[PATCH perf-tools-next v3 0/4] perf trace: Symbolise kernel virtual addresses and function pointers

[PATCH perf-tools-next v3 0/4] perf trace: Symbolise kernel virtual addresses and function pointers

[Aaron Tomlin]

When inspecting kernel execution flows using perf trace (e.g., when
monitoring workqueues, delayed work items, timer callbacks, etc.),
tracepoint payload arguments containing raw kernel virtual addresses are
currently rendered as hexadecimal values (e.g., 0xffffffff81234567).

This requires manual symbol lookups against /proc/kallsyms or vmlinux to
identify the underlying kernel function being executed.

This patch series enhances perf trace by introducing kernel virtual address
and function pointer symbolisation using perf's native symbol engine (i.e.,
machine__find_kernel_symbol()).

    Before:
      workqueue:workqueue_execute_end(work: 0xffffffffab2f1420, function: 0xffffffffa8046b50)

    After:
      workqueue:workqueue_execute_end(work: 0xffff8ac2c420f270, function: wb_update_bandwidth_workfn)

Patch 1 introduces the syscall_arg__scnprintf_ksym() (SCA_KSYM) beautifier,
which resolves virtual addresses via machine__find_kernel_symbol(),
formatting them as symbol_name+offset (or "NULL", with a graceful
hexadecimal fallback upon lookup failure).

Patch 2 updates event format initialisation in
syscall_arg_fmt__init_array() to automatically assign SCA_KSYM to
tracepoint fields typed as function pointers (such as typedefs ending in
"_func_t" or "_fn", or function prototypes matching "(*)"). It also
registers common function pointer, callback, and callsite field names
(e.g., "func", "function", "callback", "action", "handler", "caller",
"location", "call_site") in syscall_arg_fmts__by_name[], and removes the
legacy trace__field_is_ip() hex override in trace__fprintf_tp_fields().

Patch 3 extends BTF pretty-printing in trace__btf_scnprintf() with
btf_is_func_ptr() to automatically traverse BTF type hierarchies (including
nested typedefs and qualifiers) and route kernel function pointer arguments
to SCA_KSYM when BTF metadata is available, with negative caching to
prevent redundant BTF scans.

Patch 4 adds an automated regression test script, trace_ksym_beautifier.sh,
under tools/perf/tests/shell/ to verify symbolisation across both default
kallsyms and BTF routing paths.

Changes since v2:

 - Populated syscall_arg_fmts__by_name[] with common function pointer,
   callback, handler, and callsite field names ("action", "call_site",
   "callback", "caller", "callsite", "cb", "fn", "func", "function",
   "handler", "location")

 - Checked syscall_arg_fmt__find_by_name() prior to generic pointer
   fallbacks in syscall_arg_fmt__init_array(), and dropped the inline
   64-bit size check to ensure 32-bit and cross-platform compatibility

 - Removed legacy trace__field_is_ip() in trace__fprintf_tp_fields() to
   allow "call_site" and "caller_ip" to be beautified with SCA_KSYM rather
   than being forced to raw hexadecimal

 - Simplified btf_is_func_ptr() to remove the internal pointer requirement,
   correctly identifying bare prototype typedefs as function pointers

 - Prevented pointer enums (e.g., "enum foo *") from being misclassified
   and formatted as scalar enum values in
   syscall_arg_fmt__cache_btf_type(), trace__btf_scnprintf(), and
   syscall_arg__strtoul_btf_type()

 - Added negative caching (btf_type_cached) to struct syscall_arg_fmt to
   avoid repeated BTF searches on every event for unresolvable or primitive
   types

 - Widened btf_enum_scnprintf() to accept unsigned long val, eliminating
   narrowing truncation of 64-bit values to 32-bit signed integers

 - Fixed trace_ksym_beautifier.sh:
    - Quoted "$0" to support directory paths containing spaces
    - Captured output in memory to eliminate temporary file leaks on early
      skip
    - Hardened regex validation to require valid C symbol identifiers and
      reject raw hexadecimal addresses
    - Used '%s' format specifiers in printf to prevent format string
      injection

 - Link to v2: https://lore.kernel.org/lkml/20260816205921.576365-1-atomlin@atomlin.com/

Changes since v1:

 - Fixed reference leak of struct map in syscall_arg__scnprintf_ksym() by
   calling map__put() prior to returning Removed unreachable and erroneous
   entries ("action", "callsite", "call_site", "fn", "function", "work")
   from syscall_arg_fmts__by_name[]

 - Restricted name-based SCA_KSYM auto-assignment in
   syscall_arg_fmt__init_array() to pointer or 64-bit address fields,
   preventing misclassification of non-pointer integer fields

 - Updated btf_is_func_ptr() to fully unwrap typedefs and type modifiers
   below pointer targets

 - Fixed BTF type name matching in syscall_arg_fmt__cache_btf_type() to
   handle leading modifiers and strip trailing pointer asterisks before
   lookup

 - Synchronised arg->val with val in trace__btf_scnprintf() and widened val
   to unsigned long, fixing erroneous "NULL" output

 - Added shell test script,
   tools/perf/tests/shell/trace_ksym_beautifier.sh, to verify kernel symbol
   beautification for both default kallsyms and BTF routing

 - Link to v1: https://lore.kernel.org/lkml/20260815233651.527936-1-atomlin@atomlin.com/

