Build failure bft for trace-cmd and libtraceevent

Build failure bft for trace-cmd and libtraceevent

[Giulio Benetti]

Hi Steven, All,

in Buildroot I'm bumping libtraceevent to 1.9.0 and trace-cmd to 3.4 and
experiencing build failures because of the change of uapi/linux/bft.h
defines/enums

I see as possible solution to create a bft_compat.h to deal with
different Linux versions, but this is not a quick solution.

Otherwise the solution could be to switch according to Linux version
between print_args() with and without bft support, basically re-adding
the function here:
https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/commit/?id=e798103c0815e6642e74d9317c325b2c62681f2e

What do you think about it?

Best regards
Giulio Benetti

Re: Build failure bft for trace-cmd and libtraceevent

[Steven Rostedt]

On Sun, 8 Feb 2026 21:53:31 +0100
Giulio Benetti <giulio.benetti@benettiengineering.com> wrote:

> Otherwise the solution could be to switch according to Linux version
> between print_args() with and without bft support, basically re-adding
> the function here:
> https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/commit/?id=e798103c0815e6642e74d9317c325b2c62681f2e
> 
> What do you think about it?

Is the failure found at runtime? That is, the loaded BTF file doesn't
parse correctly? What is the error exactly?

I guess if the tep_btf_print_args() fails, it should just print the raw
args then.

-- Steve

Re: Build failure bft for trace-cmd and libtraceevent

[Giulio Benetti]

On 08/02/2026 22:32, Steven Rostedt wrote:
> On Sun, 8 Feb 2026 21:53:31 +0100
> Giulio Benetti <giulio.benetti@benettiengineering.com> wrote:
> 
>> Otherwise the solution could be to switch according to Linux version
>> between print_args() with and without bft support, basically re-adding
>> the function here:
>> https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/commit/?id=e798103c0815e6642e74d9317c325b2c62681f2e
>>
>> What do you think about it?
> 
> Is the failure found at runtime? That is, the loaded BTF file doesn't
> parse correctly? What is the error exactly?
> 
> I guess if the tep_btf_print_args() fails, it should just print the raw
> args then.

