[PATCH net-next 13/15] nfp: bpf: pad code with valid nops

[Jakub Kicinski]

We need to append up to 8 nops after last instruction to make
sure the CPU will not fetch garbage instructions with invalid
ECC if the code store was not initialized.

Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.com>
Reviewed-by: Simon Horman <simon.hor...@netronome.com>
---
 drivers/net/ethernet/netronome/nfp/bpf/jit.c | 12 +++++++++++-
 drivers/net/ethernet/netronome/nfp/nfp_asm.h |  2 ++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/jit.c 
b/drivers/net/ethernet/netronome/nfp/bpf/jit.c
index f4aedc89bfc8..e0600d037773 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/jit.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/jit.c
@@ -426,6 +426,11 @@ emit_ld_field(struct nfp_prog *nfp_prog, swreg dst, u8 
bmask, swreg src,
        emit_ld_field_any(nfp_prog, sc, shift, dst, bmask, src, false);
 }
 
+static void emit_nop(struct nfp_prog *nfp_prog)
+{
+       __emit_immed(nfp_prog, UR_REG_IMM, UR_REG_IMM, 0, 0, 0, 0, 0, 0, 0);
+}
+
 /* --- Wrappers --- */
 static bool pack_immed(u32 imm, u16 *val, enum immed_shift *shift)
 {
@@ -1550,7 +1555,7 @@ static void nfp_outro(struct nfp_prog *nfp_prog)
 static int nfp_translate(struct nfp_prog *nfp_prog)
 {
        struct nfp_insn_meta *meta;
-       int err;
+       int i, err;
 
        nfp_intro(nfp_prog);
        if (nfp_prog->error)
@@ -1582,6 +1587,11 @@ static int nfp_translate(struct nfp_prog *nfp_prog)
        if (nfp_prog->error)
                return nfp_prog->error;
 
+       for (i = 0; i < NFP_USTORE_PREFETCH_WINDOW; i++)
+               emit_nop(nfp_prog);
+       if (nfp_prog->error)
+               return nfp_prog->error;
+
        return nfp_fixup_branches(nfp_prog);
 }
 
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_asm.h 
b/drivers/net/ethernet/netronome/nfp/nfp_asm.h
index d95087e5fb73..c4c18dd5630a 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_asm.h
+++ b/drivers/net/ethernet/netronome/nfp/nfp_asm.h
@@ -362,6 +362,8 @@ int swreg_to_unrestricted(swreg dst, swreg lreg, swreg rreg,
 int swreg_to_restricted(swreg dst, swreg lreg, swreg rreg,
                        struct nfp_insn_re_regs *reg, bool has_imm8);
 
+#define NFP_USTORE_PREFETCH_WINDOW     8
+
 int nfp_ustore_check_valid_no_ecc(u64 insn);
 u64 nfp_ustore_calc_ecc_insn(u64 insn);
 
-- 
2.14.1