FAILED: patch "[PATCH] powerpc64/bpf: fix kfunc call support" failed to apply to 6.12-stable tree

PATCH New [email protected] 2 participants 3 messages Mar 17 – Mar 19

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Stable branch PowerPC BPF BPF JIT for PowerPC (32-bit and 64-bit)

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[email protected]

author maintainer

2026-03-17 12:58 UTC #0 lore raw

The patch below does not apply to the 6.12-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 <[email protected]>.

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-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 01b6ac72729610ae732ca2a66e3a642e23f6cd60
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026031723-runner-capable-b815@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 01b6ac72729610ae732ca2a66e3a642e23f6cd60 Mon Sep 17 00:00:00 2001
From: Hari Bathini <[email protected]>
Date: Tue, 3 Mar 2026 23:40:30 +0530
Subject: [PATCH] powerpc64/bpf: fix kfunc call support

Commit 61688a82e047 ("powerpc/bpf: enable kfunc call") inadvertently enabled kfunc call support for 32-bit powerpc but that support will not be possible until ABI mismatch between 32-bit powerpc and eBPF is handled in 32-bit powerpc JIT code. Till then, advertise support only for 64-bit powerpc. Also, in powerpc ABI, caller needs to extend the arguments properly based on signedness. The JIT code is responsible for handling this explicitly for kfunc calls as verifier can't handle this for each architecture-specific ABI needs. But this was not taken care of while kfunc call support was enabled for powerpc. Fix it by handling this with bpf_jit_find_kfunc_model() and using zero_extend() & sign_extend() helper functions.

Fixes 61688a82e047 ("powerpc/bpf: enable kfunc call")

Cc [email protected]

Signed-off-by Hari Bathini <[email protected]>

Signed-off-by Madhavan Srinivasan <[email protected]>

Link https://patch.msgid.link/[email protected] open here

arch/powerpc/net/bpf_jit_comp.c +1 -1

index 85457bcb2040..a62a9a92b7b5 100644
@@ -450,7 +450,7 @@ bool bpf_jit_supports_subprog_tailcalls(void)
 
 bool bpf_jit_supports_kfunc_call(void)
 {
-	return true;
+	return IS_ENABLED(CONFIG_PPC64);
 }
 
 bool bpf_jit_supports_arena(void)

arch/powerpc/net/bpf_jit_comp64.c +93 -8

119 lines not on this page · raw message

Sasha Levin

maintainer

2026-03-19 12:51 UTC #1 lore raw

PATCH 1/2 powerpc64/bpf: Fold bpf_jit_emit_func_call_hlp() into bpf_jit_emit_func_call_rel()

From: Naveen N Rao <[email protected]>

[ Upstream commit 9670f6d2097c4f97e15c67920dfddc664d7ee91c ]

Commit 61688a82e047 ("powerpc/bpf: enable kfunc call") enhanced bpf_jit_emit_func_call_hlp() to handle calls out to module region, where bpf progs are generated. The only difference now between bpf_jit_emit_func_call_hlp() and bpf_jit_emit_func_call_rel() is in handling of the initial pass where target function address is not known. Fold that logic into bpf_jit_emit_func_call_hlp() and rename it to bpf_jit_emit_func_call_rel() to simplify bpf function call JIT code.

We don't actually need to load/restore TOC across a call out to a different kernel helper or to a different bpf program since they all work with the kernel TOC. We only need to do it if we have to call out to a module function. So, guard TOC load/restore with appropriate conditions.

Signed-off-by Naveen N Rao <[email protected]>

Signed-off-by Michael Ellerman <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Stable-dep-of: 01b6ac727296 ("powerpc64/bpf: fix kfunc call support")

Signed-off-by Sasha Levin <[email protected]>

---
 arch/powerpc/net/bpf_jit_comp64.c | 61 +++++++++----------------------
 1 file changed, 17 insertions(+), 44 deletions(-)

arch/powerpc/net/bpf_jit_comp64.c +17 ~~-44~~

index 2cbcdf93cc197..f3be024fc6854 100644
@@ -202,14 +202,22 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
 	EMIT(PPC_RAW_BLR());
 }
 
-static int
-bpf_jit_emit_func_call_hlp(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func)
+int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func)
 {
 	unsigned long func_addr = func ? ppc_function_entry((void *)func) : 0;
 	long reladdr;
 
-	if (WARN_ON_ONCE(!kernel_text_address(func_addr)))
-		return -EINVAL;
+	/* bpf to bpf call, func is not known in the initial pass. Emit 5 nops as a placeholder */
+	if (!func) {
+		for (int i = 0; i < 5; i++)
+			EMIT(PPC_RAW_NOP());
+		/* elfv1 needs an additional instruction to load addr from descriptor */
+		if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1))
+			EMIT(PPC_RAW_NOP());
+		EMIT(PPC_RAW_MTCTR(_R12));
+		EMIT(PPC_RAW_BCTRL());
+		return 0;
+	}
 
