LD_PRELOAD is a list of additional ELF shared objects that should be loaded first.
LD_PRELOAD is a list of additional ELF shared objects that should be loaded first.
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Questions tagged [ld-preload]
265 questions
5
votes
1 answer
Setting the LD_PRELOAD environment variable for commands run without typing the full path
I'm playing around with LD_PRELOAD and have produced a library that simply wraps puts() in a function that converts the string to be printed to uppercase before printing. I then export the LD_PRELOAD variable as so
$ export…
eltommo
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4
votes
2 answers
Is it possible for an LD_PRELOAD to only affect the main executable?
The Actual Problem
I have an executable that by default uses EGL and SDL 1.2 to handle graphics and user input respectively. Using LD_PRELOAD, I have replaced both with GLFW.
This works normally unless the user has installed the Wayland version of…
TheBrokenRail
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4
votes
3 answers
Conflicting types compiling a LD_PRELOAD wrapper
I tried to use LD_PRELOAD to hook sprintf function , so I will print to file the result of buffer:
#define _GNU_SOURCE
#include
#include
int sprintf (char * src , const char * format , char* argp)
{
int…
MicrosoctCprog
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4
votes
1 answer
Why does LD_PRELOAD work with syscalls?
The idea of LD_PRELOAD is to load a shared library before the original shared library, for example I can compile mylib.so to load it before libc.so, so when process wants to use printf it searches in the so that loaded one by one and finds it in…
yfr24493AzzrggAcom
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4
votes
1 answer
Can LD_PRELOAD be used to load different versions of glibc?
Cast of characters
big-old-app is linked to an old version of glibc, say glibc-2.12. I cannot do anything to change this.
cute-new-addon.o is linked to a newer version, glibc-2.23. This glibc-2.23 is in a nonstandard path (because I don't have…
Kit
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4
votes
1 answer
LD_PRELOAD in docker
When I run docker as following:
docker run -it -e LD_PRELOAD=/bin/xyz.so bash env
It runs as expected, and the output…
BezBran
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4
votes
4 answers
LD_PRELOAD can not intercept syscalls, but only libcalls?
My code works well with malloc, but not with mmap. The code is below:
main.c
#include
#include
int main(){
int * p = (int*) malloc(sizeof(int));
printf("in main(): value p = %d\n", *p);
free(p);
}
preload.c
#define…
Richard
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4
votes
2 answers
Will a C compiled .so work with a C++ application?
If I want to dynamically link a shared library (.so) for a C++ application (which was built with g++) using LD_PRELOAD, does it matter if the .so is generated from a C source file (using gcc) or a C++ source file (using g++)? And why or why not?…
Naly Gneh
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4
votes
2 answers
Why is LD_PRELOAD usage discouraged?
I came across this piece of advice on the Google's tcmalloc documentation page.
You can use TCMalloc in applications you didn't compile yourself, by using LD_PRELOAD:
$ LD_PRELOAD="/usr/lib/libtcmalloc.so"
LD_PRELOAD is tricky, and we don't…
Sam
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4
votes
1 answer
How can I override C functions (like with LD_PRELOAD) at runtime?
I have some Python code that uses a library that implements virtual file systems. For the drivers for those virtual file systems to work a bunch of C functions (like readdir(), opendir(), fseek()) need to be overridden/replaced - with the…
false_azure
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4
votes
1 answer
How can I inject a background thread to an application with LD_PRELOAD?
I know that LD_PRELOAD can be used to intercept calls to functions in shared libraries (if the app is not statically linked). However, I do not know how it can be used to add additional features or background threads to applications.
For example, I…
feeling_lonely
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4
votes
2 answers
How to defeat framework injections?
Is anyone hardening their code in an attempt to detect injections? For example, if someone is trying to intercept a username/password via NSUrlConnection, they could use LD_PRELOAD/DYLD_LIBRARY_PATH, provide exports for my calls into…
jww
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3
votes
1 answer
How to preload library with ld_preload to wine(windows game)?
I want to learn how to preload and hook functions in wine running windows apps.
I'm trying to preload a library with ld_preload to wine(windows game(32-bit)) on Arch Linux (64-bit but I think I installed 32-bit support). I get the error wrong ELF…
JustOneMan
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3
votes
3 answers
How to set LD_PRELOAD in systemd
I want to hook some functions in libssl with LD_PRELOAD in systemd.
In systemd file I put
ExecStart=/etc/myscript.sh
and in /etc/myscript.sh I put
#!/bin/sh
LD_PRELOAD=/lib/inject_libssl.so /bin/run
When I look at /proc/RUN_PID/maps I can see that…
Kokomelom
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3
votes
1 answer
How to get command line arguments inside LD_PRELOAD library
I would like to get argv from an LD_PRELOAD library, for instance, let us assume we call
LD_PRELOAD=/path/to/my/fopen ./program input
Inside my custom fopen I would like to get "input", hence the argv[1] of my program (also the argv[2] and so…
Maray97
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