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bpf, arm64: Add support for lse atomics in bpf_arena

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When LSE atomics are available, BPF atomic instructions are implemented
as single ARM64 atomic instructions, therefore it is easy to enable
these in bpf_arena using the currently available exception handling
setup.

LL_SC atomics use loops and therefore would need more work to enable in
bpf_arena.

Enable LSE atomics based instructions in bpf_arena and use the
bpf_jit_supports_insn() callback to reject atomics in bpf_arena if LSE
atomics are not available.

All atomics and arena_atomics selftests are passing:

  [root@ip-172-31-2-216 bpf]# ./test_progs -a atomics,arena_atomics
  #3/1     arena_atomics/add:OK
  #3/2     arena_atomics/sub:OK
  #3/3     arena_atomics/and:OK
  #3/4     arena_atomics/or:OK
  #3/5     arena_atomics/xor:OK
  #3/6     arena_atomics/cmpxchg:OK
  #3/7     arena_atomics/xchg:OK
  #3       arena_atomics:OK
  #10/1    atomics/add:OK
  #10/2    atomics/sub:OK
  #10/3    atomics/and:OK
  #10/4    atomics/or:OK
  #10/5    atomics/xor:OK
  #10/6    atomics/cmpxchg:OK
  #10/7    atomics/xchg:OK
  #10      atomics:OK
  Summary: 2/14 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Link: https://lore.kernel.org/r/20240426161116.441-1-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Puranjay Mohan 2024-04-26 16:11:16 +00:00 committed by Alexei Starovoitov
parent 7e2c7a3f73
commit e612b5c1d3
2 changed files with 40 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
arch/arm64/net/bpf_jit_comp.c
View File

@ -494,20 +494,26 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
static int emit_lse_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
{
const u8 code = insn->code;
const u8 arena_vm_base = bpf2a64[ARENA_VM_START];
const u8 dst = bpf2a64[insn->dst_reg];
const u8 src = bpf2a64[insn->src_reg];
const u8 tmp = bpf2a64[TMP_REG_1];
const u8 tmp2 = bpf2a64[TMP_REG_2];
const bool isdw = BPF_SIZE(code) == BPF_DW;
const bool arena = BPF_MODE(code) == BPF_PROBE_ATOMIC;
const s16 off = insn->off;
u8 reg;
u8 reg = dst;
if (!off) {
reg = dst;
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_ADD(1, tmp, tmp, dst), ctx);
reg = tmp;
if (off || arena) {
if (off) {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_ADD(1, tmp, tmp, dst), ctx);
reg = tmp;
}
if (arena) {
emit(A64_ADD(1, tmp, reg, arena_vm_base), ctx);
reg = tmp;
}
}
switch (insn->imm) {
@ -576,6 +582,12 @@ static int emit_ll_sc_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
u8 reg;
s32 jmp_offset;
if (BPF_MODE(code) == BPF_PROBE_ATOMIC) {
/* ll_sc based atomics don't support unsafe pointers yet. */
pr_err_once("unknown atomic opcode %02x\n", code);
return -EINVAL;
}
if (!off) {
reg = dst;
} else {
@ -777,7 +789,8 @@ static int add_exception_handler(const struct bpf_insn *insn,
if (BPF_MODE(insn->code) != BPF_PROBE_MEM &&
BPF_MODE(insn->code) != BPF_PROBE_MEMSX &&
BPF_MODE(insn->code) != BPF_PROBE_MEM32)
BPF_MODE(insn->code) != BPF_PROBE_MEM32 &&
BPF_MODE(insn->code) != BPF_PROBE_ATOMIC)
return 0;
if (!ctx->prog->aux->extable ||
@ -1474,12 +1487,18 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
case BPF_STX | BPF_ATOMIC | BPF_W:
case BPF_STX | BPF_ATOMIC | BPF_DW:
case BPF_STX | BPF_PROBE_ATOMIC | BPF_W:
case BPF_STX | BPF_PROBE_ATOMIC | BPF_DW:
if (cpus_have_cap(ARM64_HAS_LSE_ATOMICS))
ret = emit_lse_atomic(insn, ctx);
else
ret = emit_ll_sc_atomic(insn, ctx);
if (ret)
return ret;
ret = add_exception_handler(insn, ctx, dst);
if (ret)
return ret;
break;
default:
@ -2527,6 +2546,19 @@ bool bpf_jit_supports_arena(void)
return true;
}
bool bpf_jit_supports_insn(struct bpf_insn *insn, bool in_arena)
{
if (!in_arena)
return true;
switch (insn->code) {
case BPF_STX | BPF_ATOMIC | BPF_W:
case BPF_STX | BPF_ATOMIC | BPF_DW:
if (!cpus_have_cap(ARM64_HAS_LSE_ATOMICS))
return false;
}
return true;
}
void bpf_jit_free(struct bpf_prog *prog)
{
if (prog->jited) {

1
tools/testing/selftests/bpf/DENYLIST.aarch64
View File

@ -10,4 +10,3 @@ fill_link_info/kprobe_multi_link_info # bpf_program__attach_kprobe_mu
fill_link_info/kretprobe_multi_link_info # bpf_program__attach_kprobe_multi_opts unexpected error: -95
fill_link_info/kprobe_multi_invalid_ubuff # bpf_program__attach_kprobe_multi_opts unexpected error: -95
missed/kprobe_recursion # missed_kprobe_recursion__attach unexpected error: -95 (errno 95)
arena_atomics