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LoongArch: BPF: Inline bpf_get_current_task/_btf() helpers

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The pointer to task_struct is always available in the $tp register, so
the calls to bpf_get_current_task() and bpf_get_current_task_btf() can
be inlined into a single move instruction.

(1) Here is the sample test.c:

  #include <linux/bpf.h>
  #include <bpf/bpf_helpers.h>

  SEC("raw_tp/sys_enter")
  long test_task(void *ctx)
  {
	  return (long)bpf_get_current_task();
  }
  char _license[] SEC("license") = "GPL";

(2) Here are the test steps:

  sudo yum install libbpf-devel kernel-devel bpftool
  clang -target bpf -O2 -c test.c -o test.o
  sudo sysctl -w net.core.bpf_jit_enable=1
  sudo bpftool prog show name test_task
  sudo rm -f /sys/fs/bpf/test_task
  sudo bpftool prog load test.o /sys/fs/bpf/test_task
  ID=$(sudo bpftool prog show pinned /sys/fs/bpf/test_task | grep -oE '^[0-9]+')
  sudo bpftool prog dump jited id $ID

(3) Here are the test results:

Before: 6 instructions

  ...
  64:	lu12i.w	$t1, 1093
  68:	ori	$t1, $t1, 3320
  6c:	lu32i.d	$t1, 0
  70:	lu52i.d	$t1, $t1, -1792
  74:	jirl	$ra, $t1, 0
  78:	move	$a5, $a0
  ...

After: 1 instruction

  ...
  64:	move	$a5, $tp
  ...

This is similar with commit 2bb138cb20 ("bpf, arm64: Inline
bpf_get_current_task/_btf() helpers").

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Tiezhu Yang 2026-06-25 13:03:53 +08:00 committed by Huacai Chen
parent 0379d10f09
commit 7f5c21fcd7
1 changed files with 18 additions and 0 deletions
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18
arch/loongarch/net/bpf_jit.c
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@ -1161,6 +1161,13 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
/* function call */
case BPF_JMP | BPF_CALL:
/* Implement helper call to bpf_get_current_task/_btf() inline */
if (insn->src_reg == 0 && (insn->imm == BPF_FUNC_get_current_task ||
insn->imm == BPF_FUNC_get_current_task_btf)) {
move_reg(ctx, regmap[BPF_REG_0], LOONGARCH_GPR_TP);
break;
}
ret = bpf_jit_get_func_addr(ctx->prog, insn, extra_pass,
&func_addr, &func_addr_fixed);
if (ret < 0)
@ -2381,3 +2388,14 @@ bool bpf_jit_supports_subprog_tailcalls(void)
{
return true;
}
bool bpf_jit_inlines_helper_call(s32 imm)
{
switch (imm) {
case BPF_FUNC_get_current_task:
case BPF_FUNC_get_current_task_btf:
return true;
default:
return false;
}
}