From: Naveen N. Rao Date: Wed, 22 Jun 2016 16:25:02 +0000 (+0530) Subject: powerpc/bpf/jit: Fix/enhance 32-bit Load Immediate implementation X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=aaf2f7e09932a08c1287d8e4c602bccbe98f60a6;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git powerpc/bpf/jit: Fix/enhance 32-bit Load Immediate implementation The existing LI32() macro can sometimes result in a sign-extended 32-bit load that does not clear the top 32-bits properly. As an example, loading 0x7fffffff results in the register containing 0xffffffff7fffffff. While this does not impact classic BPF JIT implementation (since that only uses the lower word for all operations), we would like to share this macro between classic BPF JIT and extended BPF JIT, wherein the entire 64-bit value in the register matters. Fix this by first doing a shifted LI followed by ORI. An additional optimization is with loading values between -32768 to -1, where we now only need a single LI. The new implementation now generates the same or less number of instructions. Acked-by: Alexei Starovoitov Signed-off-by: Naveen N. Rao Signed-off-by: Michael Ellerman --- diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h index 889fd199a821..a9882db9ecaa 100644 --- a/arch/powerpc/net/bpf_jit.h +++ b/arch/powerpc/net/bpf_jit.h @@ -232,10 +232,17 @@ DECLARE_LOAD_FUNC(sk_load_byte_msh); (((cond) & 0x3ff) << 16) | \ (((dest) - (ctx->idx * 4)) & \ 0xfffc)) -#define PPC_LI32(d, i) do { PPC_LI(d, IMM_L(i)); \ - if ((u32)(uintptr_t)(i) >= 32768) { \ - PPC_ADDIS(d, d, IMM_HA(i)); \ +/* Sign-extended 32-bit immediate load */ +#define PPC_LI32(d, i) do { \ + if ((int)(uintptr_t)(i) >= -32768 && \ + (int)(uintptr_t)(i) < 32768) \ + PPC_LI(d, i); \ + else { \ + PPC_LIS(d, IMM_H(i)); \ + if (IMM_L(i)) \ + PPC_ORI(d, d, IMM_L(i)); \ } } while(0) + #define PPC_LI64(d, i) do { \ if (!((uintptr_t)(i) & 0xffffffff00000000ULL)) \ PPC_LI32(d, i); \