crypto: padlock-aes - work around Nano CPU errata in ECB mode

The VIA Nano processor has a bug that makes it prefetch extra data
during encryption operations, causing spurious page faults. Extend
existing workarounds for ECB mode to copy the data to an temporary
buffer to avoid the problem.

Signed-off-by: Chuck Ebbert <[e-mail]>
Acked-by: Harald Welte <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

drivers/crypto/padlock-aes.c

···
 #include <linux/percpu.h>
 #include <linux/smp.h>
 #include <asm/byteorder.h>
+#include <asm/processor.h>
 #include <asm/i387.h>
 #include "padlock.h"
+
+/* number of data blocks actually fetched for each xcrypt insn */
+static unsigned int ecb_fetch_blocks = 2;
+static unsigned int cbc_fetch_blocks = 1;
+
+#define ecb_fetch_bytes (ecb_fetch_blocks * AES_BLOCK_SIZE)
+#define cbc_fetch_bytes (cbc_fetch_blocks * AES_BLOCK_SIZE)
 
 /* Control word. */
 struct cword {
···
  */
 
 static inline void padlock_xcrypt(const u8 *input, u8 *output, void *key,
-				  struct cword *control_word)
+				  struct cword *control_word, int count)
 {
 	asm volatile (".byte 0xf3,0x0f,0xa7,0xc8"	/* rep xcryptecb */
 		      : "+S"(input), "+D"(output)
-		      : "d"(control_word), "b"(key), "c"(1));
+		      : "d"(control_word), "b"(key), "c"(count));
 }
 
-static void aes_crypt_copy(const u8 *in, u8 *out, u32 *key, struct cword *cword)
+static void aes_crypt_copy(const u8 *in, u8 *out, u32 *key,
+			   struct cword *cword, int count)
 {
-	u8 buf[AES_BLOCK_SIZE * 2 + PADLOCK_ALIGNMENT - 1];
+	/*
+	 * Padlock prefetches extra data so we must provide mapped input buffers.
+	 * Assume there are at least 16 bytes of stack already in use.
+	 */
+	u8 buf[AES_BLOCK_SIZE * 7 + PADLOCK_ALIGNMENT - 1];
 	u8 *tmp = PTR_ALIGN(&buf[0], PADLOCK_ALIGNMENT);
 
-	memcpy(tmp, in, AES_BLOCK_SIZE);
-	padlock_xcrypt(tmp, out, key, cword);
+	memcpy(tmp, in, count * AES_BLOCK_SIZE);
+	padlock_xcrypt(tmp, out, key, cword, count);
 }
 
 static inline void aes_crypt(const u8 *in, u8 *out, u32 *key,
-			     struct cword *cword)
+			     struct cword *cword, int count)
 {
-	/* padlock_xcrypt requires at least two blocks of data. */
-	if (unlikely(!(((unsigned long)in ^ (PAGE_SIZE - AES_BLOCK_SIZE)) &
-		       (PAGE_SIZE - 1)))) {
-		aes_crypt_copy(in, out, key, cword);
+	/* Padlock in ECB mode fetches at least ecb_fetch_bytes of data.
+	 * We could avoid some copying here but it's probably not worth it.
+	 */
+	if (unlikely(((unsigned long)in & PAGE_SIZE) + ecb_fetch_bytes > PAGE_SIZE)) {
+		aes_crypt_copy(in, out, key, cword, count);
 		return;
 	}
 
-	padlock_xcrypt(in, out, key, cword);
+	padlock_xcrypt(in, out, key, cword, count);
 }
 
 static inline void padlock_xcrypt_ecb(const u8 *input, u8 *output, void *key,
 				      void *control_word, u32 count)
 {
-	if (count == 1) {
-		aes_crypt(input, output, key, control_word);
+	u32 initial = count & (ecb_fetch_blocks - 1);
+
+	if (count < ecb_fetch_blocks) {
+		aes_crypt(input, output, key, control_word, count);
 		return;
 	}
 
-	asm volatile ("test $1, %%cl;"
-		      "je 1f;"
-#ifndef CONFIG_X86_64
-		      "lea -1(%%ecx), %%eax;"
-		      "mov $1, %%ecx;"
-#else
-		      "lea -1(%%rcx), %%rax;"
-		      "mov $1, %%rcx;"
-#endif
-		      ".byte 0xf3,0x0f,0xa7,0xc8;"	/* rep xcryptecb */
-#ifndef CONFIG_X86_64
-		      "mov %%eax, %%ecx;"
-#else
-		      "mov %%rax, %%rcx;"
-#endif
-		      "1:"
-		      ".byte 0xf3,0x0f,0xa7,0xc8"	/* rep xcryptecb */
+	if (initial)
+		asm volatile (".byte 0xf3,0x0f,0xa7,0xc8"	/* rep xcryptecb */
+			      : "+S"(input), "+D"(output)
+			      : "d"(control_word), "b"(key), "c"(initial));
+
+	asm volatile (".byte 0xf3,0x0f,0xa7,0xc8"	/* rep xcryptecb */
 		      : "+S"(input), "+D"(output)
-		      : "d"(control_word), "b"(key), "c"(count)
-		      : "ax");
+		      : "d"(control_word), "b"(key), "c"(count - initial));
 }
 
 static inline u8 *padlock_xcrypt_cbc(const u8 *input, u8 *output, void *key,
···
 
 	padlock_reset_key(&ctx->cword.encrypt);
 	ts_state = irq_ts_save();
-	aes_crypt(in, out, ctx->E, &ctx->cword.encrypt);
+	aes_crypt(in, out, ctx->E, &ctx->cword.encrypt, 1);
 	irq_ts_restore(ts_state);
 	padlock_store_cword(&ctx->cword.encrypt);
 }
···
 
 	padlock_reset_key(&ctx->cword.encrypt);
 	ts_state = irq_ts_save();
-	aes_crypt(in, out, ctx->D, &ctx->cword.decrypt);
+	aes_crypt(in, out, ctx->D, &ctx->cword.decrypt, 1);
 	irq_ts_restore(ts_state);
 	padlock_store_cword(&ctx->cword.encrypt);
 }
···
 static int __init padlock_init(void)
 {
 	int ret;
+	struct cpuinfo_x86 *c = &cpu_data(0);
 
 	if (!cpu_has_xcrypt) {
 		printk(KERN_NOTICE PFX "VIA PadLock not detected.\n");
···
 		goto cbc_aes_err;
 
 	printk(KERN_NOTICE PFX "Using VIA PadLock ACE for AES algorithm.\n");
+
+	if (c->x86 == 6 && c->x86_model == 15 && c->x86_mask == 2) {
+		ecb_fetch_blocks = 8;
+		cbc_fetch_blocks = 4; /* NOTE: notused */
+		printk(KERN_NOTICE PFX "VIA Nano stepping 2 detected: enabling workaround.\n");
+	}
 
 out:
 	return ret;