tracing: probes: Fix a possible race in trace_probe_log APIs

Since the shared trace_probe_log variable can be accessed and
modified via probe event create operation of kprobe_events,
uprobe_events,

tracing: probes: Fix a possible race in trace_probe_log APIs

Since the shared trace_probe_log variable can be accessed and
modified via probe event create operation of kprobe_events,
uprobe_events, and dynamic_events, it should be protected.
In the dynamic_events, all operations are serialized by
`dyn_event_ops_mutex`. But kprobe_events and uprobe_events
interfaces are not serialized.

To solve this issue, introduces dyn_event_create(), which runs
create() operation under the mutex, for kprobe_events and
uprobe_events. This also uses lockdep to check the mutex is
held when using trace_probe_log* APIs.

Link: https://lore.kernel.org/all/174684868120.551552.3068655787654268804.stgit@devnote2/

Reported-by: Paul Cacheux <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Fixes: ab105a4fb894 ("tracing: Use tracing error_log with probe events")
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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tracing: probe-events: Add comments about entry data storing code

Add comments about entry data storing code to __store_entry_arg() and
traceprobe_get_entry_data_size(). These are a bit complicated

tracing: probe-events: Add comments about entry data storing code

Add comments about entry data storing code to __store_entry_arg() and
traceprobe_get_entry_data_size(). These are a bit complicated because of
building the entry data storing code and scanning it.

This just add comments, no behavior change.

Link: https://lore.kernel.org/all/174061715004.501424.333819546601401102.stgit@devnote2/

Reported-by: Steven Rostedt <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Reviewed-by: Steven Rostedt (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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tracing: Use __free() in trace_probe for cleanup

Use __free() in trace_probe to cleanup some gotos.

Link: https://lore.kernel.org/all/173643298860.1514810.7267350121047606213.stgit@devnote2/

Signe

tracing: Use __free() in trace_probe for cleanup

Use __free() in trace_probe to cleanup some gotos.

Link: https://lore.kernel.org/all/173643298860.1514810.7267350121047606213.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Reviewed-by: Steven Rostedt (Google) <[email protected]>

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tracing: Consider the NULL character when validating the event length

strlen() returns a string length excluding the null byte. If the string
length equals to the maximum buffer length, the buffer w

tracing: Consider the NULL character when validating the event length

strlen() returns a string length excluding the null byte. If the string
length equals to the maximum buffer length, the buffer will have no
space for the NULL terminating character.

This commit checks this condition and returns failure for it.

Link: https://lore.kernel.org/all/[email protected]/

Fixes: dec65d79fd26 ("tracing/probe: Check event name length correctly")
Signed-off-by: Leo Yan <[email protected]>
Reviewed-by: Steven Rostedt (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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tracing/probes: fix error check in parse_btf_field()

btf_find_struct_member() might return NULL or an error via the
ERR_PTR() macro. However, its caller in parse_btf_field() only checks
for the NULL

tracing/probes: fix error check in parse_btf_field()

btf_find_struct_member() might return NULL or an error via the
ERR_PTR() macro. However, its caller in parse_btf_field() only checks
for the NULL condition. Fix this by using IS_ERR() and returning the
error up the stack.

Link: https://lore.kernel.org/all/[email protected]/

Fixes: c440adfbe3025 ("tracing/probes: Support BTF based data structure field access")
Signed-off-by: Carlos López <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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tracing/probes: support '%pD' type for print struct file's name

As like '%pd' type, this patch supports print type '%pD' for print file's
name. For example "name=$arg1:%pD" casts the `$arg1` as (str

tracing/probes: support '%pD' type for print struct file's name

As like '%pd' type, this patch supports print type '%pD' for print file's
name. For example "name=$arg1:%pD" casts the `$arg1` as (struct file*),
dereferences the "file.f_path.dentry.d_name.name" field and stores it to
"name" argument as a kernel string.
Here is an example:
[tracing]# echo 'p:testprobe vfs_read name=$arg1:%pD' > kprobe_event
[tracing]# echo 1 > events/kprobes/testprobe/enable
[tracing]# grep -q "1" events/kprobes/testprobe/enable
[tracing]# echo 0 > events/kprobes/testprobe/enable
[tracing]# grep "vfs_read" trace | grep "enable"
grep-15108 [003] ..... 5228.328609: testprobe: (vfs_read+0x4/0xbb0) name="enable"

Note that this expects the given argument (e.g. $arg1) is an address of struct
file. User must ensure it.

