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A single fix for v4.19-rc3, resolving a problem with our VDSO data page

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for systems with dcache aliasing. Those systems could previously observe
 stale data, causing clock_gettime() & gettimeofday() to return incorrect
 values.
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Merge tag 'mips_fixes_4.19_1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux

Pull MIPS fix from Paul Burton:
 "A single fix for v4.19-rc3, resolving a problem with our VDSO data
  page for systems with dcache aliasing. Those systems could previously
  observe stale data, causing clock_gettime() & gettimeofday() to return
  incorrect values"

* tag 'mips_fixes_4.19_1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux:
  MIPS: VDSO: Match data page cache colouring when D$ aliases
This commit is contained in:
Linus Torvalds 2018-09-06 15:42:10 -07:00
commit 2601dd392d
1 changed files with 20 additions and 0 deletions
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20
arch/mips/kernel/vdso.c
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@ -13,6 +13,7 @@
#include <linux/err.h>
#include <linux/init.h>
#include <linux/ioport.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/slab.h>
@ -20,6 +21,7 @@
#include <asm/abi.h>
#include <asm/mips-cps.h>
#include <asm/page.h>
#include <asm/vdso.h>
/* Kernel-provided data used by the VDSO. */
@ -128,12 +130,30 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
vvar_size = gic_size + PAGE_SIZE;
size = vvar_size + image->size;
/*
* Find a region that's large enough for us to perform the
* colour-matching alignment below.
*/
if (cpu_has_dc_aliases)
size += shm_align_mask + 1;
base = get_unmapped_area(NULL, 0, size, 0, 0);
if (IS_ERR_VALUE(base)) {
ret = base;
goto out;
}
/*
* If we suffer from dcache aliasing, ensure that the VDSO data page
* mapping is coloured the same as the kernel's mapping of that memory.
* This ensures that when the kernel updates the VDSO data userland
* will observe it without requiring cache invalidations.
*/
if (cpu_has_dc_aliases) {
base = __ALIGN_MASK(base, shm_align_mask);
base += ((unsigned long)&vdso_data - gic_size) & shm_align_mask;
}
data_addr = base + gic_size;
vdso_addr = data_addr + PAGE_SIZE;