--- /dev/null
+/// -*- mode: asm; asm-comment-char: ?/ -*-
+///
+/// ARM crypto-extension-based implementation of Rijndael
+///
+/// (c) 2016 Straylight/Edgeware
+///
+
+///----- Licensing notice ---------------------------------------------------
+///
+/// This file is part of Catacomb.
+///
+/// Catacomb is free software; you can redistribute it and/or modify
+/// it under the terms of the GNU Library General Public License as
+/// published by the Free Software Foundation; either version 2 of the
+/// License, or (at your option) any later version.
+///
+/// Catacomb is distributed in the hope that it will be useful,
+/// but WITHOUT ANY WARRANTY; without even the implied warranty of
+/// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+/// GNU Library General Public License for more details.
+///
+/// You should have received a copy of the GNU Library General Public
+/// License along with Catacomb; if not, write to the Free
+/// Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+/// MA 02111-1307, USA.
+
+///--------------------------------------------------------------------------
+/// External definitions.
+
+#include "config.h"
+#include "asm-common.h"
+
+ .globl F(abort)
+ .globl F(rijndael_rcon)
+
+///--------------------------------------------------------------------------
+/// Main code.
+
+ .arch armv8-a
+ .fpu crypto-neon-fp-armv8
+
+/// The ARM crypto extension implements a little-endian version of AES
+/// (though the manual doesn't actually spell this out and you have to
+/// experiment), but Catacomb's internal interface presents as big-endian so
+/// as to work better with things like GCM. We therefore maintain the round
+/// keys in little-endian form, and have to end-swap blocks in and out.
+///
+/// For added amusement, the crypto extension doesn't implement the larger-
+/// block versions of Rijndael, so we have to end-swap the keys if we're
+/// preparing for one of those.
+
+ // Useful constants.
+ .equ maxrounds, 16 // maximum number of rounds
+ .equ maxblksz, 32 // maximum block size, in bytes
+ .equ kbufsz, maxblksz*(maxrounds + 1) // size of a key-schedule buffer
+
+ // Context structure.
+ .equ nr, 0 // number of rounds
+ .equ w, nr + 4 // encryption key words
+ .equ wi, w + kbufsz // decryption key words
+
+///--------------------------------------------------------------------------
+/// Key setup.
+
+FUNC(rijndael_setup_arm_crypto)
+
+ // Arguments:
+ // r0 = pointer to context
+ // r1 = block size in words
+ // r2 = pointer to key material
+ // r3 = key size in words
+
+ stmfd sp!, {r4-r9, r14}
+
+ // The initial round key material is taken directly from the input
+ // key, so copy it over. Unfortunately, the key material is not
+ // guaranteed to be aligned in any especially useful way, so we must
+ // sort this out.
+ add r9, r0, #w
+ mov r14, r3
+ ands r4, r2, #3
+ beq 1f
+ mov r4, r4, lsl #3
+ rsb r5, r4, #32
+ bic r2, r2, #3
+ ldr r6, [r2], #4
+
+0: ldr r7, [r2], #4
+ mov r6, r6, lsr r4
+ orr r6, r7, lsl r5
+ str r6, [r9], #4
+ mov r6, r7
+ subs r14, r14, #1
+ bhi 0b
+ b 9f
+
+1: ldr r6, [r2], #4
+ str r6, [r9], #4
+ subs r14, r14, #1
+ bhi 1b
+
+ // Find out other useful things and prepare for the main loop.
+ ldr r7, [r0, #nr] // number of rounds
+ mla r2, r1, r7, r1 // total key size in words
+ ldr r4, [r9, #-4] // most recent key word
+ leaextq r5, rijndael_rcon // round constants
+ sub r8, r2, r3 // minus what we've copied already
+ veor q1, q1 // all-zero register for the key
+ add r8, r9, r8, lsl #2 // limit of the key buffer
+
+ // Main key expansion loop. The first word of each key-length chunk
+ // needs special treatment.
+9: ldrb r14, [r5], #1 // next round constant
+ ldr r6, [r9, -r3, lsl #2]
+ vdup.32 q0, r4
+ aese.8 q0, q1 // effectively, just SubBytes
+ vmov.32 r4, d0[0]
+ eor r4, r14, r4, ror #8
+ eor r4, r4, r6
+ str r4, [r9], #4
+ cmp r9, r8
+ bcs 8f
+
+ // The next three words are simple.
+ ldr r6, [r9, -r3, lsl #2]
+ eor r4, r4, r6
+ str r4, [r9], #4
+ cmp r9, r8
+ bcs 8f
+
+ // (Word 2...)
+ ldr r6, [r9, -r3, lsl #2]
+ eor r4, r4, r6
+ str r4, [r9], #4
+ cmp r9, r8
+ bcs 8f
+
+ // (Word 3...)
+ ldr r6, [r9, -r3, lsl #2]
+ eor r4, r4, r6
+ str r4, [r9], #4
+ cmp r9, r8
+ bcs 8f
+
+ // Word 4. If the key is /more/ than 6 words long, then we must
+ // apply a substitution here.
+ cmp r3, #5
+ bcc 9b
+ ldr r6, [r9, -r3, lsl #2]
+ cmp r3, #7
+ bcc 0f
+ vdup.32 q0, r4
+ aese.8 q0, q1 // effectively, just SubBytes
+ vmov.32 r4, d0[0]
+0: eor r4, r4, r6
+ str r4, [r9], #4
+ cmp r9, r8
+ bcs 8f
+
+ // (Word 5...)
+ cmp r3, #6
+ bcc 9b
+ ldr r6, [r9, -r3, lsl #2]
+ eor r4, r4, r6
+ str r4, [r9], #4
+ cmp r9, r8
+ bcs 8f
+
+ // (Word 6...)
