Commit 96bc4432 authored Dec 09, 2019 by Paul Chaignon Committed by Daniel Borkmann Dec 11, 2019

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: Mahshid Khezri <khezri.mahshid@gmail.com>
Signed-off-by: Paul Chaignon <paul.chaignon@orange.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/966fe384383bf23a0ee1efe8d7291c78a3fb832b.1575916815.git.paul.chaignon@gmail.com

parent 24dee0c7

arch/riscv/net/bpf_jit_comp.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -631,14 +631,14 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx)
		return -1;
		emit(rv_bgeu(RV_REG_A2, RV_REG_T1, off >> 1), ctx);

		/* if (--TCC < 0)
		/* if (TCC-- < 0)
		* goto out;
		*/
		emit(rv_addi(RV_REG_T1, tcc, -1), ctx);
		off = (tc_ninsn - (ctx->ninsns - start_insn)) << 2;
		if (is_13b_check(off, insn))
		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];
		* if (!prog)

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