On 8/28/21 7:20 AM, Dave Marchevsky wrote:
This helper is meant to be "bpf_trace_printk, but with proper vararg
support". Follow bpf_snprintf's example and take a u64 pseudo-vararg
array. Write to /sys/kernel/debug/tracing/trace_pipe using the same
mechanism as bpf_trace_printk.
Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx>
lgtm, minor comments below:
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 9 ++++++
kernel/bpf/core.c | 5 ++++
kernel/bpf/helpers.c | 2 ++
kernel/trace/bpf_trace.c | 52 +++++++++++++++++++++++++++++++++-
tools/include/uapi/linux/bpf.h | 9 ++++++
6 files changed, 77 insertions(+), 1 deletion(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index be8d57e6e78a..b6c45a6cbbba 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1088,6 +1088,7 @@ bool bpf_prog_array_compatible(struct bpf_array *array, const struct bpf_prog *f
int bpf_prog_calc_tag(struct bpf_prog *fp);
const struct bpf_func_proto *bpf_get_trace_printk_proto(void);
+const struct bpf_func_proto *bpf_get_trace_vprintk_proto(void);
typedef unsigned long (*bpf_ctx_copy_t)(void *dst, const void *src,
unsigned long off, unsigned long len);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 791f31dd0abe..f171d4d33136 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4877,6 +4877,14 @@ union bpf_attr {
* Get the struct pt_regs associated with **task**.
* Return
* A pointer to struct pt_regs.
+ *
+ * u64 bpf_trace_vprintk(const char *fmt, u32 fmt_size, const void *data, u32 data_len)
s/u64/long/
+ * Description
+ * Behaves like **bpf_trace_printk**\ () helper, but takes an array of u64
nit: maybe for users it's more clear from description if you instead mention that data_len
needs to be multiple of 8 bytes? Or somehow mention the relation with data more clearly
resp. which shortcoming it addresses compared to bpf_trace_printk(), so developers can more
easily parse it.
+ * to format. Arguments are to be used as in **bpf_seq_printf**\ () helper.
+ * Return
+ * The number of bytes written to the buffer, or a negative error
+ * in case of failure.
*/
[...]
default:
return NULL;
}
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 10672ebc63b7..ea8358b0c748 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -398,7 +398,7 @@ static const struct bpf_func_proto bpf_trace_printk_proto = {
.arg2_type = ARG_CONST_SIZE,
};
-const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
+static void __set_printk_clr_event(void)
{
/*
* This program might be calling bpf_trace_printk,
@@ -410,10 +410,58 @@ const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
*/
if (trace_set_clr_event("bpf_trace", "bpf_trace_printk", 1))
pr_warn_ratelimited("could not enable bpf_trace_printk events");
+}
+const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
+{
+ __set_printk_clr_event();
return &bpf_trace_printk_proto;
}
+BPF_CALL_4(bpf_trace_vprintk, char *, fmt, u32, fmt_size, const void *, data,
+ u32, data_len)
+{
+ static char buf[BPF_TRACE_PRINTK_SIZE];
+ unsigned long flags;
+ int ret, num_args;
+ u32 *bin_args;
+
+ if (data_len & 7 || data_len > MAX_BPRINTF_VARARGS * 8 ||
+ (data_len && !data))
+ return -EINVAL;
+ num_args = data_len / 8;
+
+ ret = bpf_bprintf_prepare(fmt, fmt_size, data, &bin_args, num_args);
+ if (ret < 0)
+ return ret;
Given you have ARG_PTR_TO_MEM_OR_NULL for data, does this gracefully handle the
case where you pass in fmt string containing e.g. %ps but data being NULL? From
reading bpf_bprintf_prepare() looks like it does just fine, but might be nice
to explicitly add a tiny selftest case for it while you're at it.
+ raw_spin_lock_irqsave(&trace_printk_lock, flags);
+ ret = bstr_printf(buf, sizeof(buf), fmt, bin_args);
+
+ trace_bpf_trace_printk(buf);
+ raw_spin_unlock_irqrestore(&trace_printk_lock, flags);
+
+ bpf_bprintf_cleanup();
+
+ return ret;
+}
Thanks,
Daniel
