Support for reading cmdline from userspace

dca2a740 · Silas Boyd-Wickizer · 8d4cf586 · dca2a740 · dca2a740 · dca2a740
--- a/bin/init.cc
+++ b/bin/init.cc
@@ -22,6 +22,7 @@ static struct {
  { "/dev/sampler", 3 },
  { "/dev/lockstat", 4 },
  { "/dev/stat", 5 },
+  { "/dev/cmdline", 6},
 };

 static int

--- a/include/file.hh
+++ b/include/file.hh
@@ -86,3 +86,4 @@ extern struct devsw devsw[];
 #define SAMPLER  3
 #define DEVLOCKSTAT 4
 #define DEVSTAT  5
+#define DEVCMDLINE 6
--- a/kernel/Makefrag
+++ b/kernel/Makefrag
@@ -3,6 +3,7 @@ OBJS = \
 	bio.o \
 	bootdata.o \
 	cga.o \
+	cmdline.o \
 	condvar.o \
 	console.o \
 	cpprt.o \

--- a/kernel/cmdline.cc
+++ b/kernel/cmdline.cc
+#include "types.h"
+#include "kernel.hh"
+#include "mmu.h"
+#include "amd64.h"
+#include "spinlock.h"
+#include "condvar.h"
+#include "fs.h"
+#include "file.hh"
+
+extern char cmdline[];
+
+static int
+cmdlineread(struct inode *inode, char *dst, u32 off, u32 n)
+{
+  u32 cc;
+
+  if (off >= strlen(cmdline))
+    return 0;
+
+  cc = MIN(n, strlen(cmdline)-off);
+  memcpy(dst, &cmdline[off], cc);
+  return cc;
+}
+
+void
+initcmdline(void)
+{
+  if (VERBOSE)
+    cprintf("cmdline: %s\n", cmdline);
+
+  devsw[DEVCMDLINE].write = nullptr;
+  devsw[DEVCMDLINE].read = cmdlineread;
+}
--- a/kernel/main.cc
+++ b/kernel/main.cc
@@ -39,6 +39,7 @@ void initsperf(void);
 void initidle(void);
 void initcpprt(void);
 void initfutex(void);
+void initcmdline(void);
 void idleloop(void);

 static volatile int bstate;
@@ -109,6 +110,7 @@ cmain(u64 mbmagic, u64 mbaddr)
  initsperf();
  inittrap();
  initlapic();
+  initcmdline();
  initkalloc(mbaddr);
  initz();
  initproc();      // process table