Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755196AbWKMQxp (ORCPT ); Mon, 13 Nov 2006 11:53:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755208AbWKMQxo (ORCPT ); Mon, 13 Nov 2006 11:53:44 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:8864 "EHLO e35.co.us.ibm.com") by vger.kernel.org with ESMTP id S1755196AbWKMQxn (ORCPT ); Mon, 13 Nov 2006 11:53:43 -0500 Date: Mon, 13 Nov 2006 11:46:05 -0500 From: Vivek Goyal To: linux kernel mailing list Cc: Reloc Kernel List , ebiederm@xmission.com, akpm@osdl.org, ak@suse.de, hpa@zytor.com, magnus.damm@gmail.com, lwang@redhat.com, dzickus@redhat.com Subject: [RFC] [PATCH 12/16] x86_64: Remove the identity mapping as early as possible Message-ID: <20061113164605.GM17429@in.ibm.com> Reply-To: vgoyal@in.ibm.com References: <20061113162135.GA17429@in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061113162135.GA17429@in.ibm.com> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8927 Lines: 234 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 --- arch/x86_64/kernel/head.S | 39 ++++++++++++++------------------------- 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(+), 61 deletions(-) diff -puN arch/x86_64/kernel/head64.c~x86_64-Remove-the-identity-mapping-as-early-as-possible arch/x86_64/kernel/head64.c --- linux-2.6.19-rc5-reloc/arch/x86_64/kernel/head64.c~x86_64-Remove-the-identity-mapping-as-early-as-possible 2006-11-09 23:04:38.000000000 -0500 +++ linux-2.6.19-rc5-reloc-root/arch/x86_64/kernel/head64.c 2006-11-09 23:04:38.000000000 -0500 @@ -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) @@ -56,6 +64,8 @@ void __init x86_64_start_kernel(char * r { 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)); @@ -63,12 +73,6 @@ void __init x86_64_start_kernel(char * r 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 -puN arch/x86_64/kernel/head.S~x86_64-Remove-the-identity-mapping-as-early-as-possible arch/x86_64/kernel/head.S --- linux-2.6.19-rc5-reloc/arch/x86_64/kernel/head.S~x86_64-Remove-the-identity-mapping-as-early-as-possible 2006-11-09 23:04:38.000000000 -0500 +++ linux-2.6.19-rc5-reloc-root/arch/x86_64/kernel/head.S 2006-11-09 23:04:38.000000000 -0500 @@ -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 */ @@ -266,9 +266,19 @@ 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 @@ -299,27 +309,6 @@ 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 -puN arch/x86_64/kernel/setup64.c~x86_64-Remove-the-identity-mapping-as-early-as-possible arch/x86_64/kernel/setup64.c --- linux-2.6.19-rc5-reloc/arch/x86_64/kernel/setup64.c~x86_64-Remove-the-identity-mapping-as-early-as-possible 2006-11-09 23:04:38.000000000 -0500 +++ linux-2.6.19-rc5-reloc-root/arch/x86_64/kernel/setup64.c 2006-11-09 23:04:38.000000000 -0500 @@ -202,7 +202,6 @@ 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 -puN arch/x86_64/kernel/setup.c~x86_64-Remove-the-identity-mapping-as-early-as-possible arch/x86_64/kernel/setup.c --- linux-2.6.19-rc5-reloc/arch/x86_64/kernel/setup.c~x86_64-Remove-the-identity-mapping-as-early-as-possible 2006-11-09 23:04:38.000000000 -0500 +++ linux-2.6.19-rc5-reloc-root/arch/x86_64/kernel/setup.c 2006-11-09 23:04:38.000000000 -0500 @@ -396,8 +396,6 @@ 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 -puN arch/x86_64/mm/init.c~x86_64-Remove-the-identity-mapping-as-early-as-possible arch/x86_64/mm/init.c --- linux-2.6.19-rc5-reloc/arch/x86_64/mm/init.c~x86_64-Remove-the-identity-mapping-as-early-as-possible 2006-11-09 23:04:38.000000000 -0500 +++ linux-2.6.19-rc5-reloc-root/arch/x86_64/mm/init.c 2006-11-09 23:04:38.000000000 -0500 @@ -378,21 +378,6 @@ void __meminit init_memory_mapping(unsig __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) { @@ -576,15 +561,6 @@ 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 -puN include/asm-x86_64/pgtable.h~x86_64-Remove-the-identity-mapping-as-early-as-possible include/asm-x86_64/pgtable.h --- linux-2.6.19-rc5-reloc/include/asm-x86_64/pgtable.h~x86_64-Remove-the-identity-mapping-as-early-as-possible 2006-11-09 23:04:38.000000000 -0500 +++ linux-2.6.19-rc5-reloc-root/include/asm-x86_64/pgtable.h 2006-11-09 23:04:38.000000000 -0500 @@ -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 -puN include/asm-x86_64/proto.h~x86_64-Remove-the-identity-mapping-as-early-as-possible include/asm-x86_64/proto.h --- linux-2.6.19-rc5-reloc/include/asm-x86_64/proto.h~x86_64-Remove-the-identity-mapping-as-early-as-possible 2006-11-09 23:04:38.000000000 -0500 +++ linux-2.6.19-rc5-reloc-root/include/asm-x86_64/proto.h 2006-11-09 23:04:38.000000000 -0500 @@ -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); _ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/