Add `uptime.txt`

5 files changed, 208 insertions, 0 deletions

diff --git a/cmd/sbc_harness/CMakeLists.txt b/cmd/sbc_harness/CMakeLists.txt
index 64bf356..115361f 100644
--- a/cmd/sbc_harness/CMakeLists.txt
+++ b/cmd/sbc_harness/CMakeLists.txt
@@ -11,6 +11,8 @@ add_library(sbc_harness_objs OBJECT
 	main.c
 	usb_keyboard.c
 	tusb_log.c
+
+	fs_harness_uptime_txt.c
 )
 target_include_directories(sbc_harness_objs PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/config)
 target_include_directories(sbc_harness_objs PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
@@ -74,6 +76,7 @@ target_embed_sources(sbc_harness_objs sbc_harness static.h
 	static/Documentation/YOUR_RIGHTS_AND_OBLIGATIONS/newlib.txt
 	static/Documentation/harness_rom_bin.txt
 	static/Documentation/harness_flash_bin.txt
+	static/Documentation/harness_uptime_txt.txt
 )
 
 endif()
diff --git a/cmd/sbc_harness/fs_harness_uptime_txt.c b/cmd/sbc_harness/fs_harness_uptime_txt.c
new file mode 100644
index 0000000..9216986
--- /dev/null
+++ b/cmd/sbc_harness/fs_harness_uptime_txt.c
@@ -0,0 +1,156 @@
+/* sbc_harness/fs_harness_uptime_txt.c - 9P access to harness uptime
+ *
+ * Copyright (C) 2025  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#include <stdio.h>  /* for snprintf() */
+#include <stdlib.h> /* for malloc(), free() */
+
+#include <libhw/generic/alarmclock.h>
+#include <util9p/static.h>
+
+#include "fs_harness_uptime_txt.h"
+
+LO_IMPLEMENTATION_C(lib9p_srv_file, struct uptime_file, uptime_file, static);
+
+struct uptime_fio {
+	struct uptime_file      *parent;
+	size_t                   buf_len;
+	char                     buf[24]; /* len(str(UINT64_MAX)+"ns\n\0") */
+};
+
+LO_IMPLEMENTATION_H(lib9p_srv_fio, struct uptime_fio, uptime_fio);
+LO_IMPLEMENTATION_C(lib9p_srv_fio, struct uptime_fio, uptime_fio, static);
+
+/* srv_file *******************************************************************/
+
+static void uptime_file_free(struct uptime_file *self) {
+	assert(self);
+}
+static struct lib9p_qid uptime_file_qid(struct uptime_file *self) {
+	assert(self);
+
+	return (struct lib9p_qid){
+		.type = LIB9P_QT_FILE,
+		.vers = 1,
+		.path = self->pathnum,
+	};
+}
+
+static struct lib9p_stat uptime_file_stat(struct uptime_file *self, struct lib9p_srv_ctx *ctx) {
+	assert(self);
+	assert(ctx);
+
+	uint64_t now = LO_CALL(bootclock, get_time_ns);
+	uint64_t size = 0;
+	while (now) {
+		size++;
+		now /= 10;
+	}
+	if (!size)
+		size++;
+	size += 3;
+
+	return (struct lib9p_stat){
+		.kern_type                = 0,
+		.kern_dev                 = 0,
+		.file_qid                 = uptime_file_qid(self),
+		.file_mode                = 0444,
+		.file_atime               = UTIL9P_ATIME,
+		.file_mtime               = UTIL9P_MTIME,
+		.file_size                = size,
+		.file_name                = lib9p_str(self->name),
+		.file_owner_uid           = lib9p_str("root"),
+		.file_owner_gid           = lib9p_str("root"),
+		.file_last_modified_uid   = lib9p_str("root"),
+		.file_extension           = lib9p_str(NULL),
+		.file_owner_n_uid         = 0,
+		.file_owner_n_gid         = 0,
+		.file_last_modified_n_uid = 0,
+	};
+}
+static void uptime_file_wstat(struct uptime_file *self, struct lib9p_srv_ctx *ctx,
+                              struct lib9p_stat) {
+	assert(self);
+	assert(ctx);
+
+	lib9p_error(&ctx->basectx, LINUX_EROFS, "read-only part of filesystem");
+}
