUNIT_ASSERT()
> > > line. It would be more kernel idiomatic too because the control flow
> >
> > Yeah, I was intentionally going against that idiom. I think that idiom
> > makes test logic more complicated than it needs to be, especially if
> > the assertion failure happens in a helper function; then you have to
> > pass that error all the way back up. It is important that test code
> > should be as simple as possible to the point of being immediately
> > obviously correct at first glance because there are no tests for
> > tests.
> >
> > The idea with assertions is that you use them to state all the
> > preconditions for your test. Logically speaking, these are the
> > premises of the test case, so if a premise isn't true, there is no
> > point in continuing the test case because there are no conclusions
> > that can be drawn without the premises. Whereas, the expectation is
> > the thing you are trying to prove. It is not used universally in
> > x-unit style test frameworks, but I really like it as a convention.
> > You could still express the idea of a premise using the above idiom,
> > but I think KUNIT_ASSERT_* states the intended idea perfectly.
>
> Fair enough. It would be great if these sorts of things were described
> in the commit text.
Good point. Will fix.
>
> Is the assumption that things like held locks and refcounted elements
> won't exist when one of these assertions is made? It sounds like some of
> the cleanup logic could be fairly complicated if a helper function
> changes some state and then an assert fails and we have to unwind all
> the state from a corrupt location. A similar problem exists for a test
> timeout too. How do we get back to a sane state if the test locks up for
> a long time? Just don't try?
It depends on the situation, if it is part of a KUnit test itself
(probably not code under test), then you can use the kunit_resource
API: https://lkml.org/lkml/2019/2/14/1125; it is inspired by the
devm_* family of functions, such that when a KUnit test case ends, for
any reason, all the kunit_resources are automatically cleaned up.
Similarly, kunit_module.exit is called at the end of every test case,
regardless of how it terminates.
>
> >
> > > isn't hidden inside a macro and it isn't intimately connected with
> > > kthreads and completions.
> >
> > Yeah, I wasn't a fan of that myself, but it was broadly available. My
> > previous version (still the architecture specific version for UML, not
> > in this patchset though) relies on UML_LONGJMP, but is obviously only
> > works on UML. A number of people wanted support for other
> > architectures. Rob and Luis specifically wanted me to provide a
> > version of abort that would work on any architecture, even if it only
> > had reduced functionality; I thought this fit the bill okay.
>
> Ok.
>
> >
> > >
> > > >
> > > > diff --git a/kunit/test.c b/kunit/test.c
> > > > index d18c50d5ed671..6e5244642ab07 100644
> > > > --- a/kunit/test.c
> > > > +++ b/kunit/test.c
> > > [...]
> > > > +
> > > > +static void kunit_generic_throw(struct kunit_try_catch *try_catch)
> > > > +{
> > > > + try_catch->context.try_result = -EFAULT;
> > > > + complete_and_exit(try_catch->context.try_completion, -EFAULT);
> > > > +}
> > > > +
> > > > +static int kunit_generic_run_threadfn_adapter(void *data)
> > > > +{
> > > > + struct kunit_try_catch *try_catch = data;
> > > >
> > > > + try_catch->try(&try_catch->context);
> > > > +
> > > > + complete_and_exit(try_catch->context.try_completion, 0);
> > >
> > > The exit code doesn't matter, right? If so, it might be clearer to just
> > > return 0 from this function because kthreads exit themselves as far as I
> > > recall.
> >
> > You mean complete and then return?
>
> Yes. I was confused for a minute because I thought the exit code was
> checked, but it isn't. Instead, the try_catch->context.try_result is
> where the test result goes, so calling exit explicitly doesn't seem to
> be important here, but it is important in the throw case.
Yep.
>
> >
> > >
> > > > + else if (exit_code)
> > > > + kunit_err(test, "Unknown error: %d", exit_code);
> > > > +}
> > > > +
> > > > +void kunit_generic_try_catch_init(struct kunit_try_catch *try_catch)
> > > > +{
> > > > + try_catch->run = kunit_generic_run_try_catch;
> > >
> > > Is the idea that 'run' would be anything besides
> > > 'kunit_generic_run_try_catch'? If it isn't going to be different, then
> >
> > Yeah, it can be overridden with an architecture specific version.
