liblinux++

commit 60c196243360163e4cb21c7d1d46cb8883410363
parent 692b08eb78c7300496f236a429d85126975ac9ca
Author: Henry Wilson <henry@henryandlizzy.uk>
Date:   Thu, 19 Dec 2024 11:37:01 +0000

add mappable memory

Diffstat:
M
Tupfile
 | 
4
++--
A
paste.c
 | 
59
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
tac.c
 | 
59
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
M
x86_64.ld
 | 
14
+++++++++++---

4 files changed, 131 insertions(+), 5 deletions(-)
diff --git a/Tupfile b/Tupfile
@@ -1,8 +1,8 @@
-CFLAGS = -Os -fno-asynchronous-unwind-tables -no-pie -g
+CFLAGS = -Os -fno-asynchronous-unwind-tables -no-pie -g -fno-stack-protector
 LDFLAGS = -static -nostartfiles -nostdlib -no-pie -Xlinker --gc-sections
 
 !cc = |> cc $(CFLAGS) -c -o %o %f |> obj/%B.o
-!link = | x86_64.ld obj/start.o obj/syscall.o |> cc $(LDFLAGS) -o %o -T x86_64.ld %f obj/start.o obj/syscall.o |>
+!link = | x86_64.ld obj/start.o obj/syscall.o |> cc $(LDFLAGS) -o %o -T x86_64.ld obj/start.o obj/syscall.o %f |>
 
 : foreach *.s |> !cc |>
 : foreach *.c |> !cc |> {objs}
diff --git a/paste.c b/paste.c
@@ -0,0 +1,59 @@
+#include "syscall.h"
+#include <linux/mman.h>
+
+struct input
+{
+	int fd;
+	unsigned short start, end;
+	char buf[0x1000 - 8];
+};
+
+extern struct input mappable[];
+static int n_inputs;
+
+static char getc(struct input* in)
+{
+	if (in->start == in->end)
+	{
+		in->start = 0;
+		in->end = 0;
+		int n = read(in->fd, in->buf, 0x1000-8);
+		if (n <= 0)
+			return 0;
+		in->end = n;
+	}
+	return in->buf[in->start++];
+}
+
+int main(int argc, char* argv[])
+{
+	for (int i = 1; i < argc; ++i)
+	{
+		int fd = open(argv[i], 0, 0);
+		if (fd < 0)
+			return 1;
+		struct input* m = mmap(mappable + n_inputs++, sizeof(struct input), PROT_READ | PROT_WRITE, MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+		if ((long long)m < 0)
+			return 2;
+		m->fd = fd;
+	}
+
+	for (;;)
+	{
+		for (int i = 0; i < n_inputs; ++i)
+		{
+			struct input* in = mappable + i;
+
+			for (;;)
+			{
+				char c = getc(in);
+				if (!c)
+					return 0;
+				if (c == '\n')
+					break;
+				write(1, &c, 1);
+			}
+			write(1, i + 1 == n_inputs ? "\n" : "\t", 1);
+		}
+	}
+}
diff --git a/tac.c b/tac.c
@@ -0,0 +1,59 @@
+#include "syscall.h"
+#include <linux/mman.h>
+
+extern char mappable[];
+
+static int rd(int const fd, char* const start, char const* const end)
+{
+	char* pos = start;
+	while (pos != end)
+	{
+		int n = read(fd, pos, end - pos);
+		if (n < 0)
+			exit(2);
+		if (n == 0)
+			break;
+		pos += n;
+	}
+	return pos - start;
+}
+
+static void wr(int const fd, char const* start, char const* const end)
+{
+	while (start != end)
+	{
+		int n = write(fd, start, end - start);
+		if (n < 0)
+			exit(3);
+		start += n;
+	}
+}
+
+int main()
+{
+	char* buf = mappable;
+	size_t cap = 0;
+	size_t len = 0;
+
+	while (len == cap)
+	{
+		void* m = mmap(buf + cap, cap ?: 0x1000, PROT_READ | PROT_WRITE, MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+		if ((long long)m < 0)
+			return 1;
+		cap += cap ?: 0x1000;
+
+		len += rd(0, buf + len, buf + cap);
+	}
+
+reverse:
+	char const* end = buf + len;
+	char const* str = end;
+
+	while (--str > buf)
+	{
+		while (str > buf && str[-1] != '\n')
+			--str;
+		wr(1, str, end);
+		end = str;
+	}
+}
diff --git a/x86_64.ld b/x86_64.ld
@@ -13,14 +13,22 @@ SECTIONS
 		*(.rodata)
 	}
 	
-	.bss :
+	.data :
+		ALIGN(0x1000)
+	{
+		*(.data)
+	}
+
+	.bss (NOLOAD) :
 		ALIGN(0x1000)
 	{
 		*(.bss)
 	}
-	.data :
+
+	.mappable (OVERLAY) :
+		ALIGN(0x1000)
 	{
-		*(.data)
+		mappable = .;
 	}
 }