Re: [Crash-utility] [PATCH] add -s option to vm to display one vma at a time

----- Original Message ----- > At 2012-3-14 4:45, Dave Anderson wrote: >> >> >> ----- Original Message ----- >>> At 2012-3-13 17:56, qiaonuohan wrote: >>> >>> Hello Dave, >>> >>> When I am using "vm -p" command, I feel it is chaotic when too >>> much data is printed. I think it is clear to display one vma >>> each time. >>> >>> In the patch, I compare all vmas with the argument of -s option. >>> If an equal vma is found, it will be printed like below. >>> >>> crash> vm -ps ffff88028ff7d3a0 >>> VMA START END FLAGS FILE >>> ffff88028ff7d3a0 7fff29b71000 7fff29b87000 100173 >>> VIRTUAL PHYSICAL >>> 7fff29b71000 (not mapped) >>> 7fff29b72000 (not mapped) >>> 7fff29b73000 (not mapped) >>> 7fff29b74000 (not mapped) >>> 7fff29b75000 (not mapped) >>> 7fff29b76000 (not mapped) >>> 7fff29b77000 27faad000 >>> 7fff29b78000 2807aa000 >>> 7fff29b79000 280781000 >>> 7fff29b7a000 280787000 >>> 7fff29b7b000 280776000 >>> 7fff29b7c000 280786000 >>> 7fff29b7d000 27f2df000 >>> 7fff29b7e000 27f2e0000 >>> 7fff29b7f000 27f2e1000 >>> 7fff29b80000 27f2d7000 >>> 7fff29b81000 28b1ac000 >>> 7fff29b82000 28ecc1000 >>> 7fff29b83000 28c5c2000 >>> 7fff29b84000 28aaf4000 >>> 7fff29b85000 28aaf9000 >>> 7fff29b86000 289566000 >>> crash> >> >> Seems like a reasonable request. >> >> However, I don't like your mixing it with the "-R reference" usage, >> because it confuses things like this simple example: >> >> crash> vm -p -s ffff810ec9f57818 >> VMA START END FLAGS FILE >> ffff810ec9f57818 4010d000 40110000 101877 /usr/local/java/jdk1.5.0_19/bin/java >> VIRTUAL PHYSICAL >> 4010d000 ec89b1000 >> 4010e000 FILE: /usr/local/java/jdk1.5.0_19/bin/java OFFSET: e000 >> 4010f000 e99803000 >> crash> >> >> If the command above were to be qualified with a "-R 4010e000" reference >> check, it results in a nonsensical error message: >> >> crash> vm -p -s ffff810ec9f57818 -R 4010e000 >> vm: only one -R option allowed >> Usage: >> vm [-p | -v | -m | [-R reference] | [-f vm_flags]] [pid | >> taskp] ... >> Enter "help vm" for details. >> crash> >> >> A few suggestions: >> >> (1) Don't even bother to tie it in with the "vm -v" option, because if >> you already know the vm_area_struct address, then just print it with >> "vm_area_struct<address>". >> >> (2) Then, since it *only* applies with the -p functionality, make it >> a new "-P<vmaddr>" option, where the help page explains that the >> <vmaddr> argument must be a vm_area_struct of the current context: >> >> Usage: >> vm [-p | -P vmaddr | -v | -m | [-R reference] | [-f >> vm_flags]] [pid | taskp] ... >> >> (3) Make -P mutually exclusive with all of the other options. >> >> (4) Do not use the reference structure for this feature. Just use your new >> flag, and pass the vma address in the 3rd "vaddr" argument to vm_area_dump(), >> since it's not even being used by cmd_vm(). > > I have modified the patch, please check. OK, these are my suggestions to finalize this patch. First, fix this: # make warn ... cc -c -g -DX86_64 -DGDB_7_3_1 memory.c -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector memory.c: In function "vm_area_dump": memory.c:3503:7: warning: "single_vma" may be used uninitialized in this function [-Wuninitialized] ... Secondly, this command is no different from the other context-sensitive "vm" command options, so please always print the task header like they do. Just remove the three restrictions in cmd_vm() that do this: - if (!ref) + if (!(ref || (flag& PRINT_SINGLE_VMA))) print_task_header(fp, CURRENT_CONTEXT(), 0); Third, the option is either going to work OK or fail to find the VMA. Your patch does this if an invalid vm_area_struct address is entered: crash> vm -P ffff880617e7af44 VMA START END FLAGS FILE crash> Regardless of success or failure, the print_task_header() call in cmd_vm() should always show the task information. Then, if you actually find the VMA, print the "VMA START ..." header along with its data: crash> vm -P ffff880284cf87e0 PID: 13318 TASK: ffff8806294f2690 CPU: 11 COMMAND: "crash" VMA START END FLAGS FILE ffff880284cf87e0 400000 9fa000 8001875 /root/crash-6.0.4/crash VIRTUAL PHYSICAL 400000 28c7fa000 401000 29470a000 402000 29470b000 403000 29470c000 404000 29470d000 405000 29470e000 406000 29470f000 ... But if the command fails to find the VMA, then indicate that under the task header: crash> vm -P ffff880284cf87e8 PID: 13318 TASK: ffff8806294f2690 CPU: 11 COMMAND: "crash" (not found) crash> Lastly, please don't use subterfuge to accomplish the task at hand. The setting of PHYSADDR in the vm_area_dump() function makes no sense at all: + single_vma_header = 0; + if (flag& PRINT_SINGLE_VMA) { + flag |= PHYSADDR; + single_vma = vaddr; + vaddr = 0; + } It may "work" by doing the above, but I'm sure you can accomplish it just as easily using your PRINT_SINGLE_VMA flag and/or your new local variables, making it both easier to understand and more maintainable.

Thanks, Dave -- Crash-utility mailing list Crash-utility(a)redhat.com https://www.redhat.com/mailman/listinfo/crash-utility