Early memory patch, revised
From: H. Peter Anvin
Date: Tue Feb 24 2004 - 00:12:27 EST
Hi all,
This is the latest version of the i386 early memory cleanup patch. It
has the additional advantage that it removes some of the special casing
for VISWS -- this is still untested; if you have access to a VISWS
*please* test this out.
The main difference other than the VISWS code is that it always sets up
the GDT. I agree with Eric this is a lot cleaner.
-hpa
===================================================================
RCS file: /home/hpa/kernel/bkcvs/linux-2.5/arch/i386/boot/tools/build.c,v
retrieving revision 1.4
diff -u -r1.4 build.c
--- linux-2.5/arch/i386/boot/tools/build.c 7 Mar 2003 15:39:16 -0000 1.4
+++ linux-2.5/arch/i386/boot/tools/build.c 21 Feb 2004 01:44:11 -0000
@@ -150,10 +150,8 @@
sz = sb.st_size;
fprintf (stderr, "System is %d kB\n", sz/1024);
sys_size = (sz + 15) / 16;
- /* 0x40000*16 = 4.0 MB, reasonable estimate for the current maximum */
- if (sys_size > (is_big_kernel ? 0x40000 : DEF_SYSSIZE))
- die("System is too big. Try using %smodules.",
- is_big_kernel ? "" : "bzImage or ");
+ if (!is_big_kernel && sys_size > DEF_SYSSIZE)
+ die("System is too big. Try using bzImage or modules.");
while (sz > 0) {
int l, n;
===================================================================
RCS file: /home/hpa/kernel/bkcvs/linux-2.5/arch/i386/kernel/head.S,v
retrieving revision 1.30
diff -u -r1.30 head.S
--- linux-2.5/arch/i386/kernel/head.S 19 Feb 2004 04:55:53 -0000 1.30
+++ linux-2.5/arch/i386/kernel/head.S 23 Feb 2004 01:07:18 -0000
@@ -39,42 +39,38 @@
#define X86_CAPABILITY CPU_PARAMS+12
#define X86_VENDOR_ID CPU_PARAMS+36 /* offset dependent on NCAPINTS */
-/*
- * Initialize page tables
+/*
+ * This is how much memory *in addition to the memory covered up to
+ * and including _end* we need mapped initially. We need one bit for
+ * each possible page, which currently means 2^36/4096/8 = 2 MB
+ * (64-bit-capable chips can do more, but if you have more than 64 GB
+ * of memory you *really* should be running a 64-bit kernel. However,
+ * if this really bothers someone we could query this dynamically.)
+ *
+ * The other thing we may want to do dynamically in the future is to
+ * detect PSE and skip generating the PTEs.
+ *
+ * Modulo rounding, each megabyte assigned here requires a kilobyte of
+ * memory, which is currently unreclaimed.
+ *
+ * This should be a multiple of a page.
*/
-#define INIT_PAGE_TABLES \
- movl $pg0 - __PAGE_OFFSET, %edi; \
- /* "007" doesn't mean with license to kill, but PRESENT+RW+USER */ \
- movl $007, %eax; \
-2: stosl; \
- add $0x1000, %eax; \
- cmp $empty_zero_page - __PAGE_OFFSET, %edi; \
- jne 2b;
-
+#define INIT_MAP_BEYOND_END (2*1024*1024)
+
/*
* swapper_pg_dir is the main page directory, address 0x00101000
*
- * On entry, %esi points to the real-mode code as a 32-bit pointer.
+ * On entry, %esi points to the real-mode code as a 32-bit pointer,
+ * and %bx is zero iff this is the boot CPU.
*/
ENTRY(startup_32)
-
-#ifdef CONFIG_X86_VISWS
-/*
- * On SGI Visual Workstations boot CPU starts in protected mode.
- */
- orw %bx, %bx
- jnz 1f
- INIT_PAGE_TABLES
- movl $swapper_pg_dir - __PAGE_OFFSET, %eax
- movl %eax, %cr3
- lgdt boot_gdt
-1:
-#endif
-
/*
- * Set segments to known values
+ * Set segments to known values. Note that __BOOT_CS and __BOOT_DS
+ * must be the appropriate selectors; this is an entry condition to
+ * this function.
*/
cld
+ lgdt boot_gdt - __PAGE_OFFSET
movl $(__BOOT_DS),%eax
movl %eax,%ds
movl %eax,%es
@@ -107,7 +103,37 @@
jmp 3f
1:
#endif
- INIT_PAGE_TABLES
+
+/*
+ * Initialize page tables. This creates a PDE and a set of page
+ * tables, which are located immediately beyond _end. The variable
+ * init_pg_tables_end is set up to point to the first "safe" location.
