FAILED: patch "[PATCH] powerpc64/bpf: do not increment tailcall count when prog is" failed to apply to 6.19-stable tree

FAILED: patch "[PATCH] powerpc64/bpf: do not increment tailcall count when prog is" failed to apply to 6.19-stable tree

[gregkh]

The patch below does not apply to the 6.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.19.y
git checkout FETCH_HEAD
git cherry-pick -x 521bd39d9d28ce54cbfec7f9b89c94ad4fdb8350
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026031740-avenging-arguably-7411@gregkh' --subject-prefix 'PATCH 6.19.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 521bd39d9d28ce54cbfec7f9b89c94ad4fdb8350 Mon Sep 17 00:00:00 2001
From: Hari Bathini <hbathini@linux.ibm.com>
Date: Tue, 3 Mar 2026 23:40:25 +0530
Subject: [PATCH] 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 b1a3945ccc9f..44ce8a8783f9 100644
--- 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);