* [PATCH v2] powerpc64/bpf: Add powerpc64 JIT support for timed may_goto
@ 2026-04-02 16:10 Saket Kumar Bhaskar
2026-04-02 19:44 ` Hari Bathini
0 siblings, 1 reply; 3+ messages in thread
From: Saket Kumar Bhaskar @ 2026-04-02 16:10 UTC (permalink / raw)
To: linux-kernel, bpf, linuxppc-dev
Cc: hbathini, sachinpb, venkat88, andrii, eddyz87, ast, daniel,
martin.lau, song, yonghong.song, john.fastabend, kpsingh, sdf,
haoluo, jolsa, chleroy, maddy, mpe, adubey
When verifier sees a timed may_goto instruction, it emits a call to
arch_bpf_timed_may_goto() with a stack offset in BPF_REG_AX
(powerpc64 R12) and expects the refreshed count value to be returned
in the same register. The verifier doesn't save or restore any registers
before emitting this call.
arch_bpf_timed_may_goto() should act as a trampoline to call
bpf_check_timed_may_goto() with powerpc64 ELF ABI calling convention.
To support this custom calling convention, implement
arch_bpf_timed_may_goto() in assembly and make sure BPF caller saved
registers are preserved, then call bpf_check_timed_may_goto with
the powerpc64 ABI calling convention where first argument and return
value both are in R3. Finally, move the result back into BPF_REG_AX(R12)
before returning.
Also, introduce bpf_jit_emit_func_call() that computes the offset from
kernel_toc_addr(), validates that the target and emits the ADDIS/ADDI
sequence to load the function address before performing the indirect
branch via MTCTR/BCTRL. The existing code in bpf_jit_emit_func_call_rel()
is refactored to use this function.
Signed-off-by: Saket Kumar Bhaskar <skb99@linux.ibm.com>
---
This patch has been rebased on top of these 3 patches on powerpc-next in
the following sequence:
1. https://lore.kernel.org/bpf/20260401103215.104438-1-adubey@linux.ibm.com/
2. https://lore.kernel.org/bpf/20260401141043.41513-1-adubey@linux.ibm.com/
3. https://lore.kernel.org/bpf/20260401152133.42544-1-adubey@linux.ibm.com/
Changes since v1:
- Compile bpf_timed_may_goto.o conditionally for PPC64. (Hari)
- Moved reladdr at the beginning of the function. (Hari)
- Added error check for bpf_jit_emit_func_call() in
bpf_jit_build_body(). (Hari)
- Save registers after 32 bytes as MIN_FRAME_SIZE is 32 bytes for
powerpc ABIv2. (Hari)
---
arch/powerpc/net/Makefile | 4 ++
arch/powerpc/net/bpf_jit_comp.c | 5 +++
arch/powerpc/net/bpf_jit_comp64.c | 62 ++++++++++++++++++++++-----
arch/powerpc/net/bpf_timed_may_goto.S | 57 ++++++++++++++++++++++++
4 files changed, 117 insertions(+), 11 deletions(-)
create mode 100644 arch/powerpc/net/bpf_timed_may_goto.S
diff --git a/arch/powerpc/net/Makefile b/arch/powerpc/net/Makefile
index 8e60af32e51e..87395d7e2672 100644
--- a/arch/powerpc/net/Makefile
+++ b/arch/powerpc/net/Makefile
@@ -3,3 +3,7 @@
# Arch-specific network modules
#
obj-$(CONFIG_BPF_JIT) += bpf_jit_comp.o bpf_jit_comp$(BITS).o
+
+ifdef CONFIG_PPC64
++obj-$(CONFIG_BPF_JIT) += bpf_timed_may_goto.o
+endif
diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 50103b3794fb..9b2b456b0765 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -537,6 +537,11 @@ bool bpf_jit_supports_subprog_tailcalls(void)
return IS_ENABLED(CONFIG_PPC64);
}
+bool bpf_jit_supports_timed_may_goto(void)
+{
+ return IS_ENABLED(CONFIG_PPC64);
+}
+
bool bpf_jit_supports_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 db364d9083e7..dab106cae22b 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -451,10 +451,28 @@ void arch_bpf_stack_walk(bool (*consume_fn)(void *, u64, u64, u64), void *cookie