Aaron Tomlin (4):
  perf trace: Introduce kernel symbol beautifier for virtual addresses
  perf trace: Auto-assign kernel symbol beautifier to function pointer
    fields
  perf trace: Enhance BTF type formatting to symbolise kernel function
    pointers
  perf tests: Add shell test for kernel symbol beautifier

 tools/perf/builtin-trace.c                    | 187 ++++++++++++------
 tools/perf/tests/shell/trace_btf_general.sh   |   2 +-
 .../perf/tests/shell/trace_ksym_beautifier.sh |  43 ++++
 tools/perf/trace/beauty/beauty.h              |   3 +
 4 files changed, 178 insertions(+), 57 deletions(-)
 create mode 100755 tools/perf/tests/shell/trace_ksym_beautifier.sh

-- 
2.55.0

[PATCH perf-tools-next v3 1/4] perf trace: Introduce kernel symbol beautifier for virtual addresses

[Aaron Tomlin]

Currently, when 'perf trace' formats tracepoint payloads or system call
arguments containing raw kernel virtual addresses (e.g., a work item
function pointer work_func_t in workqueue:workqueue_execute_start),
it prints them as raw hexadecimal values (e.g., 0xffffffff81234567).
This impairs readability when tracing kernel execution flows.

Introduce a dedicated kernel symbol beautifier,
syscall_arg__scnprintf_ksym (i.e., SCA_KSYM), to resolve kernel
virtual addresses to human-readable symbol names and offsets
(e.g., "flush_to_ldisc").

The beautifier looks up the virtual address in the machine kernel maps via
machine__find_kernel_symbol(). If a valid kernel symbol is found, the
symbol name and offset are printed without requiring --libtraceevent; if
the address is zero, "NULL" is rendered; otherwise, it gracefully falls
back to hexadecimal formatting.

Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
---
 tools/perf/builtin-trace.c       | 29 +++++++++++++++++++++++++++++
 tools/perf/trace/beauty/beauty.h |  3 +++
 2 files changed, 32 insertions(+)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index c3c7f1f85c53..003048946503 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -750,6 +750,35 @@ size_t syscall_arg__scnprintf_ptr(char *bf, size_t size, struct syscall_arg *arg
 	return syscall_arg__scnprintf_hex(bf, size, arg);
 }
 
+size_t syscall_arg__scnprintf_ksym(char *bf, size_t size, struct syscall_arg *arg)
+{
+	if (arg->val == 0)
+		return scnprintf(bf, size, "NULL");
+
+	if (arg->trace && arg->trace->host) {
+		struct map *map = NULL;
+		struct symbol *sym = machine__find_kernel_symbol(arg->trace->host,
+								 arg->val, &map);
+
+		if (sym) {
+			u64 start = map__unmap_ip(map, sym->start);
+			u64 offset = arg->val - start;
+			size_t printed;
+
+			if (offset == 0)
+				printed = scnprintf(bf, size, "%s", sym->name);
+			else
+				printed = scnprintf(bf, size, "%s+0x%" PRIx64,
+						    sym->name, offset);
+			map__put(map);
+			return printed;
+		}
+		map__put(map);
+	}
+
+	return syscall_arg__scnprintf_hex(bf, size, arg);
+}
+
 size_t syscall_arg__scnprintf_int(char *bf, size_t size, struct syscall_arg *arg)
 {
 	return scnprintf(bf, size, "%d", arg->val);
diff --git a/tools/perf/trace/beauty/beauty.h b/tools/perf/trace/beauty/beauty.h
index 58a3206481ae..0f4801c61a5b 100644
--- a/tools/perf/trace/beauty/beauty.h
+++ b/tools/perf/trace/beauty/beauty.h
@@ -160,6 +160,9 @@ size_t syscall_arg__scnprintf_hex(char *bf, size_t size, struct syscall_arg *arg
 size_t syscall_arg__scnprintf_ptr(char *bf, size_t size, struct syscall_arg *arg);
 #define SCA_PTR syscall_arg__scnprintf_ptr
 
+size_t syscall_arg__scnprintf_ksym(char *bf, size_t size, struct syscall_arg *arg);
+#define SCA_KSYM syscall_arg__scnprintf_ksym
+
 size_t syscall_arg__scnprintf_int(char *bf, size_t size, struct syscall_arg *arg);
 #define SCA_INT syscall_arg__scnprintf_int
 
-- 
2.55.0

Re: [PATCH perf-tools-next v3 1/4] perf trace: Introduce kernel symbol beautifier for virtual addresses

[sashiko-bot]

> Currently, when 'perf trace' formats tracepoint payloads or system call
> arguments containing raw kernel virtual addresses (e.g., a work item
> function pointer work_func_t in workqueue:workqueue_execute_start),
> it prints them as raw hexadecimal values (e.g., 0xffffffff81234567).
> This impairs readability when tracing kernel execution flows.
> 
> Introduce a dedicated kernel symbol beautifier,
> syscall_arg__scnprintf_ksym (i.e., SCA_KSYM), to resolve kernel
> virtual addresses to human-readable symbol names and offsets
> (e.g., "flush_to_ldisc").
> 
> The beautifier looks up the virtual address in the machine kernel maps via
> machine__find_kernel_symbol(). If a valid kernel symbol is found, the
> symbol name and offset are printed without requiring --libtraceevent; if
> the address is zero, "NULL" is rendered; otherwise, it gracefully falls
> back to hexadecimal formatting.
> 
> Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260820211100.649142-1-atomlin@atomlin.com?part=1

[PATCH perf-tools-next v3 2/4] perf trace: Auto-assign kernel symbol beautifier to function pointer fields

[Aaron Tomlin]

Tracepoint fields that convey kernel function pointers, callbacks, and
call sites, such as "function", "func", "fn", "callback", "action",
"handler", "caller", "location", "callsite", and "call_site" are
currently formatted as generic hexadecimal pointers by default.

