[Qemu-devel] [PATCH]bug fix for softmmu slow_st unaligned access

[TeLeMan <geleman@gmail.com>]

For example, the memory address 0x10008000 is on an unwritable page.When the
instruction "add dword ptr [0x10007FFF],0x12345678" is executed,the OS will
set 0x10008000 page be a writable page and re-execute this instruction. But
softmmu has modifed the value of 0x10007FFF,so after re-executing this
instruction, the final result is wrong(double-added on 0x10007FFF).
Reversing the stored byte order can fix this bug.

softmmu.patch:

*** qemu.orig/softmmu_template.h	Sun Oct 28 11:15:52 2007
--- qemu/softmmu_template.h	Sun Oct 28 11:22:24 2007
*************** static void glue(glue(slow_st, SUFFIX), 
*** 282,288 ****
          } else if (((addr & ~TARGET_PAGE_MASK) + DATA_SIZE - 1) >=
TARGET_PAGE_SIZE) {
          do_unaligned_access:
              /* XXX: not efficient, but simple */
!             for(i = 0;i < DATA_SIZE; i++) {
  #ifdef TARGET_WORDS_BIGENDIAN
                  glue(slow_stb, MMUSUFFIX)(addr + i, val >> (((DATA_SIZE -
1) * 8) - (i * 8)),
                                            mmu_idx, retaddr);
--- 282,288 ----
          } else if (((addr & ~TARGET_PAGE_MASK) + DATA_SIZE - 1) >=
TARGET_PAGE_SIZE) {
          do_unaligned_access:
              /* XXX: not efficient, but simple */
!             for(i = DATA_SIZE-1;i >= 0; i--) {
  #ifdef TARGET_WORDS_BIGENDIAN
                  glue(slow_stb, MMUSUFFIX)(addr + i, val >> (((DATA_SIZE -
1) * 8) - (i * 8)),
                                            mmu_idx, retaddr);


http://www.nabble.com/file/p13449885/softmmu.patch softmmu.patch 
-- 
View this message in context: http://www.nabble.com/-PATCH-bug-fix-for-softmmu-slow_st-unaligned-access-tf4705397.html#a13449885
Sent from the QEMU - Dev mailing list archive at Nabble.com.