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// 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);
}
/* 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
}
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);
}
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