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gvisor/pkg/usermem
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Dean Deng 05c89af6ed Implement mmap for host fs in vfs2. 
In VFS1, both fs/host and fs/gofer used the same utils for host file mappings.
Refactor parts of fsimpl/gofer to create similar utils to share with
fsimpl/host (memory accounting code moved to fsutil, page rounding arithmetic
moved to usermem).

Updates #1476.

PiperOrigin-RevId: 312345090
 		2020-05-19 13:46:42 -07:00
..
BUILD
…
README.md Update package locations. 2020-01-27 15:31:32 -08:00
access_type.go Update package locations. 2020-01-27 15:31:32 -08:00
addr.go Implement mmap for host fs in vfs2. 2020-05-19 13:46:42 -07:00
addr_range_seq_test.go Update package locations. 2020-01-27 15:31:32 -08:00
addr_range_seq_unsafe.go Update package locations. 2020-01-27 15:31:32 -08:00
bytes_io.go Update package locations. 2020-01-27 15:31:32 -08:00
bytes_io_unsafe.go Update package locations. 2020-01-27 15:31:32 -08:00
usermem.go Remove obsolete TODOs for b/38173783 2020-04-13 11:02:14 -07:00
usermem_arm64.go Update package locations. 2020-01-27 15:31:32 -08:00
usermem_test.go Update package locations. 2020-01-27 15:31:32 -08:00
usermem_x86.go Fix 386 build tags 2020-04-01 10:00:03 -07:00

README.md

This package defines primitives for sentry access to application memory.

Major types:

  • The IO interface represents a virtual address space and provides I/O methods on that address space. IO is the lowest-level primitive. The primary implementation of the IO interface is mm.MemoryManager.

  • IOSequence represents a collection of individually-contiguous address ranges in a IO that is operated on sequentially, analogous to Linux's struct iov_iter.

Major usage patterns:

  • Access to a task's virtual memory, subject to the application's memory protections and while running on that task's goroutine, from a context that is at or above the level of the kernel package (e.g. most syscall implementations in syscalls/linux); use the kernel.Task.Copy* wrappers defined in kernel/task_usermem.go.

  • Access to a task's virtual memory, from a context that is at or above the level of the kernel package, but where any of the above constraints does not hold (e.g. PTRACE_POKEDATA, which ignores application memory protections); obtain the task's mm.MemoryManager by calling kernel.Task.MemoryManager, and call its IO methods directly.

  • Access to a task's virtual memory, from a context that is below the level of the kernel package (e.g. filesystem I/O); clients must pass I/O arguments from higher layers, usually in the form of an IOSequence. The kernel.Task.SingleIOSequence and kernel.Task.IovecsIOSequence functions in kernel/task_usermem.go are convenience functions for doing so.