Commit 1e37392c authored by Jiri Olsa's avatar Jiri Olsa Committed by Alexei Starovoitov
Browse files

bpf: Enable BPF_TRAMP_F_IP_ARG for trampolines with call_get_func_ip 



Enabling BPF_TRAMP_F_IP_ARG for trampolines that actually need it.

The BPF_TRAMP_F_IP_ARG adds extra 3 instructions to trampoline code
and is used only by programs with bpf_get_func_ip helper, which is
added in following patch and sets call_get_func_ip bit.

This patch ensures that BPF_TRAMP_F_IP_ARG flag is used only for
trampolines that have programs with call_get_func_ip set.

Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210714094400.396467-3-jolsa@kernel.org
parent 7e6f3cd8

include/linux/filter.h

+2 −1
Original line number Diff line number Diff line
@@ -559,7 +559,8 @@ struct bpf_prog { 
				kprobe_override:1, /* Do we override a kprobe? */

				has_callchain_buf:1, /* callchain buffer allocated? */

				enforce_expected_attach_type:1, /* Enforce expected_attach_type checking at attach time */

				call_get_stack:1; /* Do we call bpf_get_stack() or bpf_get_stackid() */

				call_get_stack:1, /* Do we call bpf_get_stack() or bpf_get_stackid() */

				call_get_func_ip:1; /* Do we call get_func_ip() */

	enum bpf_prog_type	type;		/* Type of BPF program */

	enum bpf_attach_type	expected_attach_type; /* For some prog types */

	u32			len;		/* Number of filter blocks */

kernel/bpf/trampoline.c

+9 −3
Original line number Diff line number Diff line
@@ -172,7 +172,7 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr) 
}



static struct bpf_tramp_progs *

bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total)

bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_arg)

{

	const struct bpf_prog_aux *aux;

	struct bpf_tramp_progs *tprogs;
@@ -189,9 +189,11 @@ bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total) 
		*total += tr->progs_cnt[kind];

		progs = tprogs[kind].progs;



		hlist_for_each_entry(aux, &tr->progs_hlist[kind], tramp_hlist)

		hlist_for_each_entry(aux, &tr->progs_hlist[kind], tramp_hlist) {

			*ip_arg |= aux->prog->call_get_func_ip;

			*progs++ = aux->prog;

		}

	}

	return tprogs;

}
@@ -333,9 +335,10 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr) 
	struct bpf_tramp_image *im;

	struct bpf_tramp_progs *tprogs;

	u32 flags = BPF_TRAMP_F_RESTORE_REGS;

	bool ip_arg = false;

	int err, total;



	tprogs = bpf_trampoline_get_progs(tr, &total);

	tprogs = bpf_trampoline_get_progs(tr, &total, &ip_arg);

	if (IS_ERR(tprogs))

		return PTR_ERR(tprogs);
@@ -357,6 +360,9 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr) 
	    tprogs[BPF_TRAMP_MODIFY_RETURN].nr_progs)

		flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;



	if (ip_arg)

		flags |= BPF_TRAMP_F_IP_ARG;



	err = arch_prepare_bpf_trampoline(im, im->image, im->image + PAGE_SIZE,

					  &tr->func.model, flags, tprogs,

					  tr->func.addr);