Enhance syscall_arg_fmt__init_array() to automatically detect function
pointer fields by type signature (e.g., typedefs ending with "_func_t"
or "_fn", or C function pointer types containing "(*)") and assign
SCA_KSYM as their default beautifier.

Additionally, register common function pointer and callback field names
within the sorted syscall_arg_fmts__by_name lookup table. This ensures
tracepoint arguments such as workqueue:workqueue_execute_start.function
and csd:csd_function.func are symbolised automatically without requiring
explicit per-event configuration. For example:

    ❯ sudo tools/perf/perf trace --event workqueue:workqueue_execute_end --max-events 2 --show-cpu
         0.000 [000] kworker/u32:15/236682 workqueue:workqueue_execute_end(work: 0xffffffffab2f1420, function: toggle_allocation_gate)
         0.132 [000] kworker/u32:15/236682 workqueue:workqueue_execute_end(work: 0xffff8ac2c1adc010, function: flush_to_ldisc)

Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
---
 tools/perf/builtin-trace.c | 71 +++++++++++++++++++-------------------
 1 file changed, 35 insertions(+), 36 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 003048946503..bb8f4fd9ba24 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -2096,6 +2096,17 @@ static int syscall__alloc_arg_fmts(struct syscall *sc, int nr_args)
 }
 
 static const struct syscall_arg_fmt syscall_arg_fmts__by_name[] = {
+	{ .name = "action",	.scnprintf = SCA_KSYM, },
+	{ .name = "call_site",	.scnprintf = SCA_KSYM, },
+	{ .name = "callback",	.scnprintf = SCA_KSYM, },
+	{ .name = "caller",	.scnprintf = SCA_KSYM, },
+	{ .name = "callsite",	.scnprintf = SCA_KSYM, },
+	{ .name = "cb",		.scnprintf = SCA_KSYM, },
+	{ .name = "fn",		.scnprintf = SCA_KSYM, },
+	{ .name = "func",	.scnprintf = SCA_KSYM, },
+	{ .name = "function",	.scnprintf = SCA_KSYM, },
+	{ .name = "handler",	.scnprintf = SCA_KSYM, },
+	{ .name = "location",	.scnprintf = SCA_KSYM, },
 	{ .name = "msr",	.scnprintf = SCA_X86_MSR,	  .strtoul = STUL_X86_MSR,	   },
 	{ .name = "vector",	.scnprintf = SCA_X86_IRQ_VECTORS, .strtoul = STUL_X86_IRQ_VECTORS, },
 };
@@ -2198,31 +2209,10 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field
 		    ((len >= 4 && strcmp(field->name + len - 4, "name") == 0) ||
 		     strstr(field->name, "path") != NULL)) {
 			arg->scnprintf = SCA_FILENAME;
-		} else if ((field->flags & TEP_FIELD_IS_POINTER) || strstr(field->name, "addr") ||
-			   field_has_hex_fmt(field, len))
-			arg->scnprintf = SCA_PTR;
-		else if (strcmp(field->type, "pid_t") == 0)
-			arg->scnprintf = SCA_PID;
-		else if (strcmp(field->type, "umode_t") == 0)
-			arg->scnprintf = SCA_MODE_T;
-		else if ((field->flags & TEP_FIELD_IS_ARRAY) && strstr(field->type, "char")) {
-			arg->scnprintf = SCA_CHAR_ARRAY;
-			arg->nr_entries = field->arraylen;
-		} else if ((strcmp(field->type, "int") == 0 ||
-			  strcmp(field->type, "unsigned int") == 0 ||
-			  strcmp(field->type, "long") == 0) &&
-			 len >= 2 && strcmp(field->name + len - 2, "fd") == 0) {
-			/*
-			 * /sys/kernel/tracing/events/syscalls/sys_enter*
-			 * grep -E 'field:.*fd;' .../format|sed -r 's/.*field:([a-z ]+) [a-z_]*fd.+/\1/g'|sort|uniq -c
-			 * 65 int
-			 * 23 unsigned int
-			 * 7 unsigned long
-			 */
-			arg->scnprintf = SCA_FD;
-		} else if (strstr(field->type, "enum") && use_btf != NULL) {
-			*use_btf = true;
-			arg->strtoul = STUL_BTF_TYPE;
+		} else if (field->type && (strstr(field->type, "(*)") != NULL ||
+					   strstr(field->type, "_func_t") != NULL ||
+					   strstr(field->type, "_fn") != NULL)) {
+			arg->scnprintf = SCA_KSYM;
 		} else {
 			const struct syscall_arg_fmt *fmt =
 				syscall_arg_fmt__find_by_name(field->name);
@@ -2230,6 +2220,24 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field
 			if (fmt) {
 				arg->scnprintf = fmt->scnprintf;
 				arg->strtoul   = fmt->strtoul;
+			} else if ((field->flags & TEP_FIELD_IS_POINTER) || strstr(field->name, "addr") ||
+				   field_has_hex_fmt(field, len)) {
+				arg->scnprintf = SCA_PTR;
+			} else if (strcmp(field->type, "pid_t") == 0) {
+				arg->scnprintf = SCA_PID;
+			} else if (strcmp(field->type, "umode_t") == 0) {
+				arg->scnprintf = SCA_MODE_T;
+			} else if ((field->flags & TEP_FIELD_IS_ARRAY) && strstr(field->type, "char")) {
+				arg->scnprintf = SCA_CHAR_ARRAY;
+				arg->nr_entries = field->arraylen;
+			} else if ((strcmp(field->type, "int") == 0 ||
+				    strcmp(field->type, "unsigned int") == 0 ||
+				    strcmp(field->type, "long") == 0) &&
+				   len >= 2 && strcmp(field->name + len - 2, "fd") == 0) {
+				arg->scnprintf = SCA_FD;
+			} else if (strstr(field->type, "enum") && use_btf != NULL) {
+				*use_btf = true;
+				arg->strtoul = STUL_BTF_TYPE;
 			}
 		}
 	}
@@ -3297,12 +3305,6 @@ static unsigned char bitmap_byte(const unsigned long *mask, int byte_idx)
 	return b_val;
 }
 
