From: Dave Marchevsky <davemarchevsky@fb.com>
Date: Fri, 17 Sep 2021 11:29:05 -0700
Subject: bpf: Add bpf_trace_vprintk helper
Patch-mainline: v5.16-rc1
Git-commit: 10aceb629e198429c849d5e995c3bb1ba7a9aaa3
References: jsc#PED-1377
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. The functionality of this helper was
requested in the libbpf issue tracker [0].
[0] Closes: https://github.com/libbpf/libbpf/issues/315
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210917182911.2426606-4-davemarchevsky@fb.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
include/linux/bpf.h | 1
include/uapi/linux/bpf.h | 11 ++++++++
kernel/bpf/core.c | 5 +++
kernel/bpf/helpers.c | 2 +
kernel/trace/bpf_trace.c | 52 ++++++++++++++++++++++++++++++++++++++++-
tools/include/uapi/linux/bpf.h | 11 ++++++++
6 files changed, 81 insertions(+), 1 deletion(-)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1093,6 +1093,7 @@ bool bpf_prog_array_compatible(struct bp
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);
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4898,6 +4898,16 @@ union bpf_attr {
* **-EINVAL** if *flags* is not zero.
*
* **-ENOENT** if architecture does not support branch records.
+ *
+ * long bpf_trace_vprintk(const char *fmt, u32 fmt_size, const void *data, u32 data_len)
+ * Description
+ * Behaves like **bpf_trace_printk**\ () helper, but takes an array of u64
+ * to format and can handle more format args as a result.
+ *
+ * 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.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5077,6 +5087,7 @@ union bpf_attr {
FN(get_attach_cookie), \
FN(task_pt_regs), \
FN(get_branch_snapshot), \
+ FN(trace_vprintk), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2365,6 +2365,11 @@ const struct bpf_func_proto * __weak bpf
return NULL;
}
+const struct bpf_func_proto * __weak bpf_get_trace_vprintk_proto(void)
+{
+ return NULL;
+}
+
u64 __weak
bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy)
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1435,6 +1435,8 @@ bpf_base_func_proto(enum bpf_func_id fun
return &bpf_snprintf_proto;
case BPF_FUNC_task_pt_regs:
return &bpf_task_pt_regs_proto;
+ case BPF_FUNC_trace_vprintk:
+ return bpf_get_trace_vprintk_proto();
default:
return NULL;
}
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -398,7 +398,7 @@ static const struct bpf_func_proto bpf_t
.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_tra
*/
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;
+
+ 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;
+}
+
+static const struct bpf_func_proto bpf_trace_vprintk_proto = {
+ .func = bpf_trace_vprintk,
+ .gpl_only = true,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_MEM,
+ .arg2_type = ARG_CONST_SIZE,
+ .arg3_type = ARG_PTR_TO_MEM_OR_NULL,
+ .arg4_type = ARG_CONST_SIZE_OR_ZERO,
+};
+
+const struct bpf_func_proto *bpf_get_trace_vprintk_proto(void)
+{
+ __set_printk_clr_event();
+ return &bpf_trace_vprintk_proto;
+}
+
BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size,
const void *, data, u32, data_len)
{
@@ -1160,6 +1208,8 @@ bpf_tracing_func_proto(enum bpf_func_id
return &bpf_get_func_ip_proto_tracing;
case BPF_FUNC_get_branch_snapshot:
return &bpf_get_branch_snapshot_proto;
+ case BPF_FUNC_trace_vprintk:
+ return bpf_get_trace_vprintk_proto();
default:
return bpf_base_func_proto(func_id);
}
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4901,6 +4901,16 @@ union bpf_attr {
* **-EINVAL** if *flags* is not zero.
*
* **-ENOENT** if architecture does not support branch records.
+ *
+ * long bpf_trace_vprintk(const char *fmt, u32 fmt_size, const void *data, u32 data_len)
+ * Description
+ * Behaves like **bpf_trace_printk**\ () helper, but takes an array of u64
+ * to format and can handle more format args as a result.
+ *
+ * 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.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5080,6 +5090,7 @@ union bpf_attr {
FN(get_attach_cookie), \
FN(task_pt_regs), \
FN(get_branch_snapshot), \
+ FN(trace_vprintk), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper