diff options
Diffstat (limited to 'arch/x86/mm/cpu_entry_area.c')
| -rw-r--r-- | arch/x86/mm/cpu_entry_area.c | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c new file mode 100644 index 000000000000..b9283cc27622 --- /dev/null +++ b/arch/x86/mm/cpu_entry_area.c @@ -0,0 +1,166 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <linux/spinlock.h> +#include <linux/percpu.h> + +#include <asm/cpu_entry_area.h> +#include <asm/pgtable.h> +#include <asm/fixmap.h> +#include <asm/desc.h> + +static DEFINE_PER_CPU_PAGE_ALIGNED(struct entry_stack_page, entry_stack_storage); + +#ifdef CONFIG_X86_64 +static DEFINE_PER_CPU_PAGE_ALIGNED(char, exception_stacks + [(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]); +#endif + +struct cpu_entry_area *get_cpu_entry_area(int cpu) +{ + unsigned long va = CPU_ENTRY_AREA_PER_CPU + cpu * CPU_ENTRY_AREA_SIZE; + BUILD_BUG_ON(sizeof(struct cpu_entry_area) % PAGE_SIZE != 0); + + return (struct cpu_entry_area *) va; +} +EXPORT_SYMBOL(get_cpu_entry_area); + +void cea_set_pte(void *cea_vaddr, phys_addr_t pa, pgprot_t flags) +{ + unsigned long va = (unsigned long) cea_vaddr; + + set_pte_vaddr(va, pfn_pte(pa >> PAGE_SHIFT, flags)); +} + +static void __init +cea_map_percpu_pages(void *cea_vaddr, void *ptr, int pages, pgprot_t prot) +{ + for ( ; pages; pages--, cea_vaddr+= PAGE_SIZE, ptr += PAGE_SIZE) + cea_set_pte(cea_vaddr, per_cpu_ptr_to_phys(ptr), prot); +} + +static void percpu_setup_debug_store(int cpu) +{ +#ifdef CONFIG_CPU_SUP_INTEL + int npages; + void *cea; + + if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) + return; + + cea = &get_cpu_entry_area(cpu)->cpu_debug_store; + npages = sizeof(struct debug_store) / PAGE_SIZE; + BUILD_BUG_ON(sizeof(struct debug_store) % PAGE_SIZE != 0); + cea_map_percpu_pages(cea, &per_cpu(cpu_debug_store, cpu), npages, + PAGE_KERNEL); + + cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers; + /* + * Force the population of PMDs for not yet allocated per cpu + * memory like debug store buffers. + */ + npages = sizeof(struct debug_store_buffers) / PAGE_SIZE; + for (; npages; npages--, cea += PAGE_SIZE) + cea_set_pte(cea, 0, PAGE_NONE); +#endif +} + +/* 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[]; + + /* 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 + + cea_set_pte(&get_cpu_entry_area(cpu)->gdt, get_cpu_gdt_paddr(cpu), + gdt_prot); + + cea_map_percpu_pages(&get_cpu_entry_area(cpu)->entry_stack_page, + per_cpu_ptr(&entry_stack_storage, cpu), 1, + PAGE_KERNEL); + + /* + * 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); + cea_map_percpu_pages(&get_cpu_entry_area(cpu)->tss, + &per_cpu(cpu_tss_rw, cpu), + sizeof(struct tss_struct) / PAGE_SIZE, tss_prot); + +#ifdef CONFIG_X86_32 + per_cpu(cpu_entry_area, cpu) = get_cpu_entry_area(cpu); +#endif + +#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)); + cea_map_percpu_pages(&get_cpu_entry_area(cpu)->exception_stacks, + &per_cpu(exception_stacks, cpu), + sizeof(exception_stacks) / PAGE_SIZE, PAGE_KERNEL); + + cea_set_pte(&get_cpu_entry_area(cpu)->entry_trampoline, + __pa_symbol(_entry_trampoline), PAGE_KERNEL_RX); +#endif + percpu_setup_debug_store(cpu); +} + +static __init void setup_cpu_entry_area_ptes(void) +{ +#ifdef CONFIG_X86_32 + unsigned long start, end; + + BUILD_BUG_ON(CPU_ENTRY_AREA_PAGES * PAGE_SIZE < CPU_ENTRY_AREA_MAP_SIZE); + BUG_ON(CPU_ENTRY_AREA_BASE & ~PMD_MASK); + + start = CPU_ENTRY_AREA_BASE; + end = start + CPU_ENTRY_AREA_MAP_SIZE; + + /* Careful here: start + PMD_SIZE might wrap around */ + for (; start < end && start >= CPU_ENTRY_AREA_BASE; start += PMD_SIZE) + populate_extra_pte(start); +#endif +} + +void __init setup_cpu_entry_areas(void) +{ + unsigned int cpu; + + setup_cpu_entry_area_ptes(); + + for_each_possible_cpu(cpu) + setup_cpu_entry_area(cpu); +} |