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 dmesg using the same mechanism as bpf_trace_printk.
Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx>
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 23 +++++++++++++++
kernel/bpf/core.c | 5 ++++
kernel/bpf/helpers.c | 2 ++
kernel/trace/bpf_trace.c | 52 +++++++++++++++++++++++++++++++++-
tools/include/uapi/linux/bpf.h | 23 +++++++++++++++
6 files changed, 105 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 c4f7892edb2b..899a2649d986 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4871,6 +4871,28 @@ union bpf_attr {
* Return
* Value specified by user at BPF link creation/attachment time
* or 0, if it was not specified.
+ *
+ * u64 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. Supports up to 12 arguments to print in this way.
+ * The *fmt* and *fmt_size* are for the format string itself. The *data* and
+ * *data_len* are format string arguments.
+ *
+ * Each format specifier in **fmt** corresponds to one u64 element
+ * in the **data** array. For strings and pointers where pointees
+ * are accessed, only the pointer values are stored in the *data*
+ * array. The *data_len* is the size of *data* in bytes.
+ * Formats **%s**, **%p{i,I}{4,6}** requires to read kernel memory.
+ * Reading kernel memory may fail due to either invalid address or
+ * valid address but requiring a major memory fault. If reading kernel memory
+ * fails, the string for **%s** will be an empty string, and the ip
+ * address for **%p{i,I}{4,6}** will be 0. Not returning error to
+ * bpf program is consistent with what **bpf_trace_printk**\ () does for now.
+ *
+ * Return
+ * The number of bytes written to the buffer, or a negative error
+ * in case of failure.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5048,6 +5070,7 @@ union bpf_attr {
FN(timer_cancel), \
FN(get_func_ip), \
FN(get_attach_cookie), \
+ FN(trace_vprintk), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 91f24c7b38a1..a137c550046c 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2357,6 +2357,11 @@ const struct bpf_func_proto * __weak bpf_get_trace_printk_proto(void)
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)
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 5ce19b376ef7..863e5ee68558 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1419,6 +1419,8 @@ bpf_base_func_proto(enum bpf_func_id func_id)
return &bpf_snprintf_btf_proto;
case BPF_FUNC_snprintf:
return &bpf_snprintf_proto;
+ case BPF_FUNC_trace_vprintk:
+ return bpf_get_trace_vprintk_proto();
default:
return NULL;
}
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 2cf4bfa1ab7b..8b3f1ec9e082 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 __always_inline 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;
+
+ 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)
{
@@ -1113,6 +1161,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_snprintf_proto;
case BPF_FUNC_get_func_ip:
return &bpf_get_func_ip_proto_tracing;
+ case BPF_FUNC_trace_vprintk:
+ return bpf_get_trace_vprintk_proto();
default:
return bpf_base_func_proto(func_id);
}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index c4f7892edb2b..899a2649d986 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4871,6 +4871,28 @@ union bpf_attr {
* Return
* Value specified by user at BPF link creation/attachment time
* or 0, if it was not specified.
+ *
+ * u64 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. Supports up to 12 arguments to print in this way.
+ * The *fmt* and *fmt_size* are for the format string itself. The *data* and
+ * *data_len* are format string arguments.
+ *
+ * Each format specifier in **fmt** corresponds to one u64 element
+ * in the **data** array. For strings and pointers where pointees
+ * are accessed, only the pointer values are stored in the *data*
+ * array. The *data_len* is the size of *data* in bytes.
+ * Formats **%s**, **%p{i,I}{4,6}** requires to read kernel memory.
+ * Reading kernel memory may fail due to either invalid address or
+ * valid address but requiring a major memory fault. If reading kernel memory
+ * fails, the string for **%s** will be an empty string, and the ip
+ * address for **%p{i,I}{4,6}** will be 0. Not returning error to
+ * bpf program is consistent with what **bpf_trace_printk**\ () does for now.
+ *
+ * Return
+ * The number of bytes written to the buffer, or a negative error
+ * in case of failure.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5048,6 +5070,7 @@ union bpf_attr {
FN(timer_cancel), \
FN(get_func_ip), \
FN(get_attach_cookie), \
+ FN(trace_vprintk), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.30.2
