Some ulib code that controls the sampler

08126f18 · Silas Boyd-Wickizer · 00019b41 · 08126f18 · 08126f18 · 08126f18
--- a/include/user.h
+++ b/include/user.h
@@ -59,4 +59,20 @@ void fprintf(int, const char*, ...);
 void snprintf(char *buf, unsigned int n, const char *fmt, ...);
 void die(const char* errstr, ...) __attribute__((noreturn));
 #define assert(c) if (!(c)) { fprintf(2, "%s:%d: ", __FILE__, __LINE__); die("assertion failure"); }
+
+// perf.cc
+// Default selector for AMD 10h:
+//  [35 - 32]   event mask [11 - 8]
+//  [31 - 24]   counter mask
+//  [22]        counter enable
+//  [17]        operating system mode
+//  [16]        user mode
+//  [15 - 8]    unit mask
+//  [7 - 0]     event mask [7 - 0]
+#define PERF_SELECTOR \
+  (0UL<<32 | 1<<24 | 1<<22 | 1<<20 | 1<<17 | 1<<16 | 0x00<<8 | 0x76)
+// Default period
+#define PERF_PERIOD 100000
+void perf_stop(void);
+void perf_start(u64 selector, u64 period);
 END_DECLS
--- a/lib/Makefrag
+++ b/lib/Makefrag
@@ -2,7 +2,7 @@ $(O)/lib/%.o: CFLAGS:=$(CFLAGS)
 $(O)/lib/%.o: CXXFLAGS:=$(CXXFLAGS)

 ULIB = ulib.o usys.o printf.o umalloc.o uthread.o fmt.o stream.o ipc.o \
-       threads.o crt.o wq.o
+       threads.o crt.o wq.o perf.o
 ULIB := $(addprefix $(O)/lib/, $(ULIB))

 .PRECIOUS: $(O)/lib/%.o

--- a/lib/perf.cc
+++ b/lib/perf.cc
+#include "types.h"
+#include "user.h"
+#include "fcntl.h"
+#include "sampler.h"
+
+static int perf_fd = -1;
+
+static void
+conf(int fd, sampop_t op, u64 selector = 0, u64 period = 0)
+{
+  struct sampconf c = { 
+    op: op,
+    selector: selector,
+    period: period,
+  };
+
+  if (write(fd, &c, sizeof(c)) != sizeof(c))
+    die("perf: write failed");
+}
+
+void
+perf_stop(void)
+{
+  assert(perf_fd >= 0);
+  conf(perf_fd, SAMP_DISABLE);
+}
+
+void
+perf_start(u64 selector, u64 period)
+{
+  if (perf_fd == -1) {
+    perf_fd = open("/dev/sampler", O_WRONLY);
+    if (perf_fd < 0)
+      die("perf: open failed");
+  }
+
+  conf(perf_fd, SAMP_ENABLE, selector, period);
+}