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Message-Id: <11544302462613-git-send-email-ebiederm@xmission.com>
Date: Tue, 1 Aug 2006 05:03:43 -0600
From: "Eric W. Biederman" <ebiederm@...ssion.com>
To: <fastboot@...l.org>
Cc: <linux-kernel@...r.kernel.org>, Horms <horms@...ge.net.au>,
Jan Kratochvil <lace@...kratochvil.net>,
"H. Peter Anvin" <hpa@...or.com>,
Magnus Damm <magnus.damm@...il.com>,
Vivek Goyal <vgoyal@...ibm.com>, Linda Wang <lwang@...hat.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 28/33] x86_64: Remove the identity mapping as early as possible.
With the rewrite of the SMP trampoline and the early page
allocator there is nothing that needs identity mapped pages,
once we start executing C code.
So add zap_identity_mappings into head64.c and remove
zap_low_mappings() from much later in the code. The functions
are subtly different thus the name change.
This also kills boot_level4_pgt which was from an earlier
attempt to move the identity mappings as early as possible,
and is now no longer needed. Essentially I have replaced
boot_level4_pgt with trampoline_level4_pgt in trampoline.S
Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
---
arch/x86_64/kernel/head.S | 34 ++++++++++++++--------------------
arch/x86_64/kernel/head64.c | 16 ++++++++++------
arch/x86_64/kernel/setup.c | 2 --
arch/x86_64/kernel/setup64.c | 1 -
arch/x86_64/mm/init.c | 24 ------------------------
include/asm-x86_64/pgtable.h | 1 -
include/asm-x86_64/proto.h | 2 --
7 files changed, 24 insertions(+), 56 deletions(-)
diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S
index a624586..b0b5618 100644
--- a/arch/x86_64/kernel/head.S
+++ b/arch/x86_64/kernel/head.S
@@ -73,7 +73,7 @@ startup_32:
movl %eax, %cr4
/* Setup early boot stage 4 level pagetables */
- movl $(boot_level4_pgt - __START_KERNEL_map), %eax
+ movl $(init_level4_pgt - __START_KERNEL_map), %eax
movl %eax, %cr3
/* Setup EFER (Extended Feature Enable Register) */
@@ -117,7 +117,7 @@ ENTRY(secondary_startup_64)
movq %rax, %cr4
/* Setup early boot stage 4 level pagetables. */
- movq $(boot_level4_pgt - __START_KERNEL_map), %rax
+ movq $(init_level4_pgt - __START_KERNEL_map), %rax
movq %rax, %cr3
/* Check if nx is implemented */
@@ -264,9 +264,19 @@ #define PMDS(START, PERM, COUNT) \
i = i + 1 ; \
.endr
+ /*
+ * This default setting generates an ident mapping at address 0x100000
+ * and a mapping for the kernel that precisely maps virtual address
+ * 0xffffffff80000000 to physical address 0x000000. (always using
+ * 2Mbyte large pages provided by PAE mode)
+ */
NEXT_PAGE(init_level4_pgt)
- /* This gets initialized in x86_64_start_kernel */
- .fill 512,8,0
+ .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
+ .fill 257,8,0
+ .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
+ .fill 252,8,0
+ /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
+ .quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
NEXT_PAGE(level3_ident_pgt)
.quad level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
@@ -301,22 +311,6 @@ #undef NEXT_PAGE
#ifndef CONFIG_HOTPLUG_CPU
__INITDATA
#endif
- /*
- * This default setting generates an ident mapping at address 0x100000
- * and a mapping for the kernel that precisely maps virtual address
- * 0xffffffff80000000 to physical address 0x000000. (always using
- * 2Mbyte large pages provided by PAE mode)
- */
- .align PAGE_SIZE
-ENTRY(boot_level4_pgt)
- .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
- .fill 257,8,0
- .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
- .fill 252,8,0
- /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
- .quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
-
- .data
.align 16
.globl cpu_gdt_descr
diff --git a/arch/x86_64/kernel/head64.c b/arch/x86_64/kernel/head64.c
index defef4e..99d4463 100644
--- a/arch/x86_64/kernel/head64.c
+++ b/arch/x86_64/kernel/head64.c
@@ -18,8 +18,16 @@ #include <asm/bootsetup.h>
#include <asm/setup.h>
#include <asm/desc.h>
#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
#include <asm/sections.h>
+static void __init zap_identity_mappings(void)
+{
+ pgd_t *pgd = pgd_offset_k(0UL);
+ pgd_clear(pgd);
+ __flush_tlb();
+}
+
/* Don't add a printk in there. printk relies on the PDA which is not initialized
yet. */
static void __init clear_bss(void)
@@ -78,6 +86,8 @@ void __init x86_64_start_kernel(char * r
char *s;
int i;
+ /* Make NULL pointers segfault */
+ zap_identity_mappings();
for (i = 0; i < 256; i++)
set_intr_gate(i, early_idt_handler);
asm volatile("lidt %0" :: "m" (idt_descr));
@@ -88,12 +98,6 @@ void __init x86_64_start_kernel(char * r
*/
lockdep_init();
- /*
- * switch to init_level4_pgt from boot_level4_pgt
- */
- memcpy(init_level4_pgt, boot_level4_pgt, PTRS_PER_PGD*sizeof(pgd_t));
- asm volatile("movq %0,%%cr3" :: "r" (__pa_symbol(&init_level4_pgt)));
-
for (i = 0; i < NR_CPUS; i++)
cpu_pda(i) = &boot_cpu_pda[i];
diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index 21840ca..7225f61 100644
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -568,8 +568,6 @@ #endif
dmi_scan_machine();
- zap_low_mappings(0);
-
#ifdef CONFIG_ACPI
/*
* Initialize the ACPI boot-time table parser (gets the RSDP and SDT).
