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riscv, bpf: Add support for far branching when emitting tail call

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Start use the emit_branch() function in the tail call emitter in order
to support far branching.

Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191216091343.23260-4-bjorn.topel@gmail.com
This commit is contained in:
Björn Töpel 2019-12-16 10:13:37 +01:00 committed by Daniel Borkmann
parent 7d1ef13fea
commit 29d92edd9e
1 changed files with 3 additions and 19 deletions
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22
arch/riscv/net/bpf_jit_comp.c
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@ -496,16 +496,6 @@ static int is_12b_check(int off, int insn)
return 0;
}
static int is_13b_check(int off, int insn)
{
if (!is_13b_int(off)) {
pr_err("bpf-jit: insn=%d 13b < offset=%d not supported yet!\n",
insn, (int)off);
return -1;
}
return 0;
}
static int is_21b_check(int off, int insn)
{
if (!is_21b_int(off)) {
@ -744,18 +734,14 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx)
return -1;
emit(rv_lwu(RV_REG_T1, off, RV_REG_A1), ctx);
off = (tc_ninsn - (ctx->ninsns - start_insn)) << 2;
if (is_13b_check(off, insn))
return -1;
emit(rv_bgeu(RV_REG_A2, RV_REG_T1, off >> 1), ctx);
emit_branch(BPF_JGE, RV_REG_A2, RV_REG_T1, off, ctx);
/* 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_branch(BPF_JSLT, RV_REG_T1, RV_REG_ZERO, off, ctx);
/* prog = array->ptrs[index];
* if (!prog)
@ -768,9 +754,7 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx)
return -1;
emit(rv_ld(RV_REG_T2, off, RV_REG_T2), ctx);
off = (tc_ninsn - (ctx->ninsns - start_insn)) << 2;
if (is_13b_check(off, insn))
return -1;
emit(rv_beq(RV_REG_T2, RV_REG_ZERO, off >> 1), ctx);
emit_branch(BPF_JEQ, RV_REG_T2, RV_REG_ZERO, off, ctx);
/* goto *(prog->bpf_func + 4); */
off = offsetof(struct bpf_prog, bpf_func);