From b79013ead9de2e7aef52016182e43e11971961f4 Mon Sep 17 00:00:00 2001 From: Rob Hughes Date: Thu, 2 Oct 2025 15:04:31 +0100 Subject: [PATCH] llvmpipe: Work around WSL 1 missing support for memfd_create() WSL version 1 has a known limitation that the kernel does not support the memfd_create() syscall, and it always returns -1 (see https://github.com/microsoft/WSL/issues/3542). This results in lavapipe/llvmpipe failing to create the anonymous file it needs for allocations from the pipe_screen object, which in turn results in results in failed application calls to Vulkan APIs (in the case I observed, vkMapMemory returned an invalid (0xffffffff) pointer along with VK_SUCCESS, leading to the application segfaulting). This issue can be reproduced by simply running `vkcube` (or, presumably any other simple Vulkan application) inside WSL 1, e.g.: xvfb-run -s '-screen 0 1024x768x24' vkcube --c 300 This patch addresses the issue with several changes: 1. llvmpipe_create_screen() now checks for errors from the os_create_anonymous_file function and errors out early, making it easier to track down issues similar to this. Previously, the invalid fd of -1 would be stored in the pipe_screen struct and the problems would only appear later. 2. os_create_anonymous_file() now attempts to handle the case where memfd_create() fails, by falling back to creating a file in a temporary directory. This fallback is the same as is already done for builds that don't have memfd_create available at build time - note that the difference here is that this is a _runtime_ fallback, as is needed for the case of WSL 1. 3. The fallback logic previously relied on the XDG_RUNTIME_DIR environment variable, which might not be set when running inside WSL because there is unlikely to be a desktop environment configured. This patch adds a fallback of creating a new directory inside /tmp in this case. Reviewed-by: Lucas Fryzek Part-of: --- src/gallium/drivers/llvmpipe/lp_screen.c | 5 ++ src/util/anon_file.c | 109 ++++++++++++++++++----- 2 files changed, 94 insertions(+), 20 deletions(-) diff --git a/src/gallium/drivers/llvmpipe/lp_screen.c b/src/gallium/drivers/llvmpipe/lp_screen.c index 2aec374fcd4..ab35d2516c6 100644 --- a/src/gallium/drivers/llvmpipe/lp_screen.c +++ b/src/gallium/drivers/llvmpipe/lp_screen.c @@ -1031,6 +1031,11 @@ llvmpipe_create_screen(struct sw_winsys *winsys) util_vma_heap_init(&screen->mem_heap, alignment, UINT64_MAX - alignment); screen->mem_heap.alloc_high = false; screen->fd_mem_alloc = os_create_anonymous_file(0, "allocation fd"); + if (screen->fd_mem_alloc == -1) { + mesa_loge("Failed to create anonymous file for memory allocations\n"); + llvmpipe_destroy_screen(&screen->base); + return NULL; + } #endif snprintf(screen->renderer_string, sizeof(screen->renderer_string), diff --git a/src/util/anon_file.c b/src/util/anon_file.c index bc674c4b66f..a9ad2a2aad8 100644 --- a/src/util/anon_file.c +++ b/src/util/anon_file.c @@ -1,5 +1,6 @@ /* * Copyright © 2012 Collabora, Ltd. + * Copyright (C) 2025 Arm Ltd. * * Permission is hereby granted, free of charge, to any person obtaining * a copy of this software and associated documentation files (the @@ -42,11 +43,16 @@ #elif DETECT_OS_ANDROID #include #include -#else +#endif + +#if !(defined(__FreeBSD__) || DETECT_OS_ANDROID) +#include "log.h" +#include "os_misc.h" +#include #include #endif -#if !(defined(__FreeBSD__) || defined(HAVE_MEMFD_CREATE) || defined(HAVE_MKOSTEMP) || DETECT_OS_ANDROID) +#if !