-static bool trace__field_is_ip(const char *name)
-{
-	return !strcmp(name, "__probe_ip") ||
-	       !strcmp(name, "caller_ip") ||
-	       !strcmp(name, "call_site");
-}
 
 static size_t trace__fprintf_tp_fields(struct trace *trace, struct perf_sample *sample,
 				       struct thread *thread, void *augmented_args, int augmented_args_size)
@@ -3404,14 +3406,11 @@ static size_t trace__fprintf_tp_fields(struct trace *trace, struct perf_sample *
 		 * Suppress it by default to avoid cluttering the output.
 		 * If verbose mode is enabled, ensure it is formatted as a
 		 * hexadecimal memory address rather than a signed integer.
-		 *
-		 * caller_ip and call_site are also expected to be instruction
-		 * pointers and should always be represented in hexadecimal.
 		 */
 		is_probe_ip = evsel__is_probe(evsel) && !strcmp(field->name, "__probe_ip");
 
-		if (is_probe_ip || trace__field_is_ip(field->name)) {
-			if (is_probe_ip && !verbose)
+		if (is_probe_ip) {
+			if (!verbose)
 				continue;
 
 			printed += scnprintf(bf + printed, size - printed,
-- 
2.55.0

Re: [PATCH perf-tools-next v3 2/4] perf trace: Auto-assign kernel symbol beautifier to function pointer fields

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] Mapping highly generic field names like 'action', 'cb', and 'caller' globally to `SCA_KSYM` short-circuits type-based logic, leaking perf userspace memory addresses instead of strings and breaking integers/enums.
- [Medium] Removal of `trace__field_is_ip()` and omission of `caller_ip` from the new lookup table causes kernel instruction pointers to be formatted as unreadable decimal integers.
--

--- Patch [2]: [PATCH perf-tools-next v3 2/4] perf trace: Auto-assign kernel symbol beautifier to function pointer fields ---
commit d3017d506b83550526e2692582e2544d0b006d0f
Author: Aaron Tomlin <atomlin@atomlin.com>

perf trace: Auto-assign kernel symbol beautifier to function pointer fields

This patch enhances perf trace to automatically format kernel function
pointer fields using the SCA_KSYM beautifier. It detects these fields
by type signature or by matching common function pointer and callback
field names in a lookup table.

> diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> index 0030489465032..bb8f4fd9ba244 100644
> --- a/tools/perf/builtin-trace.c
> +++ b/tools/perf/builtin-trace.c
> @@ -2096,6 +2096,17 @@ static int syscall__alloc_arg_fmts(struct syscall *sc, int nr_args)
>  }
>  
>  static const struct syscall_arg_fmt syscall_arg_fmts__by_name[] = {
> +	{ .name = "action",	.scnprintf = SCA_KSYM, },
> +	{ .name = "call_site",	.scnprintf = SCA_KSYM, },
> +	{ .name = "callback",	.scnprintf = SCA_KSYM, },
> +	{ .name = "caller",	.scnprintf = SCA_KSYM, },
> +	{ .name = "callsite",	.scnprintf = SCA_KSYM, },
> +	{ .name = "cb",		.scnprintf = SCA_KSYM, },

[ ... ]

> @@ -2230,6 +2220,24 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field
>  			if (fmt) {
>  				arg->scnprintf = fmt->scnprintf;
>  				arg->strtoul   = fmt->strtoul;
> +			} else if ((field->flags & TEP_FIELD_IS_POINTER) || strstr(field->name, "addr") ||
> +				   field_has_hex_fmt(field, len)) {
> +				arg->scnprintf = SCA_PTR;
> +			} else if (strcmp(field->type, "pid_t") == 0) {
> +				arg->scnprintf = SCA_PID;
> +			} else if (strcmp(field->type, "umode_t") == 0) {
> +				arg->scnprintf = SCA_MODE_T;
> +			} else if ((field->flags & TEP_FIELD_IS_ARRAY) && strstr(field->type, "char")) {
> +				arg->scnprintf = SCA_CHAR_ARRAY;
> +				arg->nr_entries = field->arraylen;

[Severity: High]
Does checking syscall_arg_fmt__find_by_name() earlier in this branch,
before the type-based checks like string arrays or BTF enums, short-circuit
those checks for generic field names?

If a field is named "caller", "action", or "cb" but is actually a dynamic
string or integer, it seems this early name match will blindly assign
SCA_KSYM.

Would this cause strings to be printed as raw kernel addresses by passing a
userspace perf pointer to SCA_KSYM, permanently obfuscating the trace data?

