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x86/cpu_entry_area: Move it to a separate unit
Separate the cpu_entry_area code out of cpu/common.c and the fixmap. Signed-off-by: Thomas Gleixner <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Dave Hansen <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Juergen Gross <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Signed-off-by: Ingo Molnar <[email protected]>
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,52 @@ | ||
| // SPDX-License-Identifier: GPL-2.0 | ||
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| #ifndef _ASM_X86_CPU_ENTRY_AREA_H | ||
| #define _ASM_X86_CPU_ENTRY_AREA_H | ||
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| #include <linux/percpu-defs.h> | ||
| #include <asm/processor.h> | ||
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| /* | ||
| * cpu_entry_area is a percpu region that contains things needed by the CPU | ||
| * and early entry/exit code. Real types aren't used for all fields here | ||
| * to avoid circular header dependencies. | ||
| * | ||
| * Every field is a virtual alias of some other allocated backing store. | ||
| * There is no direct allocation of a struct cpu_entry_area. | ||
| */ | ||
| struct cpu_entry_area { | ||
| char gdt[PAGE_SIZE]; | ||
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| /* | ||
| * The GDT is just below entry_stack and thus serves (on x86_64) as | ||
| * a a read-only guard page. | ||
| */ | ||
| struct entry_stack_page entry_stack_page; | ||
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| /* | ||
| * On x86_64, the TSS is mapped RO. On x86_32, it's mapped RW because | ||
| * we need task switches to work, and task switches write to the TSS. | ||
| */ | ||
| struct tss_struct tss; | ||
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| char entry_trampoline[PAGE_SIZE]; | ||
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| #ifdef CONFIG_X86_64 | ||
| /* | ||
| * Exception stacks used for IST entries. | ||
| * | ||
| * In the future, this should have a separate slot for each stack | ||
| * with guard pages between them. | ||
| */ | ||
| char exception_stacks[(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]; | ||
| #endif | ||
| }; | ||
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| #define CPU_ENTRY_AREA_SIZE (sizeof(struct cpu_entry_area)) | ||
| #define CPU_ENTRY_AREA_PAGES (CPU_ENTRY_AREA_SIZE / PAGE_SIZE) | ||
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| DECLARE_PER_CPU(struct cpu_entry_area *, cpu_entry_area); | ||
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| extern void setup_cpu_entry_areas(void); | ||
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| #endif |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,104 @@ | ||
| // SPDX-License-Identifier: GPL-2.0 | ||
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| #include <linux/spinlock.h> | ||
| #include <linux/percpu.h> | ||
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| #include <asm/cpu_entry_area.h> | ||
| #include <asm/pgtable.h> | ||
| #include <asm/fixmap.h> | ||
| #include <asm/desc.h> | ||
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| static DEFINE_PER_CPU_PAGE_ALIGNED(struct entry_stack_page, entry_stack_storage); | ||
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| #ifdef CONFIG_X86_64 | ||
| static DEFINE_PER_CPU_PAGE_ALIGNED(char, exception_stacks | ||
| [(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]); | ||
| #endif | ||
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| static void __init | ||
| set_percpu_fixmap_pages(int idx, void *ptr, int pages, pgprot_t prot) | ||
| { | ||
| for ( ; pages; pages--, idx--, ptr += PAGE_SIZE) | ||
| __set_fixmap(idx, per_cpu_ptr_to_phys(ptr), prot); | ||
| } | ||
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| /* Setup the fixmap mappings only once per-processor */ | ||
| static void __init setup_cpu_entry_area(int cpu) | ||
| { | ||
| #ifdef CONFIG_X86_64 | ||
| extern char _entry_trampoline[]; | ||
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| /* On 64-bit systems, we use a read-only fixmap GDT and TSS. */ | ||
| pgprot_t gdt_prot = PAGE_KERNEL_RO; | ||
| pgprot_t tss_prot = PAGE_KERNEL_RO; | ||
| #else | ||
| /* | ||
| * On native 32-bit systems, the GDT cannot be read-only because | ||
| * our double fault handler uses a task gate, and entering through | ||
| * a task gate needs to change an available TSS to busy. If the | ||
| * GDT is read-only, that will triple fault. The TSS cannot be | ||
| * read-only because the CPU writes to it on task switches. | ||
| * | ||
| * On Xen PV, the GDT must be read-only because the hypervisor | ||
| * requires it. | ||
| */ | ||
| pgprot_t gdt_prot = boot_cpu_has(X86_FEATURE_XENPV) ? | ||
| PAGE_KERNEL_RO : PAGE_KERNEL; | ||
| pgprot_t tss_prot = PAGE_KERNEL; | ||
| #endif | ||
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| __set_fixmap(get_cpu_entry_area_index(cpu, gdt), get_cpu_gdt_paddr(cpu), gdt_prot); | ||
| set_percpu_fixmap_pages(get_cpu_entry_area_index(cpu, entry_stack_page), | ||
| per_cpu_ptr(&entry_stack_storage, cpu), 1, | ||
| PAGE_KERNEL); | ||
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| /* | ||
| * The Intel SDM says (Volume 3, 7.2.1): | ||
| * | ||
| * Avoid placing a page boundary in the part of the TSS that the | ||
| * processor reads during a task switch (the first 104 bytes). The | ||
| * processor may not correctly perform address translations if a | ||
| * boundary occurs in this area. During a task switch, the processor | ||
| * reads and writes into the first 104 bytes of each TSS (using | ||
| * contiguous physical addresses beginning with the physical address | ||
| * of the first byte of the TSS). So, after TSS access begins, if | ||
| * part of the 104 bytes is not physically contiguous, the processor | ||
| * will access incorrect information without generating a page-fault | ||
| * exception. | ||
| * | ||
| * There are also a lot of errata involving the TSS spanning a page | ||
| * boundary. Assert that we're not doing that. | ||
| */ | ||
| BUILD_BUG_ON((offsetof(struct tss_struct, x86_tss) ^ | ||
| offsetofend(struct tss_struct, x86_tss)) & PAGE_MASK); | ||
| BUILD_BUG_ON(sizeof(struct tss_struct) % PAGE_SIZE != 0); | ||
| set_percpu_fixmap_pages(get_cpu_entry_area_index(cpu, tss), | ||
| &per_cpu(cpu_tss_rw, cpu), | ||
| sizeof(struct tss_struct) / PAGE_SIZE, | ||
| tss_prot); | ||
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| #ifdef CONFIG_X86_32 | ||
| per_cpu(cpu_entry_area, cpu) = get_cpu_entry_area(cpu); | ||
| #endif | ||
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| #ifdef CONFIG_X86_64 | ||
| BUILD_BUG_ON(sizeof(exception_stacks) % PAGE_SIZE != 0); | ||
| BUILD_BUG_ON(sizeof(exception_stacks) != | ||
| sizeof(((struct cpu_entry_area *)0)->exception_stacks)); | ||
| set_percpu_fixmap_pages(get_cpu_entry_area_index(cpu, exception_stacks), | ||
| &per_cpu(exception_stacks, cpu), | ||
| sizeof(exception_stacks) / PAGE_SIZE, | ||
| PAGE_KERNEL); | ||
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| __set_fixmap(get_cpu_entry_area_index(cpu, entry_trampoline), | ||
| __pa_symbol(_entry_trampoline), PAGE_KERNEL_RX); | ||
| #endif | ||
| } | ||
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| void __init setup_cpu_entry_areas(void) | ||
| { | ||
| unsigned int cpu; | ||
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| for_each_possible_cpu(cpu) | ||
| setup_cpu_entry_area(cpu); | ||
| } |