> >
> > > maybe it's simpler to just have a function like
> > > kunit_generic_run_try_catch() that is called by the unit tests instead
> > > of having to write 'try_catch->run(try_catch)' and indirect for the
> > > basic case. Maybe I've missed the point entirely though and this is all
> > > scaffolding for more complicated exception handling later on.
> >
> > Yeah, the idea is that different architectures can override exception
> > handling with their own implementation. This is just the generic one.
> > For example, UML has one that doesn't depend on kthreads or
> > completions; the UML version also allows recovery from some segfault
> > conditions.
>
> Ok, got it. It may still be nice to have a wrapper or macro for that
> try_catch->run(try_catch) statement so we don't have to know that a
> try_catch struct has a run member.
>
> static inline void kunit_run_try_catch(struct kunit_try_catch *try_catch)
> {
> try_catch->run(try_catch);
> }
Makes sense. Will fix in the next revision.
Use /bin/echo for console output with options like non
newline (-n) and/or backslash escape (-e).
Tom Zanussi reported that when he tested ftracetest, it
shows "-e" and "-n" options on the console, since a system
which uses dash as the alias of /bin/sh, uses dash built-in
echo command which doesn't accept "-e".
To avoid this issue, use /bin/echo instead of echo for
the output with options.
Fixes: 8f381ac4d321 ("selftests/ftrace: Add color to the PASS / FAIL results")
Link: http://lkml.kernel.org/r/cover.1542221862.git.tom.zanussi@linux.intel.com
Reported-by: Tom Zanussi <zanussi(a)kernel.org>
Suggested-by: Tom Zanussi <zanussi(a)kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat(a)kernel.org>
---
tools/testing/selftests/ftrace/ftracetest | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/ftrace/ftracetest b/tools/testing/selftests/ftrace/ftracetest
index 75244db70331..ba670b452bdb 100755
--- a/tools/testing/selftests/ftrace/ftracetest
+++ b/tools/testing/selftests/ftrace/ftracetest
@@ -173,8 +173,8 @@ strip_esc() {
}
prlog() { # messages
- echo -e "$@"
- [ "$LOG_FILE" ] && echo -e "$@" | strip_esc >> $LOG_FILE
+ /bin/echo -e "$@"
+ [ "$LOG_FILE" ] && /bin/echo -e "$@" | strip_esc >> $LOG_FILE
}
catlog() { #file
cat $1
Introduce in-kernel headers and other artifacts which are made available
as an archive through proc (/proc/kheaders.tar.xz file). This archive makes
it possible to build kernel modules, run eBPF programs, and other
tracing programs that need to extend the kernel for tracing purposes
without any dependency on the file system having headers and build
artifacts.
On Android and embedded systems, it is common to switch kernels but not
have kernel headers available on the file system. Raw kernel headers
also cannot be copied into the filesystem like they can be on other
distros, due to licensing and other issues. There's no linux-headers
package on Android. Further once a different kernel is booted, any
headers stored on the file system will no longer be useful. By storing
the headers as a compressed archive within the kernel, we can avoid these
issues that have been a hindrance for a long time.
The feature is also buildable as a module just in case the user desires
it not being part of the kernel image. This makes it possible to load
and unload the headers on demand. A tracing program, or a kernel module
builder can load the module, do its operations, and then unload the
module to save kernel memory. The total memory needed is 3.8MB.
The code to read the headers is based on /proc/config.gz code and uses
the same technique to embed the headers.
To build a module, the below steps have been tested on an x86 machine:
modprobe kheaders
rm -rf $HOME/headers
mkdir -p $HOME/headers
tar -xvf /proc/kheaders.tar.xz -C $HOME/headers >/dev/null
cd my-kernel-module
make -C $HOME/headers M=$(pwd) modules
rmmod kheaders
Additional notes:
(1)
A limitation of module building with this is, since Module.symvers is
not available in the archive due to a cyclic dependency with building of
the archive into the kernel or module binaries, the modules built using
the archive will not contain symbol versioning (modversion). This is
usually not an issue since the idea of this patch is to build a kernel
module on the fly and load it into the same kernel. An appropriate
warning is already printed by the kernel to alert the user of modules
not having modversions when built using the archive. For building with
modversions, the user can use traditional header packages. For our
tracing usecases, we build modules on the fly with this so it is not a
concern.
