Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> writes:
> Linux goes to considerable pain to ensure that stdarg.h is the only
> system header that it needs to include. stddef.h looks like it ought
> to be safe in a kernel environment, but would it not be just as easy
> to modify the files that you are adding to the build?
I'm trying to insert a Lua interpreter into the Mini-OS kernel.
Before I attempt to do something useful with the interpreter, I
decided to do a quick test to see if there are any unforeseen issues
with incorporating Lua into the kernel. My quick check involved
modifying the console program so that it uses Lua to evaluate console
input, and then prints the results on the terminal.
Keir, it would not be easy to modify the files that I'm adding.
Instead, I modify the Lua interpreter so that it no longer performs
floating point operations, but is otherwise a standard ANSI C program.
The Lua interpreter and Mini-OS are compiled and linked using a
cross-compiler combined with newlib for C library support. Making
extensive modifications to both newlib and the Lua interpreter is
unappealing, to say the least.
I have enclosed the patch for the console and the Makefile. My quick
test has uncovered an unforeseen problem. The interpreter reads,
evaluates, and prints a few times, and then a reference to a strange
address causes a page fault. I've just begun looking into the
problem, however, in the past, I've noted that typically kernels
allocate a small amount of space to its stack, and if it's too small,
something like this could happen. I suppose a bug in xmalloc would do
it too, but I just guessing at this stage. Off to studying x86_32.S.
Unfortunately, my assemble language programming skills were mostly
developed and used on a PDP-11. They may be a little rusty.
John
Xen Minimal OS!
start_info: c0035000
nr_pages: 8192 shared_inf: 00bbd000
pt_base: c0038000 mod_start: 0x0
mod_len: 0
flags: 0x0
cmd_line:
MM: Init
_text: c0000000
_etext: c001f500
_edata: c0023090
stack start: c002aa60
_end: c002cec8
start_pfn: 3d
max_pfn: 2000
Mapping memory range 0xc0400000 - 0xc2000000
MM: Initialise page allocator for c0044000(44000)-c2000000(2000000)
MM: done
Initialising timer interface
Initialising console ... Initializing Lua ... done.
Initialising scheduler, idle_thread 00000000
Thread "Idle": pointer: 0xc0045b40, stack: 0xc0046000
Thread "init_xs": pointer: 0xc0045b68, stack: 0xc0048000
Thread "xenstore": pointer: 0xc0045b90, stack: 0xc004a000
print (3)
Lua 3
print (20
Lua Page fault at linear address 0000e021, regs c0047734, code 2
------------------------------------ PATCH ---------------------------------
diff -ur oxen-3.0-testing/extras/mini-os/console/console.c
xen-3.0-testing/extras/mini-os/console/console.c
--- oxen-3.0-testing/extras/mini-os/console/console.c 2006-04-14
22:21:55.000000000 -0400
+++ xen-3.0-testing/extras/mini-os/console/console.c 2006-04-28
15:56:50.000000000 -0400
@@ -44,6 +44,98 @@
#include <xenbus.h>
#include <xen/io/console.h>
+#if defined LUA_CONSOLE
+
+#include <lua.h>
+#include <lauxlib.h>
+#include <lualib.h>
+#include <xmalloc.h>
+
+static void *luaxen_alloc(void *ud, void *ptr, size_t osize, size_t nsize)
+{
+ if (nsize == 0) {
+ free(ptr);
