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Commit e240f26a authored by Paul Chaignon's avatar Paul Chaignon Committed by Greg Kroah-Hartman
Browse files

bpf, mips: Limit to 33 tail calls 



[ Upstream commit e49e6f6db04e915dccb494ae10fa14888fea6f89 ]

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 MIPS' JIT compiler to allow
33 tail calls.

Fixes: b6bd53f9 ("MIPS: Add missing file for eBPF JIT.")
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 avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/b8eb2caac1c25453c539248e56ca22f74b5316af.1575916815.git.paul.chaignon@gmail.com


Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 4bf973a1

arch/mips/net/ebpf_jit.c

+5 −4
Original line number Diff line number Diff line
@@ -586,6 +586,7 @@ static void emit_const_to_reg(struct jit_ctx *ctx, int dst, u64 value) 
static int emit_bpf_tail_call(struct jit_ctx *ctx, int this_idx)

{

	int off, b_off;

	int tcc_reg;



	ctx->flags |= EBPF_SEEN_TC;

	/*
@@ -598,14 +599,14 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int this_idx) 
	b_off = b_imm(this_idx + 1, ctx);

	emit_instr(ctx, bne, MIPS_R_AT, MIPS_R_ZERO, b_off);

	/*

	 * if (--TCC < 0)

	 * if (TCC-- < 0)

	 *     goto out;

	 */

	/* Delay slot */

	emit_instr(ctx, daddiu, MIPS_R_T5,

		   (ctx->flags & EBPF_TCC_IN_V1) ? MIPS_R_V1 : MIPS_R_S4, -1);

	tcc_reg = (ctx->flags & EBPF_TCC_IN_V1) ? MIPS_R_V1 : MIPS_R_S4;

	emit_instr(ctx, daddiu, MIPS_R_T5, tcc_reg, -1);

	b_off = b_imm(this_idx + 1, ctx);

	emit_instr(ctx, bltz, MIPS_R_T5, b_off);

	emit_instr(ctx, bltz, tcc_reg, b_off);

	/*

	 * prog = array->ptrs[index];

	 * if (prog == NULL)