Merge pull request #31 from lumag/tqftp-1.1.1

meson.build: prepare 1.1.1 release

Makefile

@@ -1,25 +0,0 @@
-TQFTPSERV := tqftpserv
-
-CFLAGS += -Wall -g -O2
-LDFLAGS += -lqrtr
-prefix ?= /usr/local
-
-bindir := $(prefix)/bin
-servicedir := $(prefix)/lib/systemd/system
-
-SRCS := tqftpserv.c translate.c
-
-OBJS := $(SRCS:.c=.o)
-
-$(TQFTPSERV): $(OBJS)
-	$(CC) -o $@ $^ $(LDFLAGS)
-
-tqftpserv.service: tqftpserv.service.in
-	@sed 's+TQFTPSERV_PATH+$(bindir)+g' $< > $@
-
-install: $(TQFTPSERV) tqftpserv.service
-	@install -D -m 755 $(TQFTPSERV) $(DESTDIR)$(bindir)/$(TQFTPSERV)
-	@install -D -m 644 tqftpserv.service $(DESTDIR)$(servicedir)/tqftpserv.service
-
-clean:
-	rm -f $(TQFTPSERV) $(OBJS) tqftpserv.service

README.md

@@ -0,0 +1,53 @@
+# tqftpserv
+
+The tqftpserv software is an implementation of a TFTP (Trivial File Transfer Protocol) server which runs on top of the AF_QIPCRTR (a.k.a QRTR) socket type.
+
+The main purpose of tqftpserv is to serve files from the Linux file system to other processors on the Qualcomm SoCs as requested.
+
+The protocol implemented here is (loosely) based on RFC 1350 including some extensions to the protocol.
+
+In basic terms, the protocol supports RRQ (Read Request) and WRQ (Write Request) messages which read and write files respectively. A request can have some extra options, like `blksize` ior `wsize`. The meaning of those is documented in the `parse_options` function.
+
+For reference, the proprietary implementation of this that is used on practically all Qualcomm-based Android devices is called "tftp_server".
+
+## File paths
+
+There's two different virtual paths prefixes that are supported:
+* `/readonly/firmware/image/` for read-only files such as firmware files
+* `/readwrite/` for read-write (temporary) files
+
+Requests to those paths are "translated" (see `translate.c`) to paths in the Linux filesystem. In a regular setup readonly requests go to `/lib/firmware/` and readwrite requests go to `/tmp/tqftpserv/`.
+
+Translating those readonly request paths tries to take into account custom Linux firmware paths, custom "firmware-name" paths for remoteprocs, .zstd compressed firmware and more. In case of doubt, please consult the source code.
+
+For example on a QCM6490 Fairphone 5 smartphone the path for `/readonly/firmware/image/modem_pr/so/901_0_0.mbn` will be translated to `/lib/firmware/qcom/qcm6490/fairphone5/modem_pr/so/901_0_0.mbn`, based on the devicetree property `firmware-name = "qcom/qcm6490/fairphone5/modem.mbn";` in the modem/mpss DT node.
+
+The actual paths that are used and requested are dependent on the TFTP clients, which is usually the firmware that is running on the Hexagon-based modem processor on the SoC.
+
+## Example requests
+
+The following are some example requests which are grabbed from the tqftpserv log during modem bootup.
+
+* Write content to a file called "server_check.txt":
+```
+[TQFTP] WRQ: /readwrite/server_check.txt (octet)
+```
+
+* Read a file called "ota_firewall/ruleset" which does not exist:
+```
+[TQFTP] RRQ: /readwrite/ota_firewall/ruleset (mode=octet rsize=0 seek=0)
+tqftpserv: failed to open ota_firewall/ruleset: No such file or directory
+[TQFTP] unable to open /readwrite/ota_firewall/ruleset (2), reject
+```
+
+* Stat a file with the path "modem_pr/so/901_0_0.mbn", and then read it:
+```
+[TQFTP] RRQ: /readonly/firmware/image/modem_pr/so/901_0_0.mbn (mode=octet rsize=0 seek=0)
+[TQFTP] Remote returned END OF TRANSFER: 9 - End of Transfer
+[TQFTP] RRQ: /readonly/firmware/image/modem_pr/so/901_0_0.mbn (mode=octet rsize=52 seek=0)
+```
+
+In binary such a request can look like the following:
+```
+\0\1/readonly/firmware/image/modem_pr/so/901_0_0.mbn\0octet\0blksize\0007680\0timeoutms\0001000\0tsize\0000\0wsize\00010\0
+```

