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Questions tagged [usermode]

61 questions
13
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1 answer

Difference between processes running in kernel mode and running as root?

I am aware of the difference between a process running in user mode and one running in kernel mode (based on access restrictions, access to hardware etc.). But just out of curiosity, what is the difference between a process running in kernel mode…
Legend
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2 answers

Executing a user-mode executable from kernel-mode

I'm building a HW-simulator for our driver team. Now, the simulator is devided in to 2 modules: First module runs inside the driver, in kernel mode and that's where the main interface between the driver and the HW-Simulator. Second module is an…
eladidan
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Windows User Mode Scheduler (UMS) Retired?

I just came around the following post which seems to say that the user mode scheduler which was introduced with Windows 7 is (going to be) retired? Don McCrady, Microsoft: As you may know from reading other forum entries here, the UMS scheduler is…
ronag
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How to call usermode from Windows kernel?

I'd like to call my app from my driver when an interesting event happens in the Windows kernel. I need to be able to pass at least 4 bytes of data back to user mode. How to achieve this? These events might happen quite, but not too, often, so I…
Raimo Helminen
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4 answers

C and resource protection in memory

When we compile a C program, it just generates some machine-understandable code. This code can directly run on the hardware, telling from this question. So my questions are: If a C program can directly run on the hardware, how can the kernel handle…
shiv garg
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What is the main difference between drivers and user applications?

I know that user applications can run only in user mode, which is for system security. On the contrary most drivers run in kernel mode, to access I/O devices. Nevertheless some driver run in user mode, but are allowed to access I/O devices. So I…
user1289
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How to add user to a group without usermod?

Is it possible to add a user to a group without usermod? I'm working on embedded Linux 3.14.52 and I don't have the usermod command line. If it is not possible, how add this command to kernel with Buildroot?
M.Ferru
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Is there a difference in dt nt!_TEB and dt ntdll!_TEB?

I can dump types from an arbitrary module using dt modulename!type In some cases I saw e.g. dt nt!_TEB (and it works) although the module is called ntdll: 0:001> lm m nt start end module name 0:001> lm m ntdll start …
Thomas Weller
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Why driver in kernel mode must be very careful about directly reading from or writing to addresses in user space?

From msdn: Drivers that run in kernel mode must be very careful about directly reading from or writing to addresses in user space. This scenario illustrates why. A user-mode program initiates a request to read some data from a device. The program…
Nüsrat Nuriyev
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Implementing User Mode and Kernel Mode Switching in 64 bit UEFI OS

I am writing a 64 Bit UEFI OS ( GNU-EFI - Bootloader ). I am wondered about User Mode and Kernel Mode in OS, I have to Implement User Mode and Kernel Mode in My OS, I found some on the Internet but It won't works for me ( I thinks it is because of…
user16028858
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using arm LDM instruction to transfer data into user mode registers

I'm trying to restore user mode registers from svc mode on a cortex-a5 chip by using LDM instruction. I referred a technical guide for instruction LDM, the syntax is: LDM{addr_mode}{cond} Rn{!},reglist{^} '^' if specified (in a mode other than…
user3197437
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How do I get user-mode breakpoints to hit in windbg while kernel debugging?

I'm having trouble getting user mode breakpoints to hit in windbg when I am kernel debugging. I know that I have to be in the target process's context to set a user mode breakpoint, but that still doesn't seem to work reliably. Sometimes it works,…
R. Alabaster
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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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switching to user stack in kernel dumps

Is there a way to switch to user mode of a particular process in a kernel dump while doing postmortem debugging ? I remember doing this while live debugging using the .process command.
user3279954
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