KUnit test cases run on kthreads, and kthreads don't have an
adddress space (current->mm is NULL), but processes have mm.
The purpose of this patch is to allow to borrow mm to KUnit kthread
after userspace is brought up, because we know that there are processes
running, at least the process that loaded the module to borrow mm.
This allows, for example, tests such as user_copy_kunit, which uses
vm_mmap, which needs current->mm.
Signed-off-by: Vitor Massaru Iha <vitor(a)massaru.org>
---
v2:
* splitted patch in 3:
- Allows to install and load modules in root filesystem;
- Provides an userspace memory context when tests are compiled
as module;
- Convert test_user_copy to KUnit test;
* added documentation;
* added more explanation;
* tested a pointer;
* released mput();
---
Documentation/dev-tools/kunit/usage.rst | 14 ++++++++++++++
include/kunit/test.h | 12 ++++++++++++
lib/kunit/try-catch.c | 15 ++++++++++++++-
3 files changed, 40 insertions(+), 1 deletion(-)
diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst
index 3c3fe8b5fecc..9f909157be34 100644
--- a/Documentation/dev-tools/kunit/usage.rst
+++ b/Documentation/dev-tools/kunit/usage.rst
@@ -448,6 +448,20 @@ We can now use it to test ``struct eeprom_buffer``:
.. _kunit-on-non-uml:
+User-space context
+------------------
+
+I case you need a user-space context, for now this is only possible through
+tests compiled as a module. And it will be necessary to use a root filesystem
+and uml_utilities.
+
+Example:
+
+.. code-block:: bash
+
+ ./tools/testing/kunit/kunit.py run --timeout=60 --uml_rootfs_dir=.uml_rootfs
+
+
KUnit on non-UML architectures
==============================
diff --git a/include/kunit/test.h b/include/kunit/test.h
index 59f3144f009a..ae3337139c65 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -222,6 +222,18 @@ struct kunit {
* protect it with some type of lock.
*/
struct list_head resources; /* Protected by lock. */
+ /*
+ * KUnit test cases run on kthreads, and kthreads don't have an
+ * adddress space (current->mm is NULL), but processes have mm.
+ *
+ * The purpose of this mm_struct is to allow to borrow mm to KUnit kthread
+ * after userspace is brought up, because we know that there are processes
+ * running, at least the process that loaded the module to borrow mm.
+ *
+ * This allows, for example, tests such as user_copy_kunit, which uses
+ * vm_mmap, which needs current->mm.
+ */
+ struct mm_struct *mm;
};
void kunit_init_test(struct kunit *test, const char *name, char *log);
diff --git a/lib/kunit/try-catch.c b/lib/kunit/try-catch.c
index 0dd434e40487..d03e2093985b 100644
--- a/lib/kunit/try-catch.c
+++ b/lib/kunit/try-catch.c
@@ -11,7 +11,8 @@
#include <linux/completion.h>
#include <linux/kernel.h>
#include <linux/kthread.h>
-
+#include <linux/sched/mm.h>
+#include <linux/sched/task.h>
#include "try-catch-impl.h"
void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch)
@@ -24,8 +25,17 @@ EXPORT_SYMBOL_GPL(kunit_try_catch_throw);
static int kunit_generic_run_threadfn_adapter(void *data)
{
struct kunit_try_catch *try_catch = data;
+ struct kunit *test = try_catch->test;
+
+ if (test != NULL && test->mm != NULL)
+ kthread_use_mm(test->mm);
try_catch->try(try_catch->context);
+ if (test != NULL && test->mm != NULL) {
+ kthread_unuse_mm(test->mm);
+ mmput(test->mm);
+ test->mm = NULL;
+ }
complete_and_exit(try_catch->try_completion, 0);
}
@@ -65,6 +75,9 @@ void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context)
try_catch->context = context;
try_catch->try_completion = &try_completion;
try_catch->try_result = 0;
+
+ test->mm = get_task_mm(current);
+
task_struct = kthread_run(kunit_generic_run_threadfn_adapter,
try_catch,
"kunit_try_catch_thread");
base-commit: 725aca9585956676687c4cb803e88f770b0df2b2
prerequisite-patch-id: 5e5f9a8a05c5680fda1b04c9ab1b95ce91dc88b2
prerequisite-patch-id: 4d997940f4a9f303424af9bac412de1af861f9d9
prerequisite-patch-id: 582b6d9d28ce4b71628890ec832df6522ca68de0
--
2.26.2
Hey everyone,
This is a follow-up to the do_fork() cleanup from last cycle based on a
short discussion this was merged.
