[PATCH bpf-next v3 1/9] arm32, bpf: add support for 32-bit offset jmp instruction

Puranjay Mohan
2023-09-07T23:05:58Z

The cpuv4 adds unconditional jump with 32-bit offset where the immediate
field of the instruction is to be used to calculate the jump offset.

BPF_JA | BPF_K | BPF_JMP32 => gotol +imm => PC += imm.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
arch/arm/net/bpf_jit_32.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index 6a1c9fca5260..c03600fe86f6 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -1761,10 +1761,15 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx)
break;
/* JMP OFF */
case BPF_JMP | BPF_JA:
+ case BPF_JMP32 | BPF_JA:
{
- if (off == 0)
+ if (BPF_CLASS(code) == BPF_JMP32 && imm != 0)
+ jmp_offset = bpf2a32_offset(i + imm, i, ctx);
+ else if (BPF_CLASS(code) == BPF_JMP && off != 0)
+ jmp_offset = bpf2a32_offset(i + off, i, ctx);
+ else
break;
- jmp_offset = bpf2a32_offset(i+off, i, ctx);
+
check_imm24(jmp_offset);
emit(ARM_B(jmp_offset), ctx);
break;
--
2.39.2