Link: https://lore.kernel.org/all/[email protected]/
[Masami: replaced "previous patch" with '%pd' type]

Signed-off-by: Ye Bin <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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tracing/probes: support '%pd' type for print struct dentry's name

During fault locating, the file name needs to be printed based on the
dentry address. The offset needs to be calculated each time,

tracing/probes: support '%pd' type for print struct dentry's name

During fault locating, the file name needs to be printed based on the
dentry address. The offset needs to be calculated each time, which
is troublesome. Similar to printk, kprobe support print type '%pd' for
print dentry's name. For example "name=$arg1:%pd" casts the `$arg1`
as (struct dentry *), dereferences the "d_name.name" field and stores
it to "name" argument as a kernel string.
Here is an example:
[tracing]# echo 'p:testprobe dput name=$arg1:%pd' > kprobe_events
[tracing]# echo 1 > events/kprobes/testprobe/enable
[tracing]# grep -q "1" events/kprobes/testprobe/enable
[tracing]# echo 0 > events/kprobes/testprobe/enable
[tracing]# cat trace | grep "enable"
bash-14844 [002] ..... 16912.889543: testprobe: (dput+0x4/0x30) name="enable"
grep-15389 [003] ..... 16922.834182: testprobe: (dput+0x4/0x30) name="enable"
grep-15389 [003] ..... 16922.836103: testprobe: (dput+0x4/0x30) name="enable"
bash-14844 [001] ..... 16931.820909: testprobe: (dput+0x4/0x30) name="enable"

Note that this expects the given argument (e.g. $arg1) is an address of struct
dentry. User must ensure it.

Link: https://lore.kernel.org/all/[email protected]/

Signed-off-by: Ye Bin <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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tracing/probes: Fix memory leak in traceprobe_parse_probe_arg_body()

If traceprobe_parse_probe_arg_body() failed to allocate 'parg->fmt',
it jumps to the label 'out' instead of 'fail' by mistake.In

tracing/probes: Fix memory leak in traceprobe_parse_probe_arg_body()

If traceprobe_parse_probe_arg_body() failed to allocate 'parg->fmt',
it jumps to the label 'out' instead of 'fail' by mistake.In the result,
the buffer 'tmp' is not freed in this case and leaks its memory.

Thus jump to the label 'fail' in that error case.

Link: https://lore.kernel.org/all/[email protected]/

Fixes: 032330abd08b ("tracing/probes: Cleanup probe argument parser")
Signed-off-by: LuMingYin <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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bitops: make BYTES_TO_BITS() treewide-available

Avoid open-coding that simple expression each time by moving
BYTES_TO_BITS() from the probes code to <linux/bitops.h> to export
it to the rest of the

bitops: make BYTES_TO_BITS() treewide-available

Avoid open-coding that simple expression each time by moving
BYTES_TO_BITS() from the probes code to <linux/bitops.h> to export
it to the rest of the kernel.
Simplify the macro while at it. `BITS_PER_LONG / sizeof(long)` always
equals to %BITS_PER_BYTE, regardless of the target architecture.
Do the same for the tools ecosystem as well (incl. its version of
bitops.h). The previous implementation had its implicit type of long,
while the new one is int, so adjust the format literal accordingly in
the perf code.

Suggested-by: Andy Shevchenko <[email protected]>
Reviewed-by: Przemek Kitszel <[email protected]>
Acked-by: Yury Norov <[email protected]>
Signed-off-by: Alexander Lobakin <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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tracing: probes: Fix to zero initialize a local variable

Fix to initialize 'val' local variable with zero.
Dan reported that Smatch static code checker reports an error that a local
'val' variable n

tracing: probes: Fix to zero initialize a local variable

Fix to initialize 'val' local variable with zero.
Dan reported that Smatch static code checker reports an error that a local
'val' variable needs to be initialized. Actually, the 'val' is expected to
be initialized by FETCH_OP_ARG in the same loop, but it is not obvious. So
initialize it with zero.

Link: https://lore.kernel.org/all/171092223833.237219.17304490075697026697.stgit@devnote2/

Reported-by: Dan Carpenter <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Fixes: 25f00e40ce79 ("tracing/probes: Support $argN in return probe (kprobe and fprobe)")
Reviewed-by: Steven Rostedt (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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tracing/probes: Support $argN in return probe (kprobe and fprobe)

Support accessing $argN in the return probe events. This will help users to
record entry data in function return (exit) event for si

tracing/probes: Support $argN in return probe (kprobe and fprobe)

Support accessing $argN in the return probe events. This will help users to
record entry data in function return (exit) event for simplfing the function
entry/exit information in one event, and record the result values (e.g.
allocated object/initialized object) at function exit.