+static void uptime_file_remove(struct uptime_file *self, struct lib9p_srv_ctx *ctx) {
+	assert(self);
+	assert(ctx);
+
+	lib9p_error(&ctx->basectx, LINUX_EROFS, "read-only part of filesystem");
+}
+
+LIB9P_SRV_NOTDIR(struct uptime_file, uptime_file);
+
+static lo_interface lib9p_srv_fio uptime_file_fopen(struct uptime_file *self, struct lib9p_srv_ctx *ctx,
+                                                    bool LM_UNUSED(rd), bool LM_UNUSED(wr), bool LM_UNUSED(trunc)) {
+	assert(self);
+	assert(ctx);
+
+	struct uptime_fio *ret = malloc(sizeof(struct uptime_fio));
+	ret->parent = self;
+	ret->buf_len = 0;
+
+	return lo_box_uptime_fio_as_lib9p_srv_fio(ret);
+}
+
+/* srv_fio ********************************************************************/
+
+static uint32_t uptime_fio_iounit(struct uptime_fio *self) {
+	assert(self);
+	return sizeof(self->buf)-1;
+}
+
+static void uptime_fio_iofree(struct uptime_fio *self) {
+	assert(self);
+	free(self);
+}
+
+static struct lib9p_qid uptime_fio_qid(struct uptime_fio *self) {
+	assert(self);
+	assert(self->parent);
+	return uptime_file_qid(self->parent);
+}
+
+static void uptime_fio_pread(struct uptime_fio *self, struct lib9p_srv_ctx *ctx,
+                             uint32_t byte_count, uint64_t byte_offset,
+                             struct iovec *ret) {
+	assert(self);
+	assert(ctx);
+	assert(ret);
+
+	if (byte_offset == 0 || self->buf_len == 0) {
+		uint64_t now = LO_CALL(bootclock, get_time_ns);
+		self->buf_len = snprintf(self->buf, sizeof(self->buf), "%"PRIu64"ns\n", now);
+	}
+
+	if (byte_offset > (uint64_t)self->buf_len) {
+		lib9p_error(&ctx->basectx,
+		            LINUX_EINVAL, "offset is past end-of-file length");
+		return;
+	}
+
+	size_t beg_off = (size_t)byte_offset;
+	size_t end_off = beg_off + (size_t)byte_count;
+	if (end_off > self->buf_len)
+		end_off = self->buf_len;
+	*ret = (struct iovec){
+		.iov_base = &self->buf[beg_off],
+		.iov_len = end_off-beg_off,
+	};
+}
+
+static uint32_t uptime_fio_pwrite(struct uptime_fio *self, struct lib9p_srv_ctx *ctx,
+                                  void *LM_UNUSED(buf),
+                                  uint32_t LM_UNUSED(byte_count),
+                                  uint64_t LM_UNUSED(byte_offset)) {
+	assert(self);
+	assert(ctx);
+
+	lib9p_error(&ctx->basectx, LINUX_EROFS, "read-only part of filesystem");
+	return 0;
+}
diff --git a/cmd/sbc_harness/fs_harness_uptime_txt.h b/cmd/sbc_harness/fs_harness_uptime_txt.h
new file mode 100644
index 0000000..7bf2945
--- /dev/null
+++ b/cmd/sbc_harness/fs_harness_uptime_txt.h
@@ -0,0 +1,19 @@
+/* sbc_harness/fs_harness_uptime_txt.h - 9P access to harness uptime
+ *
+ * Copyright (C) 2025  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#ifndef _SBC_HARNESS_FS_HARNESS_UPTIME_TXT_H_
+#define _SBC_HARNESS_FS_HARNESS_UPTIME_TXT_H_
+
+#include <lib9p/srv.h>
+
+struct uptime_file {
+	char            *name;
+	uint64_t         pathnum;
+};
+LO_IMPLEMENTATION_H(lib9p_srv_file, struct uptime_file, uptime_file);
+#define lo_box_uptime_file_as_lib9p_srv_file(obj) util9p_box(uptime_file, obj)
+
+#endif /* _SBC_HARNESS_FS_HARNESS_UPTIME_TXT_H_ */
diff --git a/cmd/sbc_harness/main.c b/cmd/sbc_harness/main.c
index 2b2b3f8..3334bd8 100644
--- a/cmd/sbc_harness/main.c
+++ b/cmd/sbc_harness/main.c
@@ -32,6 +32,7 @@
 /* local headers */
 #include "usb_keyboard.h"
 #include "static.h"
+#include "fs_harness_uptime_txt.h"
 
