3 files changed, 111 insertions, 31 deletions

diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
index af1ab5e9a69..5c3cf2d04e4 100644
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -48,7 +48,13 @@
 /*
  * Assembly helpers from arch/powerpc/net/bpf_jit.S:
  */
-extern u8 sk_load_word[], sk_load_half[], sk_load_byte[], sk_load_byte_msh[];
+#define DECLARE_LOAD_FUNC(func) \
+        extern u8 func[], func##_negative_offset[], func##_positive_offset[]
+
+DECLARE_LOAD_FUNC(sk_load_word);
+DECLARE_LOAD_FUNC(sk_load_half);
+DECLARE_LOAD_FUNC(sk_load_byte);
+DECLARE_LOAD_FUNC(sk_load_byte_msh);
 
 #define FUNCTION_DESCR_SIZE     24
 
diff --git a/arch/powerpc/net/bpf_jit_64.S b/arch/powerpc/net/bpf_jit_64.S
index ff4506e85cc..55ba3855a97 100644
--- a/arch/powerpc/net/bpf_jit_64.S
+++ b/arch/powerpc/net/bpf_jit_64.S
@@ -31,14 +31,13 @@
  * then branch directly to slow_path_XXX if required.  (In fact, could
  * load a spare GPR with the address of slow_path_generic and pass size
  * as an argument, making the call site a mtlr, li and bllr.)
- *
- * Technically, the "is addr < 0" check is unnecessary & slowing down
- * the ABS path, as it's statically checked on generation.
  */
         .globl  sk_load_word
 sk_load_word:
         cmpdi   r_addr, 0
-        blt     bpf_error
+        blt     bpf_slow_path_word_neg
+        .globl  sk_load_word_positive_offset
+sk_load_word_positive_offset:
         /* Are we accessing past headlen? */
         subi    r_scratch1, r_HL, 4
         cmpd    r_scratch1, r_addr
@@ -51,7 +50,9 @@ sk_load_word:
         .globl  sk_load_half
 sk_load_half:
         cmpdi   r_addr, 0
-        blt     bpf_error
+        blt     bpf_slow_path_half_neg
+        .globl  sk_load_half_positive_offset
+sk_load_half_positive_offset:
         subi    r_scratch1, r_HL, 2
         cmpd    r_scratch1, r_addr
         blt     bpf_slow_path_half
@@ -61,7 +62,9 @@ sk_load_half:
         .globl  sk_load_byte
 sk_load_byte:
         cmpdi   r_addr, 0
-        blt     bpf_error
+        blt     bpf_slow_path_byte_neg
+        .globl  sk_load_byte_positive_offset
+sk_load_byte_positive_offset:
         cmpd    r_HL, r_addr
         ble     bpf_slow_path_byte
         lbzx    r_A, r_D, r_addr
@@ -69,22 +72,20 @@ sk_load_byte:
 
 /*
  * BPF_S_LDX_B_MSH: ldxb  4*([offset]&0xf)
- * r_addr is the offset value, already known positive
+ * r_addr is the offset value
  */
         .globl sk_load_byte_msh
 sk_load_byte_msh:
+        cmpdi   r_addr, 0
+        blt     bpf_slow_path_byte_msh_neg
+        .globl sk_load_byte_msh_positive_offset
+sk_load_byte_msh_positive_offset:
         cmpd    r_HL, r_addr
         ble     bpf_slow_path_byte_msh
         lbzx    r_X, r_D, r_addr
         rlwinm  r_X, r_X, 2, 32-4-2, 31-2
         blr
 