}
}
+static int bpf_jit_emit_func_call(u32 *image, struct codegen_context *ctx, u64 func_addr, int reg)
+{
+ long reladdr = func_addr - kernel_toc_addr();
+
+ if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
+ pr_err("eBPF: address of %ps out of range of kernel_toc.\n", (void *)func_addr);
+ return -ERANGE;
+ }
+
+ EMIT(PPC_RAW_ADDIS(reg, _R2, PPC_HA(reladdr)));
+ EMIT(PPC_RAW_ADDI(reg, reg, PPC_LO(reladdr)));
+ EMIT(PPC_RAW_MTCTR(reg));
+ EMIT(PPC_RAW_BCTRL());
+
+ return 0;
+}
+
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;
+ long __maybe_unused reladdr;
+ int ret;
/* bpf to bpf call, func is not known in the initial pass. Emit 5 nops as a placeholder */
if (!func) {
@@ -507,16 +525,9 @@ int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *
EMIT(PPC_RAW_BCTRL());
#else
if (core_kernel_text(func_addr)) {
- reladdr = func_addr - kernel_toc_addr();
- if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
- pr_err("eBPF: address of %ps out of range of kernel_toc.\n", (void *)func);
- return -ERANGE;
- }
-
- EMIT(PPC_RAW_ADDIS(_R12, _R2, PPC_HA(reladdr)));
- EMIT(PPC_RAW_ADDI(_R12, _R12, PPC_LO(reladdr)));
- EMIT(PPC_RAW_MTCTR(_R12));
- EMIT(PPC_RAW_BCTRL());
+ ret = bpf_jit_emit_func_call(image, ctx, func_addr, _R12);
+ if (ret)
+ return ret;
} else {
if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1)) {
/* func points to the function descriptor */
@@ -1755,6 +1766,35 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
if (ret < 0)
return ret;
+ /*
+ * Call to arch_bpf_timed_may_goto() is emitted by the
+ * verifier and called with custom calling convention with
+ * first argument and return value in BPF_REG_AX (_R12).
+ *
+ * The generic helper or bpf function call emission path
+ * may use the same scratch register as BPF_REG_AX to
+ * materialize the target address. This would clobber AX
+ * and break timed may_goto semantics.
+ *
+ * Emit a minimal indirect call sequence here using a temp
+ * register and skip the normal post-call return-value move.
+ */
+
+ if (func_addr == (u64)arch_bpf_timed_may_goto) {
+ ret = 0;
+ if (!IS_ENABLED(CONFIG_PPC_KERNEL_PCREL))
+ ret = bpf_jit_emit_func_call(image, ctx, func_addr,
+ tmp1_reg);
+
+ if (ret || IS_ENABLED(CONFIG_PPC_KERNEL_PCREL)) {
+ PPC_LI_ADDR(tmp1_reg, func_addr);
+ EMIT(PPC_RAW_MTCTR(tmp1_reg));
+ EMIT(PPC_RAW_BCTRL());
+ }
+
+ break;
+ }
+
/* Take care of powerpc ABI requirements before kfunc call */
if (insn[i].src_reg == BPF_PSEUDO_KFUNC_CALL) {
if (prepare_for_kfunc_call(fp, image, ctx, &insn[i]))
diff --git a/arch/powerpc/net/bpf_timed_may_goto.S b/arch/powerpc/net/bpf_timed_may_goto.S
new file mode 100644
index 000000000000..6fd8b1c9f4ac
--- /dev/null
+++ b/arch/powerpc/net/bpf_timed_may_goto.S
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (c) 2025 IBM Corporation, Saket Kumar Bhaskar <skb99@linux.ibm.com> */
+
+#include <linux/linkage.h>
+#include <asm/ppc_asm.h>
+
+/*
+ * arch_bpf_timed_may_goto() trampoline for powerpc64
+ *
+ * Custom BPF convention (verifier/JIT):
+ * - input: stack offset in BPF_REG_AX (r12)
+ * - output: updated count in BPF_REG_AX (r12)
+ *
+ * Call bpf_check_timed_may_goto(ptr) with normal powerpc64 ABI:
+ * - r3 = ptr, return in r3
+ *
+ * Preserve BPF regs R0-R5 (mapping: r8, r3-r7).