+ return NULL;
+ }
+ else if (ptr == NULL)
+ return malloc(nsize);
+ else if (osize >= nsize)
+ return ptr;
+ else {
+ void *p = malloc(nsize);
+ if (p == NULL)
+ return p;
+ else
+ return memcpy(p, ptr, osize);
+ }
+}
+
+/* Adapted from min.c in the Lua distribution. */
+
+static int luaxen_print(lua_State *L)
+{
+ int n = lua_gettop(L);
+ int i;
+ for (i = 1; i <= n; i++) {
+ if (i > 1) printk("\t");
+ if (lua_isstring(L, i))
+ printk("%s", lua_tostring(L, i));
+ else if (lua_isnil(L, i) == 2)
+ printk("%s", "nil");
+ else if (lua_isboolean(L, i))
+ printk("%s", lua_toboolean(L, i) ? "true" : "false");
+ else
+ printk("%s:%p", luaL_typename(L, i), lua_topointer(L, i));
+ }
+ return 0;
+}
+
+static lua_State *L;
+#define LUAXEN_BUFSIZ 256
+static char luaxen_buf[LUAXEN_BUFSIZ];
+static size_t luaxen_len;
+
+static void luaxen_init(void)
+{
+ L = lua_newstate(luaxen_alloc, NULL);
+ luaxen_len = 0;
+ lua_pushcfunction(L, luaxen_print);
+ lua_setglobal(L, "print");
+}
+
+static void luaxen_read_eval_print(const char *data, size_t len)
+{
+ size_t i;
+ size_t n = len;
+ if (n + luaxen_len > LUAXEN_BUFSIZ)
+ n = LUAXEN_BUFSIZ - luaxen_len;
+ for (i = 0; i < n; i++)
+ luaxen_buf[luaxen_len++] = data[i];
+ if (data[len - 1] != '\r')
+ return;
+ printk("\nLua\t");
+ if (luaL_loadbuffer(L, luaxen_buf, luaxen_len, "console")
+ || lua_pcall(L, 0, 0, 0)) {
+ printk("\nLua error\t%s", lua_tostring(L, -1));
+ lua_pop(L, 1);
+ }
+ printk("\n");
+ luaxen_len = 0;
+}
+
+void _exit(int status)
+{
+ do_exit();
+}
+
+void *sbrk(int inc)
+{
+ printk("Function sbrk called in Mini-OS kernel\n");
+ do_exit();
+ return NULL;
+}
+
+#endif
/* Low level functions defined in xencons_ring.c */
extern int xencons_ring_init(void);
@@ -64,8 +156,12 @@
buf[len] = '\0';
printk("%s", buf);
+#if defined LUA_CONSOLE
+ luaxen_read_eval_print(buf, len);
+#else
if(buf[len-1] == '\r')
printk("\nNo console input handler.\n");
+#endif
}
}
@@ -144,6 +240,10 @@
printk("Initialising console ... ");
xencons_ring_init();
console_initialised = 1;
+#if defined LUA_CONSOLE
+ printk("Initializing Lua ... ");
+ luaxen_init();
+#endif
/* This is also required to notify the daemon */
printk("done.\n");
}
diff -ur oxen-3.0-testing/extras/mini-os/Makefile
xen-3.0-testing/extras/mini-os/Makefile
--- oxen-3.0-testing/extras/mini-os/Makefile 2006-04-14 22:21:55.000000000
-0400
+++ xen-3.0-testing/extras/mini-os/Makefile 2006-04-28 13:45:14.000000000
-0400
@@ -20,6 +20,10 @@
LDFLAGS := -m elf_x86_64
endif
+LUA_INCLUDES=$(HOME)/src/lua-5.1-long/src
+LUA_LIBS=$(HOME)/src/lua-5.1-long/src/liblua.a -lc -lnosys
+CFLAGS += -I$(LUA_INCLUDES) -DLUA_CONSOLE -DLUA_ANSI
+
ifeq ($(debug),y)
CFLAGS += -g
else
@@ -33,7 +37,7 @@
OBJS += $(patsubst %.c,%.o,$(wildcard lib/*.c))
OBJS += $(patsubst %.c,%.o,$(wildcard xenbus/*.c))
OBJS += $(patsubst %.c,%.o,$(wildcard console/*.c))
-
+
HDRS := $(wildcard include/*.h)
HDRS += $(wildcard include/xen/*.h)
@@ -43,7 +47,7 @@
[ -e include/xen ] || ln -sf ../../../xen/include/public include/xen
$(TARGET): links $(OBJS)
- $(LD) -N -T minios-$(TARGET_ARCH).lds $(OBJS) -o $@.elf
+ $(LD) -N -T minios-$(TARGET_ARCH).lds $(OBJS) $(LUA_LIBS) -o $@.elf
gzip -f -9 -c $@.elf >$@.gz
clean:
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