linux.git/kernel/trace/fgraph.c, branch v6.6.132

tracing: arm64: Avoid missing-prototype warnings

2023-07-12T16:06:04+00:00

These are all tracing W=1 warnings in arm64 allmodconfig about missing
prototypes:

kernel/trace/trace_kprobe_selftest.c:7:5: error: no previous prototype for 'kprobe_trace_selftest_target' [-Werror=missing-pro
totypes]
kernel/trace/ftrace.c:329:5: error: no previous prototype for '__register_ftrace_function' [-Werror=missing-prototypes]
kernel/trace/ftrace.c:372:5: error: no previous prototype for '__unregister_ftrace_function' [-Werror=missing-prototypes]
kernel/trace/ftrace.c:4130:15: error: no previous prototype for 'arch_ftrace_match_adjust' [-Werror=missing-prototypes]
kernel/trace/fgraph.c:243:15: error: no previous prototype for 'ftrace_return_to_handler' [-Werror=missing-prototypes]
kernel/trace/fgraph.c:358:6: error: no previous prototype for 'ftrace_graph_sleep_time_control' [-Werror=missing-prototypes]
arch/arm64/kernel/ftrace.c:460:6: error: no previous prototype for 'prepare_ftrace_return' [-Werror=missing-prototypes]
arch/arm64/kernel/ptrace.c:2172:5: error: no previous prototype for 'syscall_trace_enter' [-Werror=missing-prototypes]
arch/arm64/kernel/ptrace.c:2195:6: error: no previous prototype for 'syscall_trace_exit' [-Werror=missing-prototypes]

Move the declarations to an appropriate header where they can be seen
by the caller and callee, and make sure the headers are included where
needed.

Link: https://lore.kernel.org/linux-trace-kernel/20230517125215.930689-1-arnd@kernel.org

Cc: Masami Hiramatsu 
Cc: Mark Rutland 
Cc: Will Deacon 
Cc: Kees Cook 
Cc: Florent Revest 
Signed-off-by: Arnd Bergmann 
Acked-by: Catalin Marinas 
[ Fixed ftrace_return_to_handler() to handle CONFIG_HAVE_FUNCTION_GRAPH_RETVAL case ]
Signed-off-by: Steven Rostedt (Google)

function_graph: Support recording and printing the return value of function

2023-06-20T22:38:37+00:00

Analyzing system call failures with the function_graph tracer can be a
time-consuming process, particularly when locating the kernel function
that first returns an error in the trace logs. This change aims to
simplify the process by recording the function return value to the
'retval' member of 'ftrace_graph_ret' and printing it when outputting
the trace log.

We have introduced new trace options: funcgraph-retval and
funcgraph-retval-hex. The former controls whether to display the return
value, while the latter controls the display format.

Please note that even if a function's return type is void, a return
value will still be printed. You can simply ignore it.

This patch only establishes the fundamental infrastructure. Subsequent
patches will make this feature available on some commonly used processor
architectures.

Here is an example:

I attempted to attach the demo process to a cpu cgroup, but it failed:

echo `pidof demo` > /sys/fs/cgroup/cpu/test/tasks
-bash: echo: write error: Invalid argument

The strace logs indicate that the write system call returned -EINVAL(-22):
...
write(1, "273\n", 4)                    = -1 EINVAL (Invalid argument)
...

To capture trace logs during a write system call, use the following
commands:

cd /sys/kernel/debug/tracing/
echo 0 > tracing_on
echo > trace
echo *sys_write > set_graph_function
echo *spin* > set_graph_notrace
echo *rcu* >> set_graph_notrace
echo *alloc* >> set_graph_notrace
echo preempt* >> set_graph_notrace
echo kfree* >> set_graph_notrace
echo $$ > set_ftrace_pid
echo function_graph > current_tracer
echo 1 > options/funcgraph-retval
echo 0 > options/funcgraph-retval-hex
echo 1 > tracing_on
echo `pidof demo` > /sys/fs/cgroup/cpu/test/tasks
echo 0 > tracing_on
cat trace > ~/trace.log

To locate the root cause, search for error code -22 directly in the file
trace.log and identify the first function that returned -22. Once you
have identified this function, examine its code to determine the root
cause.

For example, in the trace log below, cpu_cgroup_can_attach
returned -22 first, so we can focus our analysis on this function to
identify the root cause.

...

 1)          | cgroup_migrate() {
 1) 0.651 us |   cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */
 1)          |   cgroup_migrate_execute() {
 1)          |     cpu_cgroup_can_attach() {
 1)          |       cgroup_taskset_first() {
 1) 0.732 us |         cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */
 1) 1.232 us |       } /* cgroup_taskset_first = 0xffff93fc8fb20000 */
 1) 0.380 us |       sched_rt_can_attach(); /* = 0x0 */
 1) 2.335 us |     } /* cpu_cgroup_can_attach = -22 */
 1) 4.369 us |   } /* cgroup_migrate_execute = -22 */
 1) 7.143 us | } /* cgroup_migrate = -22 */

...

