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Groups > linux.kernel > #1522067 > unrolled thread
| Started by | Chris Metcalf <cmetcalf@mellanox.com> |
|---|---|
| First post | 2016-11-14 21:30 +0100 |
| Last post | 2016-11-15 08:50 +0100 |
| Articles | 3 — 3 participants |
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[PATCH v2] tile: handle __ro_after_init like parisc does Chris Metcalf <cmetcalf@mellanox.com> - 2016-11-14 21:30 +0100
Re: [PATCH v2] tile: handle __ro_after_init like parisc does Kees Cook <keescook@chromium.org> - 2016-11-14 22:20 +0100
Re: [PATCH v2] tile: handle __ro_after_init like parisc does Heiko Carstens <heiko.carstens@de.ibm.com> - 2016-11-15 08:50 +0100
| From | Chris Metcalf <cmetcalf@mellanox.com> |
|---|---|
| Date | 2016-11-14 21:30 +0100 |
| Subject | [PATCH v2] tile: handle __ro_after_init like parisc does |
| Message-ID | <sDw37-3m0-17@gated-at.bofh.it> |
The tile architecture already marks RO_DATA as read-only in the kernel, so grouping RO_AFTER_INIT_DATA with RO_DATA, as is done by default, means the kernel faults in init when it tries to write to RO_AFTER_INIT_DATA. For now, just arrange that __ro_after_init is handled like __write_once, i.e. __read_mostly. Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com> --- arch/tile/include/asm/cache.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/tile/include/asm/cache.h b/arch/tile/include/asm/cache.h index 6160761d5f61..4810e48dbbbf 100644 --- a/arch/tile/include/asm/cache.h +++ b/arch/tile/include/asm/cache.h @@ -61,4 +61,7 @@ */ #define __write_once __read_mostly +/* __ro_after_init is the generic name for the tile arch __write_once. */ +#define __ro_after_init __read_mostly + #endif /* _ASM_TILE_CACHE_H */ -- 2.7.2
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| From | Kees Cook <keescook@chromium.org> |
|---|---|
| Date | 2016-11-14 22:20 +0100 |
| Message-ID | <sDwPw-3SH-23@gated-at.bofh.it> |
| In reply to | #1522067 |
On Mon, Nov 14, 2016 at 12:29 PM, Chris Metcalf <cmetcalf@mellanox.com> wrote: > The tile architecture already marks RO_DATA as read-only in > the kernel, so grouping RO_AFTER_INIT_DATA with RO_DATA, as is > done by default, means the kernel faults in init when it tries > to write to RO_AFTER_INIT_DATA. For now, just arrange that > __ro_after_init is handled like __write_once, i.e. __read_mostly. > > Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com> Reviewed-by: Kees Cook <keescook@chromium.org> At some point here, I want to collect all the arch maintainers and discuss the options for correctly reflecting the three data memory-protection needs we have: - always read-only - read-only after init - read-only except during rare updates (The latter one doesn't exist all yet...) x86, arm, and arm64 use mark_rodata_ro