kernel/linux.git/drivers/char/mem.c, branch v6.19.11

mm: update mem char driver to use mmap_prepare

2025-11-17T01:28:13+00:00

Update the mem char driver (backing /dev/mem and /dev/zero) to use f_op->mmap_prepare hook rather than the deprecated f_op->mmap. The /dev/zero implementation has a very unique and rather concerning characteristic in that it converts MAP_PRIVATE mmap() mappings anonymous when they are, in fact, not. The new f_op->mmap_prepare() can support this, but rather than introducing a helper function to perform this hack (and risk introducing other users), utilise the success hook to do so. We utilise the newly introduced shmem_zero_setup_desc() to allow for the shared mapping case via an f_op->mmap_prepare() hook. We also use the desc->action_error_hook to filter the remap error to -EAGAIN to keep behaviour consistent. Link: https://lkml.kernel.org/r/48f60764d7a6901819d1af778fa33b775d2e8c77.1760959442.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Reviewed-by: Jason Gunthorpe Cc: Alexander Gordeev Cc: Al Viro Cc: Andreas Larsson Cc: Andrey Konovalov Cc: Arnd Bergmann Cc: Baolin Wang Cc: Baoquan He Cc: Chatre, Reinette Cc: Christian Borntraeger Cc: Christian Brauner Cc: Dan Williams Cc: Dave Jiang Cc: Dave Martin Cc: Dave Young Cc: David Hildenbrand Cc: David S. Miller Cc: Dmitriy Vyukov Cc: Greg Kroah-Hartman Cc: Guo Ren Cc: Heiko Carstens Cc: Hugh Dickins Cc: James Morse Cc: Jan Kara Cc: Jann Horn Cc: Jonathan Corbet Cc: Kevin Tian Cc: Konstantin Komarov Cc: Liam Howlett Cc: "Luck, Tony" Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Nicolas Pitre Cc: Oscar Salvador Cc: Pedro Falcato Cc: Robin Murohy Cc: Sumanth Korikkar Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: "Uladzislau Rezki (Sony)" Cc: Vasily Gorbik Cc: Vishal Verma Cc: Vivek Goyal Cc: Vlastimil Babka Cc: Will Deacon Signed-off-by: Andrew Morton

mm: consistently use current->mm in mm_get_unmapped_area()

2025-11-17T01:27:57+00:00

mm_get_unmapped_area() is a wrapper around arch_get_unmapped_area() / arch_get_unmapped_area_topdown(), both of which search current->mm for some free space. Neither take an mm_struct - they implicitly operate on current->mm. But the wrapper takes an mm_struct and uses it to decide whether to search bottom up or top down. All callers pass in current->mm for this, so everything is working consistently. But it feels like an accident waiting to happen; eventually someone will call that function with a different mm, expecting to find free space in it, but what gets returned is free space in the current mm. So let's simplify by removing the parameter and have the wrapper use current->mm to decide which end to start at. Now everything is consistent and self-documenting. Link: https://lkml.kernel.org/r/20251003155306.2147572-1-ryan.roberts@arm.com Signed-off-by: Ryan Roberts Acked-by: David Hildenbrand Reviewed-by: Oscar Salvador Reviewed-by: Dev Jain Reviewed-by: Anshuman Khandual Reviewed-by: Lorenzo Stoakes Reviewed-by: Baolin Wang Cc: Liam Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

/dev/zero: try to align PMD_SIZE for private mapping

2025-09-13T23:54:42+00:00

Attempt to map aligned to huge page size for private mapping which could achieve performance gains, the mprot_tw4m in libMicro average execution time on arm64: - Test case: mprot_tw4m - Before the patch: 22 us - After the patch: 17 us If THP config is not set, we fall back to system page size mappings. Link: https://lkml.kernel.org/r/20250731122305.2669090-1-zhangqilong3@huawei.com Signed-off-by: Zhang Qilong Reviewed-by: Lorenzo Stoakes Tested-by: Lorenzo Stoakes Acked-by: David Hildenbrand Cc: Arnd Bergmann Cc: Greg Kroah-Hartman Cc: Kefeng Wang Cc: Nanyong Sun Signed-off-by: Andrew Morton

x86/devmem: Remove duplicate range_is_allowed() definition

2025-05-01T16:43:48+00:00

17 years ago, Venki suggested [1] "A future improvement would be to avoid the range_is_allowed duplication". The only thing preventing a common implementation is that phys_mem_access_prot_allowed() expects the range check to exit immediately when PAT is disabled [2]. I.e. there is no cache conflict to manage in that case. This cleanup was noticed on the path to considering changing range_is_allowed() policy to blanket deny /dev/mem for private (confidential computing) memory. Note, however that phys_mem_access_prot_allowed() has long since stopped being relevant for managing cache-type validation due to [3], and [4]. Commit 0124cecfc85a ("x86, PAT: disable /dev/mem mmap RAM with PAT") [1] Commit 9e41bff2708e ("x86: fix /dev/mem mmap breakage when PAT is disabled") [2] Commit 1886297ce0c8 ("x86/mm/pat: Fix BUG_ON() in mmap_mem() on QEMU/i386") [3] Commit 0c3c8a18361a ("x86, PAT: Remove duplicate memtype reserve in devmem mmap") [4] Signed-off-by: Dan Williams Signed-off-by: Dave Hansen Reviewed-by: Nikolay Borisov Reviewed-by: Greg Kroah-Hartman Link: https://lore.kernel.org/all/20250430024622.1134277-2-dan.j.williams%40intel.com

