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x86/xen: Remove use of VLAs

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There's an ongoing effort to remove VLAs[1] from the kernel to eventually
turn on -Wvla. It turns out, the few VLAs in use in Xen produce only a
single entry array that is always bounded by GDT_SIZE. Clean up the code to
get rid of the VLA and the loop.

[1] https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Laura Abbott <labbott@redhat.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

[boris: Use BUG_ON(size>PAGE_SIZE) instead of GDT_SIZE]
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
This commit is contained in:
Laura Abbott 2018-04-18 10:08:32 -07:00 committed by Boris Ostrovsky
parent ebf04f331f
commit eb0b4aa89c
1 changed files with 31 additions and 55 deletions
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86
arch/x86/xen/enlighten_pv.c
View file

@ -421,45 +421,33 @@ static void xen_load_gdt(const struct desc_ptr *dtr)
{
unsigned long va = dtr->address;
unsigned int size = dtr->size + 1;
unsigned pages = DIV_ROUND_UP(size, PAGE_SIZE);
unsigned long frames[pages];
int f;
unsigned long pfn, mfn;
int level;
pte_t *ptep;
void *virt;
/*
* A GDT can be up to 64k in size, which corresponds to 8192
* 8-byte entries, or 16 4k pages..
*/
BUG_ON(size > 65536);
/* @size should be at most GDT_SIZE which is smaller than PAGE_SIZE. */
BUG_ON(size > PAGE_SIZE);
BUG_ON(va & ~PAGE_MASK);
for (f = 0; va < dtr->address + size; va += PAGE_SIZE, f++) {
int level;
pte_t *ptep;
unsigned long pfn, mfn;
void *virt;
/*
* The GDT is per-cpu and is in the percpu data area.
* That can be virtually mapped, so we need to do a
* page-walk to get the underlying MFN for the
* hypercall. The page can also be in the kernel's
* linear range, so we need to RO that mapping too.
*/
ptep = lookup_address(va, &level);
BUG_ON(ptep == NULL);
/*
* The GDT is per-cpu and is in the percpu data area.
* That can be virtually mapped, so we need to do a
* page-walk to get the underlying MFN for the
* hypercall. The page can also be in the kernel's
* linear range, so we need to RO that mapping too.
*/
ptep = lookup_address(va, &level);
BUG_ON(ptep == NULL);
pfn = pte_pfn(*ptep);
mfn = pfn_to_mfn(pfn);
virt = __va(PFN_PHYS(pfn));
pfn = pte_pfn(*ptep);
mfn = pfn_to_mfn(pfn);
virt = __va(PFN_PHYS(pfn));
make_lowmem_page_readonly((void *)va);
make_lowmem_page_readonly(virt);
frames[f] = mfn;
make_lowmem_page_readonly((void *)va);
make_lowmem_page_readonly(virt);
}
if (HYPERVISOR_set_gdt(frames, size / sizeof(struct desc_struct)))
if (HYPERVISOR_set_gdt(&mfn, size / sizeof(struct desc_struct)))
BUG();
}
@ -470,34 +458,22 @@ static void __init xen_load_gdt_boot(const struct desc_ptr *dtr)
{
unsigned long va = dtr->address;
unsigned int size = dtr->size + 1;
unsigned pages = DIV_ROUND_UP(size, PAGE_SIZE);
unsigned long frames[pages];
int f;
unsigned long pfn, mfn;
pte_t pte;
/*
* A GDT can be up to 64k in size, which corresponds to 8192
* 8-byte entries, or 16 4k pages..
*/
BUG_ON(size > 65536);
/* @size should be at most GDT_SIZE which is smaller than PAGE_SIZE. */
BUG_ON(size > PAGE_SIZE);
BUG_ON(va & ~PAGE_MASK);
for (f = 0; va < dtr->address + size; va += PAGE_SIZE, f++) {
pte_t pte;
unsigned long pfn, mfn;
pfn = virt_to_pfn(va);
mfn = pfn_to_mfn(pfn);
pfn = virt_to_pfn(va);
mfn = pfn_to_mfn(pfn);
pte = pfn_pte(pfn, PAGE_KERNEL_RO);
pte = pfn_pte(pfn, PAGE_KERNEL_RO);
if (HYPERVISOR_update_va_mapping((unsigned long)va, pte, 0))
BUG();
if (HYPERVISOR_update_va_mapping((unsigned long)va, pte, 0))
BUG();
frames[f] = mfn;
}
if (HYPERVISOR_set_gdt(frames, size / sizeof(struct desc_struct)))
if (HYPERVISOR_set_gdt(&mfn, size / sizeof(struct desc_struct)))
BUG();
}