For example, if we have a function `int init_foo(struct foo *obj, int param)`
sometimes we want to check how `obj` is initialized. In such case, we can
define a new return event like below;

# echo 'r init_foo retval=$retval param=$arg2 field1=+0($arg1)' >> kprobe_events

Thus it records the function parameter `param` and its result `obj->field1`
(the dereference will be done in the function exit timing) value at once.

This also support fprobe, BTF args and'$arg*'. So if CONFIG_DEBUG_INFO_BTF
is enabled, we can trace both function parameters and the return value
by following command.

# echo 'f target_function%return $arg* $retval' >> dynamic_events

Link: https://lore.kernel.org/all/170952365552.229804.224112990211602895.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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tracing/probes: cleanup: Set trace_probe::nr_args at trace_probe_init

Instead of incrementing the trace_probe::nr_args, init it at
trace_probe_init(). Without this change, there is no way to get the

tracing/probes: cleanup: Set trace_probe::nr_args at trace_probe_init

Instead of incrementing the trace_probe::nr_args, init it at
trace_probe_init(). Without this change, there is no way to get the number
of trace_probe arguments while parsing it.
This is a cleanup, so the behavior is not changed.

Link: https://lore.kernel.org/all/170952363585.229804.13060759900346411951.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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tracing/probes: Cleanup probe argument parser

Cleanup traceprobe_parse_probe_arg_body() to split out the
type parser and post-processing part of fetch_insn.
This makes no functional change.

Link: h

tracing/probes: Cleanup probe argument parser

Cleanup traceprobe_parse_probe_arg_body() to split out the
type parser and post-processing part of fetch_insn.
This makes no functional change.

Link: https://lore.kernel.org/all/170952362603.229804.9942703761682605372.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Reviewed-by: Steven Rostedt (Google) <[email protected]>

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tracing/probes: Fix to set arg size and fmt after setting type from BTF

Since the BTF type setting updates probe_arg::type, the type size
calculation and setting print-fmt should be done after that.

tracing/probes: Fix to set arg size and fmt after setting type from BTF

Since the BTF type setting updates probe_arg::type, the type size
calculation and setting print-fmt should be done after that.
Without this fix, the argument size and print-fmt can be wrong.

Link: https://lore.kernel.org/all/170602218196.215583.6417859469540955777.stgit@devnote2/

Fixes: b576e09701c7 ("tracing/probes: Support function parameters if BTF is available")
Cc: [email protected]
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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tracing/probes: Fix to show a parse error for bad type for $comm

Fix to show a parse error for bad type (non-string) for $comm/$COMM and
immediate-string. With this fix, error_log file shows appropr

tracing/probes: Fix to show a parse error for bad type for $comm

Fix to show a parse error for bad type (non-string) for $comm/$COMM and
immediate-string. With this fix, error_log file shows appropriate error
message as below.

/sys/kernel/tracing # echo 'p vfs_read $comm:u32' >> kprobe_events
sh: write error: Invalid argument
/sys/kernel/tracing # echo 'p vfs_read \"hoge":u32' >> kprobe_events
sh: write error: Invalid argument
/sys/kernel/tracing # cat error_log

[ 30.144183] trace_kprobe: error: $comm and immediate-string only accepts string type
Command: p vfs_read $comm:u32
^
[ 62.618500] trace_kprobe: error: $comm and immediate-string only accepts string type
Command: p vfs_read \"hoge":u32
^
Link: https://lore.kernel.org/all/170602215411.215583.2238016352271091852.stgit@devnote2/

Fixes: 3dd1f7f24f8c ("tracing: probeevent: Fix to make the type of $comm string")
Cc: [email protected]
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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tracing/probes: Add string type check with BTF

Add a string type checking with BTF information if possible.
This will check whether the given BTF argument (and field) is
signed char array or pointer

tracing/probes: Add string type check with BTF

Add a string type checking with BTF information if possible.
This will check whether the given BTF argument (and field) is
signed char array or pointer to signed char. If not, it reject
the 'string' type. If it is pointer to signed char, it adds
a dereference opration so that it can correctly fetch the
string data from memory.

# echo 'f getname_flags%return retval->name:string' >> dynamic_events
# echo 't sched_switch next->comm:string' >> dynamic_events

The above cases, 'struct filename::name' is 'char *' and
'struct task_struct::comm' is 'char []'. But in both case,
user can specify ':string' to fetch the string data.

Link: https://lore.kernel.org/all/169272159250.160970.1881112937198526188.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Acked-by: Steven Rostedt (Google) <[email protected]>

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tracing/probes: Support BTF field access from $retval

Support BTF argument on '$retval' for function return events including
kretprobe and fprobe for accessing the return value.
This also allows use

tracing/probes: Support BTF field access from $retval

Support BTF argument on '$retval' for function return events including
kretprobe and fprobe for accessing the return value.
This also allows user to access its fields if the return value is a
pointer of a data structure.

