Hi James,
On Fri, Jul 06, 2018 at 03:41:07PM +0100, James Morse wrote:
> I missed one: head.S has a call to kasan_early_init() before start_kernel(),
> this goes messing with the page tables, and calls pgd_offset_k(), which pulls
> in
> swapper_pg_dir. This one is enabled by CONFIG_KASAN.
>
> Something like that same hunk [0] in kasan_early_init() fixes it. This is
> still
> within arch/arm64, so I still think we should get away without some #ifdeffery
> to override the core-code's initial setup of swapper_pg_dir...
I'm sorry to reply you so late, I missed this email before.
In order to ensure that pgd_offset_k() works properly, I update
init_mm.pgd by introducing set_init_mm_pgd(). And its implementation is
like this:
>diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>index 65f86271f02b..e4f0868b4cfd 100644
>--- a/arch/arm64/mm/mmu.c
>+++ b/arch/arm64/mm/mmu.c
>@@ -623,6 +623,19 @@ static void __init map_kernel(pgd_t *pgdp)
> kasan_copy_shadow(pgdp);
> }
>
>+void __init set_init_mm_pgd(pgd_t *pgd)
>+{
>+ pgd_t **addr = &(init_mm.pgd);
>+
>+ asm volatile("str %x0, [%1]\n"
>+ : : "r" (pgd), "r" (addr) : "memory");
>+}
> /*
> * paging_init() sets up the page tables, initialises the zone memory
> * maps and sets up the zero page.
The purpose of using assembly is to prevent KASAN instrumentation, as
KASAN has not been initialized when this function is called:
>diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
>index c3e4b1886cde..ede2e964592b 100644
>--- a/arch/arm64/kernel/head.S
>+++ b/arch/arm64/kernel/head.S
>@@ -439,6 +438,9 @@ __primary_switched:
> bl __pi_memset
> dsb ishst // Make zero page visible to
> PTW
>
>+ adrp x0, init_pg_dir
>+ bl set_init_mm_pgd
>+
> #ifdef CONFIG_KASAN
> bl kasan_early_init
> #endif
What do you think?
