[...]
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index c3458ec1f30a..670998635eac 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3817,6 +3817,21 @@ union bpf_attr {
> * The **hash_algo** is returned on success,
> * **-EOPNOTSUP** if IMA is disabled or **-EINVAL** if
> * invalid arguments are passed.
> + *
> + * long bpf_kallsyms_lookup(u64 address, char *symbol, u32 symbol_size, char
> *module, u32 module_size)
> + * Description
> + * Uses kallsyms to write the name of the symbol at *address*
> + * into *symbol* of size *symbol_sz*. This is guaranteed to be
> + * zero terminated.
> + * If the symbol is in a module, up to *module_size* bytes of
> + * the module name is written in *module*. This is also
> + * guaranteed to be zero-terminated. Note: a module name
> + * is always shorter than 64 bytes.
> + * Return
> + * On success, the strictly positive length of the full symbol
> + * name, If this is greater than *symbol_size*, the written
> + * symbol is truncated.
> + * On error, a negative value.
> */
> #define __BPF_FUNC_MAPPER(FN) \
> FN(unspec), \
> @@ -3981,6 +3996,7 @@ union bpf_attr {
> FN(bprm_opts_set), \
> FN(ktime_get_coarse_ns), \
> FN(ima_inode_hash), \
> + FN(kallsyms_lookup), \
> /* */
>
> /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index d255bc9b2bfa..9d86e20c2b13 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -17,6 +17,7 @@
> #include <linux/error-injection.h>
> #include <linux/btf_ids.h>
> #include <linux/bpf_lsm.h>
> +#include <linux/kallsyms.h>
>
> #include <net/bpf_sk_storage.h>
>
> @@ -1260,6 +1261,44 @@ const struct bpf_func_proto bpf_snprintf_btf_proto = {
> .arg5_type = ARG_ANYTHING,
> };
>
> +BPF_CALL_5(bpf_kallsyms_lookup, u64, address, char *, symbol, u32,
> symbol_size,
> + char *, module, u32, module_size)
> +{
> + char buffer[KSYM_SYMBOL_LEN];
> + unsigned long offset, size;
> + const char *name;
> + char *modname;
> + long ret;
> +
> + name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
> + if (!name)
> + return -EINVAL;
> +
> + ret = strlen(name) + 1;
> + if (symbol_size) {
> + strncpy(symbol, name, symbol_size);
> + symbol[symbol_size - 1] = '\0';
> + }
> +
> + if (modname && module_size) {
> + strncpy(module, modname, module_size);
The return value does not seem to be impacted by the truncation of the
module name, I wonder if it is better to just use a single buffer.
For example, the proc kallsyms shows symbols as:
<symbol_name> [module_name]
https://github.com/torvalds/linux/blob/master/kernel/kallsyms.c#L648
The square brackets do seem to be a waste here, so maybe we could use
a single character as a separator?
> + module[module_size - 1] = '\0';
> + }
> +
> + return ret;
> +}
> +
> +const struct bpf_func_proto bpf_kallsyms_lookup_proto = {
> + .func = bpf_kallsyms_lookup,
> + .gpl_only = false,
> + .ret_type = RET_INTEGER,
> + .arg1_type = ARG_ANYTHING,
> + .arg2_type = ARG_PTR_TO_MEM,
> + .arg3_type = ARG_CONST_SIZE,
> + .arg4_type = ARG_PTR_TO_MEM,
> + .arg5_type = ARG_CONST_SIZE,
> +};
> +
[...]
