________________________________________ From: Jeff Haran [jharan@xxxxxxxxxxxxxx] Sent: Wednesday, February 01, 2012 6:00 AM To: Smital Desai; Kernel Newbies Subject: RE: Query regarding Kmemleak > -----Original Message----- > From: kernelnewbies-bounces@xxxxxxxxxxxxxxxxx [mailto:kernelnewbies- > bounces@xxxxxxxxxxxxxxxxx] On Behalf Of Smital Desai > Sent: Tuesday, January 31, 2012 4:02 PM > To: Kernel Newbies > Subject: Query regarding Kmemleak > > Hello , > > I am just trying to understand Kmemleak support. > > In a test program , allocating some memory using and vmalloc () and > freeing it in exit () routine. > But when i run a kmemleak , It reports this as a leak. > > But isn't it a generic reuirement to allocate something for the lifetime of > the module and free when we remove the module. ? Can somebody > explain ? > > I have provided the kmemleak output and my test program below. > > Thanks, > Smital Desai > > > ========================================================== > ======================= > > cat /sys/kernel/debug/memleak > > unreferenced object 0xe1b18000 (size 512): > comm "insmod", pid 1066, jiffies 4294953148 (age 54.630s) > hex dump (first 32 bytes): > 36 1c 00 00 02 16 00 00 3c 1c 00 00 02 16 00 00 6.......<....... > 43 1c 00 00 02 16 00 00 4f 1c 00 00 02 16 00 00 C.......O....... > backtrace: > [<c0234ecc>] __vmalloc_node_range+0x1a8/0x1d0 > [<c0234f2c>] __vmalloc_node+0x38/0x44 > [<c023507c>] vmalloc+0x28/0x30 > [<bf00200c>] 0xbf00200c > [<c0100458>] do_one_initcall+0x94/0x164 > [<c01d639c>] sys_init_module+0x70/0x190 > [<c0105d60>] ret_fast_syscall+0x0/0x30 > [<ffffffff>] 0xffffffff > unreferenced object 0xe1b1a000 (size 512): > comm "insmod", pid 1066, jiffies 4294953148 (age 54.630s) > hex dump (first 32 bytes): > 00 00 00 00 00 2c 00 00 00 00 00 00 2a 03 00 00 .....,......*... > 00 00 00 00 00 2c 00 00 bc 00 00 00 02 2e 00 00 .....,.......... > backtrace: > [<c0234ecc>] __vmalloc_node_range+0x1a8/0x1d0 > [<c0234f2c>] __vmalloc_node+0x38/0x44 > [<c023507c>] vmalloc+0x28/0x30 > [<bf00201c>] 0xbf00201c > [<c0100458>] do_one_initcall+0x94/0x164 > [<c01d639c>] sys_init_module+0x70/0x190 > [<c0105d60>] ret_fast_syscall+0x0/0x30 > [<ffffffff>] 0xffffffff > ========================================================== > =========================== > > > > "test.c" > ========================================================== > ======================== > #include <linux/init.h> > #include <linux/kernel.h> > #include <linux/module.h> > #include <linux/kmemleak.h> > > char *ptr1, *ptr2; > > /* > * Some very simple testing. This function needs to be extended for > * proper testing. > */ > static int __init kmemleak_test_init(void) > { > ptr1 = vmalloc(512); > ptr2 = vmalloc(512); > > return 0; > } > module_init(kmemleak_test_init); > > static void __exit kmemleak_test_exit(void) > { > vfree(ptr1); > vfree(ptr2); > } > module_exit(kmemleak_test_exit); > > MODULE_LICENSE("GPL"); > ========================================================== > ======================== > > > > Thanks and Regard > Smital Desai > > The contents of this e-mail and any attachment(s) may contain confidential > or privileged information for the intended recipient(s). Unintended > recipients are prohibited from taking action on the basis of information in this > e-mail and using or disseminating the information, and must notify the > sender and delete it from their system. L&T Infotech will not accept > responsibility or liability for the accuracy or completeness of, or the presence > of any virus or disabling code in this e-mail" > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >>Just to be clear: >>Did you rmmod your module before doing the cat on >>/sys/kernel/debug/memleak? >>If not, I think the above output of memleak is what would be expected. >>Jeff Haran Hello Jeff, Yeh , you are correct and i didn't remove the module . But in that case what if module stays there for the system's life time keeping the allocated memory , it will get reported by kmemleak as potential __leak__ . ( Which essentially is false postitive ) And the case i am mentioning can be pretty much the requirement of atleast few drivers which keep memory allocated for system's lifetime , how to avoid this false postitive in such cases .? Thanks, Smital Desai _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
