Searched hist:ddb55992b04d9749e7c00af7f855e4e13566a521 (Results 1 – 1 of 1) sorted by relevance
/linux/arch/arm64/net/ |
H A D | bpf_jit.h | diff ddb55992b04d9749e7c00af7f855e4e13566a521 Thu Jun 09 06:18:48 CEST 2016 Zi Shen Lim <zlim.lnx@gmail.com> arm64: bpf: implement bpf_tail_call() helper
Add support for JMP_CALL_X (tail call) introduced by commit 04fd61ab36ec ("bpf: allow bpf programs to tail-call other bpf programs").
bpf_tail_call() arguments: ctx - context pointer passed to next program array - pointer to map which type is BPF_MAP_TYPE_PROG_ARRAY index - index inside array that selects specific program to run
In this implementation arm64 JIT jumps into callee program after prologue, so callee program reuses the same stack. For tail_call_cnt, we use the callee-saved R26 (which was already saved/restored but previously unused by JIT).
With this patch a tail call generates the following code on arm64:
if (index >= array->map.max_entries) goto out;
34: mov x10, #0x10 // #16 38: ldr w10, [x1,x10] 3c: cmp w2, w10 40: b.ge 0x0000000000000074
if (tail_call_cnt > MAX_TAIL_CALL_CNT) goto out; tail_call_cnt++;
44: mov x10, #0x20 // #32 48: cmp x26, x10 4c: b.gt 0x0000000000000074 50: add x26, x26, #0x1
prog = array->ptrs[index]; if (prog == NULL) goto out;
54: mov x10, #0x68 // #104 58: ldr x10, [x1,x10] 5c: ldr x11, [x10,x2] 60: cbz x11, 0x0000000000000074
goto *(prog->bpf_func + prologue_size);
64: mov x10, #0x20 // #32 68: ldr x10, [x11,x10] 6c: add x10, x10, #0x20 70: br x10 74:
Signed-off-by: Zi Shen Lim <zlim.lnx@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
|