list.h

@@ -1,32 +1,6 @@
+// SPDX-License-Identifier: BSD-3-Clause
 /*
  * Copyright (c) 2016, Linaro Ltd.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice,
- * this list of conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice,
- * this list of conditions and the following disclaimer in the documentation
- * and/or other materials provided with the distribution.
- *
- * 3. Neither the name of the copyright holder nor the names of its contributors
- * may be used to endorse or promote products derived from this software without
- * specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
- * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
  */
 #ifndef __LIST_H__
 #define __LIST_H__

meson.build

@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: BSD-3-Clause
+
+project('tqftpserv',
+        'c',
+        version: '1.1.1',
+        default_options: [
+            'warning_level=1',
+            'buildtype=release',
+        ])
+
+prefix = get_option('prefix')
+
+zstd_dep = dependency('libzstd')
+add_project_arguments('-DHAVE_ZSTD', language : 'c')
+
+# Not required to build the executable,
+# only to automatically retrieve the install dir for unit files
+systemd = dependency('systemd', required : false)
+if get_option('systemd-unit-prefix') != ''
+  systemd_system_unit_dir = get_option('systemd-unit-prefix')
+elif systemd.found()
+  systemd_system_unit_dir = systemd.get_variable(
+    pkgconfig : 'systemdsystemunitdir',
+    pkgconfig_define: ['prefix', prefix])
+endif
+
+qrtr_dep = dependency('qrtr')
+
+tqftpserv_srcs = ['translate.c',
+                  'tqftpserv.c',
+                  'zstd-decompress.c']
+executable('tqftpserv',
+           tqftpserv_srcs,
+           dependencies : [qrtr_dep, zstd_dep],
+           install : true)
+
+if systemd_system_unit_dir != ''
+        systemd_unit_conf = configuration_data()
+        systemd_unit_conf.set('prefix', prefix)
+        configure_file(
+                input : 'tqftpserv.service.in',
+                output : 'tqftpserv.service',
+                configuration : systemd_unit_conf,
+                install_dir : systemd_system_unit_dir)
+endif

meson_options.txt

@@ -0,0 +1,4 @@
+option('systemd-unit-prefix',
+  type: 'string',
+  description: 'Directory for systemd system unit files'
+)

tqftpserv.c

@@ -1,32 +1,6 @@
+// SPDX-License-Identifier: BSD-3-Clause
 /*
  * Copyright (c) 2018, Linaro Ltd.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice,
- * this list of conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice,
- * this list of conditions and the following disclaimer in the documentation
- * and/or other materials provided with the distribution.
- *
- * 3. Neither the name of the copyright holder nor the names of its contributors
- * may be used to endorse or promote products derived from this software without
- * specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
- * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
  */
 #include <arpa/inet.h>
 #include <sys/stat.h>
@@ -72,6 +46,12 @@ struct tftp_client {
 	size_t wsize;
 	unsigned int timeoutms;
 	off_t seek;
+
+	uint8_t *blk_buf;
+	uint8_t *rw_buf;
+	size_t rw_buf_size;
+	size_t blk_offset;
+	uint16_t blk_expected;
 };
 
 static struct list_head readers = LIST_INIT(readers);
@@ -82,11 +62,8 @@ static ssize_t tftp_send_data(struct tftp_client *client,
 {
 	ssize_t len;
 	size_t send_len;
-	char *buf;
-	char *p;
-
-	buf = malloc(4 + client->blksize);
-	p = buf;
+	char *buf = client->blk_buf;
+	char *p = buf;
 
 	*p++ = 0;
 	*p++ = OP_DATA;
@@ -117,11 +94,7 @@ static ssize_t tftp_send_data(struct tftp_client *client,
 	}
 
 	// printf("[TQFTP] Sending %zd bytes of DATA\n", send_len);
-	len = send(client->sock, buf, send_len, 0);
-
-	free(buf);
-
-	return len;
+	return send(client->sock, buf, send_len, 0);
 }
 