Link: https://lkml.kernel.org/r/1fc502712c981e0e6742185ba242992170ac9da8.1680954589.git.pengdonglin@sangfor.com.cn

Tested-by: Florian Kauer 
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Donglin Peng 
Signed-off-by: Steven Rostedt (Google)

fgraph: Add declaration of "struct fgraph_ret_regs"

2023-06-20T22:34:55+00:00

In final testing of:

  https://patchwork.kernel.org/project/linux-trace-kernel/patch/1fc502712c981e0e6742185ba242992170ac9da8.1680954589.git.pengdonglin@sangfor.com.cn/
  "function_graph: Support recording and printing the return value of function"

The test failed due to a new warning found in the build:

kernel/trace/fgraph.c:243:56: warning: ‘struct fgraph_ret_regs’ declared inside parameter list will not be visible outside of this definition or declaration

Instead of asking to send another patch series, just add it and then apply
the updates.

Signed-off-by: Steven Rostedt (Google)

Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

2022-06-03T21:05:34+00:00

Pull arm64 fixes from Catalin Marinas:
 "Most of issues addressed were introduced during this merging window.

   - Initialise jump labels before setup_machine_fdt(), needed by commit
     f5bda35fba61 ("random: use static branch for crng_ready()").

   - Sparse warnings: missing prototype, incorrect __user annotation.

   - Skip SVE kselftest if not sufficient vector lengths supported"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  kselftest/arm64: signal: Skip SVE signal test if not enough VLs supported
  arm64: Initialize jump labels before setup_machine_fdt()
  arm64: hibernate: Fix syntax errors in comments
  arm64: Remove the __user annotation for the restore_za_context() argument
  ftrace/fgraph: fix increased missing-prototypes warnings

ftrace/fgraph: fix increased missing-prototypes warnings

2022-06-01T17:14:17+00:00

After commit e999995c84c3 ("ftrace: cleanup ftrace_graph_caller enable
and disable") merged into the linux-next tree, the kernel test robot
(lkp@intel.com) has send out report that there are increased missing-prototypes
warnings caused by that commit.

COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0 make.cross W=1 \
	O=build_dir ARCH=sh SHELL=/bin/bash kernel/trace/
warning: no previous prototype for 'ftrace_enable_ftrace_graph_caller' [-Wmissing-prototypes]
warning: no previous prototype for 'ftrace_disable_ftrace_graph_caller' [-Wmissing-prototypes]
warning: no previous prototype for 'ftrace_return_to_handler' [-Wmissing-prototypes]
warning: no previous prototype for 'ftrace_graph_sleep_time_control' [-Wmissing-prototypes]

BTW there are so many missing-prototypes warnings if build kernel with "W=1".

The increased warnings for 'ftrace_[enable,disable]_ftrace_graph_caller'
is caused by CONFIG_FUNCTION_GRAPH_TRACER && !CONFIG_DYNAMIC_FTRACE,
so the declarations in  can't be seen in fgraph.c.

And this warning can't reproduce on x86_64 since x86_64 select
HAVE_FUNCTION_GRAPH_TRACER only when DYNAMIC_FTRACE, so fgraph.c will
always see the declarations in .

This patch fix the increased warnings by put the definitions in
CONFIG_DYNAMIC_FTRACE although there are no real problems exist.

Signed-off-by: Chengming Zhou 
Acked-by: Steven Rostedt (Google) 
Link: https://lore.kernel.org/r/20220506032737.23375-1-zhouchengming@bytedance.com
Signed-off-by: Catalin Marinas

Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

2022-05-24T04:06:11+00:00

Pull arm64 updates from Catalin Marinas:

- Initial support for the ARMv9 Scalable Matrix Extension (SME).

SME takes the approach used for vectors in SVE and extends this to
provide architectural support for matrix operations. No KVM support
yet, SME is disabled in guests.

- Support for crashkernel reservations above ZONE_DMA via the
'crashkernel=X,high' command line option.

- btrfs search_ioctl() fix for live-lock with sub-page faults.

- arm64 perf updates: support for the Hisilicon "CPA" PMU for
monitoring coherent I/O traffic, support for Arm's CMN-650 and
CMN-700 interconnect PMUs, minor driver fixes, kerneldoc cleanup.

- Kselftest updates for SME, BTI, MTE.

- Automatic generation of the system register macros from a 'sysreg'
file describing the register bitfields.

- Update the type of the function argument holding the ESR_ELx register
value to unsigned long to match the architecture register size
(originally 32-bit but extended since ARMv8.0).

- stacktrace cleanups.

- ftrace cleanups.

