diff options
| author | Christophe Leroy <christophe.leroy@csgroup.eu> | 2023-02-01 11:04:25 +0100 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2023-02-10 12:17:34 +0100 |
| commit | d084dcf256bc4565b4b1af9b00297ac7b51c7049 (patch) | |
| tree | fe3f57b038e43029822b10bab7df63833295b13a /arch/powerpc | |
| parent | powerpc/bpf/32: No need to zeroise r4 when not doing tail call (diff) | |
| download | linux-d084dcf256bc4565b4b1af9b00297ac7b51c7049.tar.xz linux-d084dcf256bc4565b4b1af9b00297ac7b51c7049.zip | |
powerpc/bpf/32: Only set a stack frame when necessary
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/62d7b654a3cfe73d998697cb29bbc5ffd89bfdb1.1675245773.git.christophe.leroy@csgroup.eu
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/net/bpf_jit_comp32.c | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c index 4e6caee9c98a..7f54d37bede6 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; @@ -121,7 +135,8 @@ 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))); @@ -174,7 +189,8 @@ 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)); |