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Diffstat (limited to 'Documentation/s390/Debugging390.txt')
| -rw-r--r-- | Documentation/s390/Debugging390.txt | 93 |
1 files changed, 46 insertions, 47 deletions
diff --git a/Documentation/s390/Debugging390.txt b/Documentation/s390/Debugging390.txt index 844c03fe7921d6..4dd25ee549e9d1 100644 --- a/Documentation/s390/Debugging390.txt +++ b/Documentation/s390/Debugging390.txt @@ -8,8 +8,8 @@ Overview of Document: ===================== This document is intended to give an good overview of how to debug -Linux for s/390 & z/Architecture it isn't intended as a complete reference & not a -tutorial on the fundamentals of C & assembly, it dosen't go into +Linux for s/390 & z/Architecture. It isn't intended as a complete reference & not a +tutorial on the fundamentals of C & assembly. It doesn't go into 390 IO in any detail. It is intended to complement the documents in the reference section below & any other worthwhile references you get. @@ -88,7 +88,7 @@ s/390 z/Architecture 0 0 Reserved ( must be 0 ) otherwise specification exception occurs. 1 1 Program Event Recording 1 PER enabled, - PER is used to facilititate debugging e.g. single stepping. + PER is used to facilitate debugging e.g. single stepping. 2-4 2-4 Reserved ( must be 0 ). @@ -163,7 +163,7 @@ s/390 z/Architecture 1 1 64 bit 32 1=31 bit addressing mode 0=24 bit addressing mode (for backward - compatibility ), linux always runs with this bit set to 1 + compatibility), linux always runs with this bit set to 1 33-64 Instruction address. 33-63 Reserved must be 0 @@ -188,7 +188,7 @@ Bytes 0-512 ( 200 hex ) on s/390 & 0-512,4096-4544,4604-5119 currently on z/Arch are used by the processor itself for holding such information as exception indications & entry points for exceptions. Bytes after 0xc00 hex are used by linux for per processor globals on s/390 & z/Architecture -( there is a gap on z/Architecure too currently between 0xc00 & 1000 which linux uses ). +( there is a gap on z/Architecture too currently between 0xc00 & 1000 which linux uses ). The closest thing to this on traditional architectures is the interrupt vector table. This is a good thing & does simplify some of the kernel coding however it means that we now cannot catch stray NULL pointers in the @@ -239,7 +239,7 @@ they go to 64 Bit. On 390 our limitations & strengths make us slightly different. For backward compatibility we are only allowed use 31 bits (2GB) -of our 32 bit addresses,however, we use entirely separate address +of our 32 bit addresses, however, we use entirely separate address spaces for the user & kernel. This means we can support 2GB of non Extended RAM on s/390, & more @@ -317,9 +317,9 @@ Each process/thread under Linux for S390 has its own kernel task_struct defined in linux/include/linux/sched.h The S390 on initialisation & resuming of a process on a cpu sets the __LC_KERNEL_STACK variable in the spare prefix area for this cpu -( which we use for per processor globals). +(which we use for per-processor globals). -The kernel stack pointer is intimately tied with the task stucture for +The kernel stack pointer is intimately tied with the task structure for each processor as follows. s/390 @@ -354,7 +354,7 @@ static inline struct task_struct * get_current(void) } i.e. just anding the current kernel stack pointer with the mask -8192. -Thankfully because Linux dosen't have support for nested IO interrupts +Thankfully because Linux doesn't have support for nested IO interrupts & our devices have large buffers can survive interrupts being shut for short amounts of time we don't need a separate stack for interrupts. @@ -366,8 +366,8 @@ Register Usage & Stackframes on Linux for s/390 & z/Architecture Overview: --------- This is the code that gcc produces at the top & the bottom of -each function, it usually is fairly consistent & similar from -function to function & if you know its layout you can probalby +each function. It usually is fairly consistent & similar from +function to function & if you know its layout you can probably make some headway in finding the ultimate cause of a problem after a crash without a source level debugger. @@ -394,7 +394,7 @@ i.e they aren't in registers & they aren't static. back-chain: This is a pointer to the stack pointer before entering a framed functions ( see frameless function ) prologue got by -deferencing the address of the current stack pointer, +dereferencing the address of the current stack pointer, i.e. got by accessing the 32 bit value at the stack pointers current location. @@ -724,7 +724,7 @@ This is useful for debugging because 1) You can double check whether the files you expect to be included are the ones that are being included ( e.g. double check that you aren't going to the i386 asm directory ). 2) Check that macro definitions aren't clashing with typedefs, -3) Check that definitons aren't being used before they are being included. +3) Check that definitions aren't being used before they are being included. 