 /* configuration **************************************************************/
 
@@ -45,6 +46,13 @@ enum { PATH_BASE = __COUNTER__ };
 #define STATIC_FILE(STRNAME, ...) UTIL9P_STATIC_FILE(PATH_COUNTER, STRNAME, __VA_ARGS__)
 #define STATIC_DIR(STRNAME, ...)  UTIL9P_STATIC_DIR(PATH_COUNTER, STRNAME, __VA_ARGS__)
 
+#define API_FILE(STRNAME, SYMNAME, ...)                                      \
+	lo_box_##SYMNAME##_file_as_lib9p_srv_file(&((struct SYMNAME##_file){ \
+		.name = STRNAME,                                             \
+		.pathnum = PATH_COUNTER                                      \
+		__VA_OPT__(,) __VA_ARGS__                                    \
+	}))
+
 struct lib9p_srv_file root =
 		STATIC_DIR("",
 		           STATIC_DIR("Documentation",
@@ -74,6 +82,9 @@ struct lib9p_srv_file root =
 		                      STATIC_FILE("harness_flash_bin.txt",
 		                                  .data_start = _binary_static_Documentation_harness_flash_bin_txt_start,
 		                                  .data_end   = _binary_static_Documentation_harness_flash_bin_txt_end),
+		                      STATIC_FILE("harness_uptime_txt.txt",
+		                                  .data_start = _binary_static_Documentation_harness_uptime_txt_txt_start,
+		                                  .data_end   = _binary_static_Documentation_harness_uptime_txt_txt_end),
 		                      ),
 		           STATIC_DIR("harness",
 		                      STATIC_FILE("rom.bin",
@@ -83,6 +94,8 @@ struct lib9p_srv_file root =
 		                      STATIC_FILE("flash.bin",
 		                                  .data_start = (void*)0x10000000,
 		                                  .data_size  = PICO_FLASH_SIZE_BYTES),
+		                      API_FILE("uptime.txt",
+		                               uptime),
 		                      // TODO: system.log
 		                      // TODO: proc.txt
 		                      // TODO: cpuinfo.txt
diff --git a/cmd/sbc_harness/static/Documentation/harness_uptime_txt.txt b/cmd/sbc_harness/static/Documentation/harness_uptime_txt.txt
new file mode 100644
index 0000000..1ab86f7
--- /dev/null
+++ b/cmd/sbc_harness/static/Documentation/harness_uptime_txt.txt
@@ -0,0 +1,17 @@
+NAME
+	/harness/uptime.txt
+
+DESCRIPTION
+	Reading this file gives a text string of the format
+	`sprintf("%uns\n", uptime_ns)` indicating the harness's uptime
+	in an integer number of nanoseconds.
+
+BUGS
+	Using nanoseconds gives the illusion of more precision than
+	there actually is; the harness' clock only has microsecond
+	resolution; the last 3 digits of the returned nanosecond count
+	will always be 0.
+
+AUTHOR
+	Copyright (C) 2025  Luke T. Shumaker <lukeshu@lukeshu.com>
+	SPDX-License-Identifier: AGPL-3.0-or-later