+ */
+
+SYM_FUNC_START(arch_bpf_timed_may_goto)
+ /* Prologue: save LR, allocate frame */
+ mflr r0
+ std r0, 16(r1)
+ stdu r1, -112(r1)
+
+ /* Save BPF registers R0 - R5 (r8, r3-r7) */
+ std r3, 32(r1)
+ std r4, 40(r1)
+ std r5, 48(r1)
+ std r6, 56(r1)
+ std r7, 64(r1)
+ std r8, 72(r1)
+
+ /*
+ * r3 = BPF_REG_FP + BPF_REG_AX
+ * BPF_REG_FP is r31; BPF_REG_AX is r12 (stack offset in bytes).
+ */
+ add r3, r31, r12
+ bl bpf_check_timed_may_goto
+
+ /* Put return value back into AX */
+ mr r12, r3
+
+ /* Restore BPF registers R0 - R5 (r8, r3-r7) */
+ ld r3, 32(r1)
+ ld r4, 40(r1)
+ ld r5, 48(r1)
+ ld r6, 56(r1)
+ ld r7, 64(r1)
+ ld r8, 72(r1)
+
+ /* Epilogue: pop frame, restore LR, return */
+ addi r1, r1, 112
+ ld r0, 16(r1)
+ mtlr r0
+ blr
+SYM_FUNC_END(arch_bpf_timed_may_goto)
--
2.52.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] powerpc64/bpf: Add powerpc64 JIT support for timed may_goto
2026-04-02 16:10 [PATCH v2] powerpc64/bpf: Add powerpc64 JIT support for timed may_goto Saket Kumar Bhaskar
@ 2026-04-02 19:44 ` Hari Bathini
2026-04-03 9:43 ` Saket Kumar Bhaskar
0 siblings, 1 reply; 3+ messages in thread
From: Hari Bathini @ 2026-04-02 19:44 UTC (permalink / raw)
To: Saket Kumar Bhaskar, linux-kernel, bpf, linuxppc-dev
Cc: sachinpb, venkat88, andrii, eddyz87, ast, daniel, martin.lau,
song, yonghong.song, john.fastabend, kpsingh, sdf, haoluo, jolsa,
chleroy, maddy, mpe, adubey
On 02/04/26 9:40 pm, Saket Kumar Bhaskar wrote:
> When verifier sees a timed may_goto instruction, it emits a call to
> arch_bpf_timed_may_goto() with a stack offset in BPF_REG_AX
> (powerpc64 R12) and expects the refreshed count value to be returned
> in the same register. The verifier doesn't save or restore any registers
> before emitting this call.
>
> arch_bpf_timed_may_goto() should act as a trampoline to call
> bpf_check_timed_may_goto() with powerpc64 ELF ABI calling convention.
>
> To support this custom calling convention, implement
> arch_bpf_timed_may_goto() in assembly and make sure BPF caller saved
> registers are preserved, then call bpf_check_timed_may_goto with
> the powerpc64 ABI calling convention where first argument and return
> value both are in R3. Finally, move the result back into BPF_REG_AX(R12)
> before returning.
>
> Also, introduce bpf_jit_emit_func_call() that computes the offset from
> kernel_toc_addr(), validates that the target and emits the ADDIS/ADDI
> sequence to load the function address before performing the indirect
> branch via MTCTR/BCTRL. The existing code in bpf_jit_emit_func_call_rel()
> is refactored to use this function.
>
Looks good to me.