fs: move FMODE_UNSIGNED_OFFSET to fop_flags

2024-08-30T06:22:36+00:00

This is another flag that is statically set and doesn't need to use up an FMODE_* bit. Move it to ->fop_flags and free up another FMODE_* bit. (1) mem_open() used from proc_mem_operations (2) adi_open() used from adi_fops (3) drm_open_helper(): (3.1) accel_open() used from DRM_ACCEL_FOPS (3.2) drm_open() used from (3.2.1) amdgpu_driver_kms_fops (3.2.2) psb_gem_fops (3.2.3) i915_driver_fops (3.2.4) nouveau_driver_fops (3.2.5) panthor_drm_driver_fops (3.2.6) radeon_driver_kms_fops (3.2.7) tegra_drm_fops (3.2.8) vmwgfx_driver_fops (3.2.9) xe_driver_fops (3.2.10) DRM_GEM_FOPS (3.2.11) DEFINE_DRM_GEM_DMA_FOPS (4) struct memdev sets fmode flags based on type of device opened. For devices using struct mem_fops unsigned offset is used. Mark all these file operations as FOP_UNSIGNED_OFFSET and add asserts into the open helper to ensure that the flag is always set. Link: https://lore.kernel.org/r/20240809-work-fop_unsigned-v1-1-658e054d893e@kernel.org Reviewed-by: Jeff Layton Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

Merge tag 'char-misc-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc

2024-05-22T19:26:46+00:00

Pull char/misc and other driver subsystem updates from Greg KH: "Here is the big set of char/misc and other driver subsystem updates for 6.10-rc1. Nothing major here, just lots of new drivers and updates for apis and new hardware types. Included in here are: - big IIO driver updates with more devices and drivers added - fpga driver updates - hyper-v driver updates - uio_pruss driver removal, no one uses it, other drivers control the same hardware now - binder minor updates - mhi driver updates - excon driver updates - counter driver updates - accessability driver updates - coresight driver updates - other hwtracing driver updates - nvmem driver updates - slimbus driver updates - spmi driver updates - other smaller misc and char driver updates All of these have been in linux-next for a while with no reported issues" * tag 'char-misc-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (319 commits) misc: ntsync: mark driver as "broken" to prevent from building spmi: pmic-arb: Add multi bus support spmi: pmic-arb: Register controller for bus instead of arbiter spmi: pmic-arb: Make core resources acquiring a version operation spmi: pmic-arb: Make the APID init a version operation spmi: pmic-arb: Fix some compile warnings about members not being described dt-bindings: spmi: Deprecate qcom,bus-id dt-bindings: spmi: Add X1E80100 SPMI PMIC ARB schema spmi: pmic-arb: Replace three IS_ERR() calls by null pointer checks in spmi_pmic_arb_probe() spmi: hisi-spmi-controller: Do not override device identifier dt-bindings: spmi: hisilicon,hisi-spmi-controller: clean up example dt-bindings: spmi: hisilicon,hisi-spmi-controller: fix binding references spmi: make spmi_bus_type const extcon: adc-jack: Document missing struct members extcon: realtek: Remove unused of_gpio.h extcon: usbc-cros-ec: Convert to platform remove callback returning void extcon: usb-gpio: Convert to platform remove callback returning void extcon: max77843: Convert to platform remove callback returning void extcon: max3355: Convert to platform remove callback returning void extcon: intel-mrfld: Convert to platform remove callback returning void ...

