I'm looking to get a specific field of a struct from an elf file. I've found the object:
1009b184 0 NOTYPE LOCAL DEFAULT 3 $d
1009b184 8 OBJECT LOCAL DEFAULT 3 __init___device_cros_system_npcx_0
The struct has 2 fields: .init and .device, I want to get the .init field without having to "just know" that it is the first 4 bytes. Is there a way to do this?
Is there a way to do this?
If the file is compiled with debug info, then readelf -wi will print the info needed to reconstruct the type and offsets within the type.
Without debug info: no.
Related
I want to save the output of a program to a variable.
I use the following approach ,but fail.
$ PIPE RUN TEST | DEFINE/JOB VALUE #SYS$PIPE
$ x = f$logical("VALUE")
I got an error:%DCL-W-MAXPARM, too many parameters - reenter command with fewer parameters
\WORLD\
reference :
How to assign the output of a program to a variable in a DCL com script on VMS?
The usual way to do this is to write the output to a file and read from the file and put that into a DCL symbol (or logical). Although not obvious, you can do this with the PIPE command was well:
$ pipe r 2words
hello world
$ pipe r 2words |(read sys$pipe line ; line=""""+line+"""" ; def/job value &line )
$ sh log value
"VALUE" = "hello world" (LNM$JOB_85AB4440)
$
IF you are able to change the program, add some code to it to write the required values into symbols or logicals (see LIB$ routines)
If you can modify the program, using LIB$SET_SYMBOL in the program defines a DCL symbol (what you are calling a variable) for DCL. That's the cleanest way to do this. If it really needs to be a logical, then there are system calls that define logicals.
I'm doing some optimization using a model whose number of constraints and variables exceeds the cap for the student version of, say, AMPL, so I've found a webpage [http://www.neos-server.org/neos/solvers/milp:Gurobi/AMPL.html] which can solve my type of model.
I've found however that when using a solver where you can provide a commandfile (which I assume is the same as a .run file) the documentation of NEOS server tells that you should see the documentation of the input file. I'm using AMPL input which according to [http://www.neos-guide.org/content/FAQ#ampl_variables] should be able to print the decision variables using a command file with the appearance:
solve;
display _varname, _var;
The problem is that NEOS claim that you cannot add the:
data datafile;
model modelfile;
commands into the .run file, resulting in that the compiler cannot find the variables.
Does anyone know of a way to work around this?
Thanks in advance!
EDIT: If anyone else has this problem (which I believe many people have based on my Internet search). Try to remove any eventual reset; command from the .run file!
You don't need to specify model or data commands in the script file submitted to NEOS. It loads the model and data files automatically, solves the problem, and then executes the script (command file) you provide. For example submitting diet1.mod model diet1.dat data and this trivial command file
display _varname, _var;
produces the output which includes
: _varname _var :=
1 "Buy['Quarter Pounder w/ Cheese']" 0
2 "Buy['McLean Deluxe w/ Cheese']" 0
3 "Buy['Big Mac']" 0
4 "Buy['Filet-O-Fish']" 0
5 "Buy['McGrilled Chicken']" 0
6 "Buy['Fries, small']" 0
7 "Buy['Sausage McMuffin']" 0
8 "Buy['1% Lowfat Milk']" 0
9 "Buy['Orange Juice']" 0
;
As you can see this is the output from the display command.
I need to be able to read in a path file from my simple_switch.py application.I have added the following code to my simple_switch.py in python.
LOG = logging.getLogger(__name__)
CONF = cfg.CONF
CONF.register_cli_opts([
cfg.StrOpt('path-file', default='test.txt',
help='path-file')
])
I attempt to start the application as follows.
bin/ryu-manager --observe-links --path-file test.txt ryu/app/simple_switch.py
However I get the following error.
