From cfd243d4af7c7f8f52f5cb99d3932d9074b039ff Mon Sep 17 00:00:00 2001 From: Vivek Goyal Date: Wed, 2 May 2007 19:27:07 +0200 Subject: [PATCH] [PATCH] 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 Signed-off-by: Vivek Goyal Signed-off-by: Andi Kleen --- arch/x86_64/kernel/head.S | 39 ++++++++++++++------------------------- arch/x86_64/kernel/head64.c | 17 +++++++++++------ 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, 25 insertions(+), 61 deletions(-) diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S index 926aa21..c211e52 100644 --- a/arch/x86_64/kernel/head.S +++ b/arch/x86_64/kernel/head.S @@ -71,7 +71,7 @@ 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) */ @@ -115,7 +115,7 @@ 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 */ @@ -274,9 +274,19 @@ ENTRY(name) 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 @@ -307,27 +317,6 @@ NEXT_PAGE(level2_kernel_pgt) #undef NEXT_PAGE .data - -#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 cpu_gdt_descr: diff --git a/arch/x86_64/kernel/head64.c b/arch/x86_64/kernel/head64.c index 5c529c1..6c34bdd 100644 --- a/arch/x86_64/kernel/head64.c +++ b/arch/x86_64/kernel/head64.c @@ -18,8 +18,16 @@ #include #include #include +#include #include +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) @@ -57,18 +65,15 @@ void __init x86_64_start_kernel(char * real_mode_data) /* clear bss before set_intr_gate with early_idt_handler */ clear_bss(); + /* Make NULL pointers segfault */ + zap_identity_mappings(); + for (i = 0; i < IDT_ENTRIES; i++) set_intr_gate(i, early_idt_handler); asm volatile("lidt %0" :: "m" (idt_descr)); early_printk("Kernel alive\n"); - /* - * 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 65e2bc5..0e2b8df 100644 --- a/arch/x86_64/kernel/setup.c +++ b/arch/x86_64/kernel/setup.c @@ -274,8 +274,6 @@ void __init setup_arch(char **cmdline_p) 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 6a70b55..53064a9 100644 --- a/arch/x86_64/kernel/setup64.c +++ b/arch/x86_64/kernel/setup64.c @@ -201,7 +201,6 @@ 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 4ab3d40..b0a6078 100644 --- a/arch/x86_64/mm/init.c +++ b/arch/x86_64/mm/init.c @@ -378,21 +378,6 @@ void __meminit init_memory_mapping(unsigned long start, unsigned long end) __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(); -} - #ifndef CONFIG_NUMA void __init paging_init(void) { @@ -569,15 +554,6 @@ void __init mem_init(void) 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 5a5d43b..703f024 100644 --- a/include/asm-x86_64/pgtable.h +++ b/include/asm-x86_64/pgtable.h @@ -17,7 +17,6 @@ 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 7842702..3f8f285 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); -- 2.7.4