(defined(__FreeBSD__) || defined(HAVE_MKOSTEMP) || DETECT_OS_ANDROID) static int set_cloexec_or_close(int fd) { @@ -70,7 +76,7 @@ err: } #endif -#if !(defined(__FreeBSD__) || defined(HAVE_MEMFD_CREATE) || DETECT_OS_ANDROID) +#if !(defined(__FreeBSD__) || DETECT_OS_ANDROID) static int create_tmpfile_cloexec(char *tmpname) { @@ -95,6 +101,61 @@ create_tmpfile_cloexec(char *tmpname) } #endif +#if !(defined(__FreeBSD__) || DETECT_OS_ANDROID) +/* + * Gets the path to a suitable temporary directory for the current user. + * Prefers using the environment variable `XDG_RUNTIME_DIR` if set, + * otherwise falls back to creating or re-using a folder in `/tmp`. + * Copies the path into the given `buf` of length `len` and also returns + * a pointer to the same buffer for convenience. + * Returns NULL if no suitable directory can found or created. + */ +static char* +get_or_create_user_temp_dir(char* buf, size_t len) { + const char* env; + struct stat st; + int uid = getuid(); + + env = os_get_option("XDG_RUNTIME_DIR"); + if (env && env[0] != '\0') { + snprintf(buf, len, "%s", env); + return buf; + } + + snprintf(buf, len, "/tmp/xdg-runtime-mesa-%ld", (long)getuid()); + mesa_logd("%s: XDG_RUNTIME_DIR not set; falling back to temp dir %s", + __func__, buf); + if (stat(buf, &st) == 0) { + /* If already exists, confirm the owner/permissions */ + if (!S_ISDIR(st.st_mode)) { + mesa_loge( + "%s: %s exists but is not a directory", __func__, buf); + return NULL; + } + if (st.st_uid != uid) { + mesa_loge( + "%s: %s exists but has wrong owner", __func__, buf); + return NULL; + } + + return buf; + } else if (errno == ENOENT) { + /* Doesn't exist, try to create it */ + if (mkdir(buf, 0700) != 0) { + mesa_loge("%s: mkdir %s failed: %s", __func__, buf, + strerror(errno)); + return NULL; + } + + return buf; + } else { + mesa_loge("%s: stat %s failed: %s", __func__, buf, + strerror(errno)); + return NULL; + } +} +#endif + /* * Create a new, unique, anonymous file of the given size, and * return the file descriptor for it. The file descriptor is set @@ -116,7 +177,8 @@ create_tmpfile_cloexec(char *tmpname) int os_create_anonymous_file(int64_t size, const char *debug_name) { - int fd, ret; + int fd = -1, ret; + /* First try using preferred APIs */ #if defined(HAVE_MEMFD_CREATE) if (!debug_name) debug_name = "mesa-shared"; @@ -132,26 +194,33 @@ os_create_anonymous_file(int64_t size, const char *debug_name) fd = shm_mkstemp(template); if (fd != -1) shm_unlink(template); -#else - const char *path; - char *name; +#endif - path = getenv("XDG_RUNTIME_DIR"); - if (!path) { - errno = ENOENT; - return -1; - } + /* + * If preferred API failed (or not included in this build), + * fall back to using a file in a temporary dir + */ +#if !(defined(__FreeBSD__) || DETECT_OS_ANDROID) + if (fd == -1) { + char path[PATH_MAX]; + char *name; - if (debug_name) - asprintf(&name, "%s/mesa-shared-%s-XXXXXX", path, debug_name); - else - asprintf(&name, "%s/mesa-shared-XXXXXX", path); - if (!name) - return -1; + if (!get_or_create_user_temp_dir(path, sizeof(path))) { + errno = ENOENT; + return -1; + } - fd = create_tmpfile_cloexec(name); + if (debug_name) + asprintf(&name, "%s/mesa-shared-%s-XXXXXX", path, debug_name); + else + asprintf(&name, "%s/mesa-shared-XXXXXX", path); + if (!name) + return -1; - free(name); + fd = create_tmpfile_cloexec(name); + + free(name); + } #endif if (fd < 0)