Acked-by: Hari Bathini <hbathini@linux.ibm.com>
> Signed-off-by: Saket Kumar Bhaskar <skb99@linux.ibm.com>
> ---
> This patch has been rebased on top of these 3 patches on powerpc-next in
> the following sequence:
> 1. https://lore.kernel.org/bpf/20260401103215.104438-1-adubey@linux.ibm.com/
> 2. https://lore.kernel.org/bpf/20260401141043.41513-1-adubey@linux.ibm.com/
> 3. https://lore.kernel.org/bpf/20260401152133.42544-1-adubey@linux.ibm.com/
>
> Changes since v1:
> - Compile bpf_timed_may_goto.o conditionally for PPC64. (Hari)
> - Moved reladdr at the beginning of the function. (Hari)
> - Added error check for bpf_jit_emit_func_call() in
> bpf_jit_build_body(). (Hari)
> - Save registers after 32 bytes as MIN_FRAME_SIZE is 32 bytes for
> powerpc ABIv2. (Hari)
> ---
> arch/powerpc/net/Makefile | 4 ++
> arch/powerpc/net/bpf_jit_comp.c | 5 +++
> arch/powerpc/net/bpf_jit_comp64.c | 62 ++++++++++++++++++++++-----
> arch/powerpc/net/bpf_timed_may_goto.S | 57 ++++++++++++++++++++++++
> 4 files changed, 117 insertions(+), 11 deletions(-)
> create mode 100644 arch/powerpc/net/bpf_timed_may_goto.S
>
> diff --git a/arch/powerpc/net/Makefile b/arch/powerpc/net/Makefile
> index 8e60af32e51e..87395d7e2672 100644
> --- a/arch/powerpc/net/Makefile
> +++ b/arch/powerpc/net/Makefile
> @@ -3,3 +3,7 @@
> # Arch-specific network modules
> #
> obj-$(CONFIG_BPF_JIT) += bpf_jit_comp.o bpf_jit_comp$(BITS).o
> +
> +ifdef CONFIG_PPC64
> ++obj-$(CONFIG_BPF_JIT) += bpf_timed_may_goto.o
> +endif
> diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
> index 50103b3794fb..9b2b456b0765 100644
> --- a/arch/powerpc/net/bpf_jit_comp.c
> +++ b/arch/powerpc/net/bpf_jit_comp.c
> @@ -537,6 +537,11 @@ bool bpf_jit_supports_subprog_tailcalls(void)
> return IS_ENABLED(CONFIG_PPC64);
> }
>
> +bool bpf_jit_supports_timed_may_goto(void)
> +{
> + return IS_ENABLED(CONFIG_PPC64);
> +}
> +
> bool bpf_jit_supports_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 db364d9083e7..dab106cae22b 100644
> --- a/arch/powerpc/net/bpf_jit_comp64.c
> +++ b/arch/powerpc/net/bpf_jit_comp64.c
> @@ -451,10 +451,28 @@ void arch_bpf_stack_walk(bool (*consume_fn)(void *, u64, u64, u64), void *cookie
> }
> }
>
> +static int bpf_jit_emit_func_call(u32 *image, struct codegen_context *ctx, u64 func_addr, int reg)
> +{
> + long reladdr = func_addr - kernel_toc_addr();
> +
> + if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
> + pr_err("eBPF: address of %ps out of range of kernel_toc.\n", (void *)func_addr);
> + return -ERANGE;
> + }
> +
> + EMIT(PPC_RAW_ADDIS(reg, _R2, PPC_HA(reladdr)));
> + EMIT(PPC_RAW_ADDI(reg, reg, PPC_LO(reladdr)));
> + EMIT(PPC_RAW_MTCTR(reg));
> + EMIT(PPC_RAW_BCTRL());
> +
> + return 0;
> +}
> +
> 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;
> + long __maybe_unused reladdr;
> + int ret;
>
> /* bpf to bpf call, func is not known in the initial pass. Emit 5 nops as a placeholder */
> if (!func) {
> @@ -507,16 +525,9 @@ int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *
> EMIT(PPC_RAW_BCTRL());
> #else
> if (core_kernel_text(func_addr)) {
> - reladdr = func_addr - kernel_toc_addr();
> - if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
> - pr_err("eBPF: address of %ps out of range of kernel_toc.\n", (void *)func);
> - return -ERANGE;
> - }
> -
> - EMIT(PPC_RAW_ADDIS(_R12, _R2, PPC_HA(reladdr)));
> - EMIT(PPC_RAW_ADDI(_R12, _R12, PPC_LO(reladdr)));
> - EMIT(PPC_RAW_MTCTR(_R12));
> - EMIT(PPC_RAW_BCTRL());
> + ret = bpf_jit_emit_func_call(image, ctx, func_addr, _R12);
> + if (ret)
> + return ret;
> } else {
> if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1)) {
> /* func points to the function descriptor */
> @@ -1755,6 +1766,35 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
> if (ret < 0)
> return ret;
>
> + /*
> + * Call to arch_bpf_timed_may_goto() is emitted by the
> + * verifier and called with custom calling convention with
> + * first argument and return value in BPF_REG_AX (_R12).
