[9front] [patch] via padlock xstore rng for pc/pc64

[9front] [patch] via padlock xstore rng for pc/pc64

[Arne Meyer]

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this patch adds via padlock rng support to pc and pc64. *Warning* I've got no clue about cryptography. I ported https://www.fourmilab.ch/random/ to plan9 here: https://github.com/armeye/ent_random_sequence_tester and wrote a test here: https://github.com/armeye/9front_xstore. the results look right to me...
Tested on my VIA C7 Thinclient, looks good ¯\_(ツ)_/¯

I'm looking for comments about the patch:

* this adds a new line to archctl to show which hwrng is in use, if any
* the via.c is for via c7 specific code, I've got a patch for the cputemp msr in my repository.
  I would like to share the file between architectures but don't know how.
* The xstorebuf function is stupid, but it works. Can this be done better? 
* the xstore instruction is very cpu heavy with the maximum whiteout. This patch has the best value for randomness but
  it eats cpu cycles like it's nothing. I thing we can go down to even the lowest quality because the random data
  gets encrypted anyway, right?

Greetings,
Arne

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diff --git a/sys/src/9/pc/devarch.c b/sys/src/9/pc/devarch.c
index 928837848..ae053ab5c 100644
--- a/sys/src/9/pc/devarch.c
+++ b/sys/src/9/pc/devarch.c
@@ -644,10 +644,24 @@ cpuidentify(void)
 	if((m->cpuiddx & Mtrr) != 0 && getconf("*nomtrr") == nil)
 		mtrrsync();
 
+	hwrandbuf = nil;
+
 	if(strcmp(m->cpuidid, "GenuineIntel") == 0 && (m->cpuidcx & Rdrnd) != 0)
 		hwrandbuf = rdrandbuf;
-	else
-		hwrandbuf = nil;
+	else if(strcmp(m->cpuidid, "CentaurHauls") == 0 && (model >= 10)){
+		cpuid(0xC0000000, 0, regs);
+		if(regs[0] >= 0xC0000001){
+			cpuid(0xC0000001, 0, regs);
+			if(regs[3] & 4){
+				vlong cap;
+				rdmsr(0x110b, &cap);
+				cap |= 0x40;
+				wrmsr(0x110b, cap);
+
+				hwrandbuf = xstorebuf;
+			}
+		}
+	}
 	
 	if(sizeof(uintptr) == 8) {
 		/* 8-byte watchpoints are supported in Long Mode */
@@ -725,6 +739,13 @@ archctlread(Chan*, void *a, long nn, vlong offset)
 		p = seprint(p, ep, "cmpswap486\n");
 	else
 		p = seprint(p, ep, "0x%p\n", cmpswap);
+	p = seprint(p, ep, "hwrand ");
+	if(hwrandbuf == rdrandbuf)
+		p = seprint(p, ep, "rdrand\n");
+	else if(hwrandbuf == xstorebuf)
+		p = seprint(p, ep, "xstore\n");
+	else
+		p = seprint(p, ep, "none\n");
 	p = seprint(p, ep, "arch %s\n", arch->id);
 	n = p - buf;
 	n += mtrrprint(p, ep - p);
diff --git a/sys/src/9/pc/fns.h b/sys/src/9/pc/fns.h
index 994362489..4d2f71339 100644
--- a/sys/src/9/pc/fns.h
+++ b/sys/src/9/pc/fns.h
@@ -173,6 +173,8 @@ void	writeconf(void);
 int	wrmsr(int, vlong);
 int	xchgw(ushort*, int);
 void	rdrandbuf(void*, ulong);
+void	repxstore(void*, ulong);
+void	xstorebuf(void*, ulong);
 
 #define	userureg(ur)	(((ur)->cs & 3) == 3)
 #define	KADDR(a)	kaddr(a)
diff --git a/sys/src/9/pc/l.s b/sys/src/9/pc/l.s
index ede492af8..7a874b235 100644
--- a/sys/src/9/pc/l.s
+++ b/sys/src/9/pc/l.s
@@ -852,6 +852,13 @@ _rndbytes:
 _rnddone:
 	RET
 
