From: Christophe Leroy christophe.leroy@csgroup.eu
[ Upstream commit d084dcf256bc4565b4b1af9b00297ac7b51c7049 ]
Until now a stack frame was set at all time due to the need to keep tail call counter in the stack.
But since commit 89d21e259a94 ("powerpc/bpf/32: Fix Oops on tail call tests") the tail call counter is passed via register r4. It is therefore not necessary anymore to have a stack frame for that.
Just like PPC64, implement bpf_has_stack_frame() and only sets the frame when needed.
The difference with PPC64 is that PPC32 doesn't have a redzone, so the stack is required as soon as non volatile registers are used or when tail call count is set up.
Signed-off-by: Christophe Leroy christophe.leroy@csgroup.eu [mpe: Fix commit reference in change log] Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/62d7b654a3cfe73d998697cb29bbc5ffd89bfdb1.167524577... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/net/bpf_jit_comp32.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c index a379b0ce19ffa..8643b2c8b76ef 100644 --- a/arch/powerpc/net/bpf_jit_comp32.c +++ b/arch/powerpc/net/bpf_jit_comp32.c @@ -79,6 +79,20 @@ static int bpf_jit_stack_offsetof(struct codegen_context *ctx, int reg) #define SEEN_NVREG_FULL_MASK 0x0003ffff /* Non volatile registers r14-r31 */ #define SEEN_NVREG_TEMP_MASK 0x00001e01 /* BPF_REG_5, BPF_REG_AX, TMP_REG */
+static inline bool bpf_has_stack_frame(struct codegen_context *ctx) +{ + /* + * We only need a stack frame if: + * - we call other functions (kernel helpers), or + * - we use non volatile registers, or + * - we use tail call counter + * - the bpf program uses its stack area + * The latter condition is deduced from the usage of BPF_REG_FP + */ + return ctx->seen & (SEEN_FUNC | SEEN_TAILCALL | SEEN_NVREG_FULL_MASK) || + bpf_is_seen_register(ctx, bpf_to_ppc(BPF_REG_FP)); +} + void bpf_jit_realloc_regs(struct codegen_context *ctx) { unsigned int nvreg_mask; @@ -118,7 +132,8 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
#define BPF_TAILCALL_PROLOGUE_SIZE 4
- EMIT(PPC_RAW_STWU(_R1, _R1, -BPF_PPC_STACKFRAME(ctx))); + if (bpf_has_stack_frame(ctx)) + EMIT(PPC_RAW_STWU(_R1, _R1, -BPF_PPC_STACKFRAME(ctx)));
if (ctx->seen & SEEN_TAILCALL) EMIT(PPC_RAW_STW(_R4, _R1, bpf_jit_stack_offsetof(ctx, BPF_PPC_TC))); @@ -171,7 +186,8 @@ static void bpf_jit_emit_common_epilogue(u32 *image, struct codegen_context *ctx EMIT(PPC_RAW_LWZ(_R0, _R1, BPF_PPC_STACKFRAME(ctx) + PPC_LR_STKOFF));
/* Tear down our stack frame */ - EMIT(PPC_RAW_ADDI(_R1, _R1, BPF_PPC_STACKFRAME(ctx))); + if (bpf_has_stack_frame(ctx)) + EMIT(PPC_RAW_ADDI(_R1, _R1, BPF_PPC_STACKFRAME(ctx)));
if (ctx->seen & SEEN_FUNC) EMIT(PPC_RAW_MTLR(_R0));