[PATCH 6.19 309/342] powerpc64/bpf: do not increment tailcall count when prog is NULL

Greg Kroah-Hartman
2026-03-31T16:46:02Z

From: Hari Bathini <hbathini@linux.ibm.com>

commit 521bd39d9d28ce54cbfec7f9b89c94ad4fdb8350 upstream.

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
[ Conflict due to missing feature commit 2ed2d8f6fb38 ("powerpc64/bpf:
Support tailcalls with subprogs") resolved accordingly. ]
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/powerpc/net/bpf_jit_comp64.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)

--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -430,27 +430,32 @@ static int bpf_jit_emit_tail_call(u32 *i

/*
* tail_call_cnt++;
+ * 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));
- EMIT(PPC_RAW_STD(bpf_to_ppc(TMP_REG_1), _R1, bpf_jit_stack_tailcallcnt(ctx)));

/* 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)));
+ 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_1), 0));
+ 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_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)));
+ 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)));
+
+ /* Writeback updated tailcall count */
+ EMIT(PPC_RAW_STD(bpf_to_ppc(TMP_REG_1), _R1, bpf_jit_stack_tailcallcnt(ctx)));

/* tear down stack, restore NVRs, ... */
bpf_jit_emit_common_epilogue(image, ctx);