[ ... ]

> @@ -3297,12 +3305,6 @@ static unsigned char bitmap_byte(const unsigned long *mask, int byte_idx)
>  	return b_val;
>  }
>  
> -static bool trace__field_is_ip(const char *name)
> -{
> -	return !strcmp(name, "__probe_ip") ||
> -	       !strcmp(name, "caller_ip") ||
> -	       !strcmp(name, "call_site");
> -}

[Severity: Medium]
Since trace__field_is_ip() is removed here, should "caller_ip" have been
added to the new syscall_arg_fmts__by_name lookup table?

Because "caller_ip" is typed as unsigned long (not a pointer), lacks "addr"
in its name, and its TP_printk format strings do not match the strict
=0x/=%p checks in field_has_hex_fmt(), it evades all heuristics.

Will this cause kernel instruction pointers like "caller_ip" (used heavily
in XFS and OCFS2 tracepoints) to be formatted as unreadable base-10 decimal
integers?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260820211100.649142-1-atomlin@atomlin.com?part=2

Re: [PATCH perf-tools-next v3 2/4] perf trace: Auto-assign kernel symbol beautifier to function pointer fields

[Aaron Tomlin]

On Thu, Aug 20, 2026 at 09:26:12PM +0000, sashiko-bot@kernel.org wrote:
> commit d3017d506b83550526e2692582e2544d0b006d0f
> Author: Aaron Tomlin <atomlin@atomlin.com>
> 
> perf trace: Auto-assign kernel symbol beautifier to function pointer fields
> 
> This patch enhances perf trace to automatically format kernel function
> pointer fields using the SCA_KSYM beautifier. It detects these fields
> by type signature or by matching common function pointer and callback
> field names in a lookup table.
> 
> > diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> > index 0030489465032..bb8f4fd9ba244 100644
> > --- a/tools/perf/builtin-trace.c
> > +++ b/tools/perf/builtin-trace.c
> > @@ -2096,6 +2096,17 @@ static int syscall__alloc_arg_fmts(struct syscall *sc, int nr_args)
> >  }
> >  
> >  static const struct syscall_arg_fmt syscall_arg_fmts__by_name[] = {
> > +	{ .name = "action",	.scnprintf = SCA_KSYM, },
> > +	{ .name = "call_site",	.scnprintf = SCA_KSYM, },
> > +	{ .name = "callback",	.scnprintf = SCA_KSYM, },
> > +	{ .name = "caller",	.scnprintf = SCA_KSYM, },
> > +	{ .name = "callsite",	.scnprintf = SCA_KSYM, },
> > +	{ .name = "cb",		.scnprintf = SCA_KSYM, },
> 
> [ ... ]
> 
> > @@ -2230,6 +2220,24 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field
> >  			if (fmt) {
> >  				arg->scnprintf = fmt->scnprintf;
> >  				arg->strtoul   = fmt->strtoul;
> > +			} else if ((field->flags & TEP_FIELD_IS_POINTER) || strstr(field->name, "addr") ||
> > +				   field_has_hex_fmt(field, len)) {
> > +				arg->scnprintf = SCA_PTR;
> > +			} else if (strcmp(field->type, "pid_t") == 0) {
> > +				arg->scnprintf = SCA_PID;
> > +			} else if (strcmp(field->type, "umode_t") == 0) {
> > +				arg->scnprintf = SCA_MODE_T;
> > +			} else if ((field->flags & TEP_FIELD_IS_ARRAY) && strstr(field->type, "char")) {
> > +				arg->scnprintf = SCA_CHAR_ARRAY;
> > +				arg->nr_entries = field->arraylen;
> 
> [Severity: High]
> Does checking syscall_arg_fmt__find_by_name() earlier in this branch,
> before the type-based checks like string arrays or BTF enums, short-circuit
> those checks for generic field names?
> 
> If a field is named "caller", "action", or "cb" but is actually a dynamic
> string or integer, it seems this early name match will blindly assign
> SCA_KSYM.
> 
> Would this cause strings to be printed as raw kernel addresses by passing a
> userspace perf pointer to SCA_KSYM, permanently obfuscating the trace data?

I agree. This is a valid concern.

To resolve, I will guard the SCA_KSYM assignment in
syscall_arg_fmt__init_array(). Moving forward, a name-based lookup now
assigns SCA_KSYM only if the field is an actual pointer
(TEP_FIELD_IS_POINTER) or a pointer-sized non-array scalar (field->size ==
sizeof(void *) && !(field->flags & TEP_FIELD_IS_ARRAY)). If a field fails
this guard, it falls through to subsequent type checks (i.e.,
SCA_CHAR_ARRAY, BTF enum inspection, SCA_FD, etc.). Non-SCA_KSYM entries in
the lookup table (e.g., "msr" and "vector") continue to pass through
unhindered. This should work.


> [ ... ]
> 
> > @@ -3297,12 +3305,6 @@ static unsigned char bitmap_byte(const unsigned long *mask, int byte_idx)
> >  	return b_val;
> >  }
> >  
> > -static bool trace__field_is_ip(const char *name)
> > -{
> > -	return !strcmp(name, "__probe_ip") ||
> > -	       !strcmp(name, "caller_ip") ||
> > -	       !strcmp(name, "call_site");
> > -}
> 
> [Severity: Medium]
> Since trace__field_is_ip() is removed here, should "caller_ip" have been
> added to the new syscall_arg_fmts__by_name lookup table?
> 
> Because "caller_ip" is typed as unsigned long (not a pointer), lacks "addr"
> in its name, and its TP_printk format strings do not match the strict
> =0x/=%p checks in field_has_hex_fmt(), it evades all heuristics.
> 
> Will this cause kernel instruction pointers like "caller_ip" (used heavily
> in XFS and OCFS2 tracepoints) to be formatted as unreadable base-10 decimal
> integers?

