bare-metal

Bare metal without global operator new

混江龙づ霸主 提交于 2019-12-10 13:53:44
问题 Consider safety software, where dynamic allocation in general is disallowed and exceptions are disallowed. Dynamic allocation is allowed only when class explicity defines operator new and delete . Using operator new for others class should cause compilation failure. The simplest way to cause compilation failure in described situation is to remove global new operator: void* operator new(std::size_t) = delete; On the one hand this cause side effects with standard library. For example including

When does malloc return NULL in a bare-metal environment?

蓝咒 提交于 2019-12-09 18:40:59
问题 There is a c memory model as following : +--------+ Last Address of RAM | Stack | | | | | v | +--------+ RAM | | | | +--------+ | ^ | | | | | Heap | +--------+ | ZI | +--------+ | RW | +========+ First Address of RAM The stack and heap space increase in opposite directions. They would be overlapped with each other in the middle. So my questions are: In a bare-metal environment, when does malloc return NULL? In a bare-metal environment, how to prevent stack from overlapping with heap? 回答1:

What is Qt Bare Metal?

会有一股神秘感。 提交于 2019-12-09 10:13:58
问题 QtCreator has a plugin named "Bare Metal". Bare Metal means a computer without an operating system. I have not seen much about Qt Bare Metal development. Is it a way to develop Qt for a bare metal system? Does Qt run on a system with no OS? If yes, what are the advantages of this approach for embedded system development? 回答1: Is it a way to develop Qt for a bare metal system? No. Does Qt run on a system with no OS? No. Bare Metal means you usually have a few KB of RAM and ROM. I think you are

Bare metal programming Raspberry Pi 3.

泪湿孤枕 提交于 2019-12-08 13:41:24
问题 I was going through some bare metal programming tutorials. While reading about C code execution I came to know that we need to setup C execution environment like initializing stack zeroing bss etc. In some cases you have to copy data in ram , and need to provide startup code for that as well. Link of tutorial which says copy data in RAM. Now I have two doubts. If we need to copy data in RAM then why don't we copy code ie text segment. If we don't copy text segment doest it mean code is

Application hangs when calling printf to uart with bare metal raspberry pi

故事扮演 提交于 2019-12-08 12:15:26
问题 I am trying to implement a bare metal application on the raspberry pi and want to hook up stdout to the mini uart for debugging purposes. I have followed the process outlined here and here I have created a uart_putc function which seems to work perfectly, allowing me to print messages to my PC's COM port. I then implemented the _write syscall, making it call my uart_putc function for output. This works fine if I pass a single string literal into printf additional literal parameters or any non

CPU usage measurment on arm bare metal system

空扰寡人 提交于 2019-12-07 03:06:29
问题 I am working on a ARM cortex M4 evaluation board, its a bare metal application without any operating system running on it. Now I want to measure CPU usage of a given process/algorithm , what would be the best way to do so? Should i implement an operating system to measure the CPU usage that have the functionality for such demand? 回答1: The question almost answers itself. What is your bare metal application doing when it is not in that process/algorithm? Measure one or the other or both. If you

llvm optimizes with library functions

戏子无情 提交于 2019-12-05 10:59:07
Starting with code like this void lib_memset( unsigned char *dest, unsigned char c, unsigned int n) { while(n--) { *dest=c; dest++; } } using llvm as a cross compiler clang -Wall -m32 -emit-llvm -fno-builtin --target=arm-none-eabi -c lib_memset.c -o lib_memset.bc opt -std-compile-opts -strip-debug -march=arm -mcpu=mpcore -mtriple=arm-none-eabi lib_memset.bc -o lib_memset.opt.bc llc -march=arm -mcpu=mpcore -disable-simplify-libcalls lib_memset.opt.bc -o lib_memset.opt.s llc -march=arm -mcpu=mpcore -disable-simplify-libcalls lib_memset.bc -o lib_memset.s and it detects and replaces it with a

CPU usage measurment on arm bare metal system

[亡魂溺海] 提交于 2019-12-05 10:16:51
I am working on a ARM cortex M4 evaluation board, its a bare metal application without any operating system running on it. Now I want to measure CPU usage of a given process/algorithm , what would be the best way to do so? Should i implement an operating system to measure the CPU usage that have the functionality for such demand? The question almost answers itself. What is your bare metal application doing when it is not in that process/algorithm? Measure one or the other or both. If you have a bare metal application that is not completely consuming the cpu in this algorithm, then you already

How to enter 64-bit mode on a x86_64

孤街醉人 提交于 2019-12-04 23:06:43
问题 I've found a nice bit of assembly in xv6 https://github.com/chrisdew/xv6/blob/master/bootasm.S which shows me how to move from 16 bit to 32 bit protected mode. Does anyone know of a similar example for entering the 64-bit mode? (Either through or without using 32 bit mode.) 回答1: In order to enable 64 bit capabillities, you must switch the CPU to Long Mode. To enter Long Mode on a 64-bit x86 processor (x86-64): If paging is enabled, disable paging. If CR4.PAE is not already set, set it. Set

Intel Galileo bare metal UART

断了今生、忘了曾经 提交于 2019-12-04 23:04:31
问题 I want to program a little "hello world" bare metal application on the Intel Galileo board. Using UEFI to print out text (to UART-1) works well, of course, but I want to access the UART "manually", without any help from UEFI. In QEMU my code works well: .h file #define COM1_PORT (0x03F8) #define UART_PORT (COM1_PORT) enum uart_port_offs_t { // DLAB RW THR = 0, // 0 W Transmitter Holding Buffer RBR = 0, // 0 R Receiver Buffer DLL = 0, // 1 RW Divisor Latch Low Byte IER = 1, // 0 RW Interrupt