+ *
+ * Warning: don't use %ebx, %esi or the stack in this code!
+ */
+page_pde_offset = (__PAGE_OFFSET >> 20);
+
+ movl $((_end-__PAGE_OFFSET) + 0xfff), %edi
+ andl $(~0xfff), %edi
+ movl $(swapper_pg_dir - __PAGE_OFFSET), %edx
+ movl $0x007, %eax /* 0x007 = PRESENT+RW+USER */
+10:
+ leal 0x007(%edi),%ecx /* Create PDE entry */
+ movl %ecx,(%edx) /* Store identity PDE entry */
+ movl %ecx,page_pde_offset(%edx) /* Store kernel PDE entry */
+ addl $4,%edx
+ movl $1024, %ecx
+11:
+ stosl
+ addl $0x1000,%eax
+ loop 11b
+ /* End condition: we must map up to and including INIT_MAP_BEYOND_END */
+ /* bytes beyond the end of our own page tables; the +0x007 is the attribute bits */
+ leal (INIT_MAP_BEYOND_END+0x007)(%edi),%ebp
+ cmpl %ebp,%eax
+ jb 10b
+ movl %edi,(init_pg_tables_end - __PAGE_OFFSET)
+
/*
* Enable paging
*/
@@ -117,10 +143,7 @@
movl %cr0,%eax
orl $0x80000000,%eax
movl %eax,%cr0 /* ..and set paging (PG) bit */
- jmp 1f /* flush the prefetch-queue */
-1:
- movl $1f,%eax
- jmp *%eax /* make sure eip is relocated */
+ ljmp $__BOOT_CS,$1f /* Clear prefetch and normalize %eip */
1:
/* Set up the stack pointer */
lss stack_start,%esp
@@ -142,8 +165,8 @@
movl $__bss_start,%edi
movl $__bss_stop,%ecx
subl %edi,%ecx
- rep
- stosb
+ shrl $2,%ecx
+ rep ; stosl
/*
* start system 32-bit setup. We need to re-do some of the things done
@@ -379,41 +402,20 @@
.fill NR_CPUS-1,8,0 # space for the other GDT descriptors
/*
- * This is initialized to create an identity-mapping at 0-8M (for bootup
- * purposes) and another mapping of the 0-8M area at virtual address
- * PAGE_OFFSET.
+ * This is initialized to create an identity-mapping at 0-_end (for bootup
+ * purposes) and another mapping of the 0-_end area at virtual address
+ * PAGE_OFFSET. The values put here should be all invalid (zero); the valid
+ * entries are created at INIT_PAGE_TABLES.
*/
.org 0x1000
ENTRY(swapper_pg_dir)
- .long 0x00102007
- .long 0x00103007
- .fill BOOT_USER_PGD_PTRS-2,4,0
- /* default: 766 entries */
- .long 0x00102007
- .long 0x00103007
- /* default: 254 entries */
- .fill BOOT_KERNEL_PGD_PTRS-2,4,0
+ .fill 1024,4,0
-/*
- * The page tables are initialized to only 8MB here - the final page
- * tables are set up later depending on memory size.
- */
.org 0x2000
-ENTRY(pg0)
-
-.org 0x3000
-ENTRY(pg1)
-
-/*
- * empty_zero_page must immediately follow the page tables ! (The
- * initialization loop counts until empty_zero_page)
- */
-
-.org 0x4000
ENTRY(empty_zero_page)
+ .fill 4096,1,0
-.org 0x5000
-
+.org 0x3000
/*
* Real beginning of normal "text" segment
*/
@@ -428,19 +430,22 @@
.data
/*
- * The Global Descriptor Table contains 28 quadwords, per-CPU.
- */
-#if defined(CONFIG_SMP) || defined(CONFIG_X86_VISWS)
-/*
* The boot_gdt_table must mirror the equivalent in setup.S and is
- * used only by the trampoline for booting other CPUs
+ * used only for booting.
*/
+ENTRY(boot_gdt)
+ .word __BOOT_DS + 7 # gdt limit
+ .long boot_gdt_table-__PAGE_OFFSET # gdt base
+
.align L1_CACHE_BYTES
ENTRY(boot_gdt_table)
.fill GDT_ENTRY_BOOT_CS,8,0
.quad 0x00cf9a000000ffff /* kernel 4GB code at 0x00000000 */
.quad 0x00cf92000000ffff /* kernel 4GB data at 0x00000000 */
-#endif
+
+/*
+ * The Global Descriptor Table contains 28 quadwords, per-CPU.