Apologies, "caller_ip" was accidently omitted!

In the next iteration, I have added "caller_ip" to
syscall_arg_fmts__by_name[] in strict alphabetical order to ensure
bsearch() integrity. Furthermore, I have relaxed field_has_hex_fmt() to
tolerate delimiters preceding %p/%# format specifiers, ensuring tracepoint
formats utilising %pS/%ps are properly recognised too.


Kind regards,
-- 
Aaron Tomlin

[PATCH perf-tools-next v3 3/4] perf trace: Enhance BTF type formatting to symbolise kernel function pointers

[Aaron Tomlin]

When BTF (BPF Type Format) metadata is loaded from vmlinux, 'perf trace'
can inspect the precise C types of tracepoint and system call parameters.
However, function pointer arguments are currently not recognised during
BTF pretty-printing and default to hexadecimal output.

Introduce btf_is_func_ptr() to inspect BTF type hierarchies
(i.e., traversing pointers, typedefs, and type modifiers) to determine
whether a parameter resolves to a function prototype
(BTF_KIND_FUNC_PROTO).

Generalise BTF type caching via syscall_arg_fmt__cache_btf_type() to
handle structs, unions, enums, and function pointers alike. When a field
is identified as a kernel function pointer, trace__btf_scnprintf()
routes its value to syscall_arg__scnprintf_ksym(), enabling automatic
zero-config symbolisation of kernel function pointers whenever BTF is
available.

Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
---
 tools/perf/builtin-trace.c                  | 87 ++++++++++++++++-----
 tools/perf/tests/shell/trace_btf_general.sh |  2 +-
 2 files changed, 68 insertions(+), 21 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index bb8f4fd9ba24..4182906449a9 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -122,6 +122,7 @@ struct syscall_arg_fmt {
 #ifdef HAVE_LIBBPF_SUPPORT
 	const struct btf_type *type;
 	int	   type_id; /* used in btf_dump */
+	bool	   btf_type_cached;
 #endif
 };
 
@@ -979,21 +980,61 @@ static size_t syscall_arg__scnprintf_getrandom_flags(char *bf, size_t size,
 #define SCA_GETRANDOM_FLAGS syscall_arg__scnprintf_getrandom_flags
 
 #ifdef HAVE_LIBBPF_SUPPORT
-static void syscall_arg_fmt__cache_btf_enum(struct syscall_arg_fmt *arg_fmt, struct btf *btf, char *type)
+static bool btf_is_func_ptr(const struct btf *btf, const struct btf_type *type)
 {
+	while (type) {
+		if (btf_is_ptr(type) || btf_is_typedef(type) || btf_is_mod(type))
+			type = btf__type_by_id(btf, type->type);
+		else
+			break;
+	}
+	return type && btf_is_func_proto(type);
+}
+
+static void syscall_arg_fmt__cache_btf_type(struct syscall_arg_fmt *arg_fmt,
+					    struct btf *btf, const char *type)
+{
+	char name[128];
+	const char *pos;
+	size_t len = 0;
 	int id;
 
-	type = strstr(type, "enum ");
+	arg_fmt->btf_type_cached = true;
+
 	if (type == NULL)
 		return;
 
-	type += 5; // skip "enum " to get the enumeration name
+	/* Pointers to enums are memory addresses, not scalar enums */
+	if (strstr(type, "enum ") && strchr(type, '*'))
+		return;
+
+	if ((pos = strstr(type, "enum ")) != NULL)
+		pos += 5;
+	else if ((pos = strstr(type, "struct ")) != NULL)
+		pos += 7;
+	else if ((pos = strstr(type, "union ")) != NULL)
+		pos += 6;
+	else
+		pos = type;
+
+	while (isspace(*pos))
+		pos++;
 
-	id = btf__find_by_name(btf, type);
+	while ((isalnum(pos[len]) || pos[len] == '_') && len < sizeof(name) - 1) {
+		name[len] = pos[len];
+		len++;
+	}
+	name[len] = '\0';
+
+	if (len == 0)
+		return;
+
+	id = btf__find_by_name(btf, name);
 	if (id < 0)
 		return;
 
 	arg_fmt->type = btf__type_by_id(btf, id);
+	arg_fmt->type_id = id;
 }
 
 static bool syscall_arg__strtoul_btf_enum(char *bf, size_t size, struct syscall_arg *arg, u64 *val)
@@ -1027,10 +1068,8 @@ static bool syscall_arg__strtoul_btf_type(char *bf, size_t size, struct syscall_
 	if (btf == NULL)
 		return false;
 
-	if (arg->fmt->type == NULL) {
-		// See if this is an enum
-		syscall_arg_fmt__cache_btf_enum(arg->fmt, btf, type);
-	}
+	if (!arg->fmt->btf_type_cached)
+		syscall_arg_fmt__cache_btf_type(arg->fmt, btf, type);
 
 	// Now let's see if we have a BTF type resolved
 	bt = arg->fmt->type;
@@ -1038,19 +1077,22 @@ static bool syscall_arg__strtoul_btf_type(char *bf, size_t size, struct syscall_
 		return false;
 
