---
name: "tep_load_btf"
section: "3"
platform: "linux"
package: "libtraceevent"
version: "1:1.9.1-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/tep_load_btf"
---

# tep\_load\_btf(3)

Load BTF file and use it to pretty print function arguments.

## NAME

tep\_load\_btf, tep\_btf\_print\_args - Load BTF file and use it to pretty print function arguments.

## SYNOPSIS

```
#include <event-parse.h>
int tep_load_btf(struct tep_handle *tep, void *raw_data, size_t data_size);
int tep_btf_print_args(struct tep_handle *tep, struct trace_seq *s, void *args,
                       int nmem, int size, const char *func);
```

## DESCRIPTION

If the Linux kernel has BTF configured, then a binary file will exist in the path of **/sys/kernel/btf/vmlinux**. If this file is read into memory and passed to **tep\_load\_btf()** function, then it will be used to parse the arguments of a given function, if that function data is found within the BTF file.

The **tep\_load\_btf()** takes the *tep* handle and will load the *raw\_data* into it. The *data\_size* should be set to the size of the content in *raw\_data*.

The **tep\_btf\_print\_args()** takes a *tep* handle, a trace\_seq *s* pointer (that was initialized by **[trace\_seq\_init(3)](/trace_seq_init/3.md)**), an *args* array that holds either 4 byte or 8 byte values, the *nmem* that is the number of values in the *args* parameter, a *size* that is either 4 or 8 to denote the size of each value in *args*, and a *func* string that is the name of the function to find the BTF information to use for parsing. If BTF is not loaded or the *func* name is not found it will just print a hex value of all the *args* into the *s* descriptor.

## RETURN VALUE

**tep\_load\_btf()** function returns 0 on success. It returns -1 on failure and the *raw\_data* will need to be freed by the caller.

**tep\_btf\_print\_args()** returns 0 on success and -1 on failure, which happens if the *size* is not valid or the BTF file that was loaded is corrupted.

## EXAMPLE

```
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <event-parse.h>
int print_args(const char *func, unsigned long *args, int nr)
{
        struct tep_handle *tep = tep_alloc();
        struct trace_seq s;
        struct stat st;
        void *buf;
        int fd;
        int ret;
        if (!tep)
                return -1;
        fd = open("/sys/kernel/btf/vmlinux", O_RDONLY);
        if (fd < 0)
                return -1;
        if (fstat(fd, &st) < 0) {
                close(fd);
                return -1;
        }
        buf = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
        if (buf == MAP_FAILED) {
                close(fd);
                return -1;
        }
        ret = tep_load_btf(tep, buf, st.st_size);
        munmap(buf, st.st_size);
        close(fd);
        if (ret < 0)
                return -1;
        trace_seq_init(&s);
        trace_seq_printf(&s, "%s(", func);
        tep_btf_print_args(tep, &s, args, nr, sizeof(long), func);
        trace_seq_puts(&s, ")\n");
        trace_seq_do_printf(&s);
        tep_free(tep);
        return 0;
}
int main(int argc, char **argv)
{
        unsigned long args[] = {0x7ffe7d33f3d0, 0, 0, 0, 0, 0};
        print_args("getname_flags", args, 6);
        return 0;
}
...
The above may output:
  getname_flags(filename=0x7ffe7d33f3d0, flags=0)
If BTF is loaded and the function was found, or it may show:
  getname_flags(7ffe7d33f3d0, 0, 0, 0, 0, 0)
If it was not.
...
```

## FILES

```
event-parse.h
        Header file to include in order to have access to the library APIs.
-ltraceevent
        Linker switch to add when building a program that uses the library.
```

## SEE ALSO

[**libtraceevent**(3)](/libtraceevent/3.md), [**trace-cmd**(1)](/trace-cmd/1.md)

## AUTHOR

```
Steven Rostedt <rostedt@goodmis.org[1]>, author of libtraceevent.
```

## REPORTING BUGS

Report bugs to \<**linux-trace-devel@vger.kernel.org**\[2\]\>

## LICENSE

libtraceevent is Free Software licensed under the GNU LGPL 2.1

## RESOURCES

**https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/**

## NOTES

- 1\.

  rostedt@goodmis.org

  mailto:rostedt@goodmis.org

- 2\.

  linux-trace-devel@vger.kernel.org

  mailto:linux-trace-devel@vger.kernel.org