I'm very new to the C language and have been tasked with modifying GRUB. What a way to learn, right? Anyway, I'm trying to debug my modified GRUB using VMWare and GDB. I've been able to get the debugger working before, but for some reason, every time I load up my VM and connect GDB, during the loading process of GRUB, I get:
.loadsym.gdb:1: Error in sourced command file:
The address where biosdisk.module has been loaded is missing
and I have no idea what to do about it. My first thought was, "Oh, I'll just add-symbol-file <file> and that'll fix it!" but apparently that tells GDB to forget every other symbol it loaded???? So I can't add the symbol-file and set a breakpoint.
My googling only returns one semi-relevant post that doesn't really go all that in-depth on fixing the issue.
This output may also be relevant.
info file biosdisk.module
Symbols from "H:\Workspace\GRUB\Bootloader\Trunk\grub-core\kernel.exec".
Remote serial target in gdb-specific protocol:
Debugging a target over a serial line.
While running this, GDB does not access memory from...
Local exec file:
`H:\Workspace\GRUB\Bootloader\Trunk\grub-core\kernel.exec', file type elf32-i386.
Entry point: 0x9000
0x00009000 - 0x0000e6e0 is .text
0x0000e6e0 - 0x0000f68d is .rodata
0x0000f6a0 - 0x0000fe74 is .data
0x0000fe80 - 0x000175d4 is .bss
Ended up being that my codebase wasn't the same. That is, on my Windows host, I had one copy of my code and on my Ubuntu VM was another.
Using version control solved this issue.
Related
When I try to run a simulation in SE mode in gem5 I get the following output:
warn: No dot file generated. Please install pydot to generate the dot file and pdf. build/RISCV/mem/mem_interface.cc:791: warn: DRAM device capacity (8192 Mbytes) does not match the address range assigned (512 Mbytes) 0: system.remote_gdb: listening for remote gdb on port 7000 build/RISCV/sim/simulate.cc:194: info: Entering event queue # 0. Starting simulation... build/RISCV/sim/mem_state.cc:443: info: Increasing stack size by one page. build/RISCV/sim/mem_state.cc:99: panic: Someone allocated physical memory at VA 0x4000000000000000 without creating a VMA! Memory Usage: 619616 KBytes Program aborted at tick 2222000
I'm using the ELF-linux cross compiler. Compiling with the Newlib-ELF cross compiler simulates just fine, but the thing is that I need to use pthreads(openmp) and the Newlib compilation doesn't support it. To get a grip on things I tried to simulate in x86, and found out that it wont work either with a simple gnu/gcc compilation. Then I complied replicating what the test-progs folder did with docker and then it worked fine. Is this the way to go? Since the error says there are problems with physical memory, would compiling with docker help out, or am I missing an obviuos fix? How would go about compiling RISCV with docker (I couldn't find examples of docker+RISCV)?
what have i done wrong (or didn't do) that gdb is not working properly for me?
root#6be3d60ab7c6:/# cat minimal.c
int main()
{
int i = 1337;
return 0;
}
root#6be3d60ab7c6:/# gcc -g minimal.c -o minimal
root#6be3d60ab7c6:/# gdb minimal
GNU gdb (Ubuntu 7.7.1-0ubuntu5~14.04.2) 7.7.1
.
.
.
Reading symbols from minimal...done.
(gdb) break main
Breakpoint 1 at 0x4004f1: file minimal.c, line 3.
(gdb) run
Starting program: /minimal
warning: Error disabling address space randomization: Operation not permitted
During startup program exited normally.
(gdb)
(gdb) print i
No symbol "i" in current context.
If you're using Docker, you probably need the --security-opt seccomp=unconfined option (as well as enabling ptrace):
docker run --cap-add=SYS_PTRACE --security-opt seccomp=unconfined
For whatever reason, your user account doesn't have permission to disable the kernel's address space layout randomisation for this process. By default, gdb turns this off because it makes some sorts of debugging easier (in particular, it means the address of stack objects will be the same each time you run your program). Read more here.
You can work around this problem by disabling this feature of gdb with set disable-randomization off.
As for getting your user the permission needed to disable ASLR, it probably boils down to having write permission to /proc/sys/kernel/randomize_va_space. Read more here.
Building on wisbucky's answer (thank you!), here are the same settings for Docker compose:
security_opt:
- seccomp:unconfined
cap_add:
- SYS_PTRACE
The security option seccomp:unconfined fixed the address space randomization warnings.
The capability SYS_PTRACE didn't seem to have a noticeable effect even though the Docker documentation states that SYS_PTRACE is a capability that is "not granted by default". Perhaps I don't know what to look for.
My NodeMCU program has gone in to infinite reboot loop.
My code is functionally working but any action I try to do, e.g. file.remove("init.lua") or even just =node.heap(), it panics and reboots saying: PANIC: unprotected error in call to Lua API (not enough memory).
Because of this, I'm not able to change any code or delete init.lua to stop automatic code execution.
How do I recover?
I tried re-flashing another version of NodeMCU, but it started emitting garbage in serial port.
Then, I recalled that NodeMCU had two extra files: blank.bin and esp_init_data_default.bin.
I flashed them at 0x7E000 and 0x7C000 respectively.
They are also available as INTERNAL://BLANK and INTERNAL://DEFAULT in the NodeMCU flasher.
This booted the new NodeMCU firmware, all my files were gone and I'm out of infinite reboot loop.
Flash the following files:
0x00000.bin to 0x00000
0x10000.bin to 0x10000
And, the address for esp_init_data_default.bin depends on the size of your module's flash.
0x7c000 for 512 kB, modules like ESP-01, -03, -07 etc.
0xfc000 for 1 MB, modules like ESP8285, PSF-A85
0x1fc000 for 2 MB
0x3fc000 for 4 MB, modules like ESP-12E, NodeMCU devkit 1.0, WeMos D1 mini
Then, after flashing those binaries format its file system (run "file.format()" using ESPlorer) before flashing any other binaries.
Downloads Link
I've just finished working through a similar problem. In my case it was end-user error that caused a need to forcibly wipe init.lua, but I think both problems could be solved similarly. (For completeness, my problem was putting a far-too-short dsleep() call in init.lua, leaving the board resetting itself immediately upon starting init.lua.)
I tried flashing new NodeMCU firmware, writing blank.bin and esp_init_data_default.bin to 0x7E000 and 0x7C000, and also writing 0x00000.bin to 0x00000 and 0x10000.bin to 0x10000. None of these things helped in my case.
My hardware is an Adafruit Huzzah ESP8266 breakout (ESP-12), with 4MB of flash.
What worked for me was:
Download the NONOS SDK from Espressif (I used version 1.5.2 from http://bbs.espressif.com/viewtopic.php?f=46&t=1702).
Unzip it to get at boot_v1.2.bin, user1.1024.new.2.bin, blank.bin, and esp_init_data_default.bin (under bin/ and bin/at/).
Flash the following files to the specified memory locations:
boot_v1.2.bin to 0x00000
user1.1024.new.2.bin to 0x010000
esp_init_data_default.bin to 0xfc000
blank.bin to 0x7e000
Note about flashing:
I used esptool.py 1.2.1.
Because of the nature of my problem, I was only able to write changes to the flash when in programming mode (i.e. after booting with GPIO0 held down to GND).
I found that I needed to reset the board between each step (else invocations of esptool.py after the first would fail).
Erased the flash. esptool.py --port <your/port> erase_flash
Then I was able to write a new firmware. I used a stock nodeMCU 0.9.5 just to isolate variables, but I strongly suspect any firmware would work at this point.
The only think that worked for me was python flash tool esptool in ubuntu, windows flashtool never deleted init.lua and reboot loop.
Commands (ubuntu):
git clone https://github.com/themadinventor/esptool.git
cd esptool
python esptool.py -h
ls -l /dev/tty*
nodemcu_latest.bin can be downloaded from github or anywhere.
sudo python esptool.py -p /dev/ttyUSB0 --baud 460800 write_flash --flash_size=8m 0 nodemcu_latest.bin
I have an app running as a Windows Service. Today, I was notified that the service died. I found a event viewer entry whose basic info is: faulting module kernel32.dll, version 6.0.6002.18740, time stamp 0x50b58c3d, exception code 0xc0000005, fault offset 0x0003fc2e
I'm sure that there is a bug in my code. Can I determine the kernel32.dll function (where the exception came from) from the offset? I'm planning to backtrack to the call in my code.
I agree with what is said in the comments, but anyway I think the answer can be useful. Here is how you can find function name using Windows debugging tools from SDK provided that EventViewer reported offset of failing instruction in kernel32.dll.
