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16 July 2024, 22:04:21 UTC
Revision e6bc8833d80fb695515a8144aa1dc13468db9d4d authored by Alexander Potapenko on 27 February 2023, 15:44:58 UTC, committed by Alexander Potapenko on 19 June 2023, 08:56:03 UTC 
string: use __builtin_memcpy() in strlcpy/strlcat
 
lib/string.c is built with -ffreestanding, which prevents the compiler
from replacing certain functions with calls to their library versions.

On the other hand, this also prevents Clang and GCC from instrumenting
calls to memcpy() when building with KASAN, KCSAN or KMSAN:
 - KASAN normally replaces memcpy() with __asan_memcpy() with the
   additional cc-param,asan-kernel-mem-intrinsic-prefix=1;
 - KCSAN and KMSAN replace memcpy() with __tsan_memcpy() and
   __msan_memcpy() by default.

To let the tools catch memory accesses from strlcpy/strlcat, replace
the calls to memcpy() with __builtin_memcpy(), which KASAN, KCSAN and
KMSAN are able to replace even in -ffreestanding mode.

This preserves the behavior in normal builds (__builtin_memcpy() ends up
being replaced with memcpy()), and does not introduce new instrumentation
in unwanted places, as strlcpy/strlcat are already instrumented.

Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Alexander Potapenko <glider@google.com>
Link: https://lore.kernel.org/all/20230224085942.1791837-1-elver@google.com/
Acked-by: Kees Cook <keescook@chromium.org>
1 parent 11aac78
Raw File
Tip revision: e6bc8833d80fb695515a8144aa1dc13468db9d4d authored by Alexander Potapenko on 27 February 2023, 15:44:58 UTC
string: use __builtin_memcpy() in strlcpy/strlcat
Tip revision: e6bc883
swap.h 
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _MM_SWAP_H
#define _MM_SWAP_H

#ifdef CONFIG_SWAP
#include <linux/blk_types.h> /* for bio_end_io_t */

/* linux/mm/page_io.c */
int sio_pool_init(void);
struct swap_iocb;
void swap_readpage(struct page *page, bool do_poll, struct swap_iocb **plug);
void __swap_read_unplug(struct swap_iocb *plug);
static inline void swap_read_unplug(struct swap_iocb *plug)
{
	if (unlikely(plug))
		__swap_read_unplug(plug);
}
void swap_write_unplug(struct swap_iocb *sio);
int swap_writepage(struct page *page, struct writeback_control *wbc);
void __swap_writepage(struct page *page, struct writeback_control *wbc);

/* linux/mm/swap_state.c */
/* One swap address space for each 64M swap space */
#define SWAP_ADDRESS_SPACE_SHIFT	14
#define SWAP_ADDRESS_SPACE_PAGES	(1 << SWAP_ADDRESS_SPACE_SHIFT)
extern struct address_space *swapper_spaces[];
#define swap_address_space(entry)			    \
	(&swapper_spaces[swp_type(entry)][swp_offset(entry) \
		>> SWAP_ADDRESS_SPACE_SHIFT])

void show_swap_cache_info(void);
bool add_to_swap(struct folio *folio);
void *get_shadow_from_swap_cache(swp_entry_t entry);
int add_to_swap_cache(struct folio *folio, swp_entry_t entry,
		      gfp_t gfp, void **shadowp);
void __delete_from_swap_cache(struct folio *folio,
			      swp_entry_t entry, void *shadow);
void delete_from_swap_cache(struct folio *folio);
void clear_shadow_from_swap_cache(int type, unsigned long begin,
				  unsigned long end);
struct folio *swap_cache_get_folio(swp_entry_t entry,
		struct vm_area_struct *vma, unsigned long addr);
struct folio *filemap_get_incore_folio(struct address_space *mapping,
		pgoff_t index);

struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
				   struct vm_area_struct *vma,
				   unsigned long addr,
				   bool do_poll,
				   struct swap_iocb **plug);
struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
				     struct vm_area_struct *vma,
				     unsigned long addr,
				     bool *new_page_allocated);
struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t flag,
				    struct vm_fault *vmf);
struct page *swapin_readahead(swp_entry_t entry, gfp_t flag,
			      struct vm_fault *vmf);

static inline unsigned int folio_swap_flags(struct folio *folio)
{
	return page_swap_info(&folio->page)->flags;
}
#else /* CONFIG_SWAP */
struct swap_iocb;
static inline void swap_readpage(struct page *page, bool do_poll,
		struct swap_iocb **plug)
{
}
static inline void swap_write_unplug(struct swap_iocb *sio)
{
}

static inline struct address_space *swap_address_space(swp_entry_t entry)
{
	return NULL;
}

static inline void show_swap_cache_info(void)
{
}

static inline struct page *swap_cluster_readahead(swp_entry_t entry,
				gfp_t gfp_mask, struct vm_fault *vmf)
{
	return NULL;
}

static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
			struct vm_fault *vmf)
{
	return NULL;
}

static inline int swap_writepage(struct page *p, struct writeback_control *wbc)
{
	return 0;
}

static inline struct folio *swap_cache_get_folio(swp_entry_t entry,
		struct vm_area_struct *vma, unsigned long addr)
{
	return NULL;
}

static inline
struct folio *filemap_get_incore_folio(struct address_space *mapping,
		pgoff_t index)
{
	return filemap_get_folio(mapping, index);
}

static inline bool add_to_swap(struct folio *folio)
{
	return false;
}

static inline void *get_shadow_from_swap_cache(swp_entry_t entry)
{
	return NULL;
}

static inline int add_to_swap_cache(struct folio *folio, swp_entry_t entry,
					gfp_t gfp_mask, void **shadowp)
{
	return -1;
}

static inline void __delete_from_swap_cache(struct folio *folio,
					swp_entry_t entry, void *shadow)
{
}

static inline void delete_from_swap_cache(struct folio *folio)
{
}

static inline void clear_shadow_from_swap_cache(int type, unsigned long begin,
				unsigned long end)
{
}

static inline unsigned int folio_swap_flags(struct folio *folio)
{
	return 0;
}
#endif /* CONFIG_SWAP */
#endif /* _MM_SWAP_H */
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