mm/memfd.c

File Facts

System

Linux kernel

Corpus path

mm/memfd.c

Extension

.c

Size

13213 bytes

Lines

524

Domain

Core OS

Bucket

Memory Management

Inferred role

Core OS: syscall or user/kernel boundary

Status

core implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

• Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.
• Defines or participates in a user/kernel boundary; inspect argument validation, copy_from_user/copy_to_user, credentials, and dispatch target.
• Touches user memory; correctness depends on fault-safe copying and privilege boundary handling.
• Uses kernel synchronization; read lock ordering, sleepability, and interrupt context assumptions before translating.
• Allocates kernel memory; connect allocation flags and lifetime to context constraints.
• Defines or uses C structs; map object ownership, embedded links, reference counts, and lock ownership.

Dependency Surface

• linux/fs.h
• linux/vfs.h
• linux/pagemap.h
• linux/file.h
• linux/mm.h
• linux/sched/signal.h
• linux/khugepaged.h
• linux/syscalls.h
• linux/hugetlb.h
• linux/shmem_fs.h
• linux/memfd.h
• linux/pid_namespace.h
• uapi/linux/memfd.h
• swap.h

Detected Declarations

• syscall memfd_create
• function memfd_folio_has_extra_refs
• function memfd_tag_pins
• function memfd_pin_user_pages
• function get_user_pages
• function xas_for_each_marked
• function memfd_add_seals
• function memfd_get_seals
• function memfd_fcntl
• function check_sysctl_memfd_noexec
• function is_write_sealed
• function check_write_seal
• function memfd_check_seals_mmap
• function sanitize_flags

Annotated Snippet

SYSCALL_DEFINE2(memfd_create,
		const char __user *, uname,
		unsigned int, flags)
{
	char *name __free(kfree) = NULL;
	unsigned int fd_flags;
	int error;

	error = sanitize_flags(&flags);
	if (error < 0)
		return error;

	name = alloc_name(uname);
	if (IS_ERR(name))
		return PTR_ERR(name);

	fd_flags = (flags & MFD_CLOEXEC) ? O_CLOEXEC : 0;
	return FD_ADD(fd_flags, memfd_alloc_file(name, flags));
}

Annotation

• Immediate include surface: `linux/fs.h`, `linux/vfs.h`, `linux/pagemap.h`, `linux/file.h`, `linux/mm.h`, `linux/sched/signal.h`, `linux/khugepaged.h`, `linux/syscalls.h`.
• Detected declarations: `syscall memfd_create`, `function memfd_folio_has_extra_refs`, `function memfd_tag_pins`, `function memfd_pin_user_pages`, `function get_user_pages`, `function xas_for_each_marked`, `function memfd_add_seals`, `function memfd_get_seals`, `function memfd_fcntl`, `function check_sysctl_memfd_noexec`.
• Atlas domain: Core OS / Memory Management.
• Implementation status: core implementation candidate.
• This snippet crosses the user/kernel memory boundary; validate fault handling and access checks before translating the pattern.
• Synchronization appears in or near this file; preserve lock ordering, sleepability, and interrupt-context constraints.

Implementation Notes

• This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
• Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
• Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.