Commit f663a03c authored by Leon Hwang's avatar Leon Hwang Committed by Alexei Starovoitov
Browse files

bpf, x64: Remove tail call detection 



As 'prog->aux->tail_call_reachable' is correct for tail call present,
it's unnecessary to detect tail call in x86 jit.

Therefore, let's remove it.

Signed-off-by: default avatarLeon Hwang <hffilwlqm@gmail.com>
Link: https://lore.kernel.org/r/20240610124224.34673-3-hffilwlqm@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 01793ed8

arch/x86/net/bpf_jit_comp.c

+2 −9
Original line number Diff line number Diff line
@@ -1234,13 +1234,11 @@ bool ex_handler_bpf(const struct exception_table_entry *x, struct pt_regs *regs) 
}



static void detect_reg_usage(struct bpf_insn *insn, int insn_cnt,

			     bool *regs_used, bool *tail_call_seen)

			     bool *regs_used)

{

	int i;



	for (i = 1; i <= insn_cnt; i++, insn++) {

		if (insn->code == (BPF_JMP | BPF_TAIL_CALL))

			*tail_call_seen = true;

		if (insn->dst_reg == BPF_REG_6 || insn->src_reg == BPF_REG_6)

			regs_used[0] = true;

		if (insn->dst_reg == BPF_REG_7 || insn->src_reg == BPF_REG_7)
@@ -1324,7 +1322,6 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image 
	struct bpf_insn *insn = bpf_prog->insnsi;

	bool callee_regs_used[4] = {};

	int insn_cnt = bpf_prog->len;

	bool tail_call_seen = false;

	bool seen_exit = false;

	u8 temp[BPF_MAX_INSN_SIZE + BPF_INSN_SAFETY];

	u64 arena_vm_start, user_vm_start;
@@ -1336,11 +1333,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image 
	arena_vm_start = bpf_arena_get_kern_vm_start(bpf_prog->aux->arena);

	user_vm_start = bpf_arena_get_user_vm_start(bpf_prog->aux->arena);



	detect_reg_usage(insn, insn_cnt, callee_regs_used,

			 &tail_call_seen);



	/* tail call's presence in current prog implies it is reachable */

	tail_call_reachable |= tail_call_seen;

	detect_reg_usage(insn, insn_cnt, callee_regs_used);



	emit_prologue(&prog, bpf_prog->aux->stack_depth,

		      bpf_prog_was_classic(bpf_prog), tail_call_reachable,