Alexei Starovoitov
8d3b7dce86
bpf: add support for %s specifier to bpf_trace_printk()
%s specifier makes bpf program and kernel debugging easier.
To make sure that trace_printk won't crash the unsafe string
is copied into stack and unsafe pointer is substituted.
The following C program:
#include <linux/fs.h>
int foo(struct pt_regs *ctx, struct filename *filename)
{
void *name = 0;
bpf_probe_read(&name, sizeof(name), &filename->name);
bpf_trace_printk("executed %s\n", name);
return 0;
}
when attached to kprobe do_execve()
will produce output in /sys/kernel/debug/tracing/trace_pipe :
make-13492 [002] d..1 3250.997277: : executed /bin/sh
sh-13493 [004] d..1 3250.998716: : executed /usr/bin/gcc
gcc-13494 [002] d..1 3250.999822: : executed /usr/lib/gcc/x86_64-linux-gnu/4.7/cc1
gcc-13495 [002] d..1 3251.006731: : executed /usr/bin/as
gcc-13496 [002] d..1 3251.011831: : executed /usr/lib/gcc/x86_64-linux-gnu/4.7/collect2
collect2-13497 [000] d..1 3251.012941: : executed /usr/bin/ld
Suggested-by: Brendan Gregg <brendan.d.gregg@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>