usage: ryu-manager [-h] [--app-lists APP_LISTS] [--ca-certs CA_CERTS]
[--config-dir DIR] [--config-file PATH]
[--ctl-cert CTL_CERT] [--ctl-privkey CTL_PRIVKEY]
[--default-log-level DEFAULT_LOG_LEVEL] [--explicit-drop]
[--install-lldp-flow] [--log-config-file LOG_CONFIG_FILE]
[--log-dir LOG_DIR] [--log-file LOG_FILE]
[--log-file-mode LOG_FILE_MODE]
[--neutron-admin-auth-url NEUTRON_ADMIN_AUTH_URL]
[--neutron-admin-password NEUTRON_ADMIN_PASSWORD]
[--neutron-admin-tenant-name NEUTRON_ADMIN_TENANT_NAME]
[--neutron-admin-username NEUTRON_ADMIN_USERNAME]
[--neutron-auth-strategy NEUTRON_AUTH_STRATEGY]
[--neutron-controller-addr NEUTRON_CONTROLLER_ADDR]
[--neutron-url NEUTRON_URL]
[--neutron-url-timeout NEUTRON_URL_TIMEOUT]
[--noexplicit-drop] [--noinstall-lldp-flow]
[--noobserve-links] [--nouse-stderr] [--nouse-syslog]
[--noverbose] [--observe-links]
[--ofp-listen-host OFP_LISTEN_HOST]
[--ofp-ssl-listen-port OFP_SSL_LISTEN_PORT]
[--ofp-tcp-listen-port OFP_TCP_LISTEN_PORT] [--use-stderr]
[--use-syslog] [--verbose] [--version]
[--wsapi-host WSAPI_HOST] [--wsapi-port WSAPI_PORT]
[--test-switch-dir TEST-SWITCH_DIR]
[--test-switch-target TEST-SWITCH_TARGET]
[--test-switch-tester TEST-SWITCH_TESTER]
[app [app ...]]
ryu-manager: error: unrecognized arguments: --path-file
It does look like I need to register a new command line option somewhere before I can use it.Can some-one point out to me how to do that? Also can someone explain how to access the file(text.txt) inside the program?
You're on the right track, however the CONF entry that you are creating actually needs to be loaded before your app is loaded, otherwise ryu-manager has no way of knowing it exists!
The file you are looking for is flags.py, under the ryu directory of the source tree (or under the root installation directory).
This is how the ryu/tests/switch/tester.py Ryu app defines it's own arguments, so you might use that as your reference:
CONF.register_cli_opts([
# tests/switch/tester
cfg.StrOpt('target', default='0000000000000001', help='target sw dp-id'),
cfg.StrOpt('tester', default='0000000000000002', help='tester sw dp-id'),
cfg.StrOpt('dir', default='ryu/tests/switch/of13',
help='test files directory')
], group='test-switch')
Following this format, the CONF.register_cli_opts takes an array of config types exactly as you have done it (see ryu/cfg.py for the different types available).
You'll notice that when you run the ryu-manager help, i.e.
ryu-manager --help
the list that comes up is sorted by application (e.g. the group of arguments under 'test-switch options'). For that reason, you will want to specify a group name for your set of commands.
Now let us say that you used the group name 'my-app' and have an argument named 'path-file' in that group, the command line argument will be --my-app-path-file (this can get a little long), while you can access it in your application like this:
from ryu import cfg
CONF = cfg.CONF
path_file = CONF['my-app']['path_file']
Note the use of dash versus the use of underscores.
Cheers!
I was wondering if it is possible to access debug information in a running application that has been compiled with /DEBUG (Pascal and/or C), in order to retrieve information about structures used in the application.
The application can always ask the debugger to do something using SS$_DEBUG. If you send a list of commands that end with GO then the application will continue running after the debugger does its thing. I've used it to dump a bunch of structures formatted neatly without bothering to write the code.
ANALYZE/IMAGE can be used to examine the debugger data in the image file without running the application.
Although you may not see the nice debugger information, you can always look into a running program's data with ANALYZE/SYSTEM .. SET PROCESS ... EXAMINE ....
The SDA SEARCH command may come in handy to 'find' recognizable morcels of date, like a record that you know the program must have read.
Also check out FORMAT/TYPE=block-type, but to make use of data you'll have to compile your structures into .STB files.
When using SDA, you may want to try run the program yourself interactively in an other session to get sample sample addresses to work from.... easier than a link map!
If you programs use RMS a bunch (mine always do :-), then SDA> SHOW PROC/RMS=(FAB,RAB) may give handy addresses for record and key buffers, allthough those may also we managed by the RTL's and thus not be meaningful to you.
Too long for a comment ...
As far as I know, structure information about elements is not in the global symbol table.
