Start of some sampling code.

e695136b · Silas Boyd-Wickizer · 104d3497 · e695136b · e695136b
--- a/kernel.h
+++ b/kernel.h
@@ -132,6 +132,7 @@ void            lapic_tlbflush(u32);
 // mp.c
 extern int      ncpu;
+int             mpbcpu(void);
 // ns.c
 enum {
@@ -208,6 +209,7 @@ void            migrate(struct proc *);
 extern int profenable;
 void            profreset(void);
 void            profdump(void);
+void            profstart(void);
 // rcu.c
 void            rcuinit(void);

--- a/prof.c
+++ b/prof.c
@@ -6,12 +6,16 @@
 #include "file.h"
 #include "prof.h"
 #include "kernel.h"
+#include "bits.h"
+#include "amd64.h"
 extern profctr_t sprof[];
 extern profctr_t eprof[];
 int profenable;
+static void (*profconfig)(u64 ctr, u64 sel, u64 val);
 void
 profreset(void)
 {
@@ -41,3 +45,67 @@ profdump(void)
      cprintf("%s %lu\n", p->name, tot/cnt);
  }
 }
+static void
+amdconfig(u64 ctr, u64 sel, u64 val)
+{
+  writemsr(MSR_AMD_PERF_SEL0 | ctr, 0);
+  writemsr(MSR_AMD_PERF_CNT0 | ctr, val);
+  writemsr(MSR_AMD_PERF_SEL0 | ctr, sel);
+}
+static void
+intelconfig(u64 ctr, u64 sel, u64 val)
+{
+  writemsr(MSR_INTEL_PERF_SEL0 | ctr, 0);
+  writemsr(MSR_INTEL_PERF_CNT0 | ctr, val);
+  writemsr(MSR_INTEL_PERF_SEL0 | ctr, sel);
+}
+void
+profstart(void)
+{
+  u64 ctr = 0;
+  u64 sel = 0;
+  u64 val = -1000;
+  cprintf("profstart ...\n");
+  sel = 0UL << 32 |
+    1 << 24 | 
+    1 << 22 | 
+    1 << 20 |
+    1 << 17 | 
+    1 << 16 | 
+    0x00 << 8 | 
+    0x76;
+  pushcli();
+  profconfig(ctr, sel, val);
+  popcli();
+  cprintf("rdpmc %lx\n", rdpmc(0));
+}
+void
+initprof(void)
+{
+  if (cpunum() == mpbcpu()) {
+    u32 name[4];
+    char *s = (char *)name;
+    name[3] = 0;
+    cpuid(0, 0, &name[0], &name[2], &name[1]);
+    cprintf("%s\n", s);
+    if (strcmp(s, "AuthenticAMD"))
+      profconfig = amdconfig;
+    else if (strcmp(s, "GenuineIntel"))
+      profconfig = intelconfig;
+    else
+      panic("Unknown Manufacturer");
+  }
+  // enable RDPMC at CPL > 0
+  u64 cr4 = rcr4();
+  lcr4(cr4 | CR4_PCE);
+}