-bpf_error:
-        /* Entered with cr0 = lt */
-        li      r3, 0
-        /* Generated code will 'blt epilogue', returning 0. */
-        blr
-
 /* Call out to skb_copy_bits:
  * We'll need to back up our volatile regs first; we have
  * local variable space at r1+(BPF_PPC_STACK_BASIC).
@@ -136,3 +137,84 @@ bpf_slow_path_byte_msh:
         lbz     r_X, BPF_PPC_STACK_BASIC+(2*8)(r1)
         rlwinm  r_X, r_X, 2, 32-4-2, 31-2
         blr
+
+/* Call out to bpf_internal_load_pointer_neg_helper:
+ * We'll need to back up our volatile regs first; we have
+ * local variable space at r1+(BPF_PPC_STACK_BASIC).
+ * Allocate a new stack frame here to remain ABI-compliant in
+ * stashing LR.
+ */
+#define sk_negative_common(SIZE)                                \
+        mflr    r0;                                             \
+        std     r0, 16(r1);                                     \
+        /* R3 goes in parameter space of caller's frame */      \
+        std     r_skb, (BPF_PPC_STACKFRAME+48)(r1);             \
+        std     r_A, (BPF_PPC_STACK_BASIC+(0*8))(r1);           \
+        std     r_X, (BPF_PPC_STACK_BASIC+(1*8))(r1);           \
+        stdu    r1, -BPF_PPC_SLOWPATH_FRAME(r1);                \
+        /* R3 = r_skb, as passed */                             \
+        mr      r4, r_addr;                                     \
+        li      r5, SIZE;                                       \
+        bl      bpf_internal_load_pointer_neg_helper;           \
+        /* R3 != 0 on success */                                \
+        addi    r1, r1, BPF_PPC_SLOWPATH_FRAME;                 \
+        ld      r0, 16(r1);                                     \
+        ld      r_A, (BPF_PPC_STACK_BASIC+(0*8))(r1);           \
+        ld      r_X, (BPF_PPC_STACK_BASIC+(1*8))(r1);           \
+        mtlr    r0;                                             \
+        cmpldi  r3, 0;                                          \
+        beq     bpf_error_slow; /* cr0 = EQ */                  \
+        mr      r_addr, r3;                                     \
+        ld      r_skb, (BPF_PPC_STACKFRAME+48)(r1);             \
+        /* Great success! */
+
+bpf_slow_path_word_neg:
+        lis     r_scratch1,-32  /* SKF_LL_OFF */
+        cmpd    r_addr, r_scratch1      /* addr < SKF_* */
+        blt     bpf_error       /* cr0 = LT */
+        .globl  sk_load_word_negative_offset
+sk_load_word_negative_offset:
+        sk_negative_common(4)
+        lwz     r_A, 0(r_addr)
+        blr
+
+bpf_slow_path_half_neg:
+        lis     r_scratch1,-32  /* SKF_LL_OFF */
+        cmpd    r_addr, r_scratch1      /* addr < SKF_* */
+        blt     bpf_error       /* cr0 = LT */
+        .globl  sk_load_half_negative_offset
+sk_load_half_negative_offset:
+        sk_negative_common(2)
+        lhz     r_A, 0(r_addr)
+        blr
+
+bpf_slow_path_byte_neg:
+        lis     r_scratch1,-32  /* SKF_LL_OFF */
+        cmpd    r_addr, r_scratch1      /* addr < SKF_* */
+        blt     bpf_error       /* cr0 = LT */
+        .globl  sk_load_byte_negative_offset
+sk_load_byte_negative_offset:
+        sk_negative_common(1)
+        lbz     r_A, 0(r_addr)
+        blr
+
+bpf_slow_path_byte_msh_neg:
+        lis     r_scratch1,-32  /* SKF_LL_OFF */
+        cmpd    r_addr, r_scratch1      /* addr < SKF_* */
+        blt     bpf_error       /* cr0 = LT */
+        .globl  sk_load_byte_msh_negative_offset
+sk_load_byte_msh_negative_offset:
+        sk_negative_common(1)
+        lbz     r_X, 0(r_addr)
+        rlwinm  r_X, r_X, 2, 32-4-2, 31-2
+        blr
+
+bpf_error_slow:
+        /* fabricate a cr0 = lt */
+        li      r_scratch1, -1
+        cmpdi   r_scratch1, 0
+bpf_error:
+        /* Entered with cr0 = lt */
+        li      r3, 0
+        /* Generated code will 'blt epilogue', returning 0. */
+        blr
diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 73619d3aeb6..2dc8b148484 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -127,6 +127,9 @@ static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
         PPC_BLR();
 }
 
+#define CHOOSE_LOAD_FUNC(K, func) \
+        ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
+
 /* Assemble the body code between the prologue & epilogue. */
 static int bpf_jit_build_body(struct sk_filter *fp, u32 *image,
                               struct codegen_context *ctx,
@@ -391,21 +394,16 @@ static int bpf_jit_build_body(struct sk_filter *fp, u32 *image,
 
                         /*** Absolute loads from packet header/data ***/
                 case BPF_S_LD_W_ABS:
-                        func = sk_load_word;
+                        func = CHOOSE_LOAD_FUNC(K, sk_load_word);
                         goto common_load;
                 case BPF_S_LD_H_ABS:
-                        func = sk_load_half;
+                        func = CHOOSE_LOAD_FUNC(K, sk_load_half);
                         goto common_load;
                 case BPF_S_LD_B_ABS:
-                        func = sk_load_byte;
+                        func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
                 common_load:
-                        /*
-                         * Load from [K].  Reference with the (negative)
-                         * SKF_NET_OFF/SKF_LL_OFF offsets is unsupported.
-                         */
+                        /* Load from [K]. */
                         ctx->seen |= SEEN_DATAREF;
-                        if ((int)K < 0)
-                                return -ENOTSUPP;
                         PPC_LI64(r_scratch1, func);
                         PPC_MTLR(r_scratch1);
                         PPC_LI32(r_addr, K);
@@ -429,7 +427,7 @@ static int bpf_jit_build_body(struct sk_filter *fp, u32 *image,
                 common_load_ind:
                         /*
                          * Load from [X + K].  Negative offsets are tested for
-                         * in the helper functions, and result in a 'ret 0'.
+                         * in the helper functions.
                          */
                         ctx->seen |= SEEN_DATAREF | SEEN_XREG;
                         PPC_LI64(r_scratch1, func);
@@ -443,13 +441,7 @@ static int bpf_jit_build_body(struct sk_filter *fp, u32 *image,
                         break;
 
                 case BPF_S_LDX_B_MSH:
-                        /*
-                         * x86 version drops packet (RET 0) when K<0, whereas
-                         * interpreter does allow K<0 (__load_pointer, special
-                         * ancillary data).  common_load returns ENOTSUPP if K<0,
-                         * so we fall back to interpreter & filter works.
-                         */
-                        func = sk_load_byte_msh;
+                        func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
                         goto common_load;
                         break;