kernel: add kprintf() api

CMakeLists.txt

@@ -48,6 +48,7 @@ set(GAY_KERNEL_DEFINITIONS
 
 include("lib/lib.cmake")
 
+add_subdirectory("kernel")
 add_subdirectory("boot")
 
 add_executable(gaybsd_image.elf)

include/gay/kprintf.h

@@ -0,0 +1,37 @@
+/* See the end of this file for copyright and license terms. */
+
+#pragma once
+
+/**
+ * @file Header for the `printf()` family of functions.
+ */
+
+#include <stdarg.h>
+
+#include <gay/types.h>
+#include <gay/toolchain.h>
+
+__attribute__(( format(printf, 1, 2) ))
+int kprintf(const char *__restrict fmt, ...);
+
+int kvprintf(const char *__restrict fmt, va_list args);
+
+struct kprintf_renderer {
+	ssize_t (*write)(struct kprintf_renderer *renderer, const void *buf, size_t size);
+	ssize_t (*flush)(struct kprintf_renderer *renderer);
+};
+int kprintf_set_renderer(struct kprintf_renderer *renderer);
+
+/*
+ * This file is part of GayBSD.
+ * Copyright (c) 2021 fef <owo@fef.moe>.
+ *
+ * GayBSD is nonviolent software: you may only use, redistribute, and/or
+ * modify it under the terms of the Cooperative Nonviolent Public License
+ * (CNPL) as found in the LICENSE file in the source code root directory
+ * or at <https://git.pixie.town/thufie/npl-builder>; either version 7
+ * of the license, or (at your option) any later version.
+ *
+ * GayBSD comes with ABSOLUTELY NO WARRANTY, to the extent
+ * permitted by applicable law.  See the CNPL for details.
+ */

kernel/CMakeLists.txt

@@ -0,0 +1,24 @@
+# See the end of this file for copyright and license terms.
+
+add_library(gay_kernel STATIC)
+target_include_directories(gay_kernel PRIVATE ${GAY_INCLUDE_DIRS})
+target_compile_definitions(gay_kernel INTERFACE ${GAY_KERNEL_DIFINITIONS})
+
+target_link_libraries(gay_kernel PRIVATE c)
+
+target_sources(gay_kernel PRIVATE
+    kprintf.c
+    main.c
+)
+
+# This file is part of GayBSD.
+# Copyright (c) 2021 fef <owo@fef.moe>.
+#
+# GayBSD is nonviolent software: you may only use, redistribute, and/or
+# modify it under the terms of the Cooperative Nonviolent Public License
+# (CNPL) as found in the LICENSE file in the source code root directory
+# or at <https://git.pixie.town/thufie/npl-builder>; either version 7
+# of the license, or (at your option) any later version.
+#
+# GayBSD comes with ABSOLUTELY NO WARRANTY, to the extent
+# permitted by applicable law.  See the CNPL for details.

