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riscv, bpf: Add support for far jumps and exits 

This commit add support for far (offset > 21b) jumps and exits.

Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Luke Nelson <lukenels@cs.washington.edu>
Link: https://lore.kernel.org/bpf/20191216091343.23260-5-bjorn.topel@gmail.com
This commit is contained in:
Björn Töpel 2019-12-16 10:13:38 +01:00 committed by Daniel Borkmann
parent 29d92edd9e
commit 33203c02f2
1 changed files with 17 additions and 20 deletions
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37
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_21b_check(int off, int insn)
{
if (!is_21b_int(off)) {
pr_err("bpf-jit: insn=%d 21b < offset=%d not supported yet!\n",
insn, (int)off);
return -1;
}
return 0;
}
static void emit_imm(u8 rd, s64 val, struct rv_jit_context *ctx)
{
/* Note that the immediate from the add is sign-extended,
@ -820,6 +810,21 @@ static void emit_sext_32_rd(u8 *rd, struct rv_jit_context *ctx)
*rd = RV_REG_T2;
}
static void emit_jump_and_link(u8 rd, int rvoff, struct rv_jit_context *ctx)
{
s64 upper, lower;
if (is_21b_int(rvoff)) {
emit(rv_jal(rd, rvoff >> 1), ctx);
return;
}
upper = (rvoff + (1 << 11)) >> 12;
lower = rvoff & 0xfff;
emit(rv_auipc(RV_REG_T1, upper), ctx);
emit(rv_jalr(rd, RV_REG_T1, lower), ctx);
}
static bool is_signed_bpf_cond(u8 cond)
{
return cond == BPF_JSGT || cond == BPF_JSLT ||
@ -1101,13 +1106,7 @@ out_be:
/* JUMP off */
case BPF_JMP | BPF_JA:
rvoff = rv_offset(i, off, ctx);
if (!is_21b_int(rvoff)) {
pr_err("bpf-jit: insn=%d offset=%d not supported yet!\n",
i, rvoff);
return -1;
}
emit(rv_jal(RV_REG_ZERO, rvoff >> 1), ctx);
emit_jump_and_link(RV_REG_ZERO, rvoff, ctx);
break;
/* IF (dst COND src) JUMP off */
@ -1245,9 +1244,7 @@ out_be:
break;
rvoff = epilogue_offset(ctx);
if (is_21b_check(rvoff, i))
return -1;
emit(rv_jal(RV_REG_ZERO, rvoff >> 1), ctx);
emit_jump_and_link(RV_REG_ZERO, rvoff, ctx);
break;
/* dst = imm64 */