Oh, I've forgotten to post the build failure, here it is and it's due to
dealing with different Linux versions:
[8/40] Compiling C object src/libtraceevent.so.1.9.0.p/trace-btf.c.o
FAILED: [code=1] src/libtraceevent.so.1.9.0.p/trace-btf.c.o
/home/giuliobenetti/git/upstream/test-libtraceevent/bootlin-armv5-uclibc/host/bin/arm-linux-gcc 
-Isrc/libtraceevent.so.1.9.0.p -Isrc -I../src -Iinclude -I../include 
-Iinclude/traceevent -I../include/traceevent -fdiagnostics-color=always 
-Wall -Winvalid-pch -std=gnu99 -O3 -D_GNU_SOURCE 
'-DPLUGIN_DIR="/usr/lib/traceevent/plugins"' -D_LARGEFILE_SOURCE 
-D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -g0 -fPIC -MD -MQ 
src/libtraceevent.so.1.9.0.p/trace-btf.c.o -MF 
src/libtraceevent.so.1.9.0.p/trace-btf.c.o.d -o 
src/libtraceevent.so.1.9.0.p/trace-btf.c.o -c ../src/trace-btf.c
../src/trace-btf.c:60:10: error: ‘BTF_KIND_FLOAT’ undeclared here (not 
in a function); did you mean ‘BTF_KIND_CONST’?
    60 |         [BTF_KIND_FLOAT]        = "FLOAT",
       |          ^~~~~~~~~~~~~~
       |          BTF_KIND_CONST
../src/trace-btf.c:60:10: error: array index in initializer not of 
integer type
../src/trace-btf.c:60:10: note: (near initialization for ‘btf_kind_str’)
../src/trace-btf.c:60:35: warning: excess elements in array initializer
    60 |         [BTF_KIND_FLOAT]        = "FLOAT",
       |                                   ^~~~~~~
../src/trace-btf.c:60:35: note: (near initialization for ‘btf_kind_str’)
../src/trace-btf.c:61:10: error: ‘BTF_KIND_DECL_TAG’ undeclared here 
(not in a function)
    61 |         [BTF_KIND_DECL_TAG]     = "DECL_TAG",
       |          ^~~~~~~~~~~~~~~~~
../src/trace-btf.c:61:10: error: array index in initializer not of 
integer type
../src/trace-btf.c:61:10: note: (near initialization for ‘btf_kind_str’)
../src/trace-btf.c:61:35: warning: excess elements in array initializer
    61 |         [BTF_KIND_DECL_TAG]     = "DECL_TAG",
       |                                   ^~~~~~~~~~
../src/trace-btf.c:61:35: note: (near initialization for ‘btf_kind_str’)
../src/trace-btf.c:62:10: error: ‘BTF_KIND_TYPE_TAG’ undeclared here 
(not in a function); did you mean ‘BTF_KIND_TYPEDEF’?
    62 |         [BTF_KIND_TYPE_TAG]     = "TYPE_TAG",
       |          ^~~~~~~~~~~~~~~~~
       |          BTF_KIND_TYPEDEF
../src/trace-btf.c:62:10: error: array index in initializer not of 
integer type
../src/trace-btf.c:62:10: note: (near initialization for ‘btf_kind_str’)
../src/trace-btf.c:62:35: warning: excess elements in array initializer
    62 |         [BTF_KIND_TYPE_TAG]     = "TYPE_TAG",
       |                                   ^~~~~~~~~~
../src/trace-btf.c:62:35: note: (near initialization for ‘btf_kind_str’)
../src/trace-btf.c:63:10: error: ‘BTF_KIND_ENUM64’ undeclared here (not 
in a function); did you mean ‘BTF_KIND_ENUM’?
    63 |         [BTF_KIND_ENUM64]       = "ENUM64",
       |          ^~~~~~~~~~~~~~~
       |          BTF_KIND_ENUM
../src/trace-btf.c:63:10: error: array index in initializer not of 
integer type
../src/trace-btf.c:63:10: note: (near initialization for ‘btf_kind_str’)
../src/trace-btf.c:63:35: warning: excess elements in array initializer
    63 |         [BTF_KIND_ENUM64]       = "ENUM64",
       |                                   ^~~~~~~~
../src/trace-btf.c:63:35: note: (near initialization for ‘btf_kind_str’)
../src/trace-btf.c: In function ‘btf_type_size’:
../src/trace-btf.c:115:38: error: invalid application of ‘sizeof’ to 
incomplete type ‘struct btf_decl_tag’
   115 |                 return size + sizeof(struct btf_decl_tag);
       |                                      ^~~~~~
../src/trace-btf.c:119:38: error: invalid application of ‘sizeof’ to 
incomplete type ‘struct btf_enum64’
   119 |                 return size + sizeof(struct btf_enum64) * 
BTF_INFO_VLEN(type->info);
       |                                      ^~~~~~
[9/40] Compiling C object plugins/plugin_kmem.so.p/plugin_kmem.c.o
[10/40] Compiling C object plugins/plugin_tlb.so.p/plugin_tlb.c.o
[11/40] Compiling C object plugins/plugin_net.so.p/plugin_net.c.o
[12/40] Compiling C object src/libtraceevent.so.1.9.0.p/parse-utils.c.o
[13/40] Compiling C object 
plugins/plugin_sched_switch.so.p/plugin_sched_switch.c.o
[14/40] Compiling C object samples/test-event.p/test-event.c.o
[15/40] Compiling C object plugins/plugin_scsi.so.p/plugin_scsi.c.o
[16/40] Compiling C object src/libtraceevent.so.1.9.0.p/event-parse-api.c.o
[17/40] Compiling C object plugins/plugin_function.so.p/plugin_function.c.o
[18/40] Compiling C object src/libtraceevent.so.1.9.0.p/trace-seq.c.o
[19/40] Compiling C object plugins/plugin_kvm.so.p/plugin_kvm.c.o
[20/40] Compiling C object src/libtraceevent.so.1.9.0.p/event-plugin.c.o
[21/40] Compiling C object src/libtraceevent.so.1.9.0.p/kbuffer-parse.c.o
[22/40] Compiling C object src/libtraceevent.so.1.9.0.p/parse-filter.c.o
[23/40] Compiling C object src/libtraceevent.so.1.9.0.p/event-parse.c.o
ninja: build stopped: subcommand failed.
make[1]: *** [package/pkg-generic.mk:273: 
/home/giuliobenetti/git/upstream/test-libtraceevent/bootlin-armv5-uclibc/build/libtraceevent-1.9.0/.stamp_built] 
Error 1
make: *** [Makefile:83: _all] Error 2