> + *
> + * The generic helper or bpf function call emission path
> + * may use the same scratch register as BPF_REG_AX to
> + * materialize the target address. This would clobber AX
> + * and break timed may_goto semantics.
> + *
> + * Emit a minimal indirect call sequence here using a temp
> + * register and skip the normal post-call return-value move.
> + */
> +
> + if (func_addr == (u64)arch_bpf_timed_may_goto) {
> + ret = 0;
> + if (!IS_ENABLED(CONFIG_PPC_KERNEL_PCREL))
> + ret = bpf_jit_emit_func_call(image, ctx, func_addr,
> + tmp1_reg);
> +
> + if (ret || IS_ENABLED(CONFIG_PPC_KERNEL_PCREL)) {
> + PPC_LI_ADDR(tmp1_reg, func_addr);
> + EMIT(PPC_RAW_MTCTR(tmp1_reg));
> + EMIT(PPC_RAW_BCTRL());
> + }
> +
> + break;
> + }
> +
> /* Take care of powerpc ABI requirements before kfunc call */
> if (insn[i].src_reg == BPF_PSEUDO_KFUNC_CALL) {
> if (prepare_for_kfunc_call(fp, image, ctx, &insn[i]))
> diff --git a/arch/powerpc/net/bpf_timed_may_goto.S b/arch/powerpc/net/bpf_timed_may_goto.S
> new file mode 100644
> index 000000000000..6fd8b1c9f4ac
> --- /dev/null
> +++ b/arch/powerpc/net/bpf_timed_may_goto.S
> @@ -0,0 +1,57 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Copyright (c) 2025 IBM Corporation, Saket Kumar Bhaskar <skb99@linux.ibm.com> */
> +
> +#include <linux/linkage.h>
> +#include <asm/ppc_asm.h>
> +
> +/*
> + * arch_bpf_timed_may_goto() trampoline for powerpc64
> + *
> + * Custom BPF convention (verifier/JIT):
> + * - input: stack offset in BPF_REG_AX (r12)
> + * - output: updated count in BPF_REG_AX (r12)
> + *
> + * Call bpf_check_timed_may_goto(ptr) with normal powerpc64 ABI:
> + * - r3 = ptr, return in r3
> + *
> + * Preserve BPF regs R0-R5 (mapping: r8, r3-r7).
> + */
> +
> +SYM_FUNC_START(arch_bpf_timed_may_goto)
> + /* Prologue: save LR, allocate frame */
> + mflr r0
> + std r0, 16(r1)
> + stdu r1, -112(r1)
> +
> + /* Save BPF registers R0 - R5 (r8, r3-r7) */
> + std r3, 32(r1)
> + std r4, 40(r1)
> + std r5, 48(r1)
> + std r6, 56(r1)
> + std r7, 64(r1)
> + std r8, 72(r1)
> +
> + /*
> + * r3 = BPF_REG_FP + BPF_REG_AX
> + * BPF_REG_FP is r31; BPF_REG_AX is r12 (stack offset in bytes).
