Signed-off-by: Saket Kumar Bhaskar <[email protected]>
---
This patch has been rebased on top of these 3 patches on powerpc-next in
the following sequence:
1. https://lore.kernel.org/bpf/[email protected]/
2. https://lore.kernel.org/bpf/[email protected]/
3. https://lore.kernel.org/bpf/[email protected]/
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
<[email protected]> */
+
+#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)
