nfp: bpf: fix ALU32 high bits clearance bug [Linux 5.0]

This Linux kernel change "nfp: bpf: fix ALU32 high bits clearance bug" is included in the Linux 5.0 release. This change is authored by Jiong Wang <jiong.wang [at] netronome.com> on Fri Feb 22 22:36:04 2019 +0000. The commit for this change in Linux stable tree is f036ebd (patch).

nfp: bpf: fix ALU32 high bits clearance bug

NFP BPF JIT compiler is doing a couple of small optimizations when jitting
ALU imm instructions, some of these optimizations could save code-gen, for
example:

  A & -1 =  A
  A |  0 =  A
  A ^  0 =  A

However, for ALU32, high 32-bit of the 64-bit register should still be
cleared according to ISA semantics.

Fixes: cd7df56ed3e6 ("nfp: add BPF to NFP code translator")
Reviewed-by: Jakub Kicinski <[email protected]>
Signed-off-by: Jiong Wang <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>

There are 17 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/net/ethernet/netronome/nfp/bpf/jit.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/jit.c b/drivers/net/ethernet/netronome/nfp/bpf/jit.c
index a096965..0a868c8 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/jit.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/jit.c
@@ -1291,15 +1291,10 @@ static int construct_data_ld(struct nfp_prog *nfp_prog, u16 offset, u8 size)

 static int
 wrp_alu32_imm(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
-         enum alu_op alu_op, bool skip)
+         enum alu_op alu_op)
 {
    const struct bpf_insn *insn = &meta->insn;

-   if (skip) {
-       meta->skip = true;
-       return 0;
-   }
-
    wrp_alu_imm(nfp_prog, insn->dst_reg * 2, alu_op, insn->imm);
    wrp_immed(nfp_prog, reg_both(insn->dst_reg * 2 + 1), 0);

@@ -2309,7 +2304,7 @@ static int xor_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)

 static int xor_imm(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
-   return wrp_alu32_imm(nfp_prog, meta, ALU_OP_XOR, !meta->insn.imm);
+   return wrp_alu32_imm(nfp_prog, meta, ALU_OP_XOR);
 }

 static int and_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
@@ -2319,7 +2314,7 @@ static int and_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)

 static int and_imm(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
-   return wrp_alu32_imm(nfp_prog, meta, ALU_OP_AND, !~meta->insn.imm);
+   return wrp_alu32_imm(nfp_prog, meta, ALU_OP_AND);
 }

 static int or_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
@@ -2329,7 +2324,7 @@ static int or_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)

 static int or_imm(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
-   return wrp_alu32_imm(nfp_prog, meta, ALU_OP_OR, !meta->insn.imm);
+   return wrp_alu32_imm(nfp_prog, meta, ALU_OP_OR);
 }

 static int add_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
@@ -2339,7 +2334,7 @@ static int add_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)

 static int add_imm(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
-   return wrp_alu32_imm(nfp_prog, meta, ALU_OP_ADD, !meta->insn.imm);
+   return wrp_alu32_imm(nfp_prog, meta, ALU_OP_ADD);
 }

 static int sub_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
@@ -2349,7 +2344,7 @@ static int sub_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)

 static int sub_imm(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
-   return wrp_alu32_imm(nfp_prog, meta, ALU_OP_SUB, !meta->insn.imm);
+   return wrp_alu32_imm(nfp_prog, meta, ALU_OP_SUB);
 }

 static int mul_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)

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