--- /dev/null
+/*
+ * RNG driver for VIA RNGs
+ *
+ * Copyright 2005 (c) MontaVista Software, Inc.
+ *
+ * with the majority of the code coming from:
+ *
+ * Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
+ * (c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
+ *
+ * derived from
+ *
+ * Hardware driver for the AMD 768 Random Number Generator (RNG)
+ * (c) Copyright 2001 Red Hat Inc
+ *
+ * derived from
+ *
+ * Hardware driver for Intel i810 Random Number Generator (RNG)
+ * Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
+ * Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <crypto/padlock.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/hw_random.h>
+#include <linux/delay.h>
+#include <asm/cpu_device_id.h>
+#include <asm/io.h>
+#include <asm/msr.h>
+#include <asm/cpufeature.h>
+#include <asm/i387.h>
+
+
+
+
+enum {
+ VIA_STRFILT_CNT_SHIFT = 16,
+ VIA_STRFILT_FAIL = (1 << 15),
+ VIA_STRFILT_ENABLE = (1 << 14),
+ VIA_RAWBITS_ENABLE = (1 << 13),
+ VIA_RNG_ENABLE = (1 << 6),
+ VIA_NOISESRC1 = (1 << 8),
+ VIA_NOISESRC2 = (1 << 9),
+ VIA_XSTORE_CNT_MASK = 0x0F,
+
+ VIA_RNG_CHUNK_8 = 0x00, /* 64 rand bits, 64 stored bits */
+ VIA_RNG_CHUNK_4 = 0x01, /* 32 rand bits, 32 stored bits */
+ VIA_RNG_CHUNK_4_MASK = 0xFFFFFFFF,
+ VIA_RNG_CHUNK_2 = 0x02, /* 16 rand bits, 32 stored bits */
+ VIA_RNG_CHUNK_2_MASK = 0xFFFF,
+ VIA_RNG_CHUNK_1 = 0x03, /* 8 rand bits, 32 stored bits */
+ VIA_RNG_CHUNK_1_MASK = 0xFF,
+};
+
+/*
+ * Investigate using the 'rep' prefix to obtain 32 bits of random data
+ * in one insn. The upside is potentially better performance. The
+ * downside is that the instruction becomes no longer atomic. Due to
+ * this, just like familiar issues with /dev/random itself, the worst
+ * case of a 'rep xstore' could potentially pause a cpu for an
+ * unreasonably long time. In practice, this condition would likely
+ * only occur when the hardware is failing. (or so we hope :))
+ *
+ * Another possible performance boost may come from simply buffering
+ * until we have 4 bytes, thus returning a u32 at a time,
+ * instead of the current u8-at-a-time.
+ *
+ * Padlock instructions can generate a spurious DNA fault, so
+ * we have to call them in the context of irq_ts_save/restore()
+ */
+
+static inline u32 xstore(u32 *addr, u32 edx_in)
+{
+ u32 eax_out;
+ int ts_state;
+
+ ts_state = irq_ts_save();
+
+ asm(".byte 0x0F,0xA7,0xC0 /* xstore %%edi (addr=%0) */"
+ : "=m" (*addr), "=a" (eax_out), "+d" (edx_in), "+D" (addr));
+
+ irq_ts_restore(ts_state);
+ return eax_out;
+}
+
+static int via_rng_data_present(struct hwrng *rng, int wait)
+{
+ char buf[16 + PADLOCK_ALIGNMENT - STACK_ALIGN] __attribute__
+ ((aligned(STACK_ALIGN)));
+ u32 *via_rng_datum = (u32 *)PTR_ALIGN(&buf[0], PADLOCK_ALIGNMENT);
+ u32 bytes_out;
+ int i;
+
+ /* We choose the recommended 1-byte-per-instruction RNG rate,
+ * for greater randomness at the expense of speed. Larger
+ * values 2, 4, or 8 bytes-per-instruction yield greater
+ * speed at lesser randomness.
+ *
+ * If you change this to another VIA_CHUNK_n, you must also
+ * change the ->n_bytes values in rng_vendor_ops[] tables.
+ * VIA_CHUNK_8 requires further code changes.
+ *
+ * A copy of MSR_VIA_RNG is placed in eax_out when xstore
+ * completes.