(2) I have left IKHD_ST and IKHD_ED markers as is to facilitate
future patches that would extract the headers from a kernel or module
image.
Signed-off-by: Joel Fernandes (Google) <joel(a)joelfernandes.org>
---
Changes since v2:
(Thanks to Masahiro Yamada for several excellent suggestions)
- Added support for out of tree builds.
- Added incremental build support bringing down build time of
incremental builds from 50 seconds to 5 seconds.
- Fixed various small nits / cleanups.
- clean ups to kheaders.c pointed by Alexey Dobriyan.
- Fixed MODULE_LICENSE in test module and kheaders.c
- Dropped Module.symvers from archive due to circular dependency.
Changes since v1:
- removed IKH_EXTRA variable, not needed (Masahiro Yamada)
- small fix ups to selftest
- added target to main Makefile etc
- added MODULE_LICENSE to test module
- made selftest more quiet
Changes since RFC:
Both changes bring size down to 3.8MB:
- use xz for compression
- strip comments except SPDX lines
- Call out the module name in Kconfig
- Also added selftests in second patch to ensure headers are always
working.
Other notes:
By the way I still see this error (without the patch) when doing a clean
build: Makefile:594: include/config/auto.conf: No such file or directory
It appears to be because of commit 0a16d2e8cb7e ("kbuild: use 'include'
directive to load auto.conf from top Makefile")
Documentation/dontdiff | 1 +
init/Kconfig | 11 ++++++
kernel/.gitignore | 3 ++
kernel/Makefile | 36 +++++++++++++++++++
kernel/kheaders.c | 72 +++++++++++++++++++++++++++++++++++++
scripts/gen_ikh_data.sh | 76 +++++++++++++++++++++++++++++++++++++++
scripts/strip-comments.pl | 8 +++++
7 files changed, 207 insertions(+)
create mode 100644 kernel/kheaders.c
create mode 100755 scripts/gen_ikh_data.sh
create mode 100755 scripts/strip-comments.pl
diff --git a/Documentation/dontdiff b/Documentation/dontdiff
index 2228fcc8e29f..05a2319ee2a2 100644
--- a/Documentation/dontdiff
+++ b/Documentation/dontdiff
@@ -151,6 +151,7 @@ int8.c
kallsyms
kconfig
keywords.c
+kheaders_data.h*
ksym.c*
ksym.h*
kxgettext
diff --git a/init/Kconfig b/init/Kconfig
index c9386a365eea..63ff0990ae55 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -563,6 +563,17 @@ config IKCONFIG_PROC
This option enables access to the kernel configuration file
through /proc/config.gz.
+config IKHEADERS_PROC
+ tristate "Enable kernel header artifacts through /proc/kheaders.tar.xz"
+ select BUILD_BIN2C
+ depends on PROC_FS
+ help
+ This option enables access to the kernel header and other artifacts that
+ are generated during the build process. These can be used to build kernel
+ modules, and other in-kernel programs such as those generated by eBPF
+ and systemtap tools. If you build the headers as a module, a module
+ called kheaders.ko is built which can be loaded to get access to them.
