2020-04-20 05:39:33

by Christophe Leroy

Subject: [PATCH v2] powerpc/8xx: Fix STRICT_KERNEL_RWX startup test failure

WRITE_RO lkdtm test works.

But when selecting CONFIG_DEBUG_RODATA_TEST, the kernel reports
rodata_test: test data was not read only

This is because when rodata test runs, there are still old entries
in TLB.

Flush TLB after setting kernel pages RO or NX.

Fixes: d5f17ee96447 ("powerpc/8xx: don't disable large TLBs with CONFIG_STRICT_KERNEL_RWX")
Cc: [email protected]
Signed-off-by: Christophe Leroy <[email protected]>
---
arch/powerpc/mm/nohash/8xx.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/powerpc/mm/nohash/8xx.c b/arch/powerpc/mm/nohash/8xx.c
index 3189308dece4..d83a12c5bc7f 100644
--- a/arch/powerpc/mm/nohash/8xx.c
+++ b/arch/powerpc/mm/nohash/8xx.c
@@ -185,6 +185,7 @@ void mmu_mark_initmem_nx(void)
mmu_mapin_ram_chunk(etext8, einittext8, PAGE_KERNEL);
}
}
+ _tlbil_all();
}

#ifdef CONFIG_STRICT_KERNEL_RWX
@@ -199,6 +200,8 @@ void mmu_mark_rodata_ro(void)
~(LARGE_PAGE_SIZE_8M - 1)));
mmu_patch_addis(&patch__dtlbmiss_romem_top, -__pa(_sinittext));

+ _tlbil_all();
+
/* Update page tables for PTDUMP and BDI */
mmu_mapin_ram_chunk(0, sinittext, __pgprot(0));
mmu_mapin_ram_chunk(0, etext, PAGE_KERNEL_ROX);
--
2.25.0

2020-04-25 23:53:54

by Michael Ellerman

Subject: Re: [PATCH v2] powerpc/8xx: Fix STRICT_KERNEL_RWX startup test failure

On Mon, 2020-04-20 at 05:37:42 UTC, Christophe Leroy wrote:
> WRITE_RO lkdtm test works.
>
> But when selecting CONFIG_DEBUG_RODATA_TEST, the kernel reports
> rodata_test: test data was not read only
>
> This is because when rodata test runs, there are still old entries
> in TLB.
>
> Flush TLB after setting kernel pages RO or NX.
>
> Fixes: d5f17ee96447 ("powerpc/8xx: don't disable large TLBs with CONFIG_STRICT_KERNEL_RWX")
> Cc: [email protected]
> Signed-off-by: Christophe Leroy <[email protected]>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/b61c38baa98056d4802ff5be5cfb979efc2d0f7a

cheers