4) Helps put the line emitting the error under the microscope if it contains macros. For convenience the Linux kernel's makefile will do preprocessing automatically for you @@ -840,12 +840,11 @@ using the strip command to make it a more reasonable size to boot it. A source/assembly mixed dump of the kernel can be done with the line objdump --source vmlinux > vmlinux.lst -Also if the file isn't compiled -g this will output as much debugging information -as it can ( e.g. function names ), however, this is very slow as it spends lots -of time searching for debugging info, the following self explanitory line should be used -instead if the code isn't compiled -g. +Also, if the file isn't compiled -g, this will output as much debugging information +as it can (e.g. function names). This is very slow as it spends lots +of time searching for debugging info. The following self explanatory line should be used +instead if the code isn't compiled -g, as it is much faster: objdump --disassemble-all --syms vmlinux > vmlinux.lst -as it is much faster As hard drive space is valuble most of us use the following approach. 1) Look at the emitted psw on the console to find the crash address in the kernel. @@ -861,7 +860,7 @@ Linux source tree. 6) rm /arch/s390/kernel/signal.o 7) make /arch/s390/kernel/signal.o 8) watch the gcc command line emitted -9) type it in again or alernatively cut & paste it on the console adding the -g option. +9) type it in again or alternatively cut & paste it on the console adding the -g option. 10) objdump --source arch/s390/kernel/signal.o > signal.lst This will output the source & the assembly intermixed, as the snippet below shows This will unfortunately output addresses which aren't the same @@ -913,8 +912,8 @@ If you wanted to know does ping work but didn't have the source strace ping -c 1 127.0.0.1 & then look at the man pages for each of the syscalls below, ( In fact this is sometimes easier than looking at some spagetti -source which conditionally compiles for several architectures ) -Not everything that it throws out needs to make sense immeadiately +source which conditionally compiles for several architectures ). +Not everything that it throws out needs to make sense immediately. Just looking quickly you can see that it is making up a RAW socket for the ICMP protocol. @@ -974,8 +973,9 @@ through the pipe for each line containing the string open. Example 3 --------- -Getting sophistocated -telnetd crashes on & I don't know why +Getting sophisticated +telnetd crashes & I don't know why + Steps ----- 1) Replace the following line in /etc/inetd.conf @@ -1085,8 +1085,7 @@ Notes ----- Addresses & values in the VM debugger are always hex never decimal Address ranges are of the format <HexValue1>-<HexValue2> or <HexValue1>.<HexValue2> -e.g. The address range 0x2000 to 0x3000 can be described described as -2000-3000 or 2000.1000 +e.g. The address range 0x2000 to 0x3000 can be described as 2000-3000 or 2000.1000 The VM Debugger is case insensitive. @@ -1311,7 +1310,7 @@ for finding out when a particular variable changes. An alternative way of finding the STD of a currently running process is to do the following, ( this method is more complex but -could be quite convient if you aren't updating the kernel much & +could be quite convenient if you aren't updating the kernel much & so your kernel structures will stay constant for a reasonable period of time ). @@ -1413,7 +1412,7 @@ SMP Specific commands To find out how many cpus you have Q CPUS displays all the CPU's available to your virtual machine To find the cpu that the current cpu VM debugger commands are being directed at do -Q CPU to change the current cpu cpu VM debugger commands are being directed at do +Q CPU to change the current cpu VM debugger commands are being directed at do CPU <desired cpu no> On a SMP guest issue a command to all CPUs try prefixing the command with cpu all. @@ -1674,8 +1673,8 @@ channel is idle & the second for device end ( secondary status ) sometimes you g concurrently, you check how the IO went on by issuing a TEST SUBCHANNEL at each interrupt, from which you receive an Interruption response block (IRB). If you get channel & device end status in the IRB without channel checks etc. your IO probably went okay. If you didn't you -probably need a doctorto examine the IRB & extended status word etc. -If an error occurs more sophistocated control units have a facitity known as +probably need a doctor to examine the IRB & extended status word etc. +If an error occurs, more sophistocated control units have a facitity known as concurrent sense this means that if an error occurs Extended sense information will be presented in the Extended status word in the IRB if not you have to issue a subsequent SENSE CCW command after the test subchannel. @@ -1704,7 +1703,7 @@ concentrate on data processing. IOP's can use one or more links ( known as channel paths ) to talk to each IO device. It first checks for path availability & chooses an available one, then starts ( & sometimes terminates IO ). -There are two types of channel path ESCON & the Paralell IO interface. +There are two types of channel path: ESCON & the Parallel IO interface. IO devices are attached to control units, control units provide the