diff options
Diffstat (limited to 'arch/arm/net/bpf_jit_32.c')
| -rw-r--r-- | arch/arm/net/bpf_jit_32.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c index a951276f0547..a903b26cde40 100644 --- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -36,6 +36,10 @@ * +-----+ * |RSVD | JIT scratchpad * current ARM_SP => +-----+ <= (BPF_FP - STACK_SIZE + SCRATCH_SIZE) + * | ... | caller-saved registers + * +-----+ + * | ... | arguments passed on stack + * ARM_SP during call => +-----| * | | * | ... | Function call stack * | | @@ -63,6 +67,12 @@ * * When popping registers off the stack at the end of a BPF function, we * reference them via the current ARM_FP register. + * + * Some eBPF operations are implemented via a call to a helper function. + * Such calls are "invisible" in the eBPF code, so it is up to the calling + * program to preserve any caller-saved ARM registers during the call. The + * JIT emits code to push and pop those registers onto the stack, immediately + * above the callee stack frame. */ #define CALLEE_MASK (1 << ARM_R4 | 1 << ARM_R5 | 1 << ARM_R6 | \ 1 << ARM_R7 | 1 << ARM_R8 | 1 << ARM_R9 | \ @@ -70,6 +80,8 @@ #define CALLEE_PUSH_MASK (CALLEE_MASK | 1 << ARM_LR) #define CALLEE_POP_MASK (CALLEE_MASK | 1 << ARM_PC) +#define CALLER_MASK (1 << ARM_R0 | 1 << ARM_R1 | 1 << ARM_R2 | 1 << ARM_R3) + enum { /* Stack layout - these are offsets from (top of stack - 4) */ BPF_R2_HI, @@ -464,6 +476,7 @@ static inline int epilogue_offset(const struct jit_ctx *ctx) static inline void emit_udivmod(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx, u8 op) { + const int exclude_mask = BIT(ARM_R0) | BIT(ARM_R1); const s8 *tmp = bpf2a32[TMP_REG_1]; #if __LINUX_ARM_ARCH__ == 7 @@ -495,11 +508,17 @@ static inline void emit_udivmod(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx, u8 op) emit(ARM_MOV_R(ARM_R0, rm), ctx); } + /* Push caller-saved registers on stack */ + emit(ARM_PUSH(CALLER_MASK & ~exclude_mask), ctx); + /* Call appropriate function */ emit_mov_i(ARM_IP, op == BPF_DIV ? (u32)jit_udiv32 : (u32)jit_mod32, ctx); emit_blx_r(ARM_IP, ctx); + /* Restore caller-saved registers from stack */ + emit(ARM_POP(CALLER_MASK & ~exclude_mask), ctx); + /* Save return value */ if (rd != ARM_R0) emit(ARM_MOV_R(rd, ARM_R0), ctx); |