diff --git a/arch/x86_64/kernel/setup64.c b/arch/x86_64/kernel/setup64.c
index 6fe58a6..a1f3aed 100644
--- a/arch/x86_64/kernel/setup64.c
+++ b/arch/x86_64/kernel/setup64.c
@@ -197,7 +197,6 @@ void __cpuinit cpu_init (void)
/* CPU 0 is initialised in head64.c */
if (cpu != 0) {
pda_init(cpu);
- zap_low_mappings(cpu);
} else
estacks = boot_exception_stacks;
diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c
index b46566a..149f363 100644
--- a/arch/x86_64/mm/init.c
+++ b/arch/x86_64/mm/init.c
@@ -332,21 +332,6 @@ void __init init_memory_mapping(unsigned
__flush_tlb_all();
}
-void __cpuinit zap_low_mappings(int cpu)
-{
- if (cpu == 0) {
- pgd_t *pgd = pgd_offset_k(0UL);
- pgd_clear(pgd);
- } else {
- /*
- * For AP's, zap the low identity mappings by changing the cr3
- * to init_level4_pgt and doing local flush tlb all
- */
- asm volatile("movq %0,%%cr3" :: "r" (__pa_symbol(&init_level4_pgt)));
- }
- __flush_tlb_all();
-}
-
/* Compute zone sizes for the DMA and DMA32 zones in a node. */
__init void
size_zones(unsigned long *z, unsigned long *h,
@@ -667,15 +652,6 @@ #endif
reservedpages << (PAGE_SHIFT-10),
datasize >> 10,
initsize >> 10);
-
-#ifdef CONFIG_SMP
- /*
- * Sync boot_level4_pgt mappings with the init_level4_pgt
- * except for the low identity mappings which are already zapped
- * in init_level4_pgt. This sync-up is essential for AP's bringup
- */
- memcpy(boot_level4_pgt+1, init_level4_pgt+1, (PTRS_PER_PGD-1)*sizeof(pgd_t));
-#endif
}
void free_init_pages(char *what, unsigned long begin, unsigned long end)
diff --git a/include/asm-x86_64/pgtable.h b/include/asm-x86_64/pgtable.h
index 5528e8b..d0816fb 100644
--- a/include/asm-x86_64/pgtable.h
+++ b/include/asm-x86_64/pgtable.h
@@ -18,7 +18,6 @@ extern pud_t level3_kernel_pgt[512];
extern pud_t level3_ident_pgt[512];
extern pmd_t level2_kernel_pgt[512];
extern pgd_t init_level4_pgt[];
-extern pgd_t boot_level4_pgt[];
extern unsigned long __supported_pte_mask;
#define swapper_pg_dir init_level4_pgt
diff --git a/include/asm-x86_64/proto.h b/include/asm-x86_64/proto.h
index 038fe1f..978ea43 100644
--- a/include/asm-x86_64/proto.h
+++ b/include/asm-x86_64/proto.h
@@ -11,8 +11,6 @@ struct pt_regs;
extern void start_kernel(void);
extern void pda_init(int);
-extern void zap_low_mappings(int cpu);
-
extern void early_idt_handler(void);
extern void mcheck_init(struct cpuinfo_x86 *c);
--
1.4.2.rc2.g5209e
-
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