> + */
> + add r3, r31, r12
> + bl bpf_check_timed_may_goto
> +
> + /* Put return value back into AX */
> + mr r12, r3
> +
> + /* Restore BPF registers R0 - R5 (r8, r3-r7) */
> + ld r3, 32(r1)
> + ld r4, 40(r1)
> + ld r5, 48(r1)
> + ld r6, 56(r1)
> + ld r7, 64(r1)
> + ld r8, 72(r1)
> +
> + /* Epilogue: pop frame, restore LR, return */
> + addi r1, r1, 112
> + ld r0, 16(r1)
> + mtlr r0
> + blr
> +SYM_FUNC_END(arch_bpf_timed_may_goto)
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] powerpc64/bpf: Add powerpc64 JIT support for timed may_goto
2026-04-02 19:44 ` Hari Bathini
@ 2026-04-03 9:43 ` Saket Kumar Bhaskar
0 siblings, 0 replies; 3+ messages in thread
From: Saket Kumar Bhaskar @ 2026-04-03 9:43 UTC (permalink / raw)
To: Hari Bathini
Cc: linux-kernel, bpf, linuxppc-dev, sachinpb, venkat88, andrii,
eddyz87, ast, daniel, martin.lau, song, yonghong.song,
john.fastabend, kpsingh, sdf, haoluo, jolsa, chleroy, maddy, mpe,
adubey
On Fri, Apr 03, 2026 at 01:14:09AM +0530, Hari Bathini wrote:
>
>
> On 02/04/26 9:40 pm, Saket Kumar Bhaskar wrote:
> > When verifier sees a timed may_goto instruction, it emits a call to
> > arch_bpf_timed_may_goto() with a stack offset in BPF_REG_AX
> > (powerpc64 R12) and expects the refreshed count value to be returned
> > in the same register. The verifier doesn't save or restore any registers
> > before emitting this call.
> >
> > arch_bpf_timed_may_goto() should act as a trampoline to call
> > bpf_check_timed_may_goto() with powerpc64 ELF ABI calling convention.
> >
> > To support this custom calling convention, implement
> > arch_bpf_timed_may_goto() in assembly and make sure BPF caller saved
> > registers are preserved, then call bpf_check_timed_may_goto with
> > the powerpc64 ABI calling convention where first argument and return
> > value both are in R3. Finally, move the result back into BPF_REG_AX(R12)
> > before returning.
> >
> > Also, introduce bpf_jit_emit_func_call() that computes the offset from
> > kernel_toc_addr(), validates that the target and emits the ADDIS/ADDI
> > sequence to load the function address before performing the indirect
> > branch via MTCTR/BCTRL. The existing code in bpf_jit_emit_func_call_rel()
> > is refactored to use this function.
> >
>
> Looks good to me.
>
> Acked-by: Hari Bathini <hbathini@linux.ibm.com>
>
> > Signed-off-by: Saket Kumar Bhaskar <skb99@linux.ibm.com>
> > ---
> > This patch has been rebased on top of these 3 patches on powerpc-next in
> > the following sequence:
> > 1. https://lore.kernel.org/bpf/20260401103215.104438-1-adubey@linux.ibm.com/
> > 2. https://lore.kernel.org/bpf/20260401141043.41513-1-adubey@linux.ibm.com/
> > 3. https://lore.kernel.org/bpf/20260401152133.42544-1-adubey@linux.ibm.com/
> >
> > Changes since v1:
> > - Compile bpf_timed_may_goto.o conditionally for PPC64. (Hari)
> > - Moved reladdr at the beginning of the function. (Hari)
> > - Added error check for bpf_jit_emit_func_call() in
> > bpf_jit_build_body(). (Hari)
> > - Save registers after 32 bytes as MIN_FRAME_SIZE is 32 bytes for
> > powerpc ABIv2. (Hari)
> > ---
> > arch/powerpc/net/Makefile | 4 ++
> > arch/powerpc/net/bpf_jit_comp.c | 5 +++
> > arch/powerpc/net/bpf_jit_comp64.c | 62 ++++++++++++++++++++++-----
> > arch/powerpc/net/bpf_timed_may_goto.S | 57 ++++++++++++++++++++++++
> > 4 files changed, 117 insertions(+), 11 deletions(-)
> > create mode 100644 arch/powerpc/net/bpf_timed_may_goto.S
> >
> > diff --git a/arch/powerpc/net/Makefile b/arch/powerpc/net/Makefile
> > index 8e60af32e51e..87395d7e2672 100644
> > --- a/arch/powerpc/net/Makefile
> > +++ b/arch/powerpc/net/Makefile
> > @@ -3,3 +3,7 @@
> > # Arch-specific network modules
> > #
> > obj-$(CONFIG_BPF_JIT) += bpf_jit_comp.o bpf_jit_comp$(BITS).o
> > +
> > +ifdef CONFIG_PPC64
> > ++obj-$(CONFIG_BPF_JIT) += bpf_timed_may_goto.o
Apologies, a stray '+' slipped into the patch. I'll send a corrected respin shortly.