Giulio

Re: Build failure bft for trace-cmd and libtraceevent

[Steven Rostedt]

On Sun, 8 Feb 2026 22:44:24 +0100
Giulio Benetti <giulio.benetti@benettiengineering.com> wrote:

> Oh, I've forgotten to post the build failure, here it is and it's due to
> dealing with different Linux versions:

OK, if it is a build failure, we should add logic to make sure it
builds properly and if not, warn and build without BTF. Kind of like
what trace-cmd did when I was first started developing this:

  https://lore.kernel.org/20260203233451.2118849-5-rostedt@goodmis.org

-- Steve

Re: Build failure bft for trace-cmd and libtraceevent

[Giulio Benetti]

> Il giorno 8 feb 2026, alle ore 23:01, Steven Rostedt <rostedt@goodmis.org> ha scritto:
> 
> On Sun, 8 Feb 2026 22:44:24 +0100
> Giulio Benetti <giulio.benetti@benettiengineering.com> wrote:
> 
>> Oh, I've forgotten to post the build failure, here it is and it's due to
>> dealing with different Linux versions:
> 
> OK, if it is a build failure, we should add logic to make sure it
> builds properly and if not, warn and build without BTF. Kind of like
> what trace-cmd did when I was first started developing this:
> 
>  https://lore.kernel.org/20260203233451.2118849-5-rostedt@goodmis.org

Oh, ok. I’m going to follow that commit and add btf option to disable btf to trace-cmd too.
At the moment it only checks for libtraceevent version and that won’t be sufficient.

Thank you for taking care

Best regards
Giulio

> 
> -- Steve

Re: Build failure bft for trace-cmd and libtraceevent

[Steven Rostedt]

On Sun, 8 Feb 2026 23:14:32 +0100
Giulio Benetti <giulio.benetti@benettiengineering.com> wrote:

> Oh, ok. I’m going to follow that commit and add btf option to disable btf to trace-cmd too.
> At the moment it only checks for libtraceevent version and that won’t be sufficient.

I don't think you need to change trace-cmd. We can just make the
tep_btf_print_args() just print the arguments passed in if it is not
supported, and have the list_args just fail.

Here's an update to the libtraceevent Makefile to do this. Will need
something similar for the meson build.

-- Steve

diff --git a/Makefile b/Makefile
index e1a10a02a560..bd88a981d373 100644
--- a/Makefile
+++ b/Makefile
@@ -27,6 +27,13 @@ $(call allow-override,PKG_CONFIG,pkg-config)
 $(call allow-override,LD_SO_CONF_PATH,/etc/ld.so.conf.d/)
 $(call allow-override,LDCONFIG,ldconfig)
 
+# Set compile option CFLAGS
+ifdef EXTRA_CFLAGS
+  CFLAGS ?= $(EXTRA_CFLAGS)
+else
+  CFLAGS ?= -g -Wall
+endif
+
 EXT = -std=gnu99
 INSTALL = install
 
@@ -37,6 +44,20 @@ INSTALL = install
 DESTDIR ?=
 DESTDIR_SQ = '$(subst ','\'',$(DESTDIR))'
 
+test-build = $(if $(shell sh -c 'echo "$(1)" | tee /tmp/t.c| \
+	$(CC) -o /dev/null -x c - > /dev/null 2>&1 && echo y'), $2)
+
+define BTF_LATEST_SOURCE
+#include <linux/btf.h>
+int main(void) { return BTF_KIND_ENUM64; }
+endef
+
+BTF_OK := $(call test-build,$(BTF_LATEST_SOURCE),y)
+
+ifneq ($(strip $(BTF_OK)), y)
+CFLAGS += -DNO_BTF
+endif
+
 LP64 := $(shell echo __LP64__ | ${CC} ${CFLAGS} -E -x c - | tail -n 1)
 ifeq ($(LP64), 1)
   libdir_relative_temp = lib64
@@ -123,13 +144,6 @@ INCLUDES = -I. -I $(srctree)/include -I $(EP_HEADERS_DIR) $(CONFIG_INCLUDES)
 
 export LIBTRACEEVENT_STATIC LIBTRACEEVENT_SHARED EP_HEADERS_DIR
 
-# Set compile option CFLAGS
-ifdef EXTRA_CFLAGS
-  CFLAGS := $(EXTRA_CFLAGS)
-else
-  CFLAGS := -g -Wall
-endif
-
 LIBS ?= -ldl
 export LIBS
 