+
config LOG_BUF_SHIFT
int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
range 12 25
diff --git a/kernel/.gitignore b/kernel/.gitignore
index b3097bde4e9c..484018945e93 100644
--- a/kernel/.gitignore
+++ b/kernel/.gitignore
@@ -3,5 +3,8 @@
#
config_data.h
config_data.gz
+kheaders.md5
+kheaders_data.h
+kheaders_data.tar.xz
timeconst.h
hz.bc
diff --git a/kernel/Makefile b/kernel/Makefile
index 6aa7543bcdb2..0bc7cacd7da6 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -70,6 +70,7 @@ obj-$(CONFIG_UTS_NS) += utsname.o
obj-$(CONFIG_USER_NS) += user_namespace.o
obj-$(CONFIG_PID_NS) += pid_namespace.o
obj-$(CONFIG_IKCONFIG) += configs.o
+obj-$(CONFIG_IKHEADERS_PROC) += kheaders.o
obj-$(CONFIG_SMP) += stop_machine.o
obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o
obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
@@ -130,3 +131,38 @@ filechk_ikconfiggz = \
targets += config_data.h
$(obj)/config_data.h: $(obj)/config_data.gz FORCE
$(call filechk,ikconfiggz)
+
+# Build a list of in-kernel headers for building kernel modules
+ikh_file_list := include/
+ikh_file_list += arch/$(SRCARCH)/Makefile
+ikh_file_list += arch/$(SRCARCH)/include/
+ikh_file_list += scripts/
+ikh_file_list += Makefile
+
+# Things we need from the $objtree. "OBJDIR" is for the gen_ikh_data.sh
+# script to identify that this comes from the $objtree directory
+ikh_file_list += OBJDIR/scripts/
+ikh_file_list += OBJDIR/include/
+ikh_file_list += OBJDIR/arch/$(SRCARCH)/include/
+ifeq ($(CONFIG_STACK_VALIDATION), y)
+ikh_file_list += OBJDIR/tools/objtool/objtool
+endif
+
+$(obj)/kheaders.o: $(obj)/kheaders_data.h
+
+targets += kheaders_data.tar.xz
+
+quiet_cmd_genikh = GEN $(obj)/kheaders_data.tar.xz
+cmd_genikh = $(srctree)/scripts/gen_ikh_data.sh $@ $(ikh_file_list)
+$(obj)/kheaders_data.tar.xz: FORCE
+ $(call cmd,genikh)
+
+filechk_ikheadersxz = \
+ echo "static const char kernel_headers_data[] __used = KH_MAGIC_START"; \
+ cat $< | scripts/bin2c; \
+ echo "KH_MAGIC_END;"
+
+targets += kheaders_data.h
+targets += kheaders.md5
+$(obj)/kheaders_data.h: $(obj)/kheaders_data.tar.xz FORCE
+ $(call filechk,ikheadersxz)
diff --git a/kernel/kheaders.c b/kernel/kheaders.c
new file mode 100644
index 000000000000..46a6358301e5
--- /dev/null
+++ b/kernel/kheaders.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * kernel/kheaders.c
+ * Provide headers and artifacts needed to build kernel modules.
+ * (Borrowed code from kernel/configs.c)
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/init.h>
+#include <linux/uaccess.h>
+
+/*
+ * Define kernel_headers_data and kernel_headers_data_size, which contains the
+ * compressed kernel headers. The file is first compressed with xz and then
+ * bounded by two eight byte magic numbers to allow extraction from a binary
+ * kernel image:
+ *
+ * IKHD_ST
+ * <image>
+ * IKHD_ED
+ */
+#define KH_MAGIC_START "IKHD_ST"
+#define KH_MAGIC_END "IKHD_ED"
+#include "kheaders_data.h"
+
+
+#define KH_MAGIC_SIZE (sizeof(KH_MAGIC_START) - 1)
+#define kernel_headers_data_size \
+ (sizeof(kernel_headers_data) - 1 - KH_MAGIC_SIZE * 2)
+
+static ssize_t
+ikheaders_read_current(struct file *file, char __user *buf,
+ size_t len, loff_t *offset)
+{
+ return simple_read_from_buffer(buf, len, offset,
+ kernel_headers_data + KH_MAGIC_SIZE,
+ kernel_headers_data_size);
+}
+
+static const struct file_operations ikheaders_file_ops = {
+ .read = ikheaders_read_current,
+ .llseek = default_llseek,
+};
+
+static int __init ikheaders_init(void)
+{
+ struct proc_dir_entry *entry;
+
+ /* create the current headers file */
+ entry = proc_create("kheaders.tar.xz", S_IRUGO, NULL,
+ &ikheaders_file_ops);
+ if (!entry)
+ return -ENOMEM;
+
+ proc_set_size(entry, kernel_headers_data_size);
+
+ return 0;
+}
+
+static void __exit ikheaders_cleanup(void)
+{
+ remove_proc_entry("kheaders.tar.xz", NULL);
+}
+
+module_init(ikheaders_init);
+module_exit(ikheaders_cleanup);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Joel Fernandes");
+MODULE_DESCRIPTION("Echo the kernel header artifacts used to build the kernel");
diff --git a/scripts/gen_ikh_data.sh b/scripts/gen_ikh_data.sh
new file mode 100755
index 000000000000..7329262bed2f
--- /dev/null
+++ b/scripts/gen_ikh_data.sh
@@ -0,0 +1,76 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+spath="$(dirname "$(readlink -f "$0")")"
+kroot="$spath/.."