-Saket
> > +endif
> > diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
> > index 50103b3794fb..9b2b456b0765 100644
> > --- a/arch/powerpc/net/bpf_jit_comp.c
> > +++ b/arch/powerpc/net/bpf_jit_comp.c
> > @@ -537,6 +537,11 @@ bool bpf_jit_supports_subprog_tailcalls(void)
> > return IS_ENABLED(CONFIG_PPC64);
> > }
> > +bool bpf_jit_supports_timed_may_goto(void)
> > +{
> > + return IS_ENABLED(CONFIG_PPC64);
> > +}
> > +
> > bool bpf_jit_supports_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 db364d9083e7..dab106cae22b 100644
> > --- a/arch/powerpc/net/bpf_jit_comp64.c
> > +++ b/arch/powerpc/net/bpf_jit_comp64.c
> > @@ -451,10 +451,28 @@ void arch_bpf_stack_walk(bool (*consume_fn)(void *, u64, u64, u64), void *cookie
> > }
> > }
> > +static int bpf_jit_emit_func_call(u32 *image, struct codegen_context *ctx, u64 func_addr, int reg)
> > +{
> > + long reladdr = func_addr - kernel_toc_addr();
> > +
> > + if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
> > + pr_err("eBPF: address of %ps out of range of kernel_toc.\n", (void *)func_addr);
> > + return -ERANGE;
> > + }
> > +
> > + EMIT(PPC_RAW_ADDIS(reg, _R2, PPC_HA(reladdr)));
> > + EMIT(PPC_RAW_ADDI(reg, reg, PPC_LO(reladdr)));
> > + EMIT(PPC_RAW_MTCTR(reg));
> > + EMIT(PPC_RAW_BCTRL());
> > +
> > + return 0;
> > +}
> > +
> > 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;
> > + long __maybe_unused reladdr;
> > + int ret;
> > /* bpf to bpf call, func is not known in the initial pass. Emit 5 nops as a placeholder */
> > if (!func) {
> > @@ -507,16 +525,9 @@ int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *
> > EMIT(PPC_RAW_BCTRL());
> > #else
> > if (core_kernel_text(func_addr)) {
> > - reladdr = func_addr - kernel_toc_addr();
> > - if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
> > - pr_err("eBPF: address of %ps out of range of kernel_toc.\n", (void *)func);
> > - return -ERANGE;
> > - }
> > -
> > - EMIT(PPC_RAW_ADDIS(_R12, _R2, PPC_HA(reladdr)));
> > - EMIT(PPC_RAW_ADDI(_R12, _R12, PPC_LO(reladdr)));
> > - EMIT(PPC_RAW_MTCTR(_R12));
> > - EMIT(PPC_RAW_BCTRL());
> > + ret = bpf_jit_emit_func_call(image, ctx, func_addr, _R12);
> > + if (ret)
> > + return ret;
> > } else {
> > if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1)) {
> > /* func points to the function descriptor */
> > @@ -1755,6 +1766,35 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
> > if (ret < 0)
> > return ret;
> > + /*
> > + * Call to arch_bpf_timed_may_goto() is emitted by the
> > + * verifier and called with custom calling convention with
> > + * first argument and return value in BPF_REG_AX (_R12).
> > + *
> > + * The generic helper or bpf function call emission path
> > + * may use the same scratch register as BPF_REG_AX to
> > + * materialize the target address. This would clobber AX
> > + * and break timed may_goto semantics.