Re: Build failure bft for trace-cmd and libtraceevent

[Giulio Benetti]

[-- Attachment #1: Type: text/plain, Size: 2173 bytes --]

Hi Steve,

On 2/8/26 23:22, Steven Rostedt wrote:
> On Sun, 8 Feb 2026 23:14:32 +0100
> Giulio Benetti <giulio.benetti@benettiengineering.com> wrote:
> 
>> Oh, ok. I’m going to follow that commit and add btf option to disable btf to trace-cmd too.
>> At the moment it only checks for libtraceevent version and that won’t be sufficient.
> 
> I don't think you need to change trace-cmd. We can just make the
> tep_btf_print_args() just print the arguments passed in if it is not
> supported,

it is not that clear to me here

> and have the list_args just fail.

Ok.

Attached you find a patch to be tested.

Giulio

> 
> Here's an update to the libtraceevent Makefile to do this. Will need
> something similar for the meson build.
> 
> -- Steve
> 
> diff --git a/Makefile b/Makefile
> index e1a10a02a560..bd88a981d373 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -27,6 +27,13 @@ $(call allow-override,PKG_CONFIG,pkg-config)
>   $(call allow-override,LD_SO_CONF_PATH,/etc/ld.so.conf.d/)
>   $(call allow-override,LDCONFIG,ldconfig)
>   
> +# Set compile option CFLAGS
> +ifdef EXTRA_CFLAGS
> +  CFLAGS ?= $(EXTRA_CFLAGS)
> +else
> +  CFLAGS ?= -g -Wall
> +endif
> +
>   EXT = -std=gnu99
>   INSTALL = install
>   
> @@ -37,6 +44,20 @@ INSTALL = install
>   DESTDIR ?=
>   DESTDIR_SQ = '$(subst ','\'',$(DESTDIR))'
>   
> +test-build = $(if $(shell sh -c 'echo "$(1)" | tee /tmp/t.c| \
> +	$(CC) -o /dev/null -x c - > /dev/null 2>&1 && echo y'), $2)
> +
> +define BTF_LATEST_SOURCE
> +#include <linux/btf.h>
> +int main(void) { return BTF_KIND_ENUM64; }
> +endef
> +
> +BTF_OK := $(call test-build,$(BTF_LATEST_SOURCE),y)
> +
> +ifneq ($(strip $(BTF_OK)), y)
> +CFLAGS += -DNO_BTF
> +endif
> +
>   LP64 := $(shell echo __LP64__ | ${CC} ${CFLAGS} -E -x c - | tail -n 1)
>   ifeq ($(LP64), 1)
>     libdir_relative_temp = lib64
> @@ -123,13 +144,6 @@ INCLUDES = -I. -I $(srctree)/include -I $(EP_HEADERS_DIR) $(CONFIG_INCLUDES)
>   
>   export LIBTRACEEVENT_STATIC LIBTRACEEVENT_SHARED EP_HEADERS_DIR
>   
> -# Set compile option CFLAGS
> -ifdef EXTRA_CFLAGS
> -  CFLAGS := $(EXTRA_CFLAGS)
> -else
> -  CFLAGS := -g -Wall
> -endif
> -
>   LIBS ?= -ldl
>   export LIBS
>   

[-- Attachment #2: 0001-Fix-build-failure-due-to-btf-on-Linux-6.0.patch --]
[-- Type: text/x-patch, Size: 4030 bytes --]

From e14139e63b68eccd2800406c4f5ad049015a8cf6 Mon Sep 17 00:00:00 2001
From: Giulio Benetti <giulio.benetti@benettiengineering.com>
Date: Tue, 10 Feb 2026 17:57:52 +0100
Subject: [PATCH] Fix build failure due to btf on Linux < 6.0

With commit:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6089fb325cf737eeb2c4d236c94697112ca860da
enum BTF_KIND_ENUM64 has been firstly introduced and this is the latest
BTF_KIND_* enumaration to be added to libtraceevent. So let's check
in runtime, both in Makefile and meson, if BTF_KIND_ENUM64 does exist.
If it's not there let's disable btf support.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Co-authored-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
---
 Makefile        | 28 +++++++++++++++++++++-------
 src/meson.build | 12 ++++++++++++
 src/trace-btf.c |  9 +++++++++
 3 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/Makefile b/Makefile
index e1a10a0..bd88a98 100644
--- a/Makefile
+++ b/Makefile
@@ -27,6 +27,13 @@ $(call allow-override,PKG_CONFIG,pkg-config)
 $(call allow-override,LD_SO_CONF_PATH,/etc/ld.so.conf.d/)
 $(call allow-override,LDCONFIG,ldconfig)
 
+# Set compile option CFLAGS
+ifdef EXTRA_CFLAGS
+  CFLAGS ?= $(EXTRA_CFLAGS)
+else
+  CFLAGS ?= -g -Wall
+endif
+
 EXT = -std=gnu99
 INSTALL = install
 
@@ -37,6 +44,20 @@ INSTALL = install
 DESTDIR ?=
 DESTDIR_SQ = '$(subst ','\'',$(DESTDIR))'
 
+test-build = $(if $(shell sh -c 'echo "$(1)" | tee /tmp/t.c| \
+	$(CC) -o /dev/null -x c - > /dev/null 2>&1 && echo y'), $2)
+
+define BTF_LATEST_SOURCE
+#include <linux/btf.h>
+int main(void) { return BTF_KIND_ENUM64; }
+endef
+
+BTF_OK := $(call test-build,$(BTF_LATEST_SOURCE),y)
+
+ifneq ($(strip $(BTF_OK)), y)
+CFLAGS += -DNO_BTF
+endif
+
 LP64 := $(shell echo __LP64__ | ${CC} ${CFLAGS} -E -x c - | tail -n 1)
 ifeq ($(LP64), 1)
   libdir_relative_temp = lib64
@@ -123,13 +144,6 @@ INCLUDES = -I. -I $(srctree)/include -I $(EP_HEADERS_DIR) $(CONFIG_INCLUDES)
 
 export LIBTRACEEVENT_STATIC LIBTRACEEVENT_SHARED EP_HEADERS_DIR
 
-# Set compile option CFLAGS
-ifdef EXTRA_CFLAGS
-  CFLAGS := $(EXTRA_CFLAGS)
-else
-  CFLAGS := -g -Wall
-endif
-
 LIBS ?= -ldl
 export LIBS
 
diff --git a/src/meson.build b/src/meson.build
index 3a7a082..23b43ff 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -17,6 +17,18 @@ sources= [
 cc = meson.get_compiler('c')
 dl_dep = cc.find_library('dl')
 
+btf_enum64_test_code = '''
+#include <linux/btf.h>
+int main(void) {
+    int x = BTF_KIND_ENUM64;
+    return 0;
+}
+'''
+
+if cc.compiles(btf_enum64_test_code, name : 'BTF_KIND_ENUM64 check')
+    add_project_arguments('-DNO_BTF', language : 'c')
+endif
+
 libtraceevent = library(
     'traceevent',
     sources,
diff --git a/src/trace-btf.c b/src/trace-btf.c
index 859b086..c7102d8 100644
--- a/src/trace-btf.c
+++ b/src/trace-btf.c
@@ -471,6 +471,9 @@ static int init_btf_func(struct tep_btf *btf, struct trace_seq *s,
  */
 int tep_btf_list_args(struct tep_handle *tep, struct trace_seq *s, const char *func)
 {
+#ifdef NO_BTF
+	return -1;
+#else
 	struct tep_btf *btf = tep->btf;
 	struct btf_type *type = tep_btf_find_func(btf, func);
 	struct btf_param *param;
@@ -520,6 +523,7 @@ int tep_btf_list_args(struct tep_handle *tep, struct trace_seq *s, const char *f
 			trace_seq_printf(s, "%s", param_name);
 	}
 	return p;
+#endif
 }
 
 /**
@@ -543,6 +547,10 @@ int tep_btf_list_args(struct tep_handle *tep, struct trace_seq *s, const char *f
 int tep_btf_print_args(struct tep_handle *tep, struct trace_seq *s, void *args,
 		       int nmem, int size, const char *func)
 {
+#ifdef NO_BTF
+	tep_warning("BTF not supported. Args: ??? \n");
+	return -1;
+#else
 	struct tep_btf *btf = tep->btf;
 	struct btf_type *type = tep_btf_find_func(btf, func);
 	struct btf_param *param;
@@ -646,4 +654,5 @@ int tep_btf_print_args(struct tep_handle *tep, struct trace_seq *s, void *args,
 		}
 	}
 	return 0;
+#endif
 }
-- 
2.47.3