 #ifdef CONFIG_PPC_KERNEL_PCREL
 	reladdr = func_addr - local_paca->kernelbase;

@@ -266,7 +274,8 @@ bpf_jit_emit_func_call_hlp(u32 *image, u32 *fimage, struct codegen_context *ctx,
 			 * We can clobber r2 since we get called through a
 			 * function pointer (so caller will save/restore r2).
 			 */
-			EMIT(PPC_RAW_LD(_R2, bpf_to_ppc(TMP_REG_2), 8));
+			if (is_module_text_address(func_addr))
+				EMIT(PPC_RAW_LD(_R2, bpf_to_ppc(TMP_REG_2), 8));
 		} else {
 			PPC_LI64(_R12, func);
 			EMIT(PPC_RAW_MTCTR(_R12));

@@ -276,46 +285,14 @@ bpf_jit_emit_func_call_hlp(u32 *image, u32 *fimage, struct codegen_context *ctx,
 		 * Load r2 with kernel TOC as kernel TOC is used if function address falls
 		 * within core kernel text.
 		 */
-		EMIT(PPC_RAW_LD(_R2, _R13, offsetof(struct paca_struct, kernel_toc)));
+		if (is_module_text_address(func_addr))
+			EMIT(PPC_RAW_LD(_R2, _R13, offsetof(struct paca_struct, kernel_toc)));
 	}
 #endif
 
 	return 0;
 }
 
-int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func)
-{
-	unsigned int i, ctx_idx = ctx->idx;
-
-	if (WARN_ON_ONCE(func && is_module_text_address(func)))
-		return -EINVAL;
-
-	/* skip past descriptor if elf v1 */
-	func += FUNCTION_DESCR_SIZE;
-
-	/* Load function address into r12 */
-	PPC_LI64(_R12, func);
-
-	/* For bpf-to-bpf function calls, the callee's address is unknown
-	 * until the last extra pass. As seen above, we use PPC_LI64() to
-	 * load the callee's address, but this may optimize the number of
-	 * instructions required based on the nature of the address.
-	 *
-	 * Since we don't want the number of instructions emitted to increase,
-	 * we pad the optimized PPC_LI64() call with NOPs to guarantee that
-	 * we always have a five-instruction sequence, which is the maximum
-	 * that PPC_LI64() can emit.
-	 */
-	if (!image)
-		for (i = ctx->idx - ctx_idx; i < 5; i++)
-			EMIT(PPC_RAW_NOP());
-
-	EMIT(PPC_RAW_MTCTR(_R12));
-	EMIT(PPC_RAW_BCTRL());
-
-	return 0;
-}
-
 static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 out)
 {
 	/*

@@ -1102,11 +1079,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
 			if (ret < 0)
 				return ret;
 
-			if (func_addr_fixed)
-				ret = bpf_jit_emit_func_call_hlp(image, fimage, ctx, func_addr);
-			else
-				ret = bpf_jit_emit_func_call_rel(image, fimage, ctx, func_addr);
-
+			ret = bpf_jit_emit_func_call_rel(image, fimage, ctx, func_addr);
 			if (ret)
 				return ret;

Signature · 1 line

2.51.0

Sasha Levin

maintainer

2026-03-19 12:51 UTC #2 lore raw

PATCH 2/2 powerpc64/bpf: fix kfunc call support

From: Hari Bathini <[email protected]>

[ Upstream commit 01b6ac72729610ae732ca2a66e3a642e23f6cd60 ]

Fixes 61688a82e047 ("powerpc/bpf: enable kfunc call")

Cc [email protected]

Signed-off-by Hari Bathini <[email protected]>

Signed-off-by Madhavan Srinivasan <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Sasha Levin <[email protected]>

---
 arch/powerpc/net/bpf_jit_comp.c   |   2 +-
 arch/powerpc/net/bpf_jit_comp64.c | 101 +++++++++++++++++++++++++++---
 2 files changed, 94 insertions(+), 9 deletions(-)

arch/powerpc/net/bpf_jit_comp.c +1 -1

index 2a36cc2e7e9e2..55c3b64a5f3a4 100644
@@ -362,7 +362,7 @@ void bpf_jit_free(struct bpf_prog *fp)
 
 bool bpf_jit_supports_kfunc_call(void)
 {
-	return true;
+	return IS_ENABLED(CONFIG_PPC64);
 }
 
 bool bpf_jit_supports_far_kfunc_call(void)

arch/powerpc/net/bpf_jit_comp64.c +93 -8

119 lines not on this page · raw message

Signature · 1 line

2.51.0