E.g.
# echo 'f getname_flags%return +0($retval->name):string' \
> dynamic_events
# echo 1 > events/fprobes/getname_flags__exit/enable
# ls > /dev/null
# head -n 40 trace | tail
ls-87 [000] ...1. 8067.616101: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./function_profile_enabled"
ls-87 [000] ...1. 8067.616108: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./trace_stat"
ls-87 [000] ...1. 8067.616115: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_graph_notrace"
ls-87 [000] ...1. 8067.616122: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_graph_function"
ls-87 [000] ...1. 8067.616129: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_ftrace_notrace"
ls-87 [000] ...1. 8067.616135: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_ftrace_filter"
ls-87 [000] ...1. 8067.616143: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./touched_functions"
ls-87 [000] ...1. 8067.616237: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./enabled_functions"
ls-87 [000] ...1. 8067.616245: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./available_filter_functions"
ls-87 [000] ...1. 8067.616253: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_ftrace_notrace_pid"


Link: https://lore.kernel.org/all/169272158234.160970.2446691104240645205.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Acked-by: Steven Rostedt (Google) <[email protected]>

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tracing/probes: Support BTF based data structure field access

Using BTF to access the fields of a data structure. You can use this
for accessing the field with '->' or '.' operation with BTF argumen

tracing/probes: Support BTF based data structure field access

Using BTF to access the fields of a data structure. You can use this
for accessing the field with '->' or '.' operation with BTF argument.

# echo 't sched_switch next=next->pid vruntime=next->se.vruntime' \
> dynamic_events
# echo 1 > events/tracepoints/sched_switch/enable
# head -n 40 trace | tail
<idle>-0 [000] d..3. 272.565382: sched_switch: (__probestub_sched_switch+0x4/0x10) next=26 vruntime=956533179
kcompactd0-26 [000] d..3. 272.565406: sched_switch: (__probestub_sched_switch+0x4/0x10) next=0 vruntime=0
<idle>-0 [000] d..3. 273.069441: sched_switch: (__probestub_sched_switch+0x4/0x10) next=9 vruntime=956533179
kworker/0:1-9 [000] d..3. 273.069464: sched_switch: (__probestub_sched_switch+0x4/0x10) next=26 vruntime=956579181
kcompactd0-26 [000] d..3. 273.069480: sched_switch: (__probestub_sched_switch+0x4/0x10) next=0 vruntime=0
<idle>-0 [000] d..3. 273.141434: sched_switch: (__probestub_sched_switch+0x4/0x10) next=22 vruntime=956533179
kworker/u2:1-22 [000] d..3. 273.141461: sched_switch: (__probestub_sched_switch+0x4/0x10) next=0 vruntime=0
<idle>-0 [000] d..3. 273.480872: sched_switch: (__probestub_sched_switch+0x4/0x10) next=22 vruntime=956585857
kworker/u2:1-22 [000] d..3. 273.480905: sched_switch: (__probestub_sched_switch+0x4/0x10) next=70 vruntime=959533179
sh-70 [000] d..3. 273.481102: sched_switch: (__probestub_sched_switch+0x4/0x10) next=0 vruntime=0

Link: https://lore.kernel.org/all/169272157251.160970.9318175874130965571.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Reviewed-by: Alan Maguire <[email protected]>
Acked-by: Steven Rostedt (Google) <[email protected]>

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tracing/probes: Move finding func-proto API and getting func-param API to trace_btf

Move generic function-proto find API and getting function parameter API
to BTF library code from trace_probe.c. Th

tracing/probes: Move finding func-proto API and getting func-param API to trace_btf

Move generic function-proto find API and getting function parameter API
to BTF library code from trace_probe.c. This will avoid redundant efforts
on different feature.

Link: https://lore.kernel.org/all/169272155255.160970.719426926348706349.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Acked-by: Steven Rostedt (Google) <[email protected]>

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tracing/probes: Support BTF argument on module functions

Since the btf returned from bpf_get_btf_vmlinux() only covers functions in
the vmlinux, BTF argument is not available on the functions in the

tracing/probes: Support BTF argument on module functions

Since the btf returned from bpf_get_btf_vmlinux() only covers functions in
the vmlinux, BTF argument is not available on the functions in the modules.
Use bpf_find_btf_id() instead of bpf_get_btf_vmlinux()+btf_find_name_kind()
so that BTF argument can find the correct struct btf and btf_type in it.
With this fix, fprobe events can use `$arg*` on module functions as below

