sandbox: store stickypage in runtime dir

The stickypage is a hack to have a 4K hostfile persist over reboot. This
was so far done by compiling the stickypage separately and referencing
it from the device tree via the magic $build variable that expands to
the working directory.

This breaks a number of assumptions:
  - KBUILD_IMAGE: should only have a single entry, e.g.
    barebox-flash-images ends up with two files per one line

  - stickypage must be writable, which may fail if barebox is installed,
    e.g. in r/o Nix Store

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20230817073941.1261154-3-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

8 files changed, 85 insertions, 36 deletions

diff --git a/arch/sandbox/Makefile b/arch/sandbox/Makefile
index d5ba05ba86..04fb7a1f1d 100644
--- a/arch/sandbox/Makefile
+++ b/arch/sandbox/Makefile
@@ -31,7 +31,8 @@ KBUILD_CFLAGS += -Dmalloc=barebox_malloc -Dcalloc=barebox_calloc \
 		-Dclosedir=barebox_closedir -Dreadlink=barebox_readlink \
 		-Doptarg=barebox_optarg -Doptind=barebox_optind \
 		-Dsetjmp=barebox_setjmp -Dlongjmp=barebox_longjmp \
-		-Dputchar=barebox_putchar
+		-Dmkdir=barebox_mkdir -Ddirname=barebox_dirname \
+		-Dremove=barebox_remove -Dputchar=barebox_putchar
 
 machdirs := $(patsubst %,arch/sandbox/mach-%/,$(machine-y))
 
@@ -75,11 +76,7 @@ cmd_barebox__ = $(CC) -o $@ $(BAREBOX_LDFLAGS)
 
 common-y += $(BOARD) arch/sandbox/os/ arch/sandbox/lib/
 
-stickypage.bin:
-	@$(kecho) "  LN      stickypage.bin"
-	@ln -fs arch/sandbox/board/stickypage.bin stickypage.bin
-
-KBUILD_IMAGE := barebox stickypage.bin
+KBUILD_IMAGE := barebox
 
 common-$(CONFIG_OFTREE) += arch/sandbox/dts/
 
diff --git a/arch/sandbox/board/.gitignore b/arch/sandbox/board/.gitignore
index c0acd24b98..03987a7009 100644
--- a/arch/sandbox/board/.gitignore
+++ b/arch/sandbox/board/.gitignore
@@ -1,4 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
 barebox.lds
-stickypage.bin
diff --git a/arch/sandbox/board/Makefile b/arch/sandbox/board/Makefile
index 11688c5aba..b4bab02163 100644
--- a/arch/sandbox/board/Makefile
+++ b/arch/sandbox/board/Makefile
@@ -13,9 +13,4 @@ obj-$(CONFIG_LED) += led.o
 
 extra-y += barebox.lds
 
-extra-y += stickypage.bin
-
-OBJCOPYFLAGS_stickypage.bin = -O binary
-
-%.bin: %.o
-	$(call if_changed,objcopy)
+obj-y += stickypage.o
diff --git a/arch/sandbox/board/hostfile.c b/arch/sandbox/board/hostfile.c
index ca21703544..225617fe91 100644
--- a/arch/sandbox/board/hostfile.c
+++ b/arch/sandbox/board/hostfile.c
@@ -248,7 +248,20 @@ static int of_hostfile_map_fixup(struct device_node *root, void *ctx)
 	struct device_node *node;
 	int ret;
 
-	for_each_compatible_node_from(node, root, NULL, hostfile_dt_ids->compatible) {
+	for_each_compatible_node_from(node, root, NULL, "barebox,stickypage") {
+		char *filename;
+
+		filename = linux_get_stickypage_path();
+		if (!filename) {
+			pr_err("error allocating stickypage\n");
+			continue;
+		}
+
+		of_property_write_string(node, "barebox,filename", filename);
+		of_property_write_string(node, "compatible", "barebox,hostfile");
+	}
+
+	for_each_compatible_node_from(node, root, NULL, "barebox,hostfile") {
 		struct hf_info hf = {};
 		uint64_t reg[2] = {};
 
@@ -260,13 +273,6 @@ static int of_hostfile_map_fixup(struct device_node *root, void *ctx)
 			continue;
 		}
 
-		if (memcmp(hf.filename, "$build/", 7) == 0) {
-			char *fullpath = xasprintf("%s/%s", linux_get_builddir(),
-					           hf.filename + sizeof "$build/" - 1);
-
-			hf.filename = fullpath;
-		}
-
 		hf.is_blockdev = of_property_read_bool(node, "barebox,blockdev");
 		hf.is_cdev = of_property_read_bool(node, "barebox,cdev");
 		hf.is_readonly = of_property_read_bool(node, "barebox,read-only");
diff --git a/arch/sandbox/board/stickypage.S b/arch/sandbox/board/stickypage.S
index f1915ab986..1d3861c373 100644
--- a/arch/sandbox/board/stickypage.S
+++ b/arch/sandbox/board/stickypage.S
@@ -1,5 +1,8 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 
+.section .note.GNU-stack,"",%progbits
+.section .rodata.stickypage,"a"
+
 .globl stickypage;
 stickypage:
 
