xref: /linux-6.12.1/include/linux/kmsan.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * KMSAN API for subsystems.
 *
 * Copyright (C) 2017-2022 Google LLC
 * Author: Alexander Potapenko <glider@google.com>
 *
 */
#ifndef _LINUX_KMSAN_H
#define _LINUX_KMSAN_H

#include <linux/dma-direction.h>
#include <linux/gfp.h>
#include <linux/kmsan-checks.h>
#include <linux/types.h>

struct page;
struct kmem_cache;
struct task_struct;
struct scatterlist;
struct urb;

#ifdef CONFIG_KMSAN

/**
 * kmsan_task_create() - Initialize KMSAN state for the task.
 * @task: task to initialize.
 */
void kmsan_task_create(struct task_struct *task);

/**
 * kmsan_task_exit() - Notify KMSAN that a task has exited.
 * @task: task about to finish.
 */
void kmsan_task_exit(struct task_struct *task);

/**
 * kmsan_init_shadow() - Initialize KMSAN shadow at boot time.
 *
 * Allocate and initialize KMSAN metadata for early allocations.
 */
void __init kmsan_init_shadow(void);

/**
 * kmsan_init_runtime() - Initialize KMSAN state and enable KMSAN.
 */
void __init kmsan_init_runtime(void);

/**
 * kmsan_memblock_free_pages() - handle freeing of memblock pages.
 * @page:	struct page to free.
 * @order:	order of @page.
 *
 * Freed pages are either returned to buddy allocator or held back to be used
 * as metadata pages.
 */
bool __init __must_check kmsan_memblock_free_pages(struct page *page,
						   unsigned int order);

/**
 * kmsan_alloc_page() - Notify KMSAN about an alloc_pages() call.
 * @page:  struct page pointer returned by alloc_pages().
 * @order: order of allocated struct page.
 * @flags: GFP flags used by alloc_pages()
 *
 * KMSAN marks 1<<@order pages starting at @page as uninitialized, unless
 * @flags contain __GFP_ZERO.
 */
void kmsan_alloc_page(struct page *page, unsigned int order, gfp_t flags);

/**
 * kmsan_free_page() - Notify KMSAN about a free_pages() call.
 * @page:  struct page pointer passed to free_pages().
 * @order: order of deallocated struct page.
 *
 * KMSAN marks freed memory as uninitialized.
 */
void kmsan_free_page(struct page *page, unsigned int order);

/**
 * kmsan_copy_page_meta() - Copy KMSAN metadata between two pages.
 * @dst: destination page.
 * @src: source page.
 *
 * KMSAN copies the contents of metadata pages for @src into the metadata pages
 * for @dst. If @dst has no associated metadata pages, nothing happens.
 * If @src has no associated metadata pages, @dst metadata pages are unpoisoned.
 */
void kmsan_copy_page_meta(struct page *dst, struct page *src);

/**
 * kmsan_slab_alloc() - Notify KMSAN about a slab allocation.
 * @s:      slab cache the object belongs to.
 * @object: object pointer.
 * @flags:  GFP flags passed to the allocator.
 *
 * Depending on cache flags and GFP flags, KMSAN sets up the metadata of the
 * newly created object, marking it as initialized or uninitialized.
 */
void kmsan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags);

/**
 * kmsan_slab_free() - Notify KMSAN about a slab deallocation.
 * @s:      slab cache the object belongs to.
 * @object: object pointer.
 *
 * KMSAN marks the freed object as uninitialized.
 */
void kmsan_slab_free(struct kmem_cache *s, void *object);

/**
 * kmsan_kmalloc_large() - Notify KMSAN about a large slab allocation.
 * @ptr:   object pointer.
 * @size:  object size.
 * @flags: GFP flags passed to the allocator.
 *
 * Similar to kmsan_slab_alloc(), but for large allocations.
 */
void kmsan_kmalloc_large(const void *ptr, size_t size, gfp_t flags);

/**
 * kmsan_kfree_large() - Notify KMSAN about a large slab deallocation.
 * @ptr: object pointer.
 *
 * Similar to kmsan_slab_free(), but for large allocations.
 */
void kmsan_kfree_large(const void *ptr);

