[PATCH] don't abuse empty_zero_page (x86)
From: Brian Gerst (bgerst_at_didntduck.org)
Date: 03/15/04
- Previous message: Andrew Morton: "2.6.4-mm2"
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Date: Sun, 14 Mar 2004 20:32:22 -0500 To: Andrew Morton <akpm@osdl.org>
Don't abuse empty_zero_page as temporary storage for boot parameters and
command line. This is a holdover from the days before discardable init
sections.
-- Brian Gerst
diff -urN linux-bk/arch/i386/boot/setup.S linux/arch/i386/boot/setup.S
--- linux-bk/arch/i386/boot/setup.S 2004-03-12 14:00:43.000000000 -0500
+++ linux/arch/i386/boot/setup.S 2004-03-12 15:32:55.000000000 -0500
@@ -612,7 +612,7 @@
# int 13h ah=08h "Legacy Get Device Parameters"
#
# A buffer of size EDDMAXNR*(EDDEXTSIZE+EDDPARMSIZE) is reserved for our use
-# in the empty_zero_page at EDDBUF. The first four bytes of which are
+# in the boot_params at EDDBUF. The first four bytes of which are
# used to store the device number, interface support map and version
# results from fn41. The next four bytes are used to store the legacy
# cylinders, heads, and sectors from fn08. The following 74 bytes are used to
@@ -625,9 +625,9 @@
# the structure, and the fn41 and fn08 results are stored at offsets
# from there. This removes the need to increment the pointer for
# every store, and leaves it ready for the fn48 call.
-# A second one-byte buffer, EDDNR, in the empty_zero_page stores
+# A second one-byte buffer, EDDNR, in boot_params stores
# the number of BIOS devices which exist, up to EDDMAXNR.
-# In setup.c, copy_edd() stores both empty_zero_page buffers away
+# In setup.c, copy_edd() stores both boot_params buffers away
# for later use, as they would get overwritten otherwise.
# This code is sensitive to the size of the structs in edd.h
edd_start:
diff -urN linux-bk/arch/i386/kernel/head.S linux/arch/i386/kernel/head.S
--- linux-bk/arch/i386/kernel/head.S 2004-03-12 14:00:43.000000000 -0500
+++ linux/arch/i386/kernel/head.S 2004-03-12 16:58:20.000000000 -0500
@@ -18,12 +18,7 @@
#include <asm/cache.h>
#include <asm/thread_info.h>
#include <asm/asm_offsets.h>
-
-#define OLD_CL_MAGIC_ADDR 0x90020
-#define OLD_CL_MAGIC 0xA33F
-#define OLD_CL_BASE_ADDR 0x90000
-#define OLD_CL_OFFSET 0x90022
-#define NEW_CL_POINTER 0x228 /* Relative to real mode data */
+#include <asm/setup.h>
/*
* References to members of the new_cpu_data structure.
@@ -195,22 +190,15 @@
call setup_idt
/*
- * Copy bootup parameters out of the way. First 2kB of
- * _empty_zero_page is for boot parameters, second 2kB
- * is for the command line.
- *
+ * Copy bootup parameters out of the way.
* Note: %esi still has the pointer to the real-mode data.
*/
- movl $empty_zero_page,%edi
- movl $512,%ecx
+ movl $boot_params,%edi
+ movl $(PARAM_SIZE/4),%ecx
cld
rep
movsl
- xorl %eax,%eax
- movl $512,%ecx
- rep
- stosl
- movl empty_zero_page+NEW_CL_POINTER,%esi
+ movl boot_params+NEW_CL_POINTER,%esi
andl %esi,%esi
jnz 2f # New command line protocol
cmpw $(OLD_CL_MAGIC),OLD_CL_MAGIC_ADDR
@@ -218,8 +206,8 @@
movzwl OLD_CL_OFFSET,%esi
addl $(OLD_CL_BASE_ADDR),%esi
2:
- movl $empty_zero_page+2048,%edi
- movl $512,%ecx
+ movl $saved_command_line,%edi
+ movl $(COMMAND_LINE_SIZE/4),%ecx
rep
movsl
1:
diff -urN linux-bk/arch/i386/kernel/setup.c linux/arch/i386/kernel/setup.c
--- linux-bk/arch/i386/kernel/setup.c 2004-03-12 14:00:43.000000000 -0500
+++ linux/arch/i386/kernel/setup.c 2004-03-12 15:38:38.000000000 -0500
@@ -130,6 +130,8 @@
static char command_line[COMMAND_LINE_SIZE];
char saved_command_line[COMMAND_LINE_SIZE];
+unsigned char __initdata boot_params[PARAM_SIZE];
+
static struct resource code_resource = { "Kernel code", 0x100000, 0 };
static struct resource data_resource = { "Kernel data", 0, 0 };
@@ -456,7 +458,7 @@
#endif
/**
* copy_edd() - Copy the BIOS EDD information
- * from empty_zero_page into a safe place.