- Miscellaneous updates, most notably: arm64-specific huge_ptep_get(),
avoid executable mappings in kexec/hibernate code, drop TLB flushing
from get_clear_flush() (and rename it to get_clear_contig()),
ARCH_NR_GPIO bumped to 2048 for ARCH_APPLE.

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (145 commits)
arm64/sysreg: Generate definitions for FAR_ELx
arm64/sysreg: Generate definitions for DACR32_EL2
arm64/sysreg: Generate definitions for CSSELR_EL1
arm64/sysreg: Generate definitions for CPACR_ELx
arm64/sysreg: Generate definitions for CONTEXTIDR_ELx
arm64/sysreg: Generate definitions for CLIDR_EL1
arm64/sve: Move sve_free() into SVE code section
arm64: Kconfig.platforms: Add comments
arm64: Kconfig: Fix indentation and add comments
arm64: mm: avoid writable executable mappings in kexec/hibernate code
arm64: lds: move special code sections out of kernel exec segment
arm64/hugetlb: Implement arm64 specific huge_ptep_get()
arm64/hugetlb: Use ptep_get() to get the pte value of a huge page
arm64: kdump: Do not allocate crash low memory if not needed
arm64/sve: Generate ZCR definitions
arm64/sme: Generate defintions for SVCR
arm64/sme: Generate SMPRI_EL1 definitions
arm64/sme: Automatically generate SMPRIMAP_EL2 definitions
arm64/sme: Automatically generate SMIDR_EL1 defines
arm64/sme: Automatically generate defines for SMCR
...

sched/tracing: Append prev_state to tp args instead

2022-05-11T22:37:11+00:00

Commit fa2c3254d7cf (sched/tracing: Don't re-read p->state when emitting
sched_switch event, 2022-01-20) added a new prev_state argument to the
sched_switch tracepoint, before the prev task_struct pointer.

This reordering of arguments broke BPF programs that use the raw
tracepoint (e.g. tp_btf programs). The type of the second argument has
changed and existing programs that assume a task_struct* argument
(e.g. for bpf_task_storage access) will now fail to verify.

If we instead append the new argument to the end, all existing programs
would continue to work and can conditionally extract the prev_state
argument on supported kernel versions.

Fixes: fa2c3254d7cf (sched/tracing: Don't re-read p->state when emitting sched_switch event, 2022-01-20)
Signed-off-by: Delyan Kratunov 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Steven Rostedt (Google) 
Link: https://lkml.kernel.org/r/c8a6930dfdd58a4a5755fc01732675472979732b.camel@fb.com

ftrace: cleanup ftrace_graph_caller enable and disable

2022-04-29T18:21:12+00:00

The ftrace_[enable,disable]_ftrace_graph_caller() are used to do
special hooks for graph tracer, which are not needed on some ARCHs
that use graph_ops:func function to install return_hooker.

So introduce the weak version in ftrace core code to cleanup
in x86.

Signed-off-by: Chengming Zhou 
Acked-by: Steven Rostedt (Google) 
Acked-by: Mark Rutland 
Link: https://lore.kernel.org/r/20220420160006.17880-1-zhouchengming@bytedance.com
Signed-off-by: Catalin Marinas

ftrace: Make ftrace_graph_is_dead() a static branch

2022-04-02T12:40:09+00:00

ftrace_graph_is_dead() is used on hot paths, it just reads a variable
in memory and is not worth suffering function call constraints.

For instance, at entry of prepare_ftrace_return(), inlining it avoids
saving prepare_ftrace_return() parameters to stack and restoring them
after calling ftrace_graph_is_dead().

While at it using a static branch is even more performant and is
rather well adapted considering that the returned value will almost
never change.

Inline ftrace_graph_is_dead() and replace 'kill_ftrace_graph' bool
by a static branch.

The performance improvement is noticeable.

Link: https://lkml.kernel.org/r/e0411a6a0ed3eafff0ad2bc9cd4b0e202b4617df.1648623570.git.christophe.leroy@csgroup.eu

Signed-off-by: Christophe Leroy 
Signed-off-by: Steven Rostedt (Google)

sched/tracing: Don't re-read p->state when emitting sched_switch event

2022-03-01T15:18:39+00:00

As of commit

  c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu")

the following sequence becomes possible:

		      p->__state = TASK_INTERRUPTIBLE;
		      __schedule()
			deactivate_task(p);
  ttwu()
    READ !p->on_rq
    p->__state=TASK_WAKING
			trace_sched_switch()
			  __trace_sched_switch_state()
			    task_state_index()
			      return 0;

TASK_WAKING isn't in TASK_REPORT, so the task appears as TASK_RUNNING in
the trace event.

Prevent this by pushing the value read from __schedule() down the trace
event.

Reported-by: Abhijeet Dharmapurikar 
Signed-off-by: Valentin Schneider 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Steven Rostedt (Google) 
Link: https://lore.kernel.org/r/20220120162520.570782-2-valentin.schneider@arm.com