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Questions tagged [usermode]

68 questions
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Is There Ever an Advantage to User Mode Debug over Kernel Mode Debug?

From what I understand, on a high level, user mode debugging provides you with access to the private virtual address for a process. A debug session is limited to that process and it cannot overwrite or tamper w/ other process' virtual address…
mattkgross
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Decoding activation context error 0xC015000f

I need to identify the root cause of EXCEPTION_CODE: (NTSTATUS) 0xc015000f - The activation context being deactivated is not the most recently activated one. using a user mode post mortem crash dump. Callstack: # ChildEBP RetAddr Args to…
user3679359
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How to call/hook kernel mode APIs from user mode?

I'd love to dive into kernel hooking - but my problem is that I don't like C/C++. But I've over 10 years experience in VB6 programming and would call my self as an expert in this language. So my question is if it was possible to use a tiny C kernel…
c0rt3x
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Kernel mode - can it access to user mode?

As far as I know kernel mode code can access to any address available (high privilege), but if I pass a user mode pointer to a kernel mode function, will it be changed before using it? I mean: will it be resolved with paging/segmentation systems (or…
Johnny Pauling
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Usermode CPU Data cache invalidation / flush on Linux (Cortex A53)

I would like to find a way for data (L1/L2) cache invalidation and flush in usermode on a Linux platform working with heterogenous non coherent caches (ARM A53 and ARM M7 cores). My problem lies on the A53 side, where an SMP Linux is running. M7…
ØXmose
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sprintf is undefined for STM32

I'm making a cusermod for Micropython, and I'm trying to store a number in hex format in a string. I tried using sprintf however, my compiler is telling me that it's undefined. I imported stdio.h, string.h as well as some other libraries required to…
aaa
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How do I change the Default Home Directory of a user? - Xubuntu

I am trying to change the default user in ubuntu.. I already create a new home directory at the moment, the default user is me, and I'm trying to make geza as the new default user. I already tried doing usermod -d /home/geza -m geza, but it keeps…
Bernard
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qemu-user reports "mmap stack: Cannot allocate memory" in Docker

I just setup a x86-64 environment on arm64 M1 Mac Mini with the Ubuntu Docker image. I've installed relevant softwares such as the GCC AArch64 cross compiler, and user-mode QEMU. I know this setup works on Windows Subsystem for Linux (also the…
DannyNiu
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Encode additional information in pointer

My problem: I need to encode additional information about an object in a pointer to the object. What I thought I could do is use part of the pointer to do so. That is, use a few bits encode bool flags. As far as I know, the same thing is done with…
thebear8
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How to pass a variable-size array from Windows kernel driver to a user-mode process?

I'm learning Windows kernel programming, and I'm wondering how do I pass a byte array from a kernel driver to my user-mode application, where the kernel driver initiates the call? If I were to do this among user-mode processes (say, from a service…
MikeF
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How does instructions like I/O work in user mode?

I am curious because I am reading this OS book which mentions "User programs always run in user mode, which permits only a subset of the instructions [...]. Generally, all instructions involving I/O and memory protection are disallowed in user…
Faulerhund
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Privileged instructions, adding register values?

I finished homework for a graduate course in operating systems. I got a great score and I only missed one tiny point of a question. It asked which were privileged instructions and which were not. I answered all correctly except one: Adding one…
user427390
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Does User space/Kernel Space exist in RTOS?

I heard from various kernel developers that most of the RTOSes do not have any separation between user space and kernel space and therefore do not need any context switching. Is this true? In the same time, I heard from some other people that it…
Sama Azari
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How does exception dispatching change with an unhandled exception handler?

In short, MSDN describes exception dispatching for user mode application like this: the debugger gets notified of the first chance exception (if attached) an exception handler aka. try/catch is invoked (if available) the debugger gets notified of…
Thomas Weller
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is printf privileged instruction?

since I/O instructions are privileged instructions that require mode switch from user to kernel, is printf also considered a privileged instruction? is there mode switch when performing printf instructions?
yellowbowlmigration
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