* [PATCH] powerpc/32s: Fix boot failure with KASAN + SMP + JUMP_LABEL_FEATURE_CHECK_DEBUG
@ 2022-07-01 6:06 ` Christophe Leroy
0 siblings, 0 replies; 4+ messages in thread
From: Christophe Leroy @ 2022-07-01 6:06 UTC (permalink / raw)
To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman
Cc: Christophe Leroy, linux-kernel, linuxppc-dev, Erhard Furtner
Since commit 4291d085b0b0 ("powerpc/32s: Make pte_update() non
atomic on 603 core"), pte_update() has been using
mmu_has_feature(MMU_FTR_HPTE_TABLE) to avoid a useless atomic
operation on 603 cores.
When kasan_early_init() sets up the early zero shadow, it uses
__set_pte_at(). On book3s/32, __set_pte_at() calls pte_update()
when CONFIG_SMP is selected in order to ensure the preservation of
_PAGE_HASHPTE in case of concurrent update of the PTE. But that's
too early for mmu_has_feature(), so when
CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG is selected, mmu_has_feature()
calls printk(). That's too early to call printk() because KASAN
early zero shadow page is not set up yet. It leads to a deadlock.
However, when kasan_early_init() is called, there is only one CPU
running and no risk of concurrent PTE update. So __set_pte_at() can
be called with the 'percpu' flag. With that flag set, the PTE is
written directly instead of being written via pte_update().
Reported-by: Erhard Furtner <erhard_f@mailbox.org>
Fixes: 4291d085b0b0 ("powerpc/32s: Make pte_update() non atomic on 603 core")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
arch/powerpc/mm/kasan/init_32.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/mm/kasan/init_32.c b/arch/powerpc/mm/kasan/init_32.c
index f3e4d069e0ba..a70828a6d935 100644
--- a/arch/powerpc/mm/kasan/init_32.c
+++ b/arch/powerpc/mm/kasan/init_32.c
@@ -25,7 +25,7 @@ static void __init kasan_populate_pte(pte_t *ptep, pgprot_t prot)
int i;
for (i = 0; i < PTRS_PER_PTE; i++, ptep++)
- __set_pte_at(&init_mm, va, ptep, pfn_pte(PHYS_PFN(pa), prot), 0);
+ __set_pte_at(&init_mm, va, ptep, pfn_pte(PHYS_PFN(pa), prot), 1);
}
int __init kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_end)
--
2.36.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH] powerpc/32s: Fix boot failure with KASAN + SMP + JUMP_LABEL_FEATURE_CHECK_DEBUG
@ 2022-07-01 6:06 ` Christophe Leroy
0 siblings, 0 replies; 4+ messages in thread
From: Christophe Leroy @ 2022-07-01 6:06 UTC (permalink / raw)
To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman
Cc: Erhard Furtner, linuxppc-dev, linux-kernel
Since commit 4291d085b0b0 ("powerpc/32s: Make pte_update() non
atomic on 603 core"), pte_update() has been using
mmu_has_feature(MMU_FTR_HPTE_TABLE) to avoid a useless atomic
operation on 603 cores.
When kasan_early_init() sets up the early zero shadow, it uses
__set_pte_at(). On book3s/32, __set_pte_at() calls pte_update()
when CONFIG_SMP is selected in order to ensure the preservation of
_PAGE_HASHPTE in case of concurrent update of the PTE. But that's
too early for mmu_has_feature(), so when
CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG is selected, mmu_has_feature()
calls printk(). That's too early to call printk() because KASAN
early zero shadow page is not set up yet. It leads to a deadlock.
However, when kasan_early_init() is called, there is only one CPU
running and no risk of concurrent PTE update. So __set_pte_at() can
be called with the 'percpu' flag. With that flag set, the PTE is
written directly instead of being written via pte_update().
Reported-by: Erhard Furtner <erhard_f@mailbox.org>
Fixes: 4291d085b0b0 ("powerpc/32s: Make pte_update() non atomic on 603 core")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
arch/powerpc/mm/kasan/init_32.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/mm/kasan/init_32.c b/arch/powerpc/mm/kasan/init_32.c
index f3e4d069e0ba..a70828a6d935 100644
--- a/arch/powerpc/mm/kasan/init_32.c
+++ b/arch/powerpc/mm/kasan/init_32.c
@@ -25,7 +25,7 @@ static void __init kasan_populate_pte(pte_t *ptep, pgprot_t prot)
int i;
for (i = 0; i < PTRS_PER_PTE; i++, ptep++)
- __set_pte_at(&init_mm, va, ptep, pfn_pte(PHYS_PFN(pa), prot), 0);
+ __set_pte_at(&init_mm, va, ptep, pfn_pte(PHYS_PFN(pa), prot), 1);
}
int __init kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_end)
--
2.36.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] powerpc/32s: Fix boot failure with KASAN + SMP + JUMP_LABEL_FEATURE_CHECK_DEBUG
2022-07-01 6:06 ` Christophe Leroy
@ 2022-07-29 13:02 ` Michael Ellerman
-1 siblings, 0 replies; 4+ messages in thread
From: Michael Ellerman @ 2022-07-29 13:02 UTC (permalink / raw)
To: Christophe Leroy, Benjamin Herrenschmidt, Paul Mackerras,
Michael Ellerman
Cc: linuxppc-dev, Erhard Furtner, linux-kernel
On Fri, 1 Jul 2022 08:06:15 +0200, Christophe Leroy wrote:
> Since commit 4291d085b0b0 ("powerpc/32s: Make pte_update() non
> atomic on 603 core"), pte_update() has been using
> mmu_has_feature(MMU_FTR_HPTE_TABLE) to avoid a useless atomic
> operation on 603 cores.
>
> When kasan_early_init() sets up the early zero shadow, it uses
> __set_pte_at(). On book3s/32, __set_pte_at() calls pte_update()
> when CONFIG_SMP is selected in order to ensure the preservation of
> _PAGE_HASHPTE in case of concurrent update of the PTE. But that's
> too early for mmu_has_feature(), so when
> CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG is selected, mmu_has_feature()
> calls printk(). That's too early to call printk() because KASAN
> early zero shadow page is not set up yet. It leads to a deadlock.
>
> [...]
Applied to powerpc/next.
[1/1] powerpc/32s: Fix boot failure with KASAN + SMP + JUMP_LABEL_FEATURE_CHECK_DEBUG
https://git.kernel.org/powerpc/c/6042a1652d643d1d34fa89bb314cb102960c0800
cheers
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] powerpc/32s: Fix boot failure with KASAN + SMP + JUMP_LABEL_FEATURE_CHECK_DEBUG
@ 2022-07-29 13:02 ` Michael Ellerman
0 siblings, 0 replies; 4+ messages in thread
From: Michael Ellerman @ 2022-07-29 13:02 UTC (permalink / raw)
To: Christophe Leroy, Benjamin Herrenschmidt, Paul Mackerras,
Michael Ellerman
Cc: Erhard Furtner, linuxppc-dev, linux-kernel
On Fri, 1 Jul 2022 08:06:15 +0200, Christophe Leroy wrote:
> Since commit 4291d085b0b0 ("powerpc/32s: Make pte_update() non
> atomic on 603 core"), pte_update() has been using
> mmu_has_feature(MMU_FTR_HPTE_TABLE) to avoid a useless atomic
> operation on 603 cores.
>
> When kasan_early_init() sets up the early zero shadow, it uses
> __set_pte_at(). On book3s/32, __set_pte_at() calls pte_update()
> when CONFIG_SMP is selected in order to ensure the preservation of
> _PAGE_HASHPTE in case of concurrent update of the PTE. But that's
> too early for mmu_has_feature(), so when
> CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG is selected, mmu_has_feature()
> calls printk(). That's too early to call printk() because KASAN
> early zero shadow page is not set up yet. It leads to a deadlock.
>
> [...]
Applied to powerpc/next.
[1/1] powerpc/32s: Fix boot failure with KASAN + SMP + JUMP_LABEL_FEATURE_CHECK_DEBUG
https://git.kernel.org/powerpc/c/6042a1652d643d1d34fa89bb314cb102960c0800
cheers
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-07-29 13:13 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2022-07-01 6:06 [PATCH] powerpc/32s: Fix boot failure with KASAN + SMP + JUMP_LABEL_FEATURE_CHECK_DEBUG Christophe Leroy
2022-07-01 6:06 ` Christophe Leroy
2022-07-29 13:02 ` Michael Ellerman
2022-07-29 13:02 ` Michael Ellerman
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