Last cycle we removed copy_thread_tls() and the associated Kconfig
option for each architecture. Now we are only left with copy_thread().
Part of this work was removing the old do_fork() legacy clone()-style
calling convention in favor of the new struct kernel_clone args calling
convention.
The only remaining function callable outside of kernel/fork.c is
_do_fork(). It doesn't really follow the naming of kernel-internal
syscall helpers as Christoph righly pointed out. Switch all callers and
references to kernel_clone() and remove _do_fork() once and for all.
For all architectures I have done a full git rebase v5.9-rc1 -x "make
-j31". There were no built failures and the changes were fairly
mechanical.
The only helpers we have left now are kernel_thread() and kernel_clone()
where kernel_thread() just calls kernel_clone().
Thanks!
Christian
Christian Brauner (11):
fork: introduce kernel_clone()
h8300: switch to kernel_clone()
ia64: switch to kernel_clone()
m68k: switch to kernel_clone()
nios2: switch to kernel_clone()
sparc: switch to kernel_clone()
x86: switch to kernel_clone()
kprobes: switch to kernel_clone()
kgdbts: switch to kernel_clone()
tracing: switch to kernel_clone()
sched: remove _do_fork()
Documentation/trace/histogram.rst | 4 +-
arch/h8300/kernel/process.c | 2 +-
arch/ia64/kernel/process.c | 4 +-
arch/m68k/kernel/process.c | 10 ++--
arch/nios2/kernel/process.c | 2 +-
arch/sparc/kernel/process.c | 6 +--
arch/x86/kernel/sys_ia32.c | 2 +-
drivers/misc/kgdbts.c | 48 +++++++++----------
include/linux/sched/task.h | 2 +-
kernel/fork.c | 14 +++---
samples/kprobes/kprobe_example.c | 6 +--
samples/kprobes/kretprobe_example.c | 4 +-
.../test.d/dynevent/add_remove_kprobe.tc | 2 +-
.../test.d/dynevent/clear_select_events.tc | 2 +-
.../test.d/dynevent/generic_clear_event.tc | 2 +-
.../test.d/ftrace/func-filter-stacktrace.tc | 4 +-
.../ftrace/test.d/kprobe/add_and_remove.tc | 2 +-
.../ftrace/test.d/kprobe/busy_check.tc | 2 +-
.../ftrace/test.d/kprobe/kprobe_args.tc | 4 +-
.../ftrace/test.d/kprobe/kprobe_args_comm.tc | 2 +-
.../test.d/kprobe/kprobe_args_string.tc | 4 +-
.../test.d/kprobe/kprobe_args_symbol.tc | 10 ++--
.../ftrace/test.d/kprobe/kprobe_args_type.tc | 2 +-
.../ftrace/test.d/kprobe/kprobe_ftrace.tc | 14 +++---
.../ftrace/test.d/kprobe/kprobe_multiprobe.tc | 2 +-
.../test.d/kprobe/kprobe_syntax_errors.tc | 12 ++---
.../ftrace/test.d/kprobe/kretprobe_args.tc | 4 +-
.../selftests/ftrace/test.d/kprobe/profile.tc | 2 +-
28 files changed, 87 insertions(+), 87 deletions(-)
base-commit: 9123e3a74ec7b934a4a099e98af6a61c2f80bbf5
--
2.28.0
If debug_regs.c is built with newer gcc, e.g., 8.3.1 on my side, then the generated
binary looks like over-optimized by gcc:
asm volatile("ss_start: "
"xor %%rax,%%rax\n\t"
"cpuid\n\t"
"movl $0x1a0,%%ecx\n\t"
"rdmsr\n\t"
: : : "rax", "ecx");
is translated to :
000000000040194e <ss_start>:
40194e: 31 c0 xor %eax,%eax <----- rax->eax?
