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| author | Alexei Starovoitov <ast@plumgrid.com> | 2015-08-29 00:56:23 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-08-29 01:27:27 +0200 |
| commit | 8d3b7dce8622919da5c5822ef7338d6604c9fe6e (patch) | |
| tree | 8934c8b0f6aac4a01488c59c45b8dc55c64cc721 /kernel/trace | |
| parent | lib: introduce strncpy_from_unsafe() (diff) | |
| download | linux-8d3b7dce8622919da5c5822ef7338d6604c9fe6e.tar.xz linux-8d3b7dce8622919da5c5822ef7338d6604c9fe6e.zip | |
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>
Diffstat (limited to '')
| -rw-r--r-- | kernel/trace/bpf_trace.c | 32 |
1 files changed, 30 insertions, 2 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index ef9936df1b04..0fe96c7c8803 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -81,13 +81,16 @@ static const struct bpf_func_proto bpf_probe_read_proto = { /* * limited trace_printk() - * only %d %u %x %ld %lu %lx %lld %llu %llx %p conversion specifiers allowed + * only %d %u %x %ld %lu %lx %lld %llu %llx %p %s conversion specifiers allowed */ static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5) { char *fmt = (char *) (long) r1; + bool str_seen = false; int mod[3] = {}; int fmt_cnt = 0; + u64 unsafe_addr; + char buf[64]; int i; /* @@ -114,12 +117,37 @@ static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5) if (fmt[i] == 'l') { mod[fmt_cnt]++; i++; - } else if (fmt[i] == 'p') { + } else if (fmt[i] == 'p' || fmt[i] == 's') { mod[fmt_cnt]++; i++; if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0) return -EINVAL; fmt_cnt++; + if (fmt[i - 1] == 's') { + if (str_seen) + /* allow only one '%s' per fmt string */ + return -EINVAL; + str_seen = true; + + switch (fmt_cnt) { + case 1: + unsafe_addr = r3; + r3 = (long) buf; + break; + case 2: + unsafe_addr = r4; + r4 = (long) buf; + break; + case 3: + unsafe_addr = r5; + r5 = (long) buf; + break; + } + buf[0] = 0; + strncpy_from_unsafe(buf, + (void *) (long) unsafe_addr, + sizeof(buf)); + } continue; } |