Messages in this thread | | | From | Christophe Leroy <> | Subject | Re: [PATCH] powerpc/Kconfig: Force THREAD_SHIFT to at least 14 with KASAN | Date | Tue, 31 May 2022 10:41:00 +0000 |
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Le 31/05/2022 à 09:41, Christoph Hellwig a écrit : > On Tue, May 31, 2022 at 04:16:19PM +1000, Michael Ellerman wrote: >> I was thinking of doing it in C, similar to the way arm64 handles it. >> >> Something like below. It means we always double the stack size when >> KASAN is enabled. I think it's preferable, as it will always work >> regardless of whether the user has an old .config (or is bisectting)? > > Is there any reason to even offer the Kconfig? It is super cryptic and > just picking the right value directly in the header would seem much > more sensible:
Looks like it was added by commit 476134070c03 ("powerpc: Move THREAD_SHIFT config to Kconfig") in 2017. https://github.com/torvalds/linux/commit/476134070c037820bd909ff6e43e0d3eae33f376
Seems like powerpc is the only architecture with it configurable via Kconfig.
I'd be inclined to reverting that commit, and then I'd do something similar to arm64:
#ifdef CONFIG_KSAN #define KASAN_THREAD_SHIFT 1 #else #define KASAN_THREAD_SHIFT 0 #endif
#if defined(CONFIG_PPC_256K_PAGES) #define MIN_THREAD_SHIFT (15 + KASAN_THREAD_SHIFT) #elif defined(CONFIG_PPC64) #define MIN_THREAD_SHIFT (14 + KASAN_THREAD_SHIFT) #else #define MIN_THREAD_SHIFT (13 + KASAN_THREAD_SHIFT) #endif
#if defined(CONFIG_VMAP_STACK) && (MIN_THREAD_SHIFT < PAGE_SHIFT) #define THREAD_SHIFT PAGE_SHIFT #else #define THREAD_SHIFT MIN_THREAD_SHIFT #endif
And maybe the CONFIG_PPC_256K_PAGES case is already big enough and doesn't require the + 1 for KASAN.
> > #if defined(CONFIG_PPC_256K_PAGES) > #define MIN_THREAD_SHIFT 15 > #elif defined(CONFIG_PPC64) > #define MIN_THREAD_SHIFT 14 > #else > #define MIN_THREAD_SHIFT 13 > #endif > > #ifdef CONFIG_KASAN > #define THREAD_SHIFT (MIN_THREAD_SHIFT + 1) > #else > #define THREAD_SHIFT MIN_THREAD_SHIFT > #endif > > #if defined(CONFIG_VMAP_STACK) && THREAD_SHIFT < PAGE_SHIFT > #undef THREAD_SHIFT > #define THREAD_SHIFT PAGE_SHIFT > #endif
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