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Unix と C のメモ
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Hello World | |
コンパイラ | |
+---------+ +------------+ | |
| main.c | ------> | a.out | | |
+---------+ +------------+ | |
ライブラリ関数、シンボル、リンカ | |
+--------------------------------------------+ | |
| | | |
| +----------+ | | |
| | <stdio> | 0x.... +-------------+ | | |
| | | <-------- |symbol table | | | |
| +----------+ | | | | |
| | main | --------> | | | | |
| | | printf +-------------+ | | |
| +----------+ | | |
| | | |
+--------------------------------------------+ | |
a.out | |
return 200 # 0xc8 を返すだけの main | |
gcc -v <source>.c # なんか一杯リンクしている | |
ldd <exe> # 案の定 libc | |
dpkg -S <file> # libc6 パッケージ | |
apt info <package> # その説明 | |
readelf -W -a <exe> # エントリーポイント、text セグメント、_start と main | |
objdump -M intel -D a.out # 実際のコード | |
Unix でプログラム内のメモリ以外一切触らないプログラムのメモリマップ | |
+----------+ | |
Context Switch = Memory Switch |CPU assist| | |
<-----------------------> +----------+ | |
+-----------+------------+ +---------------------+ | |
| stack | (func call)| ^ | Kernel | | |
| | | | | Context | | |
| v | | | | | |
| | | +---------------------+ | |
| ^ | | system call | |
| | | | read, write | |
| heap | (malloc) | | fork, exec | |
+-----------+------------+ | | |
| block storage space | | read write | |
+------------------------+ | | |
| init rw | ^ v | |
+------------------------+ | | |
| init ro | | ^ | |
+------------------------+ | load | read only | |
| text | | program | | |
| | | | +-----------+ | |
| | v v |CPU assist | | |
+------------------------+ +-----------+ | |
Unix User Memory | |
+---------------+ | |
|Kernel | | |
| sys call | | |
| ^ | | |
| | | | |
+--------+------+ +---------------+ | |
| User | | |Service Process| | |
| | +---------------+ | |
| Stack | ^ | |
| | | | |
| | | Message | |
| Heap | | | |
| | v | |
| | +-------------+ | |
| Text | |User Process | | |
+---------------+ +-------------+ | |
user process | |
Monolithic Kernel <--------> Micro Kernel | |
直感イメージの OS = 実はマイクロカーネル型でセキュアと言われる理由 | |
実際の OS = ユーザープロセスがカーネルになって HW アクセス | |
unistd sleep(3600) | |
/proc/<pid>/ | |
pidstat -p <pid> # -w, -R, -r, -v, ... | |
init 1 | |
musllibc と alpine |
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