mm: switch mm->get_unmapped_area() to a flag

2024-04-26T03:56:25+00:00

The mm_struct contains a function pointer *get_unmapped_area(), which is set to either arch_get_unmapped_area() or arch_get_unmapped_area_topdown() during the initialization of the mm. Since the function pointer only ever points to two functions that are named the same across all arch's, a function pointer is not really required. In addition future changes will want to add versions of the functions that take additional arguments. So to save a pointers worth of bytes in mm_struct, and prevent adding additional function pointers to mm_struct in future changes, remove it and keep the information about which get_unmapped_area() to use in a flag. Add the new flag to MMF_INIT_MASK so it doesn't get clobbered on fork by mmf_init_flags(). Most MM flags get clobbered on fork. In the pre-existing behavior mm->get_unmapped_area() would get copied to the new mm in dup_mm(), so not clobbering the flag preserves the existing behavior around inheriting the topdown-ness. Introduce a helper, mm_get_unmapped_area(), to easily convert code that refers to the old function pointer to instead select and call either arch_get_unmapped_area() or arch_get_unmapped_area_topdown() based on the flag. Then drop the mm->get_unmapped_area() function pointer. Leave the get_unmapped_area() pointer in struct file_operations alone. The main purpose of this change is to reorganize in preparation for future changes, but it also converts the calls of mm->get_unmapped_area() from indirect branches into a direct ones. The stress-ng bigheap benchmark calls realloc a lot, which calls through get_unmapped_area() in the kernel. On x86, the change yielded a ~1% improvement there on a retpoline config. In testing a few x86 configs, removing the pointer unfortunately didn't result in any actual size reductions in the compiled layout of mm_struct. But depending on compiler or arch alignment requirements, the change could shrink the size of mm_struct. Link: https://lkml.kernel.org/r/20240326021656.202649-3-rick.p.edgecombe@intel.com Signed-off-by: Rick Edgecombe Acked-by: Dave Hansen Acked-by: Liam R. Howlett Reviewed-by: Kirill A. Shutemov Acked-by: Alexei Starovoitov Cc: Dan Williams Cc: Andy Lutomirski Cc: Aneesh Kumar K.V Cc: Borislav Petkov (AMD) Cc: Christophe Leroy Cc: Deepak Gupta Cc: Guo Ren Cc: Helge Deller Cc: H. Peter Anvin (Intel) Cc: Ingo Molnar Cc: "James E.J. Bottomley" Cc: Kees Cook Cc: Mark Brown Cc: Michael Ellerman Cc: Naveen N. Rao Cc: Nicholas Piggin Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Andrew Morton

/dev/port: don't compile file operations without CONFIG_DEVPORT

2024-04-11T13:26:55+00:00

In the future inb() and friends will not be available when compiling with CONFIG_HAS_IOPORT=n so we must only try to access them here if CONFIG_DEVPORT is set which depends on HAS_IOPORT. Co-developed-by: Arnd Bergmann Signed-off-by: Arnd Bergmann Signed-off-by: Niklas Schnelle Link: https://lore.kernel.org/r/20240404114917.3627747-2-schnelle@linux.ibm.com Signed-off-by: Greg Kroah-Hartman

Merge tag 'char-misc-6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc

2023-11-04T00:51:08+00:00

Pull char/misc updates from Greg KH: "Here is the big set of char/misc and other small driver subsystem changes for 6.7-rc1. Included in here are: - IIO subsystem driver updates and additions (largest part of this pull request) - FPGA subsystem driver updates - Counter subsystem driver updates - ICC subsystem driver updates - extcon subsystem driver updates - mei driver updates and additions - nvmem subsystem driver updates and additions - comedi subsystem dependency fixes - parport driver fixups - cdx subsystem driver and core updates - splice support for /dev/zero and /dev/full - other smaller driver cleanups All of these have been in linux-next for a while with no reported issues" * tag 'char-misc-6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (326 commits) cdx: add sysfs for subsystem, class and revision cdx: add sysfs for bus reset cdx: add support for bus enable and disable cdx: Register cdx bus as a device on cdx subsystem cdx: Create symbol namespaces for cdx subsystem cdx: Introduce lock to protect controller ops cdx: Remove cdx controller list from cdx bus system dts: ti: k3-am625-beagleplay: Add beaglecc1352 greybus: Add BeaglePlay Linux Driver dt-bindings: net: Add ti,cc1352p7 dt-bindings: eeprom: at24: allow NVMEM cells based on old syntax dt-bindings: nvmem: SID: allow NVMEM cells based on old syntax Revert "nvmem: add new config option" MAINTAINERS: coresight: Add missing Coresight files misc: pci_endpoint_test: Add deviceID for J721S2 PCIe EP device support firmware: xilinx: Move EXPORT_SYMBOL_GPL next to zynqmp_pm_feature definition uacce: make uacce_class constant ocxl: make ocxl_class constant cxl: make cxl_class constant misc: phantom: make phantom_class constant ...

drivers/char/mem: implement splice() for /dev/zero, /dev/full

2023-10-05T11:34:05+00:00

This allows splicing zeroed pages into a pipe, and allows discarding pages from a pipe by splicing them to /dev/zero. Writing to /dev/zero should have the same effect as writing to /dev/null, and a "splice_write" implementation exists only for /dev/null. (The /dev/zero splice_read implementation could be optimized by pushing references to the global zero page to the pipe, but that's an optimization for another day.) Signed-off-by: Max Kellermann Link: https://lore.kernel.org/r/20230919073743.1066313-1-max.kellermann@ionos.com Signed-off-by: Greg Kroah-Hartman