What I did, on Linux, but that should work on VMS/ELF files as well:
$ cat tests.c
struct {
int ii;
short ss;
float ff;
char cc;
double dd;
char bb:1;
void *pp;
} theStruct;
...
$ cc -g -c tests.c
$ ../extruct/extruct
-e-insarg, supply an ELF object file.
Usage: ../extruct/extruct [OPTION]... elf-file variable
Display offset and size of members of the named struct/union variable
extracted from the dwarf info in the elf file.
Options are:
-b bit offsets and bit sizes for all members
-lLEVEL display level for nested structures
-n only the member names
-t print base types
$ ../extruct/extruct -t ./tests.o theStruct
size of theStruct: 0x20
offset size type name
0x0000 0x0004 int ii
0x0004 0x0002 short int ss
0x0008 0x0004 float ff
0x000c 0x0001 char cc
0x0010 0x0008 double dd
0x0018 0x0001 char bb:1
0x001c 0x0004 pp
$
This question already has answers here:
Solution needed for building a static IDT and GDT at assemble/compile/link time
(1 answer)
How to do computations with addresses at compile/linking time?
(2 answers)
Closed 5 days ago.
I'm working on a project that has tight boot time requirements. The targeted architecture is an IA-32 based processor running in 32 bit protected mode. One of the areas identified that can be improved is that the current system dynamically initializes the processor's IDT (interrupt descriptor table). Since we don't have any plug-and-play devices and the system is relatively static, I want to be able to use a statically built IDT.
However, this proving to be troublesome for the IA-32 arch since the 8 byte interrupt gate descriptors splits the ISR address. The low 16 bits of the ISR appear in the first 2 bytes of the descriptor, some other bits fill in the next 4 bytes, and then finally the last 16 bits of the ISR appear in the last 2 bytes.
I wanted to use a const array to define the IDT and then simply point the IDT register at it like so:
typedef struct s_myIdt {
unsigned short isrLobits;
unsigned short segSelector;
unsigned short otherBits;
unsigned short isrHibits;
} myIdtStruct;
myIdtStruct myIdt[256] = {
{ (unsigned short)myIsr0, 1, 2, (unsigned short)(myIsr0 >> 16)},
{ (unsigned short)myIsr1, 1, 2, (unsigned short)(myIsr1 >> 16)},
etc.
Obviously this won't work as it is illegal to do this in C because myIsr is not constant. Its value is resolved by the linker (which can do only a limited amount of math) and not by the compiler.
Any recommendations or other ideas on how to do this?
You ran into a well known x86 wart. I don't believe the linker can stuff the address of your isr routines in the swizzled form expected by the IDT entry.
If you are feeling ambitious, you could create an IDT builder script that does something like this (Linux based) approach. I haven't tested this scheme and it probably qualifies as a nasty hack anyway, so tread carefully.
Step 1: Write a script to run 'nm' and capture the stdout.
Step 2: In your script, parse the nm output to get the memory address of all your interrupt service routines.
Step 3: Output a binary file, 'idt.bin' that has the IDT bytes all setup and ready for the LIDT instruction. Your script obviously outputs the isr addresses in the correct swizzled form.
Step 4: Convert his raw binary into an elf section with objcopy:
objcopy -I binary -O elf32-i386 idt.bin idt.elf
Step 5: Now idt.elf file has your IDT binary with the symbol something like this:
> nm idt.elf
000000000000000a D _binary_idt_bin_end
000000000000000a A _binary_idt_bin_size
0000000000000000 D _binary_idt_bin_start
Step 6: relink your binary including idt.elf. In your assembly stubs and linker scripts, you can refer to symbol _binary_idt_bin_start as the base of the IDT. For example, your linker script can place the symbol _binary_idt_bin_start at any address you like.
Be careful that relinking with the IDT section doesn't move anyting else in your binary, e.g. your isr routines. Manage this in your linker script (.ld file) by puting the IDT into it's own dedicated section.
---EDIT---
From comments, there seems to be confusion about the problem. The 32-bit x86 IDT expects the address of the interrupt service routine to be split into two different 16-bit words, like so:
31 16 15 0
+---------------+---------------+
| Address 31-16 | |
+---------------+---------------+
| | Address 15-0 |
+---------------+---------------+
A linker is thus unable to plug-in the ISR address as a normal relocation. So, at boot time, software must construct this split format, which slows boot time.