The struct_ops system allows BPF monitors to be assigned reactors transparently, but calling rv_react() is something the monitors should do and BPF monitors cannot, as well as they cannot easily get a pointer to the rv_monitor structure.
Add a bpf_rv_react kfunc that finds the monitor pointer given its name and triggers a reaction. Since variadic functions are complicated in BPF, this kfunc receives a plain string, that should be populated by the caller with some sort of sprintf(). Signed-off-by: Gabriele Monaco <[email protected]> --- kernel/trace/rv/rv_bpf.c | 62 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 59 insertions(+), 3 deletions(-) diff --git a/kernel/trace/rv/rv_bpf.c b/kernel/trace/rv/rv_bpf.c index 0450bcaf1b79..90ac7af1edff 100644 --- a/kernel/trace/rv/rv_bpf.c +++ b/kernel/trace/rv/rv_bpf.c @@ -13,7 +13,9 @@ #include <linux/btf.h> #include <linux/btf_ids.h> #include <linux/filter.h> +#include <linux/uaccess.h> #include <linux/rv.h> +#include "rv.h" static int bpf_rv_monitor_init(struct btf *btf) { @@ -111,8 +113,62 @@ static struct bpf_struct_ops bpf_rv_monitor_ops = { .owner = THIS_MODULE, }; -static int __init bpf_rv_monitor_init_ops(void) +__bpf_kfunc_start_defs(); + +/** + * bpf_rv_react - trigger a reactor from BPF + * @name: monitor name + * @msg: pre-formatted message string + * @msg__sz: size of the msg buffer + * + * This kfunc allows BPF monitors to trigger reactors with a message. + * The message should be pre-formatted by the BPF program using bpf_snprintf. + */ +__bpf_kfunc void bpf_rv_react(char *name__str, char *msg, u32 msg__sz) +{ + struct rv_monitor *monitor; + char safe_msg[256]; + + if (msg__sz == 0) + return; + msg__sz = min_t(u32, msg__sz, sizeof(safe_msg)); + if (strncpy_from_kernel_nofault(safe_msg, msg, msg__sz) < 0) + return; + safe_msg[msg__sz - 1] = '\0'; + + guard(rcu)(); + monitor = rv_get_monitor_by_name(name__str); + + if (monitor) + rv_react(monitor, "%s", safe_msg); +} + +__bpf_kfunc_end_defs(); + +BTF_KFUNCS_START(rv_kfunc_set_ids) +BTF_ID_FLAGS(func, bpf_rv_react) +BTF_KFUNCS_END(rv_kfunc_set_ids) + +static const struct btf_kfunc_id_set rv_kfunc_set = { + .owner = THIS_MODULE, + .set = &rv_kfunc_set_ids, +}; + +static int __init rv_monitor_init_bpf(void) { - return register_bpf_struct_ops(&bpf_rv_monitor_ops, rv_monitor); + int ret; + + ret = register_bpf_struct_ops(&bpf_rv_monitor_ops, rv_monitor); + if (ret) { + pr_err("rv: Failed to register struct_ops (%pe)\n", ERR_PTR(ret)); + return ret; + } + + ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &rv_kfunc_set); + if (ret) { + pr_err("rv: Failed to register reactor kfunc (%pe)\n", ERR_PTR(ret)); + return ret; + } + return 0; } -late_initcall(bpf_rv_monitor_init_ops); +late_initcall(rv_monitor_init_bpf); -- 2.55.0