+ cmp r3, #7
+ bcc 9b
+ ldr r6, [r9, -r3, lsl #2]
+ eor r4, r4, r6
+ str r4, [r9], #4
+ cmp r9, r8
+ bcs 8f
+
+ // (Word 7...)
+ cmp r3, #8
+ bcc 9b
+ ldr r6, [r9, -r3, lsl #2]
+ eor r4, r4, r6
+ str r4, [r9], #4
+ cmp r9, r8
+ bcs 8f
+
+ // Must be done by now.
+ b 9b
+
+ // Next job is to construct the decryption keys. The keys for the
+ // first and last rounds don't need to be mangled, but the remaining
+ // ones do -- and they all need to be reordered too.
+ //
+ // The plan of action, then, is to copy the final encryption round's
+ // keys into place first, then to do each of the intermediate rounds
+ // in reverse order, and finally do the first round.
+ //
+ // Do all the heavy lifting with NEON registers. The order we're
+ // doing this in means that it's OK if we read or write too much, and
+ // there's easily enough buffer space for the over-enthusiastic reads
+ // and writes because the context has space for 32-byte blocks, which
+ // is our maximum and an exact fit for two Q-class registers.
+8: add r5, r0, #wi
+ add r4, r0, #w
+ add r4, r4, r2, lsl #2
+ sub r4, r4, r1, lsl #2 // last round's keys
+
+ // Copy the last encryption round's keys.
+ teq r1, #4
+ vldmiaeq r4, {d0, d1}
+ vldmiane r4, {d0-d3}
+ vstmiaeq r5, {d0, d1}
+ vstmiane r5, {d0-d3}
+
+ // Update the loop variables and stop if we've finished.
+9: sub r4, r4, r1, lsl #2
+ add r5, r5, r1, lsl #2
+ subs r7, r7, #1
+ beq 0f
+
+ // Do another middle round's keys...
+ teq r1, #4
+ vldmiaeq r4, {d0, d1}
+ vldmiane r4, {d0-d3}
+ aesimc.8 q0, q0
+ vstmiaeq r5, {d0, d1}
+ beq 9b
+ aesimc.8 q1, q1
+ vstmia r5, {d0-d3}
+ b 9b
+
+ // Finally do the first encryption round.
+0: teq r1, #4
+ vldmiaeq r4, {d0, d1}
+ vldmiane r4, {d0-d3}
+ vstmiaeq r5, {d0, d1}
+ vstmiane r5, {d0-d3}
+
+ // If the block size is not exactly four words then we must end-swap
+ // everything. We can use fancy NEON toys for this.
+ beq 0f
+
+ // End-swap the encryption keys.
+ add r1, r0, #w
+ bl endswap_block
+
+ // And the decryption keys
+ add r1, r0, #wi
+ bl endswap_block
+
+ // All done.
+0: ldmfd sp!, {r4-r9, pc}
+
+endswap_block:
+ // End-swap R2 words starting at R1. R1 is clobbered; R2 is not.
+ // It's OK to work in 16-byte chunks.
+ mov r4, r2
+0: vldmia r1, {d0, d1}
+ vrev32.8 q0, q0
+ vstmia r1!, {d0, d1}
+ subs r4, r4, #4
+ bhi 0b
+ bx r14
+
+ENDFUNC
+
+///--------------------------------------------------------------------------
+/// Encrypting and decrypting blocks.
+
+FUNC(rijndael_eblk_arm_crypto)
+
+ // Arguments:
+ // r0 = pointer to context
+ // r1 = pointer to input block
+ // r2 = pointer to output block
+
+ // Set things up ready.
+ ldr r3, [r0, #nr]
+ add r0, r0, #w
+ vldmia r1, {d0, d1}
+ vrev32.8 q0, q0
+
+ // Dispatch according to the number of rounds.
+ add r3, r3, r3, lsl #1
+ rsbs r3, r3, #3*14
+ addcs pc, pc, r3, lsl #2
+ callext F(abort)
+
+ // The last round doesn't have MixColumns, so do it separately.
+ .rept 13
+ vldmia r0!, {d2, d3}
+ aese.8 q0, q1
+ aesmc.8 q0, q0
+ .endr
+
+ // Final round.
+ vldmia r0!, {d2, d3}
+ aese.8 q0, q1
+
+ // Final whitening.
+ vldmia r0!, {d2, d3}
+ veor q0, q1
+
+ // All done.
+ vrev32.8 q0, q0
+ vstmia r2, {d0, d1}
+ bx r14
+
+ENDFUNC
+
+FUNC(rijndael_dblk_arm_crypto)
+
+ // Arguments:
+ // r0 = pointer to context
+ // r1 = pointer to input block
+ // r2 = pointer to output block
+
+ // Set things up ready.
+ ldr r3, [r0, #nr]
+ add r0, r0, #wi
+ vldmia r1, {d0, d1}
+ vrev32.8 q0, q0
+
+ // Dispatch according to the number of rounds.
+ add r3, r3, r3, lsl #1
+ rsbs r3, r3, #3*14
+ addcs pc, pc, r3, lsl #2
+ callext F(abort)
+
+ // The last round doesn't have MixColumns, so do it separately.
+ .rept 13
+ vldmia r0!, {d2, d3}
+ aesd.8 q0, q1
+ aesimc.8 q0, q0
+ .endr
+
+ // Final round.
+ vldmia r0!, {d2, d3}
+ aesd.8 q0, q1
+
+ // Final whitening.
+ vldmia r0!, {d2, d3}
+ veor q0, q1
+
+ // All done.
+ vrev32.8 q0, q0
+ vstmia r2, {d0, d1}
+ bx r14
+
+ENDFUNC
+
+///----- That's all, folks --------------------------------------------------
~mdw / catacomb / commitdiff