> > + *
> > + * Emit a minimal indirect call sequence here using a temp
> > + * register and skip the normal post-call return-value move.
> > + */
> > +
> > + if (func_addr == (u64)arch_bpf_timed_may_goto) {
> > + ret = 0;
> > + if (!IS_ENABLED(CONFIG_PPC_KERNEL_PCREL))
> > + ret = bpf_jit_emit_func_call(image, ctx, func_addr,
> > + tmp1_reg);
> > +
> > + if (ret || IS_ENABLED(CONFIG_PPC_KERNEL_PCREL)) {
> > + PPC_LI_ADDR(tmp1_reg, func_addr);
> > + EMIT(PPC_RAW_MTCTR(tmp1_reg));
> > + EMIT(PPC_RAW_BCTRL());
> > + }
> > +
> > + break;
> > + }
> > +
> > /* Take care of powerpc ABI requirements before kfunc call */
> > if (insn[i].src_reg == BPF_PSEUDO_KFUNC_CALL) {
> > if (prepare_for_kfunc_call(fp, image, ctx, &insn[i]))
> > diff --git a/arch/powerpc/net/bpf_timed_may_goto.S b/arch/powerpc/net/bpf_timed_may_goto.S
> > new file mode 100644
> > index 000000000000..6fd8b1c9f4ac
> > --- /dev/null
> > +++ b/arch/powerpc/net/bpf_timed_may_goto.S
> > @@ -0,0 +1,57 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/* Copyright (c) 2025 IBM Corporation, Saket Kumar Bhaskar <skb99@linux.ibm.com> */
> > +
> > +#include <linux/linkage.h>
> > +#include <asm/ppc_asm.h>
> > +
> > +/*
> > + * arch_bpf_timed_may_goto() trampoline for powerpc64
> > + *
> > + * Custom BPF convention (verifier/JIT):
> > + * - input: stack offset in BPF_REG_AX (r12)
> > + * - output: updated count in BPF_REG_AX (r12)
> > + *
> > + * Call bpf_check_timed_may_goto(ptr) with normal powerpc64 ABI:
> > + * - r3 = ptr, return in r3
> > + *
> > + * Preserve BPF regs R0-R5 (mapping: r8, r3-r7).
> > + */
> > +
> > +SYM_FUNC_START(arch_bpf_timed_may_goto)
> > + /* Prologue: save LR, allocate frame */
> > + mflr r0
> > + std r0, 16(r1)
> > + stdu r1, -112(r1)
> > +
> > + /* Save BPF registers R0 - R5 (r8, r3-r7) */
> > + std r3, 32(r1)
> > + std r4, 40(r1)
> > + std r5, 48(r1)
> > + std r6, 56(r1)
> > + std r7, 64(r1)
> > + std r8, 72(r1)
> > +
> > + /*
> > + * r3 = BPF_REG_FP + BPF_REG_AX
> > + * BPF_REG_FP is r31; BPF_REG_AX is r12 (stack offset in bytes).
> > + */
> > + add r3, r31, r12
> > + bl bpf_check_timed_may_goto
> > +
> > + /* Put return value back into AX */
> > + mr r12, r3
> > +
> > + /* Restore BPF registers R0 - R5 (r8, r3-r7) */
> > + ld r3, 32(r1)
> > + ld r4, 40(r1)
> > + ld r5, 48(r1)
> > + ld r6, 56(r1)
> > + ld r7, 64(r1)
> > + ld r8, 72(r1)
> > +
> > + /* Epilogue: pop frame, restore LR, return */
> > + addi r1, r1, 112
> > + ld r0, 16(r1)
> > + mtlr r0
> > + blr
> > +SYM_FUNC_END(arch_bpf_timed_may_goto)
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2026-04-03 9:44 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-04-02 16:10 [PATCH v2] powerpc64/bpf: Add powerpc64 JIT support for timed may_goto Saket Kumar Bhaskar
2026-04-02 19:44 ` Hari Bathini
2026-04-03 9:43 ` Saket Kumar Bhaskar
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox