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arm64 fixes:

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- Report correct timer frequency to userspace when trapping CNTFRQ_EL0
 
 - Fix race with hardware page table updates when updating access flags
 
 - Silence clang overflow warning in VA_START and PAGE_OFFSET calculations
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Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 fixes from Will Deacon:
 "Here are some more arm64 fixes for 4.13. The main one is the PTE race
  with the hardware walker, but there are a couple of other things too.

   - Report correct timer frequency to userspace when trapping
     CNTFRQ_EL0

   - Fix race with hardware page table updates when updating access
     flags

   - Silence clang overflow warning in VA_START and PAGE_OFFSET
     calculations"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: avoid overflow in VA_START and PAGE_OFFSET
  arm64: Fix potential race with hardware DBM in ptep_set_access_flags()
  arm64: Use arch_timer_get_rate when trapping CNTFRQ_EL0
This commit is contained in:
Linus Torvalds 2017-08-04 12:11:48 -07:00
commit b3c6858fb1
3 changed files with 13 additions and 10 deletions
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6
arch/arm64/include/asm/memory.h
View File

@ -64,8 +64,10 @@
* TASK_UNMAPPED_BASE - the lower boundary of the mmap VM area.
*/
#define VA_BITS (CONFIG_ARM64_VA_BITS)
#define VA_START (UL(0xffffffffffffffff) << VA_BITS)
#define PAGE_OFFSET (UL(0xffffffffffffffff) << (VA_BITS - 1))
#define VA_START (UL(0xffffffffffffffff) - \
(UL(1) << VA_BITS) + 1)
#define PAGE_OFFSET (UL(0xffffffffffffffff) - \
(UL(1) << (VA_BITS - 1)) + 1)
#define KIMAGE_VADDR (MODULES_END)
#define MODULES_END (MODULES_VADDR + MODULES_VSIZE)
#define MODULES_VADDR (VA_START + KASAN_SHADOW_SIZE)

2
arch/arm64/kernel/traps.c
View File

@ -523,7 +523,7 @@ static void cntfrq_read_handler(unsigned int esr, struct pt_regs *regs)
{
int rt = (esr & ESR_ELx_SYS64_ISS_RT_MASK) >> ESR_ELx_SYS64_ISS_RT_SHIFT;
pt_regs_write_reg(regs, rt, read_sysreg(cntfrq_el0));
pt_regs_write_reg(regs, rt, arch_timer_get_rate());
regs->pc += 4;
}

15
arch/arm64/mm/fault.c
View File

@ -163,26 +163,27 @@ int ptep_set_access_flags(struct vm_area_struct *vma,
/* only preserve the access flags and write permission */
pte_val(entry) &= PTE_AF | PTE_WRITE | PTE_DIRTY;
/*
* PTE_RDONLY is cleared by default in the asm below, so set it in
* back if necessary (read-only or clean PTE).
*/
/* set PTE_RDONLY if actual read-only or clean PTE */
if (!pte_write(entry) || !pte_sw_dirty(entry))
pte_val(entry) |= PTE_RDONLY;
/*
* Setting the flags must be done atomically to avoid racing with the
* hardware update of the access/dirty state.
* hardware update of the access/dirty state. The PTE_RDONLY bit must
* be set to the most permissive (lowest value) of *ptep and entry
* (calculated as: a & b == ~(~a | ~b)).
*/
pte_val(entry) ^= PTE_RDONLY;
asm volatile("// ptep_set_access_flags\n"
" prfm pstl1strm, %2\n"
"1: ldxr %0, %2\n"
" and %0, %0, %3 // clear PTE_RDONLY\n"
" eor %0, %0, %3 // negate PTE_RDONLY in *ptep\n"
" orr %0, %0, %4 // set flags\n"
" eor %0, %0, %3 // negate final PTE_RDONLY\n"
" stxr %w1, %0, %2\n"
" cbnz %w1, 1b\n"
: "=&r" (old_pteval), "=&r" (tmp), "+Q" (pte_val(*ptep))
: "L" (~PTE_RDONLY), "r" (pte_val(entry)));
: "L" (PTE_RDONLY), "r" (pte_val(entry)));
flush_tlb_fix_spurious_fault(vma, address);
return 1;