+outdir="$(pwd)"
+tarfile=$1
+cpio_dir=$outdir/$tarfile.tmp
+
+src_file_list=""
+for f in $file_list; do
+ src_file_list="$src_file_list $(echo $f | grep -v OBJDIR)"
+done
+
+obj_file_list=""
+for f in $file_list; do
+ f=$(echo $f | grep OBJDIR | sed -e 's/OBJDIR\///g')
+ obj_file_list="$obj_file_list $f";
+done
+
+# Support incremental builds by skipping archive generation
+# if timestamps of files being archived are not changed.
+
+# This block is useful for debugging the incremental builds.
+# Uncomment it for debugging.
+# iter=1
+# if [ ! -f /tmp/iter ]; then echo 1 > /tmp/iter;
+# else; iter=$(($(cat /tmp/iter) + 1)); fi
+# find $src_file_list -type f | xargs ls -lR > /tmp/src-ls-$iter
+# find $obj_file_list -type f | xargs ls -lR > /tmp/obj-ls-$iter
+
+# modules.order and include/generated/compile.h are ignored because these are
+# touched even when none of the source files changed. This causes pointless
+# regeneration, so let us ignore them for md5 calculation.
+pushd $kroot > /dev/null
+src_files_md5="$(find $src_file_list -type f ! -name modules.order |
+ grep -v "include/generated/compile.h" |
+ xargs ls -lR | md5sum | cut -d ' ' -f1)"
+popd > /dev/null
+obj_files_md5="$(find $obj_file_list -type f ! -name modules.order |
+ grep -v "include/generated/compile.h" |
+ xargs ls -lR | md5sum | cut -d ' ' -f1)"
+
+if [ -f $tarfile ]; then tarfile_md5="$(md5sum $tarfile | cut -d ' ' -f1)"; fi
+if [ -f kernel/kheaders.md5 ] &&
+ [ "$(cat kernel/kheaders.md5|head -1)" == "$src_files_md5" ] &&
+ [ "$(cat kernel/kheaders.md5|head -2|tail -1)" == "$obj_files_md5" ] &&
+ [ "$(cat kernel/kheaders.md5|tail -1)" == "$tarfile_md5" ]; then
+ exit
+fi
+
+rm -rf $cpio_dir
+mkdir $cpio_dir
+
+pushd $kroot > /dev/null
+for f in $src_file_list;
+ do find "$f" ! -name "*.c" ! -name "*.o" ! -name "*.cmd" ! -name ".*";
+done | cpio --quiet -pd $cpio_dir
+popd > /dev/null
+
+# The second CPIO can complain if files already exist which can
+# happen with out of tree builds. Just silence CPIO for now.
+for f in $obj_file_list;
+ do find "$f" ! -name "*.c" ! -name "*.o" ! -name "*.cmd" ! -name ".*";
+done | cpio --quiet -pd $cpio_dir >/dev/null 2>&1
+
+find $cpio_dir -type f -print0 |
+ xargs -0 -P8 -n1 -I {} sh -c "$spath/strip-comments.pl {}"
+
+tar -Jcf $tarfile -C $cpio_dir/ . > /dev/null
+
+echo "$src_files_md5" > kernel/kheaders.md5
+echo "$obj_files_md5" >> kernel/kheaders.md5
+echo "$(md5sum $tarfile | cut -d ' ' -f1)" >> kernel/kheaders.md5
+
+rm -rf $cpio_dir
diff --git a/scripts/strip-comments.pl b/scripts/strip-comments.pl
new file mode 100755
index 000000000000..f8ada87c5802
--- /dev/null
+++ b/scripts/strip-comments.pl
@@ -0,0 +1,8 @@
+#!/usr/bin/perl -pi
+# SPDX-License-Identifier: GPL-2.0
+
+# This script removes /**/ comments from a file, unless such comments
+# contain "SPDX". It is used when building compressed in-kernel headers.
+
+BEGIN {undef $/;}
+s/\/\*((?!SPDX).)*?\*\///smg;
--
2.21.0.rc2.261.ga7da99ff1b-goog