[PATCH v3 2/2] powerpc32/bpf: Add fsession support

[adubey@linux.ibm.com]

From: Abhishek Dubey <adubey@linux.ibm.com>

Extend JIT support of fsession in powerpc64 trampoline, since
ppc64 and ppc32 shares common trampoline implementation.
Arch specific helpers handle 64-bit data copy using 32 bit regs.

Need to validate fsession support along with trampoline support.

Signed-off-by: Abhishek Dubey <adubey@linux.ibm.com>
---

v2->v3:
  Address comments around PPC_LI32
v1->v2:
  No change since v1
    
[v2]: https://lore.kernel.org/bpf/20260226041217.18059-1-adubey@linux.ibm.com
[v1]: https://lore.kernel.org/bpf/20260216155310.38457-1-adubey@linux.ibm.com

 arch/powerpc/net/bpf_jit_comp.c   |  8 ++++++-
 arch/powerpc/net/bpf_jit_comp32.c | 35 +++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 16d15ff3145a..b2fdf8ff9c60 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -542,7 +542,13 @@ bool bpf_jit_supports_private_stack(void)
 
 bool bpf_jit_supports_fsession(void)
 {
-	return IS_ENABLED(CONFIG_PPC64);
+	/*
+	 * TODO: Remove after validating support
+	 * for fsession and trampoline on ppc32.
+	 */
+	if (IS_ENABLED(CONFIG_PPC32))
+		return -EOPNOTSUPP;
+	return true;
 }
 
 bool bpf_jit_supports_arena(void)
diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
index 3087e744fb25..f3ae89e1d1d0 100644
--- a/arch/powerpc/net/bpf_jit_comp32.c
+++ b/arch/powerpc/net/bpf_jit_comp32.c
@@ -123,6 +123,41 @@ void bpf_jit_realloc_regs(struct codegen_context *ctx)
 	}
 }
 
+void prepare_for_fsession_fentry(u32 *image, struct codegen_context *ctx, int cookie_cnt,
+						int cookie_off, int retval_off)
+{
+	/*
+	 * Set session cookies value
+	 * Clear cookies field on stack
+	 * Ensure retval to be cleared on fentry
+	 */
+	EMIT(PPC_RAW_LI(bpf_to_ppc(TMP_REG), 0));
+
+	for (int i = 0; i < cookie_cnt; i++) {
+		EMIT(PPC_RAW_STW(bpf_to_ppc(TMP_REG), _R1, cookie_off + 4 * i));
+		EMIT(PPC_RAW_STW(bpf_to_ppc(TMP_REG), _R1, cookie_off + 4 * i + 4));
+	}
+
+	EMIT(PPC_RAW_STW(bpf_to_ppc(TMP_REG), _R1, retval_off));
+	EMIT(PPC_RAW_STW(bpf_to_ppc(TMP_REG), _R1, retval_off + 4));
+}
+
+void store_func_meta(u32 *image, struct codegen_context *ctx,
+					u64 func_meta, int func_meta_off)
+{
+	/*
+	 * Store func_meta to stack: [R1 + func_meta_off] = func_meta
+	 * func_meta := argument count in first byte + cookie value
+	 */
+	/* Store lower word */
+	EMIT(PPC_RAW_LI32(bpf_to_ppc(TMP_REG), (u32)func_meta));
+	EMIT(PPC_RAW_STW(bpf_to_ppc(TMP_REG), _R1, func_meta_off));
+
+	/* Store upper word */
+	EMIT(PPC_RAW_LI32(bpf_to_ppc(TMP_REG), (u32)(func_meta >> 32)));
+	EMIT(PPC_RAW_STW(bpf_to_ppc(TMP_REG), _R1, func_meta_off + 4));
+}
+
 void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
 {
 	int i;
-- 
2.52.0