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// SPDX-License-Identifier: GPL-2.0
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include "bpf_misc.h"
struct {
__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
__uint(max_entries, 1);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(__u32));
} jmp_table SEC(".maps");
/* The tail call target sets up a 2 KiB frame of its own and uses both of its ends. */
SEC("tc")
__naked int classifier_0(void)
{
asm volatile (" \
r1 = 42; \
*(u64 *)(r10 - 2048) = r1; \
r1 = 7; \
*(u64 *)(r10 - 8) = r1; \
r0 = *(u64 *)(r10 - 2048); \
r1 = *(u64 *)(r10 - 8); \
r0 += r1; \
exit; \
" ::: __clobber_all);
}
/*
* The frame of the subprog doing the tail call is unwound by it, so it may be
* large; only the frames of its callers stay behind and are limited to 256
* bytes in total. Returns 1 when the tail call falls through.
*/
__used __naked
static int subprog_tail(void)
{
asm volatile (" \
r2 = 1; \
*(u64 *)(r10 - 1536) = r2; \
r2 = %[jmp_table] ll; \
r3 = 0; \
call %[bpf_tail_call]; \
r0 = 1; \
exit; \
" :
: __imm(bpf_tail_call),
__imm_addr(jmp_table)
: __clobber_all);
}
SEC("tc")
__naked int entry(void)
{
asm volatile (" \
r2 = 2; \
*(u64 *)(r10 - 240) = r2; \
call subprog_tail; \
exit; \
" ::: __clobber_all);
}
char _license[] SEC("license") = "GPL";
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