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bpf, x64: Remove tail call detection

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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: Leon Hwang <hffilwlqm@gmail.com>
Link: https://lore.kernel.org/r/20240610124224.34673-3-hffilwlqm@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Leon Hwang 2024-06-10 20:42:24 +08:00 committed by Alexei Starovoitov
parent 01793ed86b
commit f663a03c8e
1 changed files with 2 additions and 9 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

11
arch/x86/net/bpf_jit_comp.c
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@ -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,