Thus spake Alexander Kotelnikov: > Hello. > > Can anyone tell me, what do mean these entries in kern.log? > > Jul 9 22:38:26 vinci kernel: mplayer(3683): unaligned trap at 000000012004e258: 0000000120456b4c 29 9 Blatantly stolen from http://www.alphalinux.org/faq/FAQ-1.html#ss1.2 (which I had bookmarked after seeing similar messages with other programs). On some platforms unaligned accesses will cause the program to crash, whereas on others the kernel emulates the access and lets the program continue running. Unaligned accesses: The Alpha, like all real RISC CPUs, requires that memory accesses are naturally aligned. For example, reading a 4 byte integer from memory requires that the address of the integer be a multiple of 4. Similarly, 8 byte integers need to start at an address that is a multiple of 8. If the CPU attempts to access a word that is not properly aligned, the CPU will trap into the kernel and issue a warning message. The kernel will then go ahead and emulate the unaligned access so that the user-level process executes as if nothing had happened (except for a substantial slow-down due to the fault). Typically, an unaligned fault message looks like this: X(26738): unaligned trap at 000000012004b6f0: 00000001401b20ca 28 1 What this means is that the process executing command X (the X11 server) with process id 26738 caused an unaligned fault accessing address 0x1401b20ca. This access was performed by the instruction located at address 0x12004b6f0. The other numbers are less important, but if you check the kernel sources, you'll find that they tell you more info on what kind of instruction caused the fault (e.g., a load vs. a store). You do not need to be overly alarmed when seeing such a message. The program causing the faults will work correctly. Eventually, all unaligned accesses will be fixed, but in the meantime, just ignore these messages (if you're a programmer, please take a minute and fix the source of the unaligned access instead...). -- Nathan Poznick <poznick@conwaycorp.net> The automobile has not merely taken over the street, it has dissolved the living tissue of the city...Gas-filled, noisy and hazardous, our streets have become the most inhumane landscape in the world. - James M. Fitch
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