)]}'
{
  "commit": "cfe79c00a2f4f687eed8b7534d1d3d3d35540c29",
  "tree": "62c603938e7b740ca16ce1012a6ee7ab08b3f727",
  "parents": [
    "04e4f2b18c8de1389d1e00fef0f42a8099910daf"
  ],
  "author": {
    "name": "Mike Frysinger",
    "email": "vapier.adi@gmail.com",
    "time": "Wed Jan 06 17:23:23 2010 +0000"
  },
  "committer": {
    "name": "Linus Torvalds",
    "email": "torvalds@linux-foundation.org",
    "time": "Wed Jan 06 18:16:02 2010 -0800"
  },
  "message": "NOMMU: Avoiding duplicate icache flushes of shared maps\n\nWhen working with FDPIC, there are many shared mappings of read-only\ncode regions between applications (the C library, applet packages like\nbusybox, etc.), but the current do_mmap_pgoff() function will issue an\nicache flush whenever a VMA is added to an MM instead of only doing it\nwhen the map is initially created.\n\nThe flush can instead be done when a region is first mmapped PROT_EXEC.\nNote that we may not rely on the first mapping of a region being\nexecutable - it\u0027s possible for it to be PROT_READ only, so we have to\nremember whether we\u0027ve flushed the region or not, and then flush the\nentire region when a bit of it is made executable.\n\nHowever, this also affects the brk area.  That will no longer be\nexecutable.  We can mprotect() it to PROT_EXEC on MPU-mode kernels, but\nfor NOMMU mode kernels, when it increases the brk allocation, making\nsys_brk() flush the extra from the icache should suffice.  The brk area\nprobably isn\u0027t used by NOMMU programs since the brk area can only use up\nthe leavings from the stack allocation, where the stack allocation is\nlarger than requested.\n\nSigned-off-by: David Howells \u003cdhowells@redhat.com\u003e\nSigned-off-by: Mike Frysinger \u003cvapier@gentoo.org\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@linux-foundation.org\u003e\n",
  "tree_diff": [
    {
      "type": "modify",
      "old_id": "84a524afb3dcdffdd60c7ef1eaf2672acd7731ca",
      "old_mode": 33188,
      "old_path": "include/linux/mm_types.h",
      "new_id": "84d020bed0830eecb4ffd3e678d2c64f7ff4ddc1",
      "new_mode": 33188,
      "new_path": "include/linux/mm_types.h"
    },
    {
      "type": "modify",
      "old_id": "6f9248f89bdefbd6470bb0c4b68fb50b134866d2",
      "old_mode": 33188,
      "old_path": "mm/nommu.c",
      "new_id": "a8d17521624ab57b1066755d21a25bcc419550a5",
      "new_mode": 33188,
      "new_path": "mm/nommu.c"
    }
  ]
}