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[PATCH v2 16/17] MIPS: bpf: Use 32 or 64-bit load instruction to load an

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Subject: [PATCH v2 16/17] MIPS: bpf: Use 32 or 64-bit load instruction to load an address to register
From: Markos Chandras <markos.chandras@imgtec.com>
Date: Wed, 25 Jun 2014 09:39:38 +0100
Cc: Markos Chandras <markos.chandras@imgtec.com>, "David S. Miller" <davem@davemloft.net>, Daniel Borkmann <dborkman@redhat.com>, "Alexei Starovoitov" <ast@plumgrid.com>, <netdev@vger.kernel.org>
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When loading a pointer to register we need to use the appropriate
32 or 64bit instruction to preserve the pointers' top 32bits.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
---
Changes since v1:
- Change function name to make it clear that we are loading a
pointer to a register, not an address
---
 arch/mips/net/bpf_jit.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
index 4505e2e6ab53..6e3963425b64 100644
--- a/arch/mips/net/bpf_jit.c
+++ b/arch/mips/net/bpf_jit.c
@@ -453,6 +453,17 @@ static inline void emit_wsbh(unsigned int dst, unsigned 
int src,
        emit_instr(ctx, wsbh, dst, src);
 }
 
+/* load pointer to register */
+static inline void emit_load_ptr(unsigned int dst, unsigned int src,
+                                    int imm, struct jit_ctx *ctx)
+{
+       /* src contains the base addr of the 32/64-pointer */
+       if (config_enabled(CONFIG_64BIT))
+               emit_instr(ctx, ld, dst, imm, src);
+       else
+               emit_instr(ctx, lw, dst, imm, src);
+}
+
 /* load a function pointer to register */
 static inline void emit_load_func(unsigned int reg, ptr imm,
                                  struct jit_ctx *ctx)
@@ -1277,7 +1288,8 @@ jmp_cmp:
                        /* A = skb->dev->ifindex */
                        ctx->flags |= SEEN_SKB | SEEN_A | SEEN_S0;
                        off = offsetof(struct sk_buff, dev);
-                       emit_load(r_s0, r_skb, off, ctx);
+                       /* Load *dev pointer */
+                       emit_load_ptr(r_s0, r_skb, off, ctx);
                        /* error (0) in the delay slot */
                        emit_bcond(MIPS_COND_EQ, r_s0, r_zero,
                                   b_imm(prog->len, ctx), ctx);
-- 
2.0.0


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