diff --git a/arch/sandbox/dts/sandbox.dts b/arch/sandbox/dts/sandbox.dts
index 6a0ae77d65..f3fe6ce65c 100644
--- a/arch/sandbox/dts/sandbox.dts
+++ b/arch/sandbox/dts/sandbox.dts
@@ -56,8 +56,7 @@
 	};
 
 	stickypage: stickypage {
-		compatible = "barebox,hostfile", "syscon";
-		barebox,filename = "$build/stickypage.bin";
+		compatible = "barebox,stickypage", "syscon";
 		reg = <0 0 0 4096>;
 		barebox,cdev; /* no caching allowed */
 		barebox,feature-controller;
diff --git a/arch/sandbox/mach-sandbox/include/mach/linux.h b/arch/sandbox/mach-sandbox/include/mach/linux.h
index 028bc2fa90..f4d91f08de 100644
--- a/arch/sandbox/mach-sandbox/include/mach/linux.h
+++ b/arch/sandbox/mach-sandbox/include/mach/linux.h
@@ -15,7 +15,7 @@ int linux_register_device(const char *name, void *start, void *end);
 int tap_alloc(const char *dev);
 uint64_t linux_get_time(void);
 int linux_open(const char *filename, int readwrite);
-const char *linux_get_builddir(void);
+char *linux_get_stickypage_path(void);
 int linux_open_hostfile(struct hf_info *hf);
 int linux_read(int fd, void *buf, size_t count);
 int linux_read_nonblock(int fd, void *buf, size_t count);
diff --git a/arch/sandbox/os/common.c b/arch/sandbox/os/common.c
index 2878eda29e..3446074f99 100644
--- a/arch/sandbox/os/common.c
+++ b/arch/sandbox/os/common.c
@@ -75,6 +75,15 @@ static void cookmode(void)
 	tcsetattr(0, TCSANOW, &term_orig);
 }
 
+static char *stickypage_path;
+
+static void prepare_exit(void)
+{
+	cookmode();
+	if (stickypage_path)
+		remove(stickypage_path);
+}
+
 int linux_tstc(int fd)
 {
 	struct timeval tv = {
@@ -122,7 +131,7 @@ uint64_t linux_get_time(void)
 
 void __attribute__((noreturn)) linux_exit(void)
 {
-	cookmode();
+	prepare_exit();
 	exit(0);
 }
 
@@ -167,7 +176,7 @@ void linux_reexec(void)
 
 void linux_hang(void)
 {
-	cookmode();
+	prepare_exit();
 	/* falls through to generic hang() */
 }
 
@@ -329,19 +338,60 @@ static int add_image(const char *_str, char *devname_template, int *devname_numb
 	return ret;
 }
 
-const char *linux_get_builddir(void)
+extern uint8_t stickypage[4096];
+
+char *linux_get_stickypage_path(void)
 {
-	static char path[4097];
-	int ret;
+	size_t nwritten;
+	ssize_t ret;
+	int fd;
 
-	if (!path[0]) {
-		ret = selfpath(path, sizeof(path));
-		if (ret < 0)
-			return NULL;
-		dirname(path);
+	ret = asprintf(&stickypage_path, "%s/barebox/stickypage.%lu",
+		       getenv("XDG_RUNTIME_DIR") ?: "/run", (long)getpid());
+	if (ret < 0)
+		goto err_asprintf;
+
+	ret = mkdir(dirname(stickypage_path), 0755);
+	if (ret < 0 && errno != EEXIST) {
+		perror("mkdir");
+		goto err_creat;
 	}
 
-	return path;
+	stickypage_path[strlen(stickypage_path)] = '/';
+
+	fd = open(stickypage_path, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
+	if (fd < 0) {
+		if (errno == EEXIST)
+			return stickypage_path;
+
+		perror("open");
+		goto err_creat;
+	}
+
+	for (nwritten = 0; nwritten < sizeof(stickypage); ) {
+		ret = write(fd, &stickypage[nwritten], sizeof(stickypage) - nwritten);
+		if (ret < 0) {
+			if (errno == EINTR || errno == EAGAIN)
+				continue;
+			perror("write");
+			goto err_write;
+		}
+
+		nwritten += ret;
+	}
+
+	close(fd);
+
+	return stickypage_path;
+
+err_write:
+	close(fd);
+err_creat:
+	free(stickypage_path);
+err_asprintf:
+	stickypage_path = NULL;
+
+	return NULL;
 }
 
 int linux_open_hostfile(struct hf_info *hf)
@@ -469,7 +519,7 @@ int main(int argc, char *argv[])
 	char *aux;
 
 #ifdef CONFIG_ASAN
-	__sanitizer_set_death_callback(cookmode);
+	__sanitizer_set_death_callback(prepare_exit);
 #endif
 
 	while (1) {