+TEXT repxstore(SB), $-4
+	MOVL $3, DX
+	MOVL buf+0(FP), DI
+	MOVL count+4(FP), CX
+	BYTE $0xF3; BYTE $0x0F; BYTE $0xA7; BYTE $0xC0
+	RET
+
 /* debug register access */
 
 TEXT putdr(SB), $0
diff --git a/sys/src/9/pc/mkfile b/sys/src/9/pc/mkfile
index 3bc3d5fca..d70cfda81 100644
--- a/sys/src/9/pc/mkfile
+++ b/sys/src/9/pc/mkfile
@@ -57,6 +57,7 @@ OBJ=\
 	mmu.$O\
 	irq.$O\
 	trap.$O\
+	via.$O\
 	bootargs.$O\
 	$CONF.root.$O\
 	$CONF.rootc.$O\
diff --git a/sys/src/9/pc/via.c b/sys/src/9/pc/via.c
new file mode 100644
index 000000000..7a4e608cc
--- /dev/null
+++ b/sys/src/9/pc/via.c
@@ -0,0 +1,21 @@
+#include "u.h"
+#include "../port/lib.h"
+
+extern void    repxstore(void*, ulong);
+
+void
+xstorebuf(void *b1, ulong l)
+{
+        ulong i;
+        static char buf[8+8];
+        char *b = b1;
+
+        for(i = 0; i < l>>3; i++){
+                repxstore(buf, 8);
+                memmove(b, buf, 8);
+                b+=8;
+        }
+
+        repxstore(buf, 8);
+        memmove(b, buf, l&7);
+}
diff --git a/sys/src/9/pc64/fns.h b/sys/src/9/pc64/fns.h
index 687ec50af..e188e7a0e 100644
--- a/sys/src/9/pc64/fns.h
+++ b/sys/src/9/pc64/fns.h
@@ -175,6 +175,7 @@ void	writeconf(void);
 int	wrmsr(int, vlong);
 int	xchgw(ushort*, int);
 void	rdrandbuf(void*, ulong);
+void	xstorebuf(void*, ulong);
 
 #define	userureg(ur)	(((ur)->cs & 3) == 3)
 #define	KADDR(a)	kaddr(a)
diff --git a/sys/src/9/pc64/l.s b/sys/src/9/pc64/l.s
index 423fad623..6934f9576 100644
--- a/sys/src/9/pc64/l.s
+++ b/sys/src/9/pc64/l.s
@@ -703,6 +703,14 @@ loop32:
 	JCC		loop32
 	RET
 
+TEXT repxstore(SB), $-4
+        MOVL $3, DX
+        MOVL buf+0(FP), DI
+        MOVL count+4(FP), CX
+        BYTE $0xF3; BYTE $0x0F; BYTE $0xA7; BYTE $0xC0
+        RET
+
+
 TEXT rdrand64(SB), $-4
 loop64:
 	RDRAND64AX
diff --git a/sys/src/9/pc64/mkfile b/sys/src/9/pc64/mkfile
index 083ab92f9..b1131ebb9 100644
--- a/sys/src/9/pc64/mkfile
+++ b/sys/src/9/pc64/mkfile
@@ -55,6 +55,7 @@ OBJ=\
 	mmu.$O\
 	irq.$O\
 	trap.$O\
+	via.$O\
 	bootargs.$O\
 	$CONF.root.$O\
 	$CONF.rootc.$O\
diff --git a/sys/src/9/pc64/via.c b/sys/src/9/pc64/via.c
new file mode 100644
index 000000000..7a4e608cc
--- /dev/null
+++ b/sys/src/9/pc64/via.c
@@ -0,0 +1,21 @@
+#include "u.h"
+#include "../port/lib.h"
+
+extern void    repxstore(void*, ulong);
+
+void
+xstorebuf(void *b1, ulong l)
+{
+        ulong i;
+        static char buf[8+8];
+        char *b = b1;
+
+        for(i = 0; i < l>>3; i++){
+                repxstore(buf, 8);
+                memmove(b, buf, 8);
+                b+=8;
+        }
+
+        repxstore(buf, 8);
+        memmove(b, buf, l&7);
+}