+ */
+
+ for (i = 0; i < 20; i++) {
+ *via_rng_datum = 0; /* paranoia, not really necessary */
+ bytes_out = xstore(via_rng_datum, VIA_RNG_CHUNK_1);
+ bytes_out &= VIA_XSTORE_CNT_MASK;
+ if (bytes_out || !wait)
+ break;
+ udelay(10);
+ }
+ rng->priv = *via_rng_datum;
+ return bytes_out ? 1 : 0;
+}
+
+static int via_rng_data_read(struct hwrng *rng, u32 *data)
+{
+ u32 via_rng_datum = (u32)rng->priv;
+
+ *data = via_rng_datum;
+
+ return 1;
+}
+
+static int via_rng_init(struct hwrng *rng)
+{
+ struct cpuinfo_x86 *c = &cpu_data(0);
+ u32 lo, hi, old_lo;
+
+ /* VIA Nano CPUs don't have the MSR_VIA_RNG anymore. The RNG
+ * is always enabled if CPUID rng_en is set. There is no
+ * RNG configuration like it used to be the case in this
+ * register */
+ if ((c->x86 == 6) && (c->x86_model >= 0x0f)) {
+ if (!cpu_has_xstore_enabled) {
+ pr_err(PFX "can't enable hardware RNG "
+ "if XSTORE is not enabled\n");
+ return -ENODEV;
+ }
+ return 0;
+ }
+
+ /* Control the RNG via MSR. Tread lightly and pay very close
+ * close attention to values written, as the reserved fields
+ * are documented to be "undefined and unpredictable"; but it
+ * does not say to write them as zero, so I make a guess that
+ * we restore the values we find in the register.
+ */
+ rdmsr(MSR_VIA_RNG, lo, hi);
+
+ old_lo = lo;
+ lo &= ~(0x7f << VIA_STRFILT_CNT_SHIFT);
+ lo &= ~VIA_XSTORE_CNT_MASK;
+ lo &= ~(VIA_STRFILT_ENABLE | VIA_STRFILT_FAIL | VIA_RAWBITS_ENABLE);
+ lo |= VIA_RNG_ENABLE;
+ lo |= VIA_NOISESRC1;
+
+ /* Enable secondary noise source on CPUs where it is present. */
+
+ /* Nehemiah stepping 8 and higher */
+ if ((c->x86_model == 9) && (c->x86_mask > 7))
+ lo |= VIA_NOISESRC2;
+
+ /* Esther */
+ if (c->x86_model >= 10)
+ lo |= VIA_NOISESRC2;
+
+ if (lo != old_lo)
+ wrmsr(MSR_VIA_RNG, lo, hi);
+
+ /* perhaps-unnecessary sanity check; remove after testing if
+ unneeded */
+ rdmsr(MSR_VIA_RNG, lo, hi);
+ if ((lo & VIA_RNG_ENABLE) == 0) {
+ pr_err(PFX "cannot enable VIA C3 RNG, aborting\n");
+ return -ENODEV;
+ }
+
+ return 0;
+}
+
+
+static struct hwrng via_rng = {
+ .name = "via",
+ .init = via_rng_init,
+ .data_present = via_rng_data_present,
+ .data_read = via_rng_data_read,
+};
+
+
+static int __init mod_init(void)
+{
+ int err;
+
+ if (!cpu_has_xstore)
+ return -ENODEV;
+ pr_info("VIA RNG detected\n");
+ err = hwrng_register(&via_rng);
+ if (err) {
+ pr_err(PFX "RNG registering failed (%d)\n",
+ err);
+ goto out;
+ }
+out:
+ return err;
+}
+
+static void __exit mod_exit(void)
+{
+ hwrng_unregister(&via_rng);
+}
+
+module_init(mod_init);
+module_exit(mod_exit);
+
+static struct x86_cpu_id __maybe_unused via_rng_cpu_id[] = {
+ X86_FEATURE_MATCH(X86_FEATURE_XSTORE),
+ {}
+};
+
+MODULE_DESCRIPTION("H/W RNG driver for VIA CPU with PadLock");
+MODULE_LICENSE("GPL");
+MODULE_DEVICE_TABLE(x86cpu, via_rng_cpu_id);
Code Review / kvmfornfv.git / blobdiff