logic to interface the channel paths & channel path IO protocols to @@ -1743,11 +1742,11 @@ controllers or a control unit which connects to 1000 3270 terminals ). The 390 IO systems come in 2 flavours the current 390 machines support both -The Older 360 & 370 Interface,sometimes called the paralell I/O interface, +The Older 360 & 370 Interface,sometimes called the Parallel I/O interface, sometimes called Bus-and Tag & sometimes Original Equipment Manufacturers Interface (OEMI). -This byte wide paralell channel path/bus has parity & data on the "Bus" cable +This byte wide Parallel channel path/bus has parity & data on the "Bus" cable & control lines on the "Tag" cable. These can operate in byte multiplex mode for sharing between several slow devices or burst mode & monopolize the channel for the whole burst. Upto 256 devices can be addressed on one of these cables. These cables are @@ -1777,7 +1776,7 @@ Consoles 3270 & 3215 ( a teletype emulated under linux for a line mode console ) DASD's direct access storage devices ( otherwise known as hard disks ). Tape Drives. CTC ( Channel to Channel Adapters ), -ESCON or Paralell Cables used as a very high speed serial link +ESCON or Parallel Cables used as a very high speed serial link between 2 machines. We use 2 cables under linux to do a bi-directional serial link. @@ -1803,8 +1802,8 @@ OSA 7C09 ON OSA 7C09 SUBCHANNEL = 0001 OSA 7C14 ON OSA 7C14 SUBCHANNEL = 0002 OSA 7C15 ON OSA 7C15 SUBCHANNEL = 0003 -If you have a guest with certain priviliges you may be able to see devices -which don't belong to you to avoid this do add the option V. +If you have a guest with certain privileges you may be able to see devices +which don't belong to you. To avoid this, add the option V. e.g. Q V OSA @@ -1837,7 +1836,7 @@ RDRLIST RECEIVE / LOG TXT A1 ( replace 8) filel & press F11 to look at it -You should see someting like. +You should see something like: 00020942' SSCH B2334000 0048813C CC 0 SCH 0000 DEV 7C08 CPA 000FFDF0 PARM 00E2C9C4 KEY 0 FPI C0 LPM 80 @@ -1916,7 +1915,7 @@ Assembly -------- info registers: displays registers other than floating point. info all-registers: displays floating points as well. -disassemble: dissassembles +disassemble: disassembles e.g. disassemble without parameters will disassemble the current function disassemble $pc $pc+10 @@ -1935,7 +1934,7 @@ undisplay : undo's display's info breakpoints: shows all current breakpoints -info stack: shows stack back trace ( if this dosent work too well, I'll show you the +info stack: shows stack back trace ( if this doesn't work too well, I'll show you the stacktrace by hand below ). info locals: displays local variables. @@ -2045,13 +2044,13 @@ what gdb does when the victim receives certain signals. list: e.g. list lists current function source -list 1,10 list first 10 lines of curret file. +list 1,10 list first 10 lines of current file. list test.c:1,10 directory: Adds directories to be searched for source if gdb cannot find the source. -(note it is a bit sensititive about slashes ) +(note it is a bit sensititive about slashes) e.g. To add the root of the filesystem to the searchpath do directory // @@ -2123,9 +2122,9 @@ p/x (*(**$sp+56))&0x7fffffff Disassembling instructions without debug info --------------------------------------------- -gdb typically compains if there is a lack of debugging -symbols in the disassemble command with -"No function contains specified address." to get around +gdb typically complains if there is a lack of debugging +symbols in the disassemble command with +"No function contains specified address." To get around this do x/<number lines to disassemble>xi <address> e.g. @@ -2184,7 +2183,7 @@ ps -aux | grep gdb kill -SIGSEGV <gdb's pid> or alternatively use killall -SIGSEGV gdb if you have the killall command. Now look at the core dump. -./gdb ./gdb core +./gdb core Displays the following GNU gdb 4.18 Copyright 1998 Free Software Foundation, Inc. @@ -2316,7 +2315,7 @@ Showing us the shared libraries init uses where they are in memory /proc/1/mem is the current running processes memory which you can read & write to like a file. strace uses this sometimes as it is a bit faster than the -rather inefficent ptrace interface for peeking at DATA. +rather inefficient ptrace interface for peeking at DATA. cat status @@ -2446,7 +2445,7 @@ displays the following lines as it executes them. + RELSTATUS=release + MACHTYPE=i586-pc-linux-gnu -perl -d <scriptname> runs the perlscript in a fully intercative debugger +perl -d <scriptname> runs the perlscript in a fully interactive debugger <like gdb>. Type 'h' in the debugger for help. @@ -2477,7 +2476,7 @@ Lcrash is a perfectly normal program,however, it requires 2 additional files, Kerntypes which is built using a patch to the linux kernel sources in the linux root directory & the System.map. -Kerntypes is an an objectfile whose sole purpose in life +Kerntypes is an objectfile whose sole purpose in life is to provide stabs debug info to lcrash, to do this Kerntypes is built from kerntypes.c which just includes the most commonly referenced header files used when debugging, lcrash can then read the |