 
@@ -277,7 +250,7 @@ static void handle_rrq(const char *buf, size_t len, struct sockaddr_qrtr *sq)
 	size_t blksize = 512;
 	unsigned int timeoutms = 1000;
 	size_t rsize = 0;
-	size_t wsize = 0;
+	size_t wsize = 1;
 	off_t seek = 0;
 	bool do_oack = false;
 	int sock;
@@ -341,6 +314,19 @@ static void handle_rrq(const char *buf, size_t len, struct sockaddr_qrtr *sq)
 	client->wsize = wsize;
 	client->timeoutms = timeoutms;
 	client->seek = seek;
+	client->rw_buf_size = blksize * wsize;
+
+	client->blk_buf = calloc(1, blksize + 4);
+	if (!client->blk_buf) {
+		printf("[TQFTP] Memory allocation failure\n");
+		return;
+	}
+
+	client->rw_buf = calloc(1, client->rw_buf_size);
+	if (!client->rw_buf) {
+		printf("[TQFTP] Memory allocation failure\n");
+		return;
+	}
 
 	// printf("[TQFTP] new reader added\n");
 
@@ -368,7 +354,7 @@ static void handle_wrq(const char *buf, size_t len, struct sockaddr_qrtr *sq)
 	size_t blksize = 512;
 	unsigned int timeoutms = 1000;
 	size_t rsize = 0;
-	size_t wsize = 0;
+	size_t wsize = 1;
 	off_t seek = 0;
 	bool do_oack = false;
 	int sock;
@@ -423,6 +409,20 @@ static void handle_wrq(const char *buf, size_t len, struct sockaddr_qrtr *sq)
 	client->wsize = wsize;
 	client->timeoutms = timeoutms;
 	client->seek = seek;
+	client->rw_buf_size = blksize * wsize;
+	client->blk_expected = 1;
+
+	client->blk_buf = calloc(1, blksize + 4);
+	if (!client->blk_buf) {
+		printf("[TQFTP] Memory allocation failure\n");
+		return;
+	}
+
+	client->rw_buf = calloc(1, client->rw_buf_size);
+	if (!client->rw_buf) {
+		printf("[TQFTP] Memory allocation failure\n");
+		return;
+	}
 
 	// printf("[TQFTP] new writer added\n");
 
@@ -519,14 +519,14 @@ static int handle_writer(struct tftp_client *client)
 	struct sockaddr_qrtr sq;
 	uint16_t block;
 	size_t payload;
-	char buf[516];
+	uint8_t *buf = client->blk_buf;
 	socklen_t sl;
 	ssize_t len;
 	int opcode;
 	int ret;
 
 	sl = sizeof(sq);
-	len = recvfrom(client->sock, buf, sizeof(buf), 0, (void *)&sq, &sl);
+	len = recvfrom(client->sock, buf, client->blksize + 4, 0, (void *)&sq, &sl);
 	if (len < 0) {
 		ret = -errno;
 		if (ret != -ENETRESET)
@@ -548,17 +548,48 @@ static int handle_writer(struct tftp_client *client)
 	}
 
 	payload = len - 4;
+	buf += 4;
+
+	/* Check if we recieved expected block */
+	if (block != client->blk_expected) {
+		uint16_t blk_expected = client->blk_expected;
+
+		printf("[TQFTP] Block number out of sequence: %d (expected %d)\n",
+			 block, blk_expected);
+		tftp_send_error(client->sock, 4, "Block number out of sequence");
+
+		/* Set blk_expected to beginning of current window */
+		if ((blk_expected % client->wsize) == 0)
+			blk_expected -= client->wsize + 1;
+		else
+			blk_expected -= (blk_expected % client->wsize) - 1;
+
+		client->blk_expected = blk_expected;
+		client->blk_offset = 0;
 
-	ret = write(client->fd, buf + 4, payload);
-	if (ret < 0) {
-		/* XXX: report error */
-		printf("[TQFTP] failed to write data\n");
 		return -1;
 	}
 
-	tftp_send_ack(client->sock, block);
+	client->blk_expected++;
 
