[−][src]Function solana_rbpf::helpers::bpf_trace_printf
pub fn bpf_trace_printf(
unused1: u64,
unused2: u64,
arg3: u64,
arg4: u64,
arg5: u64
) -> u64
Prints its last three arguments to standard output. The first two arguments are unused. Returns the number of bytes written.
By ignoring the first two arguments, it creates a helper that will have a behavior similar to
the one of the equivalent helper bpf_trace_printk()
from Linux kernel.
Examples
use solana_rbpf::helpers; let res = helpers::bpf_trace_printf(0, 0, 1, 15, 32); assert_eq!(res as usize, "bpf_trace_printf: 0x1, 0xf, 0x20\n".len());
This will print bpf_trace_printf: 0x1, 0xf, 0x20
.
The eBPF code needed to perform the call in this example would be nearly identical to the code obtained by compiling the following code from C to eBPF with clang:
#include <linux/bpf.h>
#include "path/to/linux/samples/bpf/bpf_helpers.h"
int main(struct __sk_buff *skb)
{
// Only %d %u %x %ld %lu %lx %lld %llu %llx %p %s conversion specifiers allowed.
// See <https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/kernel/trace/bpf_trace.c>.
char *fmt = "bpf_trace_printk %llx, %llx, %llx\n";
return bpf_trace_printk(fmt, sizeof(fmt), 1, 15, 32);
}
This would equally print the three numbers in /sys/kernel/debug/tracing
file each time the
program is run.