liblinux++

commit b8f04aa6fc6abab81fb8af1f0a0b58994fe2df25
Author: Henry Wilson <henry@henryandlizzy.uk>
Date:   Fri,  6 Dec 2024 16:15:41 +0000

Initial working version in AT&T syntax

Diffstat:
A
Tupfile
 | 
7
+++++++
A
Tupfile.ini
 | 
0

A
crt0.s
 | 
12
++++++++++++
A
crt1.c
 | 
14
++++++++++++++
A
echo.c
 | 
52
++++++++++++++++++++++++++++++++++++++++++++++++++++
A
syscall.h
 | 
14
++++++++++++++
A
syscall.s
 | 
100
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

7 files changed, 199 insertions(+), 0 deletions(-)
diff --git a/Tupfile b/Tupfile
@@ -0,0 +1,7 @@
+CFLAGS = -Os -fno-asynchronous-unwind-tables
+LDFLAGS = -static -nostartfiles -nostdlib -Xlinker --gc-sections
+
+: foreach *.c *.s |> cc $(CFLAGS) -c -o %o %f |> x86_64/%B.o {objs.x86_64}
+: {objs.x86_64} |> cc $(LDFLAGS) -o %o %f |> echo.x86_64
+
+.gitignore
diff --git a/Tupfile.ini b/Tupfile.ini
diff --git a/crt0.s b/crt0.s
@@ -0,0 +1,12 @@
+.global _start
+
+.text
+
+_start: # _start is the entry point known to the linker
+	xor	%ebp,			%ebp	# effectively RBP := 0, mark the end of stack frames
+	mov	(%rsp),			%edi	# get argc from the stack (implicitly zero-extended to 64-bit)
+	lea	8(%rsp),		%rsi	# take the address of argv from the stack
+	lea	16(%rsp,%rdi,8),	%rdx	# take the address of envp from the stack
+	xor	%eax,			%eax	# per ABI and compatibility with icc
+	jmp	start				# %edi, %rsi, %rdx are the three args (of which first two are C standard) to main
+
diff --git a/crt1.c b/crt1.c
@@ -0,0 +1,14 @@
+#include "syscall.h"
+
+extern char __bss_start[], _end[];
+extern int main(int, char**, char**);
+
+__attribute__((noreturn))
+void start(int argc, char* argv[], char* envp[])
+{
+	for (char* p = __bss_start; p < _end; ++p)
+		*p = 0;
+
+	exit(main(argc, argv, envp));
+	__builtin_trap();
+}
diff --git a/echo.c b/echo.c
@@ -0,0 +1,52 @@
+#include "syscall.h"
+
+static char buf[0x1000];
+static unsigned bufsize;
+
+static void putflush()
+{
+	if (bufsize && write(1, buf, bufsize) != bufsize)
+		exit(1);
+	bufsize = 0;
+}
+
+static void putch(char c)
+{
+	buf[bufsize++] = c;
+	if (c == '\n' || bufsize == sizeof buf)
+		putflush();
+}
+
+static void putstr(char const* s)
+{
+	while(*s)
+		putch(*s++);
+}
+/*
+static void* sbrk(unsigned size)
+{
+	static void* end;
+
+	if (!end)
+		end = brk(NULL);
+
+	end += size;
+
+	if (brk(end) != end)
+		exit(1);
+
+	return end;
+}
+*/
+int main(int argc, char* argv[])
+{
+//	sbrk(0);
+	if (argc > 1)
+		putstr(argv[1]);
+	for (int i = 2; i < argc; ++i)
+	{
+		putch(' ');
+		putstr(argv[i]);
+	}
+	putch('\n');
+}
diff --git a/syscall.h b/syscall.h
@@ -0,0 +1,14 @@
+#include <stddef.h>
+
+extern int read(int fd, char* data, size_t count);
+extern int write(int fd, char const* data, size_t count);
+extern int open(char const* name, int flags, int mode);
+extern int close(int fd);
+extern void* mmap(void* addr, unsigned long len, unsigned long prot, unsigned long flags, unsigned long fd, unsigned long off);
+
+extern void* brk(void* new_brk);
+
+__attribute__((noreturn))
+extern void exit(int error_code);
+
+extern int ftruncate(int fd, unsigned long length);
diff --git a/syscall.s b/syscall.s
@@ -0,0 +1,100 @@
+.macro syscall3, num, name
+.global \name
+.section .text.\name
+\name:
+	push	%r11
+	push	%rcx
+	mov	$\num,	%rax
+	syscall
+	pop	%rcx
+	pop	%r11
+	ret
+.endm
+
+.macro syscall6, num, name
+.global \name
+.section .text.\name
+\name:
+	push	%r11
+	mov	$\num,	%rax
+	mov	%rcx,	%r10
+	syscall
+	pop	%r11
+	ret
+.endm
+
+.text
+.global exit
+
+syscall3	0	read
+syscall3	1	write
+syscall3	2	open
+syscall3	3	close
+syscall3	4	stat
+syscall3	5	fstat
+syscall3	6	lstat
+syscall3	7	poll
+syscall3	8	lseek
+syscall6	9	mmap
+syscall3	10	mprotect
+syscall3	11	munmap
+syscall3	12	brk
+syscall6	13	rt_sigaction
+syscall6	14	rt_sigprocmask
+syscall3	15	rt_sigreturn
+syscall3	16	ioctl
+syscall6	17	pread64
+syscall6	18	pwrite64
+syscall3	19	readv
+syscall3	20	writev
+syscall3	21	access
+syscall3	22	pipe
+syscall6	23	select
+syscall3	24	yield
+syscall6	25	mremap
+syscall3	26	msync
+syscall3	27	mincore
+syscall3	28	madvise
+syscall3	29	shmget
+syscall3	30	shmat
+syscall3	31	shmctl
+syscall3	32	dup
+syscall3	33	dup2
+syscall3	34	pause
+syscall3	35	nanosleep
+syscall3	36	getitimer
+syscall3	37	alarm
+syscall3	38	setitimer
+syscall3	39	getpid
+syscall6	40	sendfile
+syscall3	41	socket
+syscall3	42	connect
+syscall3	43	accept
+syscall6	44	sendto
+syscall6	45	recvfrom
+syscall3	46	sendmsg
+syscall3	47	recvmsg
+syscall3	48	shutdown
+syscall3	49	bind
+syscall3	50	listen
+syscall3	51	getsockname
+syscall3	52	getpeername
+syscall3	53	socketpair
+syscall6	54	setsockopt
+syscall6	55	getsockopt
+syscall3	56	clone
+syscall3	57	fork
+syscall3	58	vfork
+syscall3	59	execve
+
+.section .text.exit
+exit:	mov $60,	%rax
+	syscall
+
+syscall6	61	wait4
+syscall3	62	kill
+syscall3	63	uname
+syscall3	64	semget
+syscall3	65	semop
+
+syscall3	77	ftruncate