# grep nf_log_ip_packet /proc/kallsyms
ffffffffa0005c00 t nf_log_ip_packet [nf_log_syslog]
ffffffffa0005bf0 t __pfx_nf_log_ip_packet [nf_log_syslog]
# echo 'f nf_log_ip_packet $arg*' > dynamic_events
# cat dynamic_events
f:fprobes/nf_log_ip_packet__entry nf_log_ip_packet net=net pf=pf hooknum=hooknum skb=skb in=in out=out loginfo=loginfo prefix=prefix

To support the module's btf which is removable, the struct btf needs to be
ref-counted. So this also records the btf in the traceprobe_parse_context
and returns the refcount when the parse has done.

Link: https://lore.kernel.org/all/169272154223.160970.3507930084247934031.stgit@devnote2/

Suggested-by: Alexei Starovoitov <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Acked-by: Steven Rostedt (Google) <[email protected]>

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tracing/probes: Fix to add NULL check for BTF APIs

Since find_btf_func_param() abd btf_type_by_id() can return NULL,
the caller must check the return value correctly.

Link: https://lore.kernel.org/

tracing/probes: Fix to add NULL check for BTF APIs

Since find_btf_func_param() abd btf_type_by_id() can return NULL,
the caller must check the return value correctly.

Link: https://lore.kernel.org/all/169024903951.395371.11361556840733470934.stgit@devnote2/

Fixes: b576e09701c7 ("tracing/probes: Support function parameters if BTF is available")
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Reviewed-by: Steven Rostedt (Google) <[email protected]>

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Revert "tracing: Add "(fault)" name injection to kernel probes"

This reverts commit 2e9906f84fc7c99388bb7123ade167250d50f1c0.

It was turned out that commit 2e9906f84fc7 ("tracing: Add "(fault)"
nam

Revert "tracing: Add "(fault)" name injection to kernel probes"

This reverts commit 2e9906f84fc7c99388bb7123ade167250d50f1c0.

It was turned out that commit 2e9906f84fc7 ("tracing: Add "(fault)"
name injection to kernel probes") did not work correctly and probe
events still show just '(fault)' (instead of '"(fault)"'). Also,
current '(fault)' is more explicit that it faulted.

This also moves FAULT_STRING macro to trace.h so that synthetic
event can keep using it, and uses it in trace_probe.c too.

Link: https://lore.kernel.org/all/168908495772.123124.1250788051922100079.stgit@devnote2/
Link: https://lore.kernel.org/all/[email protected]/

Cc: [email protected]
Cc: Andrew Morton <[email protected]>
Cc: Tom Zanussi <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Reviewed-by: Steven Rostedt (Google) <[email protected]>

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tracing/probes: Fix tracepoint event with $arg* to fetch correct argument

To hide the first dummy 'data' argument on the tracepoint probe events,
the BTF argument array was modified (skip the first

tracing/probes: Fix tracepoint event with $arg* to fetch correct argument

To hide the first dummy 'data' argument on the tracepoint probe events,
the BTF argument array was modified (skip the first argument for tracepoint),
but the '$arg*' meta argument parser missed that.

Fix to increment the argument index if it is tracepoint probe. And decrement
the index when searching the type of the argument.

Link: https://lore.kernel.org/all/168657113778.3038017.12245893750241701312.stgit@mhiramat.roam.corp.google.com/

Reviewed-by: Steven Rostedt (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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tracing/probes: Fix to return NULL and keep using current argc

Fix to return NULL and keep using current argc when there is
$argN and the BTF is not available.

Link: https://lore.kernel.org/all/168

tracing/probes: Fix to return NULL and keep using current argc

Fix to return NULL and keep using current argc when there is
$argN and the BTF is not available.

Link: https://lore.kernel.org/all/168584574094.2056209.2694238431743782342.stgit@mhiramat.roam.corp.google.com/

Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Reviewed-by: Steven Rostedt (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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tracing/probes: Add BTF retval type support

Check the target function has non-void retval type and set the correct
fetch type if user doesn't specify it.
If the function returns void, $retval is rej

tracing/probes: Add BTF retval type support

Check the target function has non-void retval type and set the correct
fetch type if user doesn't specify it.
If the function returns void, $retval is rejected as below;

# echo 'f unregister_kprobes%return $retval' >> dynamic_events
sh: write error: No such file or directory
# cat error_log
[ 37.488397] trace_fprobe: error: This function returns 'void' type
Command: f unregister_kprobes%return $retval
^
Link: https://lore.kernel.org/all/168507476195.913472.16290308831790216609.stgit@mhiramat.roam.corp.google.com/

Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

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