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Re: [Xen-devel] [PATCH v3] vsprintf: Make sure argument to %pX specifier is valid

Hi Boris,

On 18/02/2015 15:39, Boris Ostrovsky wrote:
If invalid pointer (i.e. something smaller than HYPERVISOR_VIRT_START)
is passed for %*ph/%pv/%ps/%pS format specifiers then print value of the
pointer in parentheses.

For example:

  struct vcpu *v0 = NULL;
  struct vcpu *v1 = (void *)0xffUL;
  unsigned val = 0xab;
  unsigned *ptr = &val;
  unsigned *badptr = (void *)0xab;
  printk("v0 = %pv, v1 = %pv, curr = %pv\n", v0, v1, current);
  printk("badptr = %*ph, ptr = %*ph\n", 1, badptr, 1, ptr);

will produce
  v0 = (0), v1 = (ff), curr = d0v3
  badptr = (ab), ptr = ab

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
  xen/common/vsprintf.c |   23 ++++++++++++++++++++++-
  1 files changed, 22 insertions(+), 1 deletions(-)

  * Print value of the bad pointer in parentheses.
    (I understand Andrew's dislike of additional switch but I
    think this is the cleanest way)

  * Print "(NULL)" instead of specifier-specific string
  * Consider all addresses under HYPERVISOR_VIRT_START as invalid. (I think
    this is true for both x86 and ARM but I don't have ARM platform to test).

This assumption is valid on ARM too. Although, we may have some mappings after HYPERVISOR_VIRT_START why are not valid.

On ARM, HYPERVISOR_VIRT_END marks the end of mapping which is not always mapped (such as the domheap). Would it make sense to test it? Although it seems that x86 doesn't have the same meaning for this macro.


Julien Grall

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