-	return payload == 512 ? 1 : 0;
+	/* Copy the data to the destination buffer */
+	memcpy(client->rw_buf + client->blk_offset, buf, payload);
+	client->blk_offset += payload;
+
+	/* Write to file if all the wsize blocks are recieved */
+	if (block % client->wsize == 0) {
+		ret = write(client->fd, client->rw_buf, client->blk_offset);
+		if (ret < 0) {
+			/* XXX: report error */
+			printf("[TQFTP] failed to write data\n");
+			return -1;
+		}
+
+		client->blk_offset = 0;
+		tftp_send_ack(client->sock, block);
+	}
+
+	return payload == client->blksize ? 1 : 0;
 }
 
 static void client_close_and_free(struct tftp_client *client)
@@ -566,6 +597,8 @@ static void client_close_and_free(struct tftp_client *client)
 	list_del(&client->node);
 	close(client->sock);
 	close(client->fd);
+	free (client->blk_buf);
+	free (client->rw_buf);
 	free(client);
 }
 

tqftpserv.service.in

@@ -1,10 +1,8 @@
 [Unit]
 Description=QRTR TFTP service
-Requires=qrtr-ns.service
-After=qrtr-ns.service
 
 [Service]
-ExecStart=TQFTPSERV_PATH/tqftpserv
+ExecStart=@prefix@/bin/tqftpserv
 Restart=always
 
 [Install]

translate.c

@@ -1,32 +1,6 @@
+// SPDX-License-Identifier: BSD-3-Clause
 /*
  * Copyright (c) 2019, Linaro Ltd.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice,
- * this list of conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice,
- * this list of conditions and the following disclaimer in the documentation
- * and/or other materials provided with the distribution.
- *
- * 3. Neither the name of the copyright holder nor the names of its contributors
- * may be used to endorse or promote products derived from this software without
- * specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
- * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
  */
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -42,6 +16,7 @@
 #include <unistd.h>
 
 #include "translate.h"
+#include "zstd-decompress.h"
 
 #define READONLY_PATH	"/readonly/firmware/image/"
 #define READWRITE_PATH	"/readwrite/"
@@ -49,11 +24,14 @@
 #ifndef ANDROID
 #define FIRMWARE_BASE	"/lib/firmware/"
 #define TQFTPSERV_TMP	"/tmp/tqftpserv"
+#define UPDATES_DIR	"updates/"
 #else
 #define FIRMWARE_BASE	"/vendor/firmware/"
 #define TQFTPSERV_TMP	"/data/vendor/tmp/tqftpserv"
 #endif
 
+static int open_maybe_compressed(const char *path);
+
 static void read_fw_path_from_sysfs(char *outbuffer, size_t bufsize)
 {
 	size_t pathsize;
@@ -144,7 +122,7 @@ static int translate_readonly(const char *file)
 			strcat(path, "/");
 			strcat(path, file);
 
-			fd = open(path, O_RDONLY);
+			fd = open_maybe_compressed(path);
 			if (fd >= 0)
 				break;
 			if (errno != ENOENT)
@@ -152,16 +130,25 @@ static int translate_readonly(const char *file)
 		}
 
 		/* now try with base path */
-		if (strlen(FIRMWARE_BASE) + strlen(firmware_value) + 1 +
+		if (strlen(FIRMWARE_BASE) + strlen(UPDATES_DIR) + strlen(firmware_value) + 1 +
 		    strlen(file) + 1 > sizeof(path))
 			continue;
 
 		strcpy(path, FIRMWARE_BASE);
+		strcat(path, UPDATES_DIR);
 		strcat(path, firmware_path);
 		strcat(path, "/");
 		strcat(path, file);
 
-		fd = open(path, O_RDONLY);
+		fd = open_maybe_compressed(path);
+		if (fd < 0) {
+			strcpy(path, FIRMWARE_BASE);
+			strcat(path, firmware_path);
+			strcat(path, "/");
+			strcat(path, file);
+
+			fd = open_maybe_compressed(path);
+		}
 		if (fd >= 0)
 			break;
 
