Messages in this thread | | | Date | Tue, 31 May 2005 23:51:53 +0530 | From | vamsi krishna <> | Subject | kernel generating SIGBUS while handling pagefault. |
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Hello,
I have a program which is trying to access its virtual memory segments (listed in /proc/<pid>/maps file). But while reading the following virtual memory segment as below. <--------------------------------------------------------------------------------------------------------------------> 0x2a95556000 0x2a9566b000 0x115000 0 /lib64/ld-2.3.2.so 0x2a9566b000 0x2a9566c000 0x1000 0x15000 /lib64/ld-2.3.2.so <--------------------------------------------------------------------------------------------------------------------> generate SIGBUS with siginfo as BUS_ADRERR (Non-existent physical address), I traced back into the kernel code to get the detail on why this BUS_ADRERR is set and found that, if the kernel could not handle pagefault it generates BUS_ADRERR.
In the file /usr/src/linux-2.4.21-20.EL/mm/memory.c at line 1746. <-------------------------------------------------------------------> new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, 0);
if (new_page == NULL) /* no page was available -- SIGBUS */ return 0; if (new_page == NOPAGE_OOM) return -1; <-------------------------------------------------------------------> So is the kernel trying to get a page (map a page) into the swap space from file, and failing to map the file ? due to lack of swap space??. Currently the kernel runs on a amd64 machine with 5GB RAM and 33GB swap space.
But if I run the same program(executable) on amd64 machine with kernel 2.4.21-4 with 8GB RAM and 16GB swap space, there were no page faults and I see only 1 virtual address mapping for /lib64/ld-2.3.2.so on this machine.
I analyzed the strace on the machine failing with SIGBUS and found the following in the strace output <--------------------------------------------------------------------> mmap(NULL, 1061968, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0x2a95687000 mprotect(0x2a9568b000, 1045584, PROT_NONE) = 0 mmap(0x2a95787000, 16384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0) = 0x2a95787000 close(3) = 0 mprotect(0x7fbff09000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC|PROT_GROWSDOWN) = -1 EINVAL (Invalid argument) mprotect(0x7fbff02000, 32768, PROT_READ|PROT_WRITE|PROT_EXEC) = -1 ENOMEM (Cannot allocate memory) mprotect(0x7fbff06000, 16384, PROT_READ|PROT_WRITE|PROT_EXEC) = -1 ENOMEM (Cannot allocate memory) mprotect(0x7fbff08000, 8192, PROT_READ|PROT_WRITE|PROT_EXEC) = 0 mprotect(0x7fbff06000, 8192, PROT_READ|PROT_WRITE|PROT_EXEC) = -1 ENOMEM (Cannot allocate memory) mprotect(0x7fbff07000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC) = -1 ENOMEM (Cannot allocate memory) <--------------------------------------------------------------------> I see some system calls failing with 'Cannot allocate memory', is this because that I use only 5GB of RAM for a 64-bit machine?
Can some mm hackers kindly give some inputs in this?
Thanks in advance.
Best, Vamsi kundeti. India. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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