powerpc64/bpf: do not increment tailcall count when prog is NULL

Do not increment tailcall count, if tailcall did not succeed due to
missing BPF program.

Fixes: ce0761419fae ("powerpc/bpf: Implement support for tail calls")
Cc: stable@vger.kernel.org
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260303181031.390073-2-hbathini@linux.ibm.com

diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index b1a3945ccc9fd7a44f5adba23a57f42f52c133a1..44ce8a8783f942a954ce5adec8342204fbe694a8 100644 (file)
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -522,9 +522,30 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o
 
        /*
         * tail_call_info++; <- Actual value of tcc here
+        * Writeback this updated value only if tailcall succeeds.
         */
        EMIT(PPC_RAW_ADDI(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1), 1));
 
+       /* prog = array->ptrs[index]; */
+       EMIT(PPC_RAW_MULI(bpf_to_ppc(TMP_REG_2), b2p_index, 8));
+       EMIT(PPC_RAW_ADD(bpf_to_ppc(TMP_REG_2), bpf_to_ppc(TMP_REG_2), b2p_bpf_array));
+       EMIT(PPC_RAW_LD(bpf_to_ppc(TMP_REG_2), bpf_to_ppc(TMP_REG_2),
+                       offsetof(struct bpf_array, ptrs)));
+
+       /*
+        * if (prog == NULL)
+        *   goto out;
+        */
+       EMIT(PPC_RAW_CMPLDI(bpf_to_ppc(TMP_REG_2), 0));
+       PPC_BCC_SHORT(COND_EQ, out);
+
+       /* goto *(prog->bpf_func + prologue_size); */
+       EMIT(PPC_RAW_LD(bpf_to_ppc(TMP_REG_2), bpf_to_ppc(TMP_REG_2),
+                       offsetof(struct bpf_prog, bpf_func)));
+       EMIT(PPC_RAW_ADDI(bpf_to_ppc(TMP_REG_2), bpf_to_ppc(TMP_REG_2),
+                         FUNCTION_DESCR_SIZE + bpf_tailcall_prologue_size));
+       EMIT(PPC_RAW_MTCTR(bpf_to_ppc(TMP_REG_2)));
+
        /*
         * Before writing updated tail_call_info, distinguish if current frame
         * is storing a reference to tail_call_info or actual tcc value in
@@ -539,24 +560,6 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o
        /* Writeback updated value to tail_call_info */
        EMIT(PPC_RAW_STD(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_2), 0));
 
-       /* prog = array->ptrs[index]; */
-       EMIT(PPC_RAW_MULI(bpf_to_ppc(TMP_REG_1), b2p_index, 8));
-       EMIT(PPC_RAW_ADD(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1), b2p_bpf_array));
-       EMIT(PPC_RAW_LD(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1), offsetof(struct bpf_array, ptrs)));
-
-       /*
-        * if (prog == NULL)
-        *   goto out;
-        */
-       EMIT(PPC_RAW_CMPLDI(bpf_to_ppc(TMP_REG_1), 0));
-       PPC_BCC_SHORT(COND_EQ, out);
-
-       /* goto *(prog->bpf_func + prologue_size); */
-       EMIT(PPC_RAW_LD(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1), offsetof(struct bpf_prog, bpf_func)));
-       EMIT(PPC_RAW_ADDI(bpf_to_ppc(TMP_REG_1), bpf_to_ppc(TMP_REG_1),
-                       FUNCTION_DESCR_SIZE + bpf_tailcall_prologue_size));
-       EMIT(PPC_RAW_MTCTR(bpf_to_ppc(TMP_REG_1)));
-
        /* tear down stack, restore NVRs, ... */
        bpf_jit_emit_common_epilogue(image, ctx);