Commit 5ec5ac4c authored by Tiezhu Yang's avatar Tiezhu Yang Committed by Huacai Chen
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LoongArch: Rework KASAN initialization for PTW-enabled systems 



kasan_init_generic() indicates that kasan is fully initialized, so it
should be put at end of kasan_init().

Otherwise bringing up the primary CPU failed when CONFIG_KASAN is set
on PTW-enabled systems, here are the call chains:

    kernel_entry()
      start_kernel()
        setup_arch()
          kasan_init()
            kasan_init_generic()

The reason is PTW-enabled systems have speculative accesses which means
memory accesses to the shadow memory after kasan_init() may be executed
by hardware before. However, accessing shadow memory is safe only after
kasan fully initialized because kasan_init() uses a temporary PGD table
until we have populated all levels of shadow page tables and writen the
PGD register. Moving kasan_init_generic() later can defer the occasion
of kasan_enabled(), so as to avoid speculative accesses on shadow pages.

After moving kasan_init_generic() to the end, kasan_init() can no longer
call kasan_mem_to_shadow() for shadow address conversion because it will
always return kasan_early_shadow_page. On the other hand, we should keep
the current logic of kasan_mem_to_shadow() for both the early and final
stage because there may be instrumentation before kasan_init().

To solve this, we factor out a new mem_to_shadow() function from current
kasan_mem_to_shadow() for the shadow address conversion in kasan_init().

Cc: stable@vger.kernel.org
Signed-off-by: default avatarTiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent 7cb37af6

arch/loongarch/mm/kasan_init.c

+40 −38
Original line number Diff line number Diff line
@@ -40,14 +40,11 @@ static pgd_t kasan_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE); 
#define __pte_none(early, pte) (early ? pte_none(pte) : \

((pte_val(pte) & _PFN_MASK) == (unsigned long)__pa(kasan_early_shadow_page)))



void *kasan_mem_to_shadow(const void *addr)

static void *mem_to_shadow(const void *addr)

{

	if (!kasan_enabled()) {

		return (void *)(kasan_early_shadow_page);

	} else {

	unsigned long offset = 0;

	unsigned long maddr = (unsigned long)addr;

	unsigned long xrange = (maddr >> XRANGE_SHIFT) & 0xffff;

		unsigned long offset = 0;



	if (maddr >= FIXADDR_START)

		return (void *)(kasan_early_shadow_page);
@@ -73,6 +70,13 @@ void *kasan_mem_to_shadow(const void *addr) 


	return (void *)((maddr >> KASAN_SHADOW_SCALE_SHIFT) + offset);

}



void *kasan_mem_to_shadow(const void *addr)

{

	if (kasan_enabled())

		return mem_to_shadow(addr);

	else

		return (void *)(kasan_early_shadow_page);

}



const void *kasan_shadow_to_mem(const void *shadow_addr)
@@ -293,11 +297,8 @@ void __init kasan_init(void) 
	/* Maps everything to a single page of zeroes */

	kasan_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, NUMA_NO_NODE, true);



	kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START),

					kasan_mem_to_shadow((void *)KFENCE_AREA_END));



	/* Enable KASAN here before kasan_mem_to_shadow(). */

	kasan_init_generic();

	kasan_populate_early_shadow(mem_to_shadow((void *)VMALLOC_START),

					mem_to_shadow((void *)KFENCE_AREA_END));



	/* Populate the linear mapping */

	for_each_mem_range(i, &pa_start, &pa_end) {
@@ -307,13 +308,13 @@ void __init kasan_init(void) 
		if (start >= end)

			break;



		kasan_map_populate((unsigned long)kasan_mem_to_shadow(start),

			(unsigned long)kasan_mem_to_shadow(end), NUMA_NO_NODE);

		kasan_map_populate((unsigned long)mem_to_shadow(start),

			(unsigned long)mem_to_shadow(end), NUMA_NO_NODE);

	}



	/* Populate modules mapping */

	kasan_map_populate((unsigned long)kasan_mem_to_shadow((void *)MODULES_VADDR),

		(unsigned long)kasan_mem_to_shadow((void *)MODULES_END), NUMA_NO_NODE);

	kasan_map_populate((unsigned long)mem_to_shadow((void *)MODULES_VADDR),

		(unsigned long)mem_to_shadow((void *)MODULES_END), NUMA_NO_NODE);

	/*

	 * KAsan may reuse the contents of kasan_early_shadow_pte directly, so we

	 * should make sure that it maps the zero page read-only.
@@ -328,4 +329,5 @@ void __init kasan_init(void) 


	/* At this point kasan is fully initialized. Enable error messages */

	init_task.kasan_depth = 0;

	kasan_init_generic();

}