Commit 96bc4432 authored by Paul Chaignon's avatar Paul Chaignon Committed by Daniel Borkmann

bpf, riscv: Limit to 33 tail calls

All BPF JIT compilers except RISC-V's and MIPS' enforce a 33-tail calls
limit at runtime.  In addition, a test was recently added, in tailcalls2,
to check this limit.

This patch updates the tail call limit in RISC-V's JIT compiler to allow
33 tail calls.  I tested it using the above selftest on an emulated
RISCV64.

Fixes: 2353ecc6 ("bpf, riscv: add BPF JIT for RV64G")
Reported-by: default avatarMahshid Khezri <khezri.mahshid@gmail.com>
Signed-off-by: default avatarPaul Chaignon <paul.chaignon@orange.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarBjörn Töpel <bjorn.topel@gmail.com>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/966fe384383bf23a0ee1efe8d7291c78a3fb832b.1575916815.git.paul.chaignon@gmail.com
parent 24dee0c7
...@@ -631,14 +631,14 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx) ...@@ -631,14 +631,14 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx)
return -1; return -1;
emit(rv_bgeu(RV_REG_A2, RV_REG_T1, off >> 1), ctx); emit(rv_bgeu(RV_REG_A2, RV_REG_T1, off >> 1), ctx);
/* if (--TCC < 0) /* if (TCC-- < 0)
* goto out; * goto out;
*/ */
emit(rv_addi(RV_REG_T1, tcc, -1), ctx); emit(rv_addi(RV_REG_T1, tcc, -1), ctx);
off = (tc_ninsn - (ctx->ninsns - start_insn)) << 2; off = (tc_ninsn - (ctx->ninsns - start_insn)) << 2;
if (is_13b_check(off, insn)) if (is_13b_check(off, insn))
return -1; return -1;
emit(rv_blt(RV_REG_T1, RV_REG_ZERO, off >> 1), ctx); emit(rv_blt(tcc, RV_REG_ZERO, off >> 1), ctx);
/* prog = array->ptrs[index]; /* prog = array->ptrs[index];
* if (!prog) * if (!prog)
......
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