kernel/kprintf.c

@@ -0,0 +1,231 @@
+/* See the end of this file for copyright and license terms. */
+
+#include <stdarg.h> /* from clang */
+#include <string.h>
+
+#include <gay/config.h>
+#include <gay/errno.h>
+#include <gay/kprintf.h>
+#include <gay/types.h>
+#include <gay/util.h>
+
+#if __SIZEOF_INT__ == 2
+	/* 5 decimal digits of 65535 (2 ** 16 - 1) */
+#	define PRINTF_UINT_BUFSZ 5
+#elif __SIZEOF_INT__ == 4
+	/* 10 decimal digits of 4294967295 (2 ** 32 - 1) */
+#	define PRINTF_UINT_BUFSZ 10
+#elif __SIZEOF_INT__ == 8
+	/* 20 decimal digits of 18446744073709551616 (2 ** 64 - 1) */
+#	define PRINTF_UINT_BUFSZ 20
+#else
+#	error "Unsupported int size"
+#endif
+
+static struct kprintf_renderer *renderer = NULL;
+
+int kprintf_set_renderer(struct kprintf_renderer *new)
+{
+	int ret = 0;
+
+	if (renderer != NULL)
+		ret = renderer->flush(renderer);
+
+	renderer = new;
+	return ret;
+}
+
+static int fmt_handle_ptr(uintptr_t ptr)
+{
+	static const char table[] = {
+		'0', '1', '2', '3',
+		'4', '5', '6', '7',
+		'8', '9', 'a', 'b',
+		'c', 'd', 'e', 'f',
+	};
+
+	int ret;
+	/* 2 chars per byte, plus 2 for the "0x" hex prefix */
+	char str[2 * sizeof(uintptr_t) + 2];
+	char *pos = &str[2 * sizeof(uintptr_t) + 1];
+
+	str[0] = '0';
+	str[1] = 'x';
+
+	do {
+		*pos-- = table[ptr % ARRAY_SIZE(table)];
+		ptr >>= 4;
+	} while (pos != &str[2]);
+
+	ret = renderer->write(renderer, str, 2 * sizeof(uintptr_t) + 2);
+	return ret;
+}
+
+static int fmt_handle_uint(unsigned int u)
+{
+	char str[PRINTF_UINT_BUFSZ];
+	char *pos = &str[PRINTF_UINT_BUFSZ - 1];
+
+	do {
+		/* stupid big endian humans, forcing us to do the whole thing in reverse */
+		*pos-- = (char)(u % 10) + '0'; /* convert to ASCII */
+		u /= 10;
+	} while (u != 0);
+	pos++;
+
+	return (int)renderer->write(renderer, pos, PRINTF_UINT_BUFSZ - (pos - str));
+}
+
+static inline int fmt_handle_int(int i)
+{
+	int ret = 0;
+	char minus = '-';
+
+	if (i < 0) {
+		ret = renderer->write(renderer, &minus, sizeof(minus));
+		i = -i;
+	}
+
+	if (ret >= 0) {
+		int uint_ret = fmt_handle_uint((unsigned int)i);
+		if (uint_ret < 0)
+			ret = uint_ret;
+		else if (ret < 0)
+			ret += uint_ret;
+	}
+
+	return ret;
+}
+
+/**
+ * @brief Parse a formatting escape sequence, fetch the parameter from the `va_arg`
+ * stack, and print the resulting string to the standard serial console.
+ *
+ * @param pos A reference to the pointer to the fmt sequence beginner (`%`).
+ *	This is updated to point to the first character *after* the entire
+ *	escape sequence.
+ * @param args A pointer to the varargs list.  Will be manipulated.
+ * @returns The amount of bytes written, or a negative POSIX error code.
+ */
+static inline int fmt_handle(const char **pos, va_list args)
+{
+	int ret = 0;
+	union {
+		char c;
+		int d;
+		uintptr_t p;
+		char *s;
+		unsigned int u;
+	} val;
+
+	switch (**pos) {
+	case '%': /* literal percent sign */
+		ret = renderer->write(renderer, *pos, sizeof(**pos));
+		break;
+
+	case 'c': /* char */
+		val.c = va_arg(args, int); /* POSIX says chars are cast to an int */
+		ret = renderer->write(renderer, &val.c, sizeof(val.c));
+		break;
+
+	case 'd': /* int */
+		val.d = va_arg(args, typeof(val.d));
+		ret = fmt_handle_int(val.d);
+		break;
+
+	case 'p': /* ptr */
+		val.p = va_arg(args, typeof(val.p));
+		ret = fmt_handle_ptr(val.p);
+		break;
+
+	case 's': /* string */
+		val.s = va_arg(args, typeof(val.s));
+		ret = (int)strlen(val.s);
+		ret = renderer->write(renderer, val.s, (size_t)ret);
+		break;
+
+	case 'u': /* unsigned int */
+		val.u = va_arg(args, typeof(val.u));
+		ret = fmt_handle_uint(val.u);
+		break;
+	}
+
+	(*pos)++;
+
+	return ret;
+}
+
+int kvprintf(const char *fmt, va_list args)
+{
+	ssize_t ret = 0;
+	const char *tmp = fmt;
+
+	while (*tmp != '\0') {
+		if (*tmp++ == '%') {
+			/* flush out everything we have so far (minus one char for %) */
+			ssize_t write_ret = renderer->write(
+				renderer,
+				fmt,
+				(size_t)tmp - (size_t)fmt - 1
+			);
+			if (write_ret < 0) {
+				ret = write_ret;
+				break;
+			}
+			ret += write_ret;
+
+			ssize_t fmt_ret = fmt_handle(&tmp, args);
+			/*
+			 * act as if the current position were the beginning in
+			 * order to make the first step of this if block easier
+			 */
+			fmt = tmp;
+
+			if (fmt_ret < 0)
+				break;
+			ret += fmt_ret;
+		}
+	}
+
+	if (tmp != fmt && ret >= 0) {
+		ssize_t render_ret = renderer->write(renderer, fmt, (size_t)tmp - (size_t)fmt);
+		if (render_ret < 0)
+			ret = render_ret;
+		else
+			ret += render_ret;
+	}
+
+	ssize_t flush_ret = renderer->flush(renderer);
+	if (flush_ret < 0)
+		ret = flush_ret;
+	else
+		ret += flush_ret;
+
+	return (int)ret;
+}
+
+int kprintf(const char *fmt, ...)
+{
+	int ret;
+	va_list args;
+
+	va_start(args, fmt);
+	ret = kvprintf(fmt, args);
+	va_end(args);
+
+	return ret;
+}
+
+/*
+ * This file is part of GayBSD.
+ * Copyright (c) 2021 fef <owo@fef.moe>.
+ *
+ * GayBSD is nonviolent software: you may only use, redistribute, and/or
+ * modify it under the terms of the Cooperative Nonviolent Public License
+ * (CNPL) as found in the LICENSE file in the source code root directory
+ * or at <https://git.pixie.town/thufie/npl-builder>; either version 7
+ * of the license, or (at your option) any later version.
+ *
+ * GayBSD comes with ABSOLUTELY NO WARRANTY, to the extent
+ * permitted by applicable law.  See the CNPL for details.
+ */