/**
 * kmsan_map_kernel_range_noflush() - Notify KMSAN about a vmap.
 * @start:	start of vmapped range.
 * @end:	end of vmapped range.
 * @prot:	page protection flags used for vmap.
 * @pages:	array of pages.
 * @page_shift:	page_shift passed to vmap_range_noflush().
 *
 * KMSAN maps shadow and origin pages of @pages into contiguous ranges in
 * vmalloc metadata address range. Returns 0 on success, callers must check
 * for non-zero return value.
 */
int __must_check kmsan_vmap_pages_range_noflush(unsigned long start,
						unsigned long end,
						pgprot_t prot,
						struct page **pages,
						unsigned int page_shift);

/**
 * kmsan_vunmap_kernel_range_noflush() - Notify KMSAN about a vunmap.
 * @start: start of vunmapped range.
 * @end:   end of vunmapped range.
 *
 * KMSAN unmaps the contiguous metadata ranges created by
 * kmsan_map_kernel_range_noflush().
 */
void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end);

/**
 * kmsan_ioremap_page_range() - Notify KMSAN about a ioremap_page_range() call.
 * @addr:	range start.
 * @end:	range end.
 * @phys_addr:	physical range start.
 * @prot:	page protection flags used for ioremap_page_range().
 * @page_shift:	page_shift argument passed to vmap_range_noflush().
 *
 * KMSAN creates new metadata pages for the physical pages mapped into the
 * virtual memory. Returns 0 on success, callers must check for non-zero return
 * value.
 */
int __must_check kmsan_ioremap_page_range(unsigned long addr, unsigned long end,
					  phys_addr_t phys_addr, pgprot_t prot,
					  unsigned int page_shift);

/**
 * kmsan_iounmap_page_range() - Notify KMSAN about a iounmap_page_range() call.
 * @start: range start.
 * @end:   range end.
 *
 * KMSAN unmaps the metadata pages for the given range and, unlike for
 * vunmap_page_range(), also deallocates them.
 */
void kmsan_iounmap_page_range(unsigned long start, unsigned long end);

/**
 * kmsan_handle_dma() - Handle a DMA data transfer.
 * @page:   first page of the buffer.
 * @offset: offset of the buffer within the first page.
 * @size:   buffer size.
 * @dir:    one of possible dma_data_direction values.
 *
 * Depending on @direction, KMSAN:
 * * checks the buffer, if it is copied to device;
 * * initializes the buffer, if it is copied from device;
 * * does both, if this is a DMA_BIDIRECTIONAL transfer.
 */
void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
		      enum dma_data_direction dir);

/**
 * kmsan_handle_dma_sg() - Handle a DMA transfer using scatterlist.
 * @sg:    scatterlist holding DMA buffers.
 * @nents: number of scatterlist entries.
 * @dir:   one of possible dma_data_direction values.
 *
 * Depending on @direction, KMSAN:
 * * checks the buffers in the scatterlist, if they are copied to device;
 * * initializes the buffers, if they are copied from device;
 * * does both, if this is a DMA_BIDIRECTIONAL transfer.
 */
void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
			 enum dma_data_direction dir);

/**
 * kmsan_handle_urb() - Handle a USB data transfer.
 * @urb:    struct urb pointer.
 * @is_out: data transfer direction (true means output to hardware).
 *
 * If @is_out is true, KMSAN checks the transfer buffer of @urb. Otherwise,
 * KMSAN initializes the transfer buffer.
 */
void kmsan_handle_urb(const struct urb *urb, bool is_out);

/**
 * kmsan_unpoison_entry_regs() - Handle pt_regs in low-level entry code.
 * @regs:	struct pt_regs pointer received from assembly code.
 *
 * KMSAN unpoisons the contents of the passed pt_regs, preventing potential
 * false positive reports. Unlike kmsan_unpoison_memory(),
 * kmsan_unpoison_entry_regs() can be called from the regions where
 * kmsan_in_runtime() returns true, which is the case in early entry code.
 */
void kmsan_unpoison_entry_regs(const struct pt_regs *regs);

/**
 * kmsan_get_metadata() - Return a pointer to KMSAN shadow or origins.
 * @addr:      kernel address.
 * @is_origin: whether to return origins or shadow.
 *
 * Return NULL if metadata cannot be found.
 */
void *kmsan_get_metadata(void *addr, bool is_origin);

/**
 * kmsan_enable_current(): Enable KMSAN for the current task.
 *
 * Each kmsan_enable_current() current call must be preceded by a
 * kmsan_disable_current() call. These call pairs may be nested.
 */
void kmsan_enable_current(void);

/**
 * kmsan_disable_current(): Disable KMSAN for the current task.
 *
 * Each kmsan_disable_current() current call must be followed by a
 * kmsan_enable_current() call. These call pairs may be nested.
 */
void kmsan_disable_current(void);

/**
 * memset_no_sanitize_memory(): Fill memory without KMSAN instrumentation.
 * @s: address of kernel memory to fill.
 * @c: constant byte to fill the memory with.
 * @n: number of bytes to fill.
 *
 * This is like memset(), but without KMSAN instrumentation.
 */
static inline void *memset_no_sanitize_memory(void *s, int c, size_t n)
{
	return __memset(s, c, n);
}

extern bool kmsan_enabled;
extern int panic_on_kmsan;

/*
 * KMSAN performs a lot of consistency checks that are currently enabled by
 * default. BUG_ON is normally discouraged in the kernel, unless used for
 * debugging, but KMSAN itself is a debugging tool, so it makes little sense to
 * recover if something goes wrong.
 */
#define KMSAN_WARN_ON(cond)                                           \
	({                                                            \
		const bool __cond = WARN_ON(cond);                    \
		if (unlikely(__cond)) {                               \
			WRITE_ONCE(kmsan_enabled, false);             \
			if (panic_on_kmsan) {                         \
				/* Can't call panic() here because */ \
				/* of uaccess checks. */              \
				BUG();                                \
			}                                             \
		}                                                     \
		__cond;                                               \
	})

#else

static inline void kmsan_init_shadow(void)
{
}

static inline void kmsan_init_runtime(void)
{
}

static inline bool __must_check kmsan_memblock_free_pages(struct page *page,
							  unsigned int order)
{
	return true;
}

static inline void kmsan_task_create(struct task_struct *task)
{
}

static inline void kmsan_task_exit(struct task_struct *task)
{
}

static inline void kmsan_alloc_page(struct page *page, unsigned int order,
				    gfp_t flags)
{
}

static inline void kmsan_free_page(struct page *page, unsigned int order)
{
}

static inline void kmsan_copy_page_meta(struct page *dst, struct page *src)
{
}

static inline void kmsan_slab_alloc(struct kmem_cache *s, void *object,
				    gfp_t flags)
{
}

static inline void kmsan_slab_free(struct kmem_cache *s, void *object)
{
}

static inline void kmsan_kmalloc_large(const void *ptr, size_t size,
				       gfp_t flags)
{
}

static inline void kmsan_kfree_large(const void *ptr)
{
}

static inline int __must_check kmsan_vmap_pages_range_noflush(
	unsigned long start, unsigned long end, pgprot_t prot,
	struct page **pages, unsigned int page_shift)
{
	return 0;
}

static inline void kmsan_vunmap_range_noflush(unsigned long start,
					      unsigned long end)
{
}

static inline int __must_check kmsan_ioremap_page_range(unsigned long start,
							unsigned long end,
							phys_addr_t phys_addr,
							pgprot_t prot,
							unsigned int page_shift)
{
	return 0;
}

static inline void kmsan_iounmap_page_range(unsigned long start,
					    unsigned long end)
{
}

static inline void kmsan_handle_dma(struct page *page, size_t offset,
				    size_t size, enum dma_data_direction dir)
{
}

static inline void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
				       enum dma_data_direction dir)
{
}

static inline void kmsan_handle_urb(const struct urb *urb, bool is_out)
{
}

static inline void kmsan_unpoison_entry_regs(const struct pt_regs *regs)
{
}

static inline void kmsan_enable_current(void)
{
}

static inline void kmsan_disable_current(void)
{
}

static inline void *memset_no_sanitize_memory(void *s, int c, size_t n)
{
	return memset(s, c, n);
}

#define KMSAN_WARN_ON WARN_ON

#endif

#endif /* _LINUX_KMSAN_H */