questions

[YKG]

How it works

• systemtap
• kprobe/kretprobe
• uprobe/uretprobe
• ptrace
• gdb
• eBPF
• kutrace
• docker
• KVM
• rr
• Linux
• MySQL
• PostgreSQL
• Redis
• cpython

Where it use

• COW (Copy-On-Write)

[YKG]

Linux

• What is the difference between make tinyconfig and make allnoconfig
• What is the minimum requirements to boot the minimum kernel with QEMU and how
• How to debug the kernel
• What is skipped when we use the -k bzImage option with QEMU compare to a real machine? (Bootloader phrase skipped?)
• Why we need -initrd ramdisk.img option to get the shell
• Why we need to turn on 64-Bit kernel
• Why we need to turn on printk
• Why we need to add serial port driver (Serial: 8250/16550 driver)
• Why we need to increase the memory to 512MB so that the kernel can boot? Why the default 128MB is insufficient?
• Why it take almost 3s to process initramfs?
• What does T0 or C0 mean when CONFIG_PRINTK_CALLER is turned on?
• Why it only takes about 200ms to process initramfs when we add -enable-kvm option?

[YKG]

• What is the difference between i386, x86, and x86_64 in the linux kernel source arch directory

[YKG]

• Does the character S in console=ttyS0 means Serial?

[YKG]

• What is the diffrence between qemu-x86_64 and qemu-system-x86_64?

Answer:

• qemu-x86_64 is for user-mode emulation, qemu-system-x86_64 is system emulation.
• qemu-x86_64 /bin/ls will run /bin/ls directyly

[YKG]

• How to compile assembly code to executable?

Answer:

$ cat  >prog.s << EOF
    .global _start
    .intel_syntax noprefix

_start:
    mov rdi, 0x0
    mov rax, 0x3c
    syscall
EOF
$ gcc -nostdlib prog.s -o prog
$ objdump -d prog # check

[YKG]

• How to write a simple debugger?

Refer: https://stackoverflow.com/questions/64016087/writing-the-simplest-assembly-debugger