text: // SPDX-License-Identifier: GPL-2.0 OR MIT
  /*
   * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
   */
  
  #include <asm/hwcap.h>
  #include <asm/neon.h>
  
  asmlinkage void poly1305_init_arm(void *ctx, const u8 key[16]);
  asmlinkage void poly1305_blocks_arm(void *ctx, const u8 *inp, const size_t len,
  				    const u32 padbit);
  asmlinkage void poly1305_emit_arm(void *ctx, u8 mac[16], const u32 nonce[4]);
  asmlinkage void poly1305_blocks_neon(void *ctx, const u8 *inp, const size_t len,
  				     const u32 padbit);
  asmlinkage void poly1305_emit_neon(void *ctx, u8 mac[16], const u32 nonce[4]);
  
  static bool poly1305_use_neon __ro_after_init;
  static bool *const poly1305_nobs[] __initconst = { &poly1305_use_neon };
  
  static void __init poly1305_fpu_init(void)
  {
  #if defined(CONFIG_ZINC_ARCH_ARM64)
  	poly1305_use_neon = elf_hwcap & HWCAP_ASIMD;
  #elif defined(CONFIG_ZINC_ARCH_ARM)
  	poly1305_use_neon = elf_hwcap & HWCAP_NEON;
  #endif
  }
  
  #if defined(CONFIG_ZINC_ARCH_ARM64)
  struct poly1305_arch_internal {
  	union {
  		u32 h[5];
  		struct {
  			u64 h0, h1, h2;
  		};
  	};
  	u64 is_base2_26;
  	u64 r[2];
  };
  #elif defined(CONFIG_ZINC_ARCH_ARM)
  struct poly1305_arch_internal {
  	union {
  		u32 h[5];
  		struct {
  			u64 h0, h1;
  			u32 h2;
  		} __packed;
  	};
  	u32 r[4];
  	u32 is_base2_26;
  };
  #endif
  
  /* The NEON code uses base 2^26, while the scalar code uses base 2^64 on 64-bit
   * and base 2^32 on 32-bit. If we hit the unfortunate situation of using NEON
   * and then having to go back to scalar -- because the user is silly and has
   * called the update function from two separate contexts -- then we need to
   * convert back to the original base before proceeding. The below function is
   * written for 64-bit integers, and so we have to swap words at the end on
   * big-endian 32-bit. It is possible to reason that the initial reduction below
   * is sufficient given the implementation invariants. However, for an avoidance
   * of doubt and because this is not performance critical, we do the full
   * reduction anyway.
   */
  static void convert_to_base2_64(void *ctx)
  {
  	struct poly1305_arch_internal *state = ctx;
  	u32 cy;
  
  	if (!IS_ENABLED(CONFIG_KERNEL_MODE_NEON) || !state->is_base2_26)
  		return;
  
  	cy = state->h[0] >> 26; state->h[0] &= 0x3ffffff; state->h[1] += cy;
  	cy = state->h[1] >> 26; state->h[1] &= 0x3ffffff; state->h[2] += cy;
  	cy = state->h[2] >> 26; state->h[2] &= 0x3ffffff; state->h[3] += cy;
  	cy = state->h[3] >> 26; state->h[3] &= 0x3ffffff; state->h[4] += cy;
  	state->h0 = ((u64)state->h[2] << 52) | ((u64)state->h[1] << 26) | state->h[0];
  	state->h1 = ((u64)state->h[4] << 40) | ((u64)state->h[3] << 14) | (state->h[2] >> 12);
  	state->h2 = state->h[4] >> 24;
  	if (IS_ENABLED(CONFIG_ZINC_ARCH_ARM) && IS_ENABLED(CONFIG_CPU_BIG_ENDIAN)) {
  		state->h0 = rol64(state->h0, 32);
  		state->h1 = rol64(state->h1, 32);
  	}
  #define ULT(a, b) ((a ^ ((a ^ b) | ((a - b) ^ b))) >> (sizeof(a) * 8 - 1))
  	cy = (state->h2 >> 2) + (state->h2 & ~3ULL);
  	state->h2 &= 3;
  	state->h0 += cy;
  	state->h1 += (cy = ULT(state->h0, cy));
  	state->h2 += ULT(state->h1, cy);
  #undef ULT
  	state->is_base2_26 = 0;
  }
  
  static inline bool poly1305_init_arch(void *ctx,
  				      const u8 key[POLY1305_KEY_SIZE])
  {
  	poly1305_init_arm(ctx, key);
  	return true;
  }
  
  static inline bool poly1305_blocks_arch(void *ctx, const u8 *inp,
  					size_t len, const u32 padbit,
  					simd_context_t *simd_context)
  {
  	/* SIMD disables preemption, so relax after processing each page. */
  	BUILD_BUG_ON(PAGE_SIZE < POLY1305_BLOCK_SIZE ||
  		     PAGE_SIZE % POLY1305_BLOCK_SIZE);
  
  	if (!IS_ENABLED(CONFIG_KERNEL_MODE_NEON) || !poly1305_use_neon ||
  	    !simd_use(simd_context)) {
  		convert_to_base2_64(ctx);
  		poly1305_blocks_arm(ctx, inp, len, padbit);
  		return true;
  	}
  
  	for (;;) {
  		const size_t bytes = min_t(size_t, len, PAGE_SIZE);
  
  		poly1305_blocks_neon(ctx, inp, bytes, padbit);
  		len -= bytes;
  		if (!len)
  			break;
  		inp += bytes;
  		simd_relax(simd_context);
  	}
  	return true;
  }
  
  static inline bool poly1305_emit_arch(void *ctx, u8 mac[POLY1305_MAC_SIZE],
  				      const u32 nonce[4],
  				      simd_context_t *simd_context)
  {
  	if (!IS_ENABLED(CONFIG_KERNEL_MODE_NEON) || !poly1305_use_neon ||
  	    !simd_use(simd_context)) {
  		convert_to_base2_64(ctx);
  		poly1305_emit_arm(ctx, mac, nonce);
  	} else
  		poly1305_emit_neon(ctx, mac, nonce);
  	return true;
  }
  