Laurent Pinchart
93d9751945
uClibc doesn't provide memfd_create(), which led libcamera to open-code the call using syscall(). Sprinkling the code with #ifdef's isn't the most readable option, so improve it by providing a local implementation of memfd_create(), and call the function unconditionally from MemFd::create(). This makes the main code path more readable. Suggested-by: Nicolas Dufresne <nicolas@ndufresne.ca> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Tested-by: Milan Zamazal <mzamazal@redhat.com> Tested-by: Hans de Goede <hdegoede@redhat.com> Reviewed-by: Hans de Goede <hdegoede@redhat.com> Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
124 lines
2.7 KiB
C++
124 lines
2.7 KiB
C++
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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/*
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* Copyright (C) 2024, Ideas on Board Oy
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*
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* Anonymous file creation
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*/
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#include <libcamera/base/memfd.h>
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#include <fcntl.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <sys/syscall.h>
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#include <unistd.h>
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#include <libcamera/base/log.h>
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/**
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* \file base/memfd.h
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* \brief Anonymous file creation
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*/
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#ifndef __DOXYGEN__
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namespace {
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/* uClibc doesn't provide the file sealing API. */
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#if not HAVE_FILE_SEALS
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#define F_ADD_SEALS 1033
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#define F_SEAL_SHRINK 0x0002
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#define F_SEAL_GROW 0x0004
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#endif
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#if not HAVE_MEMFD_CREATE
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int memfd_create(const char *name, unsigned int flags)
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{
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return syscall(SYS_memfd_create, name, flags);
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}
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#endif
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} /* namespace */
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#endif /* __DOXYGEN__ */
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namespace libcamera {
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LOG_DECLARE_CATEGORY(File)
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/**
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* \class MemFd
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* \brief Helper class to create anonymous files
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*
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* Anonymous files behave like regular files, and can be modified, truncated,
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* memory-mapped and so on. Unlike regular files, they however live in RAM and
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* don't have permanent backing storage.
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*/
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/**
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* \enum MemFd::Seal
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* \brief Seals for the MemFd::create() function
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* \var MemFd::Seal::None
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* \brief No seals (used as default value)
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* \var MemFd::Seal::Shrink
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* \brief Prevent the memfd from shrinking
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* \var MemFd::Seal::Grow
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* \brief Prevent the memfd from growing
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*/
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/**
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* \typedef MemFd::Seals
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* \brief A bitwise combination of MemFd::Seal values
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*/
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/**
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* \brief Create an anonymous file
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* \param[in] name The file name (displayed in symbolic links in /proc/self/fd/)
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* \param[in] size The file size
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* \param[in] seals The file seals
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*
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* This function is a helper that wraps anonymous file (memfd) creation and
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* sets the file size and optional seals.
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*
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* \return The descriptor of the anonymous file if creation succeeded, or an
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* invalid UniqueFD otherwise
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*/
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UniqueFD MemFd::create(const char *name, std::size_t size, Seals seals)
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{
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int ret = memfd_create(name, MFD_ALLOW_SEALING | MFD_CLOEXEC);
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if (ret < 0) {
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ret = errno;
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LOG(File, Error)
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<< "Failed to allocate memfd storage for " << name
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<< ": " << strerror(ret);
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return {};
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}
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UniqueFD memfd(ret);
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ret = ftruncate(memfd.get(), size);
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if (ret < 0) {
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ret = errno;
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LOG(File, Error)
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<< "Failed to set memfd size for " << name
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<< ": " << strerror(ret);
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return {};
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}
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if (seals) {
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int fileSeals = (seals & Seal::Shrink ? F_SEAL_SHRINK : 0)
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| (seals & Seal::Grow ? F_SEAL_GROW : 0);
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ret = fcntl(memfd.get(), F_ADD_SEALS, fileSeals);
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if (ret < 0) {
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ret = errno;
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LOG(File, Error)
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<< "Failed to seal the memfd for " << name
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<< ": " << strerror(ret);
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return {};
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}
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}
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return memfd;
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}
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} /* namespace libcamera */
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