[PATCH v2 0/3] kmemleak: Fix false positive with special scan
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From: Hiroshi DOYU on 1 Jun 2010 06:30 Hi, There is a false positive case that a pointer is calculated by other methods than the usual container_of macro. "kmemleak_ignore" can cover such a false positive, but it would loose the advantage of memory leak detection. This patch allows kmemleak to work with such false positives by introducing a new special memory block with a specified calculation formula. A client module can register its area with a conversion function, with which function kmemleak scan could calculate a correct pointer. For this version 2, to avoid client kernel module being unloaded before unregistering special conversion, module reference count is used. This was pointed by Phil Carmody. A typical use case could be the IOMMU pagetable allocation which stores pointers to the second level of page tables with some conversion, for example, a physical address with attribution bits. Right now I don't have other use cases but I hope that there could be some that this special scan works with. Test: # echo scan > kmemleak # modprobe kmemleak-special-test [ 1328.260162] Stored 1024(a)dfc5ac00 -> 9fc5ac01 [ 1328.264984] Stored 1024(a)dfc5b800 -> 9fc5b801 [ 1328.269500] Stored 1024(a)dfc5b400 -> 9fc5b401 [ 1328.273895] Stored 1024(a)dfc5b000 -> 9fc5b001 [ 1328.278381] Stored 1024(a)deb9bc00 -> 9eb9bc01 [ 1328.282714] Stored 1024(a)deea6c00 -> 9eea6c01 [ 1328.287139] Stored 1024(a)deea7c00 -> 9eea7c01 [ 1328.291473] Stored 1024(a)deea7800 -> 9eea7801 # echo scan > kmemleak [ 1344.062591] kmemleak: 8 new suspected memory leaks (see /sys/kernel/debug/kmemleak) # rmmod kmemleak-special-test # echo scan > kmemleak # modprobe kmemleak-special-test timeout=60 [ 71.758850] Stored 1024(a)dfc5b000 -> 9fc5b001 [ 71.763702] Stored 1024(a)dfc5b400 -> 9fc5b401 [ 71.768066] Stored 1024(a)dfc5b800 -> 9fc5b801 [ 71.772583] Stored 1024(a)dfc5bc00 -> 9fc5bc01 [ 71.776977] Stored 1024(a)deea6000 -> 9eea6001 [ 71.781341] Stored 1024(a)deea6400 -> 9eea6401 [ 71.785736] Stored 1024(a)deea6800 -> 9eea6801 [ 71.790069] Stored 1024(a)deea6c00 -> 9eea6c01 [ 71.794433] kmemleak_special_init: Registered special scan: bf000360 # echo scan > kmemleak [ 79.588836] custom_conversion: Converted 9fc5b001 -> dfc5b000 [ 79.594696] custom_conversion: Converted 9fc5b401 -> dfc5b400 [ 79.600494] custom_conversion: Converted 9fc5b801 -> dfc5b800 [ 79.606292] custom_conversion: Converted 9fc5bc01 -> dfc5bc00 [ 79.612060] custom_conversion: Converted 9eea6001 -> deea6000 [ 79.617889] custom_conversion: Converted 9eea6401 -> deea6400 [ 79.623687] custom_conversion: Converted 9eea6801 -> deea6800 [ 79.629486] custom_conversion: Converted 9eea6c01 -> deea6c00 # rmmod kmemleak-special-test rmmod: cannot unload 'kmemleak_special_test': Resource temporarily unavailable # lsmod kmemleak-special-test Module Size Used by Not tainted kmemleak_special_test 1467 1 # [ 131.800354] no_special_func: Unregistered special scan bf000360 # lsmod kmemleak-special-test Module Size Used by Not tainted kmemleak_special_test 1467 0 # rmmod kmemleak-special-test Hiroshi DOYU (3): kmemleak: Fix false positives with special scan kmemleak: Add special scan test case omap iommu: kmemleak: Fix false positive with special scan arch/arm/plat-omap/iommu.c | 19 +++++++ include/linux/kmemleak.h | 5 ++ mm/Makefile | 2 +- mm/kmemleak-special-test.c | 94 ++++++++++++++++++++++++++++++++++++ mm/kmemleak.c | 114 ++++++++++++++++++++++++++++++++++++++++++- 5 files changed, 230 insertions(+), 4 deletions(-) create mode 100644 mm/kmemleak-special-test.c -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |