I am trying to use google breakpad, but I am facing a strange issue.
i am working in linux. I have my own library, my_lib.so, which I process with dump_syms and generates this symbol :
$ dump_syms my_lib.so|head -2
MODULE Linux mips 3BB485681467218D36EB2FF02287096C0 my_lib.so
INFO CODE_ID 6885B43B67148D2136EB2FF02287096C
I create the symbols directory with the appropiate subdirectories. I then generate a minidump for the program that uses a stripped version of my_lib.so, but when I try to process it with minidump_stackwalk:
0x77dce000 - 0x77e23fff my_lib.so ??? (WARNING: No symbols, my_lib.so, AC40136B433E5A68F66CCE8C2C2E6C250)
It is seaching for a differente ID, AC40136B433E5A68F66CCE8C2C2E6C250, so it does not find the symbols. Why the mismatch?
Knowing that it searches for AC40136B433E5A68F66CCE8C2C2E6C250 I manually changed the tree directory in symbols, to match that one, just to test. I also changed the id inside the my_lib.so.sym file, and then minidump_stalkwalk does not complain about not finding the symbols, but still I can't see the stack trace.
Any ideas about this mismatch?
by the way, if I run readelf -n over the original library and the stripped one, I get the same GNU BUILD ID.
Related
I designed RISCV32IM processor, and I used "riscv32-unknown-elf-gcc" to generate code for testing.
However, the PC(instruction memory address) value and data memory address of the generated code had arbitrary values. I used this command:
riscv32-unknown-elf-gcc -march=rv32im -mabi=ilp32 -nostartfiles test.c
Can I know if I can set the instruction and data memory address I want?
Thanks.
Thank you for answer.
I designed only HW, and this is my first time using the SW tool chain.
Even if my question is rudimentary, please understand.
The figure is the result of the "-v" option.
enter image description here
I can't modify the script file because I use riscv tool chain in DOCKER environment.
So, I tried to copy the script file (elf32lriscv.x), modify it.
I modified it to 0x10000 ==> 0x00000.
The file name of the copied script is "test5.x".
And it was executed as follows.
What am I doing wrong?
enter image description here
The riscv compiler is using the default linker script to place text and date section... .
If you add -v option to your command line riscv32-unknown-elf-gcc -v -march=rv32im -mabi=ilp32 -nostartfiles test.c, you will see the linker script used by collect 2 ( normally it will be -melf32lriscv . you can find the linker script in ${path_to_toolchain}/riscv32-unknown-elf/lib/ldscripts/ (the default one is .x).
You can also use riscv32-unknown-elf-ld --verbose like explained by #Frant. However , you need to be careful if the toolchain was compiled with enable multilib and you compile for rv64 but the default is rv32 or vice versa. It is not the case probably, but to be sure you can specify the arch with -A elf32riscv for an rv32.
To Set the addresses you can create your own linker script or copy and modify the default one. You can only modify the executable start like explained by #Frant or make more modification and place whatever you want where you want.
Once your own linker script ready you can pass it to the linker with -Wl,-T,${own_linker_script }. you command will be riscv32-unknown-elf-gcc -march=rv32im -mabi=ilp32 -nostartfiles test.c -Wl,-T,${own_linker_script }
I would like to find the recipe writing out /lib/systemd/system/getty#.service so I can create an append.
First I tried to find out the creating package, which should be systemd:
$ oe-pkgdata-util find-path /lib/systemd/system/getty#.service
systemd: /lib/systemd/system/getty#.service
Thus, I looked up meta/recipes-core/systemd/systemd_244.3.bb (and the systemd.inc), but didn't find anything of value. Only the following line looked like a hit:
RDEPENDS_${PN} += "kmod dbus util-linux-mount util-linux-umount udev (= ${EXTENDPKGV}) util-linux-agetty util-linux-fsck"
This made the impression as if this file might get pulled in as a dependency, and is actually created by util-linux-agetty.
So I looked up the creating recipe:
$ oe-pkgdata-util lookup-recipe util-linux-agetty
util-linux
But in meta/recipes-core/util-linux/util-linux_2.35.1.bb and util-linux.inc I can't find creation of that file either.
I'm genuinely puzzled.
My image is equal to core-image-minimal except that it uses systemd as init manager.
I am working on a project where our verification test scripts need to locate symbol addresses within the build of software being tested. This might be used for setting breakpoints or reading static data from memory. What I am after is to create a map file containing symbol names, base address in memory, and size. Our build outputs an ELF file which has the information I want. I've been trying to use the readelf, nm, and objdump tools to try and to gain the symbol addresses I need.
I originally tried readelf -s file.elf and that seemed to access some symbols, particularly those which were written in assembler. However, many of the symbols that I wanted were not in there - specifically those that originated within our Ada code.
I used readelf --debug-dump file.elf to dump all debug information. From that I do see all symbols, including those that were in the Ada code. However, the format seems to be in the DWARF format. Does anyone know why these symbols would not be output by readelf when I ask it to list the symbolic information? Perhaps there is simply an option I am missing.
Now I could go to the trouble of writing a custom DWARF parser to get the information but if I can get it using one of the Binutils (nm, readelf, objdump) then I'd really like prefer a standard solution.
DWARF is the debug information and tries to reflect the relation of the original source code. Taking following code as an example
static int one() {
// something
return 1;
}
int main(int ac, char **av) {
return one();
}
After you compile it using gcc -O3 -g, the static function one will be inlined into main. So when you use readelf -s, you will never see the symbol one. However, when you use readelf --debug-dump, you can see one is a function which is inlined.
So, in this example, compiler does not prohibit you use optimization with -g, so you can still debug the executable. In that example, even the function is optimized and inlined, gdb still can use DWARF information to know the function and source/line from current code block inside inlined function.
Above is just a case of compiler optimization. There might be plenty of reasons that could lead to mismatch symbols address between readelf -s and DWARF.
QDB is a database provided by QNX Neutrino package. I went through the QDB documentation to add a user defined SQL function: http://www.qnx.com/developers/docs/6.5.0/topic/com.qnx.doc.qdb_en_dev_guide/writing_functions.html?cp=2_0_8
I created a source file which had my user define SQL function written in C and qdb_function structure definition. I built it with a make file to create libudf.so.
As suggested by QDB I added Function = udftag#libudf.so in the qdb.cfg. But while running the qdb in the shell prompt, it is giving the error (in bold):
qdb -I basic -V -R set -v -c /etc/sql/qdb.cfg -s de_DE#cldr -o tempstore=/fs/tmpfs
QDB: No script registered for handling corrupt database.
qdb: processing [TempMainAddressBook]Function - Can't access shared library
and qdb is getting exited immediately.
I have tried following things:
made sure sqlite3 library is added in the make file
source code is in strictly in C by using directive : extern "C" to avoid name mangling as the file extension is .cpp. I also tried with .c extension.
given the absolute path of the libudf.so in qdb.cfg as : Function = udftag#/usr/lib/libudf.so
qdb_funcion struct is properly defined in library's source code only.
tried without using the static declaration of function(mentioned in the qdb docs)
After trying all hits and trials also, I am getting the same error every time which is Can't access shared library
If any one has any idea to resolve this error please share.
Suggestion 1: run qdb by setting LD_DEBUG=1, like in:
LD_DEBUG=1 qdb command line options
This will output a lot of debug information from the dynamic loader as it attempts to locate and then load the .so files. Check what is the path that it output before the "Can't access" message is displayed.
Suggestion 2: obvious but make sure that the permissions are OK for the .so file. Do you have the execution permission set?
Suggestion 3: check if the error message is identical if you completely remove the .so file from the system
Suggestion 4: increase the number of lower-case 'v'-s. QDB likely supports more, with progressively more verbose information provided as you increase the numbers (6 should be enough for full verbosity)
On Linux, I'm trying to strip a statically linked ELF file to the bare essentials. When I run:
strip --strip-unneeded foo
or
strip --strip-all foo
The resulting file still has a fat .notes section that appears to be full of funky strings.
Is the .notes section really needed or can I safely force it out with --remove-section?
Thanks for any help.
From experience and from looking at the man page for strip, it looks like strip isn't supposed to get rid of any and all sections and strings that aren't needed; just symbols. Quoth the man page:
GNU strip discards all symbols from object files objfile.
That being said, from experience, strip, even without --strip-all, removes sections unneeded for loading, such as .symtab and .strtab, and you can, as you note, remove sections you want it with --remove-section.
As an example of a .notes section, I took /bin/ls from my Ubuntu 11.10 64-bit box:
$ readelf -Wn /bin/ls
Notes at offset 0x00000254 with length 0x00000020:
Owner Data size Description
GNU 0x00000010 NT_GNU_ABI_TAG (ABI version tag)
OS: Linux, ABI: 2.6.15
Notes at offset 0x00000274 with length 0x00000024:
Owner Data size Description
GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring)
Build ID: 3e6f3159144281f709c3c5ffd41e376f53b47952
That encompasses the .note.ABI-tag section and the .note.gnu.build-id section. It looks like they contain data that isn't necessary to load the program, but also isn't standard, and isn't known by strip to not be necessary for the proper running of the program, since an ELF can have any number of additional "unknown" sections that aren't safe to remove. So rather using a virtual whitelist (which would fail miserably), it uses a blacklist of sections that it knows it can get rid of, and does so.
Short version: these sections don't seem to be standard and could be used for various things, so strip can't know it's safe to remove them. But based on the info inside the one I took above, if it's your own program, it's almost certainly safe to remove it.