[bpf-next 3/6] bpf,powerpc: Implement bpf_addr_space_cast instruction

[Saket Kumar Bhaskar]

LLVM generates bpf_addr_space_cast instruction while translating
pointers between native (zero) address space and
__attribute__((address_space(N))). The addr_space=0 is reserved as
bpf_arena address space.

rY = addr_space_cast(rX, 0, 1) is processed by the verifier and
converted to normal 32-bit move: wX = wY.

rY = addr_space_cast(rX, 1, 0) : used to convert a bpf arena pointer to
a pointer in the userspace vma. This has to be converted by the JIT.

Signed-off-by: Saket Kumar Bhaskar <sk...@linux.ibm.com>
---
 arch/powerpc/net/bpf_jit.h        |  1 +
 arch/powerpc/net/bpf_jit_comp.c   |  6 ++++++
 arch/powerpc/net/bpf_jit_comp64.c | 11 +++++++++++
 3 files changed, 18 insertions(+)

diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
index 2d095a873305..748e30e8b5b4 100644
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -165,6 +165,7 @@ struct codegen_context {
        unsigned int exentry_idx;
        unsigned int alt_exit_addr;
        u64 arena_vm_start;
+       u64 user_vm_start;
 };
 
 #define bpf_to_ppc(r)  (ctx->b2p[r])
diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 35bfdf4d8785..2b3f90930c27 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -205,6 +205,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
        /* Make sure that the stack is quadword aligned. */
        cgctx.stack_size = round_up(fp->aux->stack_depth, 16);
        cgctx.arena_vm_start = bpf_arena_get_kern_vm_start(fp->aux->arena);
+       cgctx.user_vm_start = bpf_arena_get_user_vm_start(fp->aux->arena);
 
        /* Scouting faux-generate pass 0 */
        if (bpf_jit_build_body(fp, NULL, NULL, &cgctx, addrs, 0, false)) {
@@ -441,6 +442,11 @@ bool bpf_jit_supports_kfunc_call(void)
        return true;
 }
 
+bool bpf_jit_supports_arena(void)
+{
+       return IS_ENABLED(CONFIG_PPC64);
+}
+
 bool bpf_jit_supports_far_kfunc_call(void)
 {
        return IS_ENABLED(CONFIG_PPC64);
diff --git a/arch/powerpc/net/bpf_jit_comp64.c 
b/arch/powerpc/net/bpf_jit_comp64.c
index 16e62766c757..d4fe4dacf2d6 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -812,6 +812,17 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, 
u32 *fimage, struct code
                 */
                case BPF_ALU | BPF_MOV | BPF_X: /* (u32) dst = src */
                case BPF_ALU64 | BPF_MOV | BPF_X: /* dst = src */
+
+                       if (insn_is_cast_user(&insn[i])) {
+                               EMIT(PPC_RAW_RLDICL(tmp1_reg, src_reg, 0, 32));
+                               PPC_LI64(dst_reg, (ctx->user_vm_start & 
0xffffffff00000000UL));
+                               EMIT(PPC_RAW_CMPDI(tmp1_reg, 0));
+                               PPC_BCC_SHORT(COND_EQ, (ctx->idx + 2) * 4);
+                               EMIT(PPC_RAW_OR(tmp1_reg, dst_reg, tmp1_reg));
+                               EMIT(PPC_RAW_MR(dst_reg, tmp1_reg));
+                               break;
+                       }
+
                        if (imm == 1) {
                                /* special mov32 for zext */
                                EMIT(PPC_RAW_RLWINM(dst_reg, dst_reg, 0, 0, 
31));
-- 
2.43.5