 	// If it is an enum:
-	if (btf_is_enum(arg->fmt->type))
+	if (btf_is_enum(arg->fmt->type)) {
+		if (type && strchr(type, '*'))
+			return false;
 		return syscall_arg__strtoul_btf_enum(bf, size, arg, val);
+	}
 
 	return false;
 }
 
-static size_t btf_enum_scnprintf(const struct btf_type *type, struct btf *btf, char *bf, size_t size, int val)
+static size_t btf_enum_scnprintf(const struct btf_type *type, struct btf *btf, char *bf, size_t size, unsigned long val)
 {
 	struct btf_enum *be = btf_enum(type);
 	const unsigned int nr_entries = btf_vlen(type);
 
 	for (unsigned int i = 0; i < nr_entries; ++i, ++be) {
-		if (be->val == val) {
+		if ((unsigned long)(__u32)be->val == val || (unsigned long)be->val == val) {
 			return scnprintf(bf, size, "%s",
 					 btf__name_by_offset(btf, be->name_off));
 		}
@@ -1108,33 +1150,37 @@ static size_t btf_struct_scnprintf(const struct btf_type *type, struct btf *btf,
 }
 
 static size_t trace__btf_scnprintf(struct trace *trace, struct syscall_arg *arg, char *bf,
-				   size_t size, int val, char *type)
+				   size_t size, unsigned long val, char *type)
 {
 	struct syscall_arg_fmt *arg_fmt = arg->fmt;
 
 	if (trace->btf == NULL)
 		return 0;
 
-	if (arg_fmt->type == NULL) {
-		// Check if this is an enum and if we have the BTF type for it.
-		syscall_arg_fmt__cache_btf_enum(arg_fmt, trace->btf, type);
-	}
+	if (!arg_fmt->btf_type_cached)
+		syscall_arg_fmt__cache_btf_type(arg_fmt, trace->btf, type);
 
 	// Did we manage to find a BTF type for the syscall/tracepoint argument?
 	if (arg_fmt->type == NULL)
 		return 0;
 
-	if (btf_is_enum(arg_fmt->type))
+	if (btf_is_enum(arg_fmt->type)) {
+		if (type && strchr(type, '*'))
+			return 0;
 		return btf_enum_scnprintf(arg_fmt->type, trace->btf, bf, size, val);
-	else if (btf_is_struct(arg_fmt->type) || btf_is_union(arg_fmt->type))
+	} else if (btf_is_struct(arg_fmt->type) || btf_is_union(arg_fmt->type))
 		return btf_struct_scnprintf(arg_fmt->type, trace->btf, bf, size, arg);
+	else if (btf_is_func_ptr(trace->btf, arg_fmt->type)) {
+		arg->val = val;
+		return syscall_arg__scnprintf_ksym(bf, size, arg);
+	}
 
 	return 0;
 }
 
 #else // HAVE_LIBBPF_SUPPORT
 static size_t trace__btf_scnprintf(struct trace *trace __maybe_unused, struct syscall_arg *arg __maybe_unused,
-				   char *bf __maybe_unused, size_t size __maybe_unused, int val __maybe_unused,
+				   char *bf __maybe_unused, size_t size __maybe_unused, unsigned long val __maybe_unused,
 				   char *type __maybe_unused)
 {
 	return 0;
@@ -2566,7 +2612,8 @@ static size_t syscall__scnprintf_args(struct syscall *sc, char *bf, size_t size,
 
 			default_scnprintf = sc->arg_fmt[arg.idx].scnprintf;
 
-			if (trace->force_btf || default_scnprintf == NULL || default_scnprintf == SCA_PTR) {
+			if (trace->force_btf || default_scnprintf == NULL ||
+			    default_scnprintf == SCA_PTR || default_scnprintf == SCA_KSYM) {
 				btf_printed = trace__btf_scnprintf(trace, &arg, bf + printed,
 								   size - printed, val, field->type);
 				if (btf_printed) {
diff --git a/tools/perf/tests/shell/trace_btf_general.sh b/tools/perf/tests/shell/trace_btf_general.sh
index 7a94a5743924..255468eff128 100755
--- a/tools/perf/tests/shell/trace_btf_general.sh
+++ b/tools/perf/tests/shell/trace_btf_general.sh
@@ -49,7 +49,7 @@ trace_test_buffer() {
 trace_test_struct_btf() {
   echo "Testing perf trace's struct augmentation"
   output="$(perf trace --sort-events -e clock_nanosleep --force-btf --max-events=1 -- sleep 1 2>&1)"
-  if ! echo "$output" | grep -q -E "^sleep/[0-9]+ clock_nanosleep\(0, 0, \{1,.*\}, 0x[0-9a-f]+\) += +[0-9]+$"
+  if ! echo "$output" | grep -q -E "sleep/[0-9]+ clock_nanosleep\(.*(struct __kernel_timespec|\{1,).*\) = [0-9]+"
   then
 	printf "BTF struct augmentation test failed, output:\n$output\n"
     err=1
-- 
2.55.0

Re: [PATCH perf-tools-next v3 3/4] perf trace: Enhance BTF type formatting to symbolise kernel function pointers

[sashiko-bot]

> When BTF (BPF Type Format) metadata is loaded from vmlinux, 'perf trace'
> can inspect the precise C types of tracepoint and system call parameters.
> However, function pointer arguments are currently not recognised during
> BTF pretty-printing and default to hexadecimal output.
> 
> Introduce btf_is_func_ptr() to inspect BTF type hierarchies
> (i.e., traversing pointers, typedefs, and type modifiers) to determine
> whether a parameter resolves to a function prototype
> (BTF_KIND_FUNC_PROTO).
> 
> Generalise BTF type caching via syscall_arg_fmt__cache_btf_type() to
> handle structs, unions, enums, and function pointers alike. When a field
> is identified as a kernel function pointer, trace__btf_scnprintf()
> routes its value to syscall_arg__scnprintf_ksym(), enabling automatic
> zero-config symbolisation of kernel function pointers whenever BTF is
> available.
> 
> Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260820211100.649142-1-atomlin@atomlin.com?part=3

[PATCH perf-tools-next v3 4/4] perf tests: Add shell test for kernel symbol beautifier

[Aaron Tomlin]

Add a dedicated shell test script, trace_ksym_beautifier.sh, to verify
that 'perf trace' properly symbolises kernel virtual addresses and
function pointers using both the default kallsyms beautifier (SCA_KSYM)
and BTF type routing i.e., --force-btf.

Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
---
 .../perf/tests/shell/trace_ksym_beautifier.sh | 43 +++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100755 tools/perf/tests/shell/trace_ksym_beautifier.sh

diff --git a/tools/perf/tests/shell/trace_ksym_beautifier.sh b/tools/perf/tests/shell/trace_ksym_beautifier.sh
new file mode 100755
index 000000000000..30a8429669dd
--- /dev/null
+++ b/tools/perf/tests/shell/trace_ksym_beautifier.sh
@@ -0,0 +1,43 @@
+#!/bin/bash
+# perf trace kernel symbol beautifier tests
+# SPDX-License-Identifier: GPL-2.0
+
+err=0
+
+# shellcheck source=lib/probe.sh
+. "$(dirname "$0")"/lib/probe.sh
+skip_if_no_perf_trace || exit 2
+[ "$(id -u)" = 0 ] || exit 2
+
+test_ksym_kallsyms() {
+  echo "Testing perf trace kernel symbol beautifier (default kallsyms)"
+  output="$(perf trace -e kmem:kmalloc --max-events=1 2>&1)"
+  if ! echo "$output" | grep -q -E "call_site: [a-zA-Z_][a-zA-Z0-9_]*" || echo "$output" | grep -q -E "call_site: 0x[0-9a-fA-F]+"
+  then
+    printf "Default kallsyms function symbolization failed, output:\n%s\n" "$output"
+    err=1
+  fi
+}
+
+test_ksym_btf() {
+  echo "Testing perf trace kernel symbol beautifier (BTF)"
+  if [ ! -f /sys/kernel/btf/vmlinux ]; then
+    echo "Skipping BTF test due to missing vmlinux BTF"
+    return
+  fi
+
+  output="$(perf trace -e kmem:kmalloc --force-btf --max-events=1 2>&1)"
+  if ! echo "$output" | grep -q -E "call_site: [a-zA-Z_][a-zA-Z0-9_]*" || echo "$output" | grep -q -E "call_site: 0x[0-9a-fA-F]+"
+  then
+    printf "BTF function symbolization failed, output:\n%s\n" "$output"
+    err=1
+  fi
+}
+
+test_ksym_kallsyms
+
+if [ $err = 0 ]; then
+  test_ksym_btf
+fi
+
+exit $err
-- 
2.55.0

Re: [PATCH perf-tools-next v3 4/4] perf tests: Add shell test for kernel symbol beautifier

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The BTF type routing test does not actually test BTF symbolization, as it silently falls back to the default kallsyms beautifier.
--

--- Patch [4]: [PATCH perf-tools-next v3 4/4] perf tests: Add shell test for kernel symbol beautifier ---
commit c8c43ea37c4e0f26131dd9e871af4241cd478b77
Author: Aaron Tomlin <atomlin@atomlin.com>

perf tests: Add shell test for kernel symbol beautifier

This commit adds a shell test script, trace_ksym_beautifier.sh, to verify
that perf trace symbolises kernel virtual addresses and function pointers
using both the default kallsyms beautifier and BTF type routing.

> diff --git a/tools/perf/tests/shell/trace_ksym_beautifier.sh b/tools/perf/tests/shell/trace_ksym_beautifier.sh
> new file mode 100755
> index 0000000000000..30a8429669dd5
> --- /dev/null
> +++ b/tools/perf/tests/shell/trace_ksym_beautifier.sh
[ ... ]
> +test_ksym_btf() {
> +  echo "Testing perf trace kernel symbol beautifier (BTF)"
> +  if [ ! -f /sys/kernel/btf/vmlinux ]; then
> +    echo "Skipping BTF test due to missing vmlinux BTF"
> +    return
> +  fi
> +
> +  output="$(perf trace -e kmem:kmalloc --force-btf --max-events=1 2>&1)"

[Severity: Medium]
Does this actually test the BTF type routing as intended?

Looking at the kmem:kmalloc tracepoint, the call_site field is defined as an
unsigned long, rather than a function pointer. When trace__btf_scnprintf()
evaluates this, it determines it is an integer rather than a function
pointer, and returns 0.

This causes perf to silently fall back to the default SCA_KSYM beautifier.
Consequently, the test passes via the fallback path rather than truly
exercising the BTF routing.

Would it be better to use a tracepoint with a field explicitly typed as a
function pointer for the --force-btf test?

> +  if ! echo "$output" | grep -q -E "call_site: [a-zA-Z_][a-zA-Z0-9_]*" || echo "$output" | grep -q -E "call_site: 0x[0-9a-fA-F]+"
> +  then
> +    printf "BTF function symbolization failed, output:\n%s\n" "$output"
> +    err=1
> +  fi
> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260820211100.649142-1-atomlin@atomlin.com?part=4