@@ -227,3 +214,30 @@ int translate_open(const char *path, int flags)
 	errno = ENOENT;
 	return -1;
 }
+
+/* linux-firmware uses .zst as file extension */
+#define ZSTD_EXTENSION ".zst"
+
+/**
+ * open_maybe_compressed() - open a file and maybe decompress it if necessary
+ * @filename:	path to a file that may be compressed (should not include compression format extension)
+ *
+ * Return: opened fd on success, -1 on error
+ */
+static int open_maybe_compressed(const char *path)
+{
+	char *path_with_zstd_extension = NULL;
+	int fd = -1;
+
+	if (access(path, F_OK) == 0)
+		return open(path, O_RDONLY);
+
+	asprintf(&path_with_zstd_extension, "%s%s", path, ZSTD_EXTENSION);
+
+	if (access(path_with_zstd_extension, F_OK) == 0)
+		fd = zstd_decompress_file(path_with_zstd_extension);
+
+	free(path_with_zstd_extension);
+
+	return fd;
+}

zstd-decompress.c

@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: BSD-3-Clause
+/*
+ * Copyright (c) 2024, Stefan Hansson
+ * Copyright (c) 2024, Emil Velikov
+ */
+
+/* For memfd_create */
+#define _GNU_SOURCE
+
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <zstd.h>
+
+#include "zstd-decompress.h"
+
+/**
+ * zstd_decompress_file() - decompress a zstd-compressed file
+ * @filename:	path to a file to decompress
+ *
+ * Return: opened fd on success, -1 on error
+ */
+int zstd_decompress_file(const char *filename)
+{
+	/* Figure out the size of the file. */
+	struct stat file_stat;
+	if (stat(filename, &file_stat) == -1) {
+		fprintf(stderr, "stat %s failed (%s)\n", filename, strerror(errno));
+		return -1;
+	}
+
+	const size_t file_size = file_stat.st_size;
+
+	const int input_file_fd = open(filename, O_RDONLY);
+	if (input_file_fd == -1) {
+		perror("open failed");
+		return -1;
+	}
+
+	void* const compressed_buffer = mmap(NULL, file_size, PROT_READ, MAP_POPULATE | MAP_PRIVATE, input_file_fd, 0);
+	if (compressed_buffer == MAP_FAILED) {
+		perror("mmap failed");
+		close(input_file_fd);
+		return -1;
+	}
+	close(input_file_fd);
+
+	const unsigned long long decompressed_size = ZSTD_getFrameContentSize(compressed_buffer, file_size);
+	if (decompressed_size == ZSTD_CONTENTSIZE_UNKNOWN) {
+		fprintf(stderr, "Content size could not be determined for %s\n", filename);
+		munmap(compressed_buffer, file_size);
+		return -1;
+	}
+	if (decompressed_size == ZSTD_CONTENTSIZE_ERROR) {
+		fprintf(stderr, "Error getting content size for %s\n", filename);
+		munmap(compressed_buffer, file_size);
+		return -1;
+	}
+
+	void* const decompressed_buffer = malloc((size_t)decompressed_size);
+	if (decompressed_buffer == NULL) {
+		perror("malloc failed");
+		munmap(compressed_buffer, file_size);
+		return -1;
+	}
+
+	const size_t return_size = ZSTD_decompress(decompressed_buffer, decompressed_size, compressed_buffer, file_size);
+	if (ZSTD_isError(return_size)) {
+		fprintf(stderr, "ZSTD_decompress failed: %s\n", ZSTD_getErrorName(return_size));
+		free(decompressed_buffer);
+		munmap(compressed_buffer, file_size);
+		return -1;
+	}
+
+	const int output_file_fd = memfd_create(filename, 0);
+	if (output_file_fd == -1) {
+		perror("memfd_create failed");
+		free(decompressed_buffer);
+		munmap(compressed_buffer, file_size);
+		return -1;
+	}
+
+	if (write(output_file_fd, decompressed_buffer, decompressed_size) != decompressed_size) {
+		perror("write failed");
+		close(output_file_fd);
+		free(decompressed_buffer);
+		munmap(compressed_buffer, file_size);
+		return -1;
+	}
+
+	return output_file_fd;
+}

zstd-decompress.h

@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: BSD-3-Clause
+/*
+ * Copyright (c) 2024, Stefan Hansson
+ */
+
+#ifndef __ZSTD_DECOMPRESS_H__
+#define __ZSTD_DECOMPRESS_H__
+
+#include <stdbool.h>
+
+#ifdef HAVE_ZSTD
+int zstd_decompress_file(const char *filename);
+#else
+static int zstd_decompress_file(const char *filename)
+{
+	fprintf(stderr, "Built without ZSTD support\n");
+	return -1;
+}
+#endif
+
+#endif