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Questions tagged [usermode]

61 questions
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Why my cpu seems to lose the ability to decode

I meet this problem when finishing the lab of my OS course. We are trying to implement a kernel with the function of system call (platform: QEMU/i386). When testing the kernel, problem occurred that after kernel load user program to memory and…
StupidPanther
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Link Error when Compile c program without kernel32.lib

I'm want to Create App that just use ntdll and use security check for it. but when I remove kernel32.lib or uncheck "inherit from parent or project defaults" I get link errors when I build my project. Link Errors #include #include…
aliMahdavi
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RTE instruction in the computer user mode

What happens if you try to execute an RTE instruction in the computer user mode (on the MC 68000 processor)? Will it happen that the instruction will not start executing because the compiler will detect an unauthorized instruction or an interrupt…
Skar
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How to debug qemu user program with coredump

I get a coredump file by executing qemu-riscv32 myprogram and I can normally debug 'myprogram' like this qemu-riscv32 -singlestep -g 2000 myprogram riscv32-unknown-linux-gnu-gdb myprogram target remote localhost:2000 but how can I debug with the…
Coco
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Can a x32 bit usermode application communicate via IOCTL with x64 driver?

Hello i am trying to make work communication from my x32 bits application to my x64 driver, but the communication return always false (the driver is loaded and working with the x64 app but not the x32 app) The source i am using for both is this…
Mov Eax
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How to implement SVC handler on ARM926EJ-S?

I'm writing an amateur operating system for ARM-based devices and currently trying to make it working in QEMU's versatilepb (ARM926EJ-S). The problem arrives when I try to implement syscalls to my kernel. The idea is pretty simple: to implement…
Alexander Perechnev
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Can WinDBG display information about an arbitrary heap address?

Does WinDBG provide a way of displaying type information (dt?) for a plain heap address? I am looking at a scenario where paged heap and user mode stack traces are not available. While analysing the heap I was tracking down excessive heap usage and…
Samuel
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Windbg: USER mode dump, windows event is set or not

I am trying to debug dump, my USER mode STOPPED_PENDING service, just checking whether service stop event "MySvcStopEvent" is Set or Not, I got event handle, tried to dump handle details, 0:002> !handle 0x00000000`00000164 f Handle…
user3664223
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User mode and kernel mode: different program at same time

Is it possible that one process is running in kernel mode and another in user mode at the same time? I know, it's not a coding question but please guide me if someone knows answer.
Harshil Shah
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Need to sign a user-mode driver but can't locate a matching cross-certificate - Windows and TFS build

I've been handed source code for a user-mode USB Plug-n-Play driver and a certificate from Go Daddy and been instructed to set up a TFS build for the source code and to make the driver "signed." Having never done this, and nobody else here has done…
Dar
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RISCV user mode breakpoint support needs more "hardware" for GDB support

Just finished to read the RISCV spec, more specifically "Volume II: RISC-V Privileged Architectures" and have a question on how GDB (or any other debugger) is supposed to work. Basically there are two ways to compile standard GDB: either hardware or…
Etienne
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How to enable user shell?

I was checking users permissons with less /etc/passwd cassandra:x:123:130:Cassandra database,,,:/var/lib/cassandra:/bin/false I want to unlock the account. How to do this with usermod or in any other manner?
Richard Rublev
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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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When a C-program with empy main body executes, would it only involves user-mode?

Typically, when a program starts executing, it begins in user-mode and then depending on the body of the code, if required enters kernel/system mode, and eventually exits in the user-mode where it exits legitimately. But consider the following C…
stacker stuck
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Is changing the value of any register(DR, IR etc) requires switching from user mode to kernel mode?

1)So in the book that I'm reading it says for example changing IR register does not require switching from user mode to kernel mode, but i don't get it, how can i know if it requires switching or not? 2)also what about other registers, like DR, PSW,…
Richard Jones
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