401950: 0f a2 cpuid
401952: b9 a0 01 00 00 mov $0x1a0,%ecx
401957: 0f 32 rdmsr
As you can see rax is replaced with eax in taret binary code.
But if I replace %%rax with %%r8 or any GPR from r8~15, then I get below
expected binary:
0000000000401950 <ss_start>:
401950: 45 31 ff xor %r15d,%r15d
401953: 0f a2 cpuid
401955: b9 a0 01 00 00 mov $0x1a0,%ecx
40195a: 0f 32 rdmsr
The difference is the length of xor instruction(2 Byte vs 3 Byte),
so this makes below hard-coded instruction length cannot pass runtime check:
/* Instruction lengths starting at ss_start */
int ss_size[4] = {
3, /* xor */ <-------- 2 or 3?
2, /* cpuid */
5, /* mov */
2, /* rdmsr */
};
Note:
Use 8.2.1 or older gcc, it generates expected 3 bytes xor target code.
I use the default Makefile to build the binaries, and I cannot figure out why this
happens, so it comes this patch, maybe you have better solution to resolve the
issue. If you know how things work in this way, please let me know, thanks!
Below is the capture from my environments:
========================================================================
gcc (GCC) 8.3.1 20190223 (Red Hat 8.3.1-2)
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
0000000000401950 <ss_start>:
401950: 45 31 ff xor %r15d,%r15d
401953: 0f a2 cpuid
401955: b9 a0 01 00 00 mov $0x1a0,%ecx
40195a: 0f 32 rdmsr
000000000040194f <ss_start>:
40194f: 31 db xor %ebx,%ebx
401951: 0f a2 cpuid
401953: b9 a0 01 00 00 mov $0x1a0,%ecx
401958: 0f 32 rdmsr
000000000040194e <ss_start>:
40194e: 31 c0 xor %eax,%eax
401950: 0f a2 cpuid
401952: b9 a0 01 00 00 mov $0x1a0,%ecx
401957: 0f 32 rdmsr
==========================================================================
gcc (GCC) 8.2.1 20180905 (Red Hat 8.2.1-3)
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
0000000000401750 <ss_start>:
401750: 48 31 c0 xor %rax,%rax
401753: 0f a2 cpuid
401755: b9 a0 01 00 00 mov $0x1a0,%ecx
40175a: 0f 32 rdmsr
Signed-off-by: Yang Weijiang <weijiang.yang(a)intel.com>
---
tools/testing/selftests/kvm/x86_64/debug_regs.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/kvm/x86_64/debug_regs.c b/tools/testing/selftests/kvm/x86_64/debug_regs.c
index 8162c58a1234..74641cfa8ace 100644
--- a/tools/testing/selftests/kvm/x86_64/debug_regs.c
+++ b/tools/testing/selftests/kvm/x86_64/debug_regs.c
@@ -40,11 +40,11 @@ static void guest_code(void)
/* Single step test, covers 2 basic instructions and 2 emulated */
asm volatile("ss_start: "
- "xor %%rax,%%rax\n\t"
+ "xor %%r15,%%r15\n\t"
"cpuid\n\t"
"movl $0x1a0,%%ecx\n\t"
"rdmsr\n\t"
- : : : "rax", "ecx");
+ : : : "r15", "ecx");
/* DR6.BD test */
asm volatile("bd_start: mov %%dr0, %%rax" : : : "rax");
--
2.17.2