First, install Windows debugging tools and configure path to Microsoft public symbol server. Instructions are available online, for example, this video: http://channel9.msdn.com/Shows/Defrag-Tools/Defrag-Tools-Building-your-USB-thumbdrive
Start windows debugger attached to your process or just any process in the system. kernel32.dll is one of the first DLLs any process loads, it is very unlikely that it is rebased. So kernel32.dll’s base address is the same in all processes.
Get base address of kernel32.dll by running “list modules” command in debugger
0:006> lm m kernel32
start end module name
7c800000 7c8f6000 kernel32 (pdb symbols) c:\debuggers\symbols\kernel32.pdb\A22E3A9843CC45B4A2BFA31377127D422\kernel32.pdb
So the base address is 7c800000. Now run “disassemble single instruction” command using DLL base address and offset:
0:006> u 0x7c800000+0x0003fc2e l 1
kernel32!BasepCopyFileExW+0x859:
7c83fc2e 53 push ebx
So BasepCopyFileExW is the function name. (The result on your system may be different.)
My program loads a dynamic library, but after it tries to load it (it doesn't seem to, or at least something's amiss with the loading. A free() throws an error, and I commented out that line.)
I get the following in gdb.
Program received signal SIGSEGV, Segmentation fault.
__strlen_ia32 () at ../sysdeps/i386/i686/multiarch/../../i586/strlen.S:99
99 ../sysdeps/i386/i686/multiarch/../../i586/strlen.S: No such file or directory.
in ../sysdeps/i386/i686/multiarch/../../i586/strlen.S
How would I go about addressing this?
EDIT1:
The above issue was due to me not having an xml file where it should have been.
Here's the first error that I covered up to get to the initial error I showed.
(gdb) s
__dlopen (file=0xbfffd03c "/usr/lib/libvisual-0.5/actor/actor_AVS.so", mode=1)
at dlopen.c:76
76 dlopen.c: No such file or directory.
in dlopen.c
(gdb) bt
#0 __dlopen (file=0xbfffd03c "/usr/lib/libvisual-0.5/actor/actor_AVS.so",
mode=1) at dlopen.c:76
#1 0xb7f8680d in visual_plugin_get_references (
pluginpath=0xbfffd03c "/usr/lib/libvisual-0.5/actor/actor_AVS.so",
count=0xbfffd020) at lv_plugin.c:834
#2 0xb7f86168 in plugin_add_dir_to_list (list=0x804e428,
dir=0x804e288 "/usr/lib/libvisual-0.5/actor") at lv_plugin.c:609
#3 0xb7f86b2b in visual_plugin_get_list (paths=0x804e3d8,
ignore_non_existing=1) at lv_plugin.c:943
#4 0xb7f9c5db in visual_init (argc=0xbffff170, argv=0xbffff174)
at lv_libvisual.c:370
#5 0x080494b7 in main (argc=2, argv=0xbffff204) at client.c:32
(gdb) quit
A debugging session is active.
Inferior 1 [process 3704] will be killed.
Quit anyway? (y or n) y
starlon#lyrical:client$ ls /usr/lib/libvisual-0.5/actor/actor_AVS.so
/usr/lib/libvisual-0.5/actor/actor_AVS.so
starlon#lyrical:client$
The file exists. Not sure what's up. Not sure what code to provide either.
Edit2: More info on the file. Permissions are ok.
816K -rwxr-xr-x 1 root root 814K 2011-11-08 15:06 /usr/lib/libvisual-0.5/actor/actor_AVS.so
You didn't tell what dynamic library it is.
If it is a free dynamic library -or a library whose source is accessible to you- you can compile it and use it with debugging enabled.
Several Linux distributions -notably Debian & Ubuntu- provide debugging variant of many libraries (e.g. GLibc, GTK, Qt, etc...), so you don't need to rebuild them. For example, Debian has libgtk-3-0 package (the binary libraries mostly), libgtk-3-dev the development files for it (headers, etc...) and libgtk-3-0-dbg (the debugging variant of the library). You need to set LD_LIBRARY_PATH appropriately to use it (since it is in /usr/lib/debug/usr/lib/libgdk-3.so.0.200.1).
Sometimes, using the debugging variants of system libraries help you to find bugs in your own code. (Of course, you also need to compile with -g -Wall your own code)
Turned out this was due to a faulty hard drive. Looks like I need a new one.