+ * from boot_params into a safe place.
*
*/
static inline void copy_edd(void)
@@ -485,12 +487,11 @@
static void __init parse_cmdline_early (char ** cmdline_p)
{
- char c = ' ', *to = command_line, *from = COMMAND_LINE;
+ char c = ' ', *to = command_line, *from = saved_command_line;
int len = 0;
int userdef = 0;
/* Save unparsed command line copy for /proc/cmdline */
- memcpy(saved_command_line, COMMAND_LINE, COMMAND_LINE_SIZE);
saved_command_line[COMMAND_LINE_SIZE-1] = '\0';
for (;;) {
diff -urN linux-bk/arch/i386/mm/init.c linux/arch/i386/mm/init.c
--- linux-bk/arch/i386/mm/init.c 2004-02-15 00:41:30.000000000 -0500
+++ linux/arch/i386/mm/init.c 2004-03-12 15:41:51.000000000 -0500
@@ -474,9 +474,6 @@
high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
#endif
- /* clear the zero-page */
- memset(empty_zero_page, 0, PAGE_SIZE);
-
/* this will put all low memory onto the freelists */
totalram_pages += __free_all_bootmem();
diff -urN linux-bk/Documentation/i386/zero-page.txt linux/Documentation/i386/zero-page.txt
--- linux-bk/Documentation/i386/zero-page.txt 2004-03-12 14:00:43.000000000 -0500
+++ linux/Documentation/i386/zero-page.txt 2004-03-12 17:38:15.000000000 -0500
@@ -1,7 +1,7 @@
-Summary of empty_zero_page layout (kernel point of view)
+Summary of boot_params layout (kernel point of view)
( collected by Hans Lermen and Martin Mares )
-The contents of empty_zero_page are used to pass parameters from the
+The contents of boot_params are used to pass parameters from the
16-bit realmode code of the kernel to the 32-bit part. References/settings
to it mainly are in:
@@ -76,9 +76,3 @@
0x2d0 - 0x600 E820MAP
0x600 - 0x7ff EDDBUF (setup.S) for disk signature read sector
0x600 - 0x7eb EDDBUF (setup.S) for edd data
-
-0x800 string, 2K max COMMAND_LINE, the kernel commandline as
- copied using CL_OFFSET.
- Note: this will be copied once more by setup.c
- into a local buffer which is only 256 bytes long.
- ( #define COMMAND_LINE_SIZE 256 )
diff -urN linux-bk/include/asm-i386/setup.h linux/include/asm-i386/setup.h
--- linux-bk/include/asm-i386/setup.h 2004-02-18 01:37:26.000000000 -0500
+++ linux/include/asm-i386/setup.h 2004-03-12 15:44:17.000000000 -0500
@@ -16,10 +16,22 @@
#define MAXMEM_PFN PFN_DOWN(MAXMEM)
#define MAX_NONPAE_PFN (1 << 20)
+#define PARAM_SIZE 2048
+#define COMMAND_LINE_SIZE 256
+
+#define OLD_CL_MAGIC_ADDR 0x90020
+#define OLD_CL_MAGIC 0xA33F
+#define OLD_CL_BASE_ADDR 0x90000
+#define OLD_CL_OFFSET 0x90022
+#define NEW_CL_POINTER 0x228 /* Relative to real mode data */
+
+#ifndef __ASSEMBLY__
/*
* This is set up by the setup-routine at boot-time
*/
-#define PARAM ((unsigned char *)empty_zero_page)
+extern unsigned char boot_params[PARAM_SIZE];
+
+#define PARAM (boot_params)
#define SCREEN_INFO (*(struct screen_info *) (PARAM+0))
#define EXT_MEM_K (*(unsigned short *) (PARAM+2))
#define ALT_MEM_K (*(unsigned long *) (PARAM+0x1e0))
@@ -47,7 +59,7 @@
#define DISK80_SIGNATURE (*(unsigned int*) (PARAM+DISK80_SIG_BUFFER))
#define EDD_NR (*(unsigned char *) (PARAM+EDDNR))
#define EDD_BUF ((struct edd_info *) (PARAM+EDDBUF))
-#define COMMAND_LINE ((char *) (PARAM+2048))
-#define COMMAND_LINE_SIZE 256
+
+#endif /* __ASSEMBLY__ */
#endif /* _i386_SETUP_H */
-
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