+ */
.align L1_CACHE_BYTES
ENTRY(cpu_gdt_table)
.quad 0x0000000000000000 /* NULL descriptor */
@@ -488,4 +493,3 @@
#ifdef CONFIG_SMP
.fill (NR_CPUS-1)*GDT_ENTRIES,8,0 /* other CPU's GDT */
#endif
-
===================================================================
RCS file: /home/hpa/kernel/bkcvs/linux-2.5/arch/i386/kernel/setup.c,v
retrieving revision 1.107
diff -u -r1.107 setup.c
--- linux-2.5/arch/i386/kernel/setup.c 19 Feb 2004 04:45:13 -0000 1.107
+++ linux-2.5/arch/i386/kernel/setup.c 21 Feb 2004 04:44:02 -0000
@@ -50,6 +50,11 @@
#include "setup_arch_pre.h"
#include "mach_resources.h"
+/* This value is set up by the early boot code to point to the value
+ immediately after the boot time page tables. It contains a *physical*
+ address, and must not be in the .bss segment! */
+unsigned long init_pg_tables_end __initdata = ~0UL;
+
int disable_pse __initdata = 0;
static inline char * __init machine_specific_memory_setup(void);
@@ -115,7 +120,6 @@
extern void dmi_scan_machine(void);
extern void generic_apic_probe(char *);
extern int root_mountflags;
-extern char _end[];
unsigned long saved_videomode;
@@ -785,7 +789,7 @@
* partially used pages are not usable - thus
* we are rounding upwards:
*/
- start_pfn = PFN_UP(__pa(_end));
+ start_pfn = PFN_UP(init_pg_tables_end);
find_max_pfn();
@@ -1097,7 +1101,7 @@
init_mm.start_code = (unsigned long) _text;
init_mm.end_code = (unsigned long) _etext;
init_mm.end_data = (unsigned long) _edata;
- init_mm.brk = (unsigned long) _end;
+ init_mm.brk = init_pg_tables_end + PAGE_OFFSET;
code_resource.start = virt_to_phys(_text);
code_resource.end = virt_to_phys(_etext)-1;
===================================================================
RCS file: /home/hpa/kernel/bkcvs/linux-2.5/arch/i386/kernel/trampoline.S,v
retrieving revision 1.9
diff -u -r1.9 trampoline.S
--- linux-2.5/arch/i386/kernel/trampoline.S 26 May 2003 23:59:47 -0000 1.9
+++ linux-2.5/arch/i386/kernel/trampoline.S 23 Feb 2004 01:00:23 -0000
@@ -63,13 +63,5 @@
.word 0 # idt limit = 0
.word 0, 0 # idt base = 0L
-#
-# NOTE: here we actually use CPU#0's GDT - but that is OK, we reload
-# the proper GDT shortly after booting up the secondary CPUs.
-#
-ENTRY(boot_gdt)
- .word __BOOT_DS + 7 # gdt limit
- .long boot_gdt_table-__PAGE_OFFSET # gdt base = gdt (first SMP CPU)
-
.globl trampoline_end
trampoline_end:
===================================================================
RCS file: /home/hpa/kernel/bkcvs/linux-2.5/arch/i386/kernel/vmlinux.lds.S,v
retrieving revision 1.2
diff -u -r1.2 vmlinux.lds.S
--- linux-2.5/arch/i386/kernel/vmlinux.lds.S 18 Aug 2003 18:17:01 -0000 1.2
+++ linux-2.5/arch/i386/kernel/vmlinux.lds.S 21 Feb 2004 05:03:08 -0000
@@ -105,6 +105,7 @@
__bss_start = .; /* BSS */
.bss : { *(.bss) }
+ . = ALIGN(4);
__bss_stop = .;
_end = . ;
===================================================================
RCS file: /home/hpa/kernel/bkcvs/linux-2.5/arch/i386/mm/discontig.c,v
retrieving revision 1.16
diff -u -r1.16 discontig.c
--- linux-2.5/arch/i386/mm/discontig.c 21 Sep 2003 22:39:20 -0000 1.16
+++ linux-2.5/arch/i386/mm/discontig.c 21 Feb 2004 01:48:30 -0000
@@ -66,7 +66,7 @@
extern void one_highpage_init(struct page *, int, int);
extern struct e820map e820;
-extern char _end;
+extern unsigned long init_pg_tables_end;
extern unsigned long highend_pfn, highstart_pfn;
extern unsigned long max_low_pfn;
extern unsigned long totalram_pages;
@@ -237,7 +237,7 @@
reserve_pages = calculate_numa_remap_pages();
/* partially used pages are not usable - thus round upwards */
- system_start_pfn = min_low_pfn = PFN_UP(__pa(&_end));
+ system_start_pfn = min_low_pfn = PFN_UP(init_pg_tables_end);
find_max_pfn();
system_max_low_pfn = max_low_pfn = find_max_low_pfn();