// SPDX-License-Identifier: GPL-2.0
/*
* KMSAN shadow implementation.
*
* Copyright (C) 2017-2022 Google LLC
* Author: Alexander Potapenko <[email protected]>
*
*/
#include <asm/kmsan.h>
#include <asm/tlbflush.h>
#include <linux/cacheflush.h>
#include <linux/memblock.h>
#include <linux/mm_types.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/stddef.h>
#include "../internal.h"
#include "kmsan.h"
#define shadow_page_for(page) ((page)->kmsan_shadow)
#define origin_page_for(page) ((page)->kmsan_origin)
static void *shadow_ptr_for(struct page *page)
{
return page_address(shadow_page_for(page));
}
static void *origin_ptr_for(struct page *page)
{
return page_address(origin_page_for(page));
}
static bool page_has_metadata(struct page *page)
{
return shadow_page_for(page) && origin_page_for(page);
}
static void set_no_shadow_origin_page(struct page *page)
{
shadow_page_for(page) = NULL;
origin_page_for(page) = NULL;
}
/*
* Dummy load and store pages to be used when the real metadata is unavailable.
* There are separate pages for loads and stores, so that every load returns a
* zero, and every store doesn't affect other loads.
*/
static char dummy_load_page[PAGE_SIZE] __aligned(PAGE_SIZE);
static char dummy_store_page[PAGE_SIZE] __aligned(PAGE_SIZE);
static unsigned long vmalloc_meta(void *addr, bool is_origin)
{
unsigned long addr64 = (unsigned long)addr, off;
KMSAN_WARN_ON(is_origin && !IS_ALIGNED(addr64, KMSAN_ORIGIN_SIZE));
if (kmsan_internal_is_vmalloc_addr(addr)) {
off = addr64 - VMALLOC_START;
return off + (is_origin ? KMSAN_VMALLOC_ORIGIN_START :
KMSAN_VMALLOC_SHADOW_START);
}
if (kmsan_internal_is_module_addr(addr)) {
off = addr64 - MODULES_VADDR;
return off + (is_origin ? KMSAN_MODULES_ORIGIN_START :
KMSAN_MODULES_SHADOW_START);
}
return 0;
}
static struct page *virt_to_page_or_null(void *vaddr)
{
if (kmsan_virt_addr_valid(vaddr))
return virt_to_page(vaddr);
else
return NULL;
}
struct shadow_origin_ptr kmsan_get_shadow_origin_ptr(void *address, u64 size,
bool store)
{
struct shadow_origin_ptr ret;
void *shadow;
/*
* Even if we redirect this memory access to the dummy page, it will
* go out of bounds.
*/
KMSAN_WARN_ON(size > PAGE_SIZE);
if (!kmsan_enabled)
goto return_dummy;
KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(address, size));
shadow = kmsan_get_metadata(address, KMSAN_META_SHADOW);
if (!shadow)
goto return_dummy;
ret.shadow = shadow;
ret.origin = kmsan_get_metadata(address, KMSAN_META_ORIGIN);
return ret;
return_dummy:
if (store) {
/* Ignore this store. */
ret.shadow = dummy_store_page;
ret.origin = dummy_store_page;
} else {
/* This load will return zero. */
ret.shadow = dummy_load_page;
ret.origin = dummy_load_page;
}
return ret;
}
/*
* Obtain the shadow or origin pointer for the given address, or NULL if there's
* none. The caller must check the return value for being non-NULL if needed.
* The return value of this function should not depend on whether we're in the
* runtime or not.
*/
void *kmsan_get_metadata(void *address, bool is_origin)
{
u64 addr = (u64)address, off;
struct page *page;
void *ret;
if (is_origin)
addr = ALIGN_DOWN(addr, KMSAN_ORIGIN_SIZE);
address = (void *)addr;
if (kmsan_internal_is_vmalloc_addr(address) ||
kmsan_internal_is_module_addr(address))
return (void *)vmalloc_meta(address, is_origin);
ret = arch_kmsan_get_meta_or_null(address, is_origin);
if (ret)
return ret;
page = virt_to_page_or_null(address);
if (!page)
return NULL;
if (!page_has_metadata(page))
return NULL;
off = offset_in_page(addr);
return (is_origin ? origin_ptr_for(page) : shadow_ptr_for(page)) + off;
}
void kmsan_copy_page_meta(struct page *dst, struct page *src)
{
if (!kmsan_enabled || kmsan_in_runtime())
return;
if (!dst || !page_has_metadata(dst))
return;
if (!src || !page_has_metadata(src)) {
kmsan_internal_unpoison_memory(page_address(dst), PAGE_SIZE,
/*checked*/ false);
return;
}
kmsan_enter_runtime();
__memcpy(shadow_ptr_for(dst), shadow_ptr_for(src), PAGE_SIZE);
__memcpy(origin_ptr_for(dst), origin_ptr_for(src), PAGE_SIZE);
kmsan_leave_runtime();
}
EXPORT_SYMBOL(kmsan_copy_page_meta);
void kmsan_alloc_page(struct page *page, unsigned int order, gfp_t flags)
{
bool initialized = (flags & __GFP_ZERO) || !kmsan_enabled;
struct page *shadow, *origin;
depot_stack_handle_t handle;
int pages = 1 << order;
if (!page)
return;
shadow = shadow_page_for(page);
origin = origin_page_for(page);
if (initialized) {
__memset(page_address(shadow), 0, PAGE_SIZE * pages);
__memset(page_address(origin), 0, PAGE_SIZE * pages);
return;
}
/* Zero pages allocated by the runtime should also be initialized. */
if (kmsan_in_runtime())
return;
__memset(page_address(shadow), -1, PAGE_SIZE * pages);
kmsan_enter_runtime();
handle = kmsan_save_stack_with_flags(flags, /*extra_bits*/ 0);
kmsan_leave_runtime();
/*
* Addresses are page-aligned, pages are contiguous, so it's ok
* to just fill the origin pages with @handle.
*/
for (int i = 0; i < PAGE_SIZE * pages / sizeof(handle); i++)
((depot_stack_handle_t *)page_address(origin))[i] = handle;
}
void kmsan_free_page(struct page *page, unsigned int order)
{
if (!kmsan_enabled || kmsan_in_runtime())
return;
kmsan_enter_runtime();
kmsan_internal_poison_memory(page_address(page),
page_size(page),
GFP_KERNEL,
KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
kmsan_leave_runtime();
}
int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,
pgprot_t prot, struct page **pages,
unsigned int page_shift)
{
unsigned long shadow_start, origin_start, shadow_end, origin_end;
struct page **s_pages, **o_pages;
int nr, mapped, err = 0;
if (!kmsan_enabled)
return 0;
shadow_start = vmalloc_meta((void *)start, KMSAN_META_SHADOW);
shadow_end = vmalloc_meta((void *)end, KMSAN_META_SHADOW);
if (!shadow_start)
return 0;
nr = (end - start) / PAGE_SIZE;
s_pages = kcalloc(nr, sizeof(*s_pages), GFP_KERNEL);
o_pages = kcalloc(nr, sizeof(*o_pages), GFP_KERNEL);
if (!s_pages || !o_pages) {
err = -ENOMEM;
goto ret;
}
for (int i = 0; i < nr; i++) {
s_pages[i] = shadow_page_for(pages[i]);
o_pages[i] = origin_page_for(pages[i]);
}
prot = PAGE_KERNEL;
origin_start = vmalloc_meta((void *)start, KMSAN_META_ORIGIN);
origin_end = vmalloc_meta((void *)end, KMSAN_META_ORIGIN);
kmsan_enter_runtime();
mapped = __vmap_pages_range_noflush(shadow_start, shadow_end, prot,
s_pages, page_shift);
if (mapped) {
err = mapped;
goto ret;
}
mapped = __vmap_pages_range_noflush(origin_start, origin_end, prot,
o_pages, page_shift);
if (mapped) {
err = mapped;
goto ret;
}
kmsan_leave_runtime();
flush_tlb_kernel_range(shadow_start, shadow_end);
flush_tlb_kernel_range(origin_start, origin_end);
flush_cache_vmap(shadow_start, shadow_end);
flush_cache_vmap(origin_start, origin_end);
ret:
kfree(s_pages);
kfree(o_pages);
return err;
}
/* Allocate metadata for pages allocated at boot time. */
void __init kmsan_init_alloc_meta_for_range(void *start, void *end)
{
struct page *shadow_p, *origin_p;
void *shadow, *origin;
struct page *page;
u64 size;
start = (void *)PAGE_ALIGN_DOWN((u64)start);
size = PAGE_ALIGN((u64)end - (u64)start);
shadow = memblock_alloc(size, PAGE_SIZE);
origin = memblock_alloc(size, PAGE_SIZE);
if (!shadow || !origin)
panic("%s: Failed to allocate metadata memory for early boot range of size %llu",
__func__, size);
for (u64 addr = 0; addr < size; addr += PAGE_SIZE) {
page = virt_to_page_or_null((char *)start + addr);
shadow_p = virt_to_page((char *)shadow + addr);
set_no_shadow_origin_page(shadow_p);
shadow_page_for(page) = shadow_p;
origin_p = virt_to_page((char *)origin + addr);
set_no_shadow_origin_page(origin_p);
origin_page_for(page) = origin_p;
}
}
void kmsan_setup_meta(struct page *page, struct page *shadow,
struct page *origin, int order)
{
for (int i = 0; i < (1 << order); i++) {
set_no_shadow_origin_page(&shadow[i]);
set_no_shadow_origin_page(&origin[i]);
shadow_page_for(&page[i]) = &shadow[i];
origin_page_for(&page[i]) = &origin[i];
}
}
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