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Groups > linux.kernel > #1283166
| From | Daniel Cashman <dcashman@android.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS. |
| Date | 2015-12-03 17:20 +0100 |
| Message-ID | <qBELU-7sA-19@gated-at.bofh.it> (permalink) |
| References | <qAZz4-5UF-13@gated-at.bofh.it> <qAZz4-5UF-15@gated-at.bofh.it> <qAZz4-5UF-17@gated-at.bofh.it> <qAZz4-5UF-11@gated-at.bofh.it> <qBB1E-4Pm-9@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 12/3/15 4:17 AM, Will Deacon wrote: >> + select HAVE_ARCH_MMAP_RND_BITS if MMU >> + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT > > You can drop the 'if MMU' bits, since we don't support !MMU on arm64. Ok, will do. I was a little uneasy leaving it implicit, but even if something w/out MMU on arm64 shows up, it'll easily be corrected. >> +config ARCH_MMAP_RND_BITS_MIN >> + default 15 if ARM64_64K_PAGES >> + default 17 if ARM64_16K_PAGES >> + default 19 > > Is this correct? We currently have a mask of 0x3ffff, so that's 18 bits. Off-by-one errors provide a good example of why hardening features are useful? =/ Will change. >> +config ARCH_MMAP_RND_BITS_MAX >> + default 19 if ARM64_VA_BITS=36 >> + default 20 if ARM64_64K_PAGES && ARM64_VA_BITS=39 >> + default 22 if ARM64_16K_PAGES && ARM64_VA_BITS=39 >> + default 24 if ARM64_VA_BITS=39 >> + default 23 if ARM64_64K_PAGES && ARM64_VA_BITS=42 >> + default 25 if ARM64_16K_PAGES && ARM64_VA_BITS=42 >> + default 27 if ARM64_VA_BITS=42 >> + default 30 if ARM64_VA_BITS=47 >> + default 29 if ARM64_64K_PAGES && ARM64_VA_BITS=48 >> + default 31 if ARM64_16K_PAGES && ARM64_VA_BITS=48 >> + default 33 if ARM64_VA_BITS=48 >> + default 15 if ARM64_64K_PAGES >> + default 17 if ARM64_16K_PAGES >> + default 19 > > Could you add a comment above this with the formula > (VA_BITS - PAGE_SHIFT - 3), please, so that we can update this easily in > the future if we need to? > Yes, seems reasonable. Time will tell if this remains true for all architectures, or even here, but it would be good to document it where someone considering a change could easily find it. Thank You, Dan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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[PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS. Daniel Cashman <dcashman@android.com> - 2015-12-01 21:20 +0100
[PATCH v5 4/4] x86: mm: support ARCH_MMAP_RND_BITS. Daniel Cashman <dcashman@android.com> - 2015-12-01 21:20 +0100
Re: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS. Will Deacon <will.deacon@arm.com> - 2015-12-03 13:20 +0100
Re: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS. Daniel Cashman <dcashman@android.com> - 2015-12-03 17:20 +0100
Re: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS. Jon Hunter <jonathanh@nvidia.com> - 2015-12-07 11:30 +0100
Re: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS. Arnd Bergmann <arnd@arndb.de> - 2015-12-07 12:20 +0100
Re: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS. Daniel Cashman <dcashman@android.com> - 2015-12-07 19:30 +0100
Re: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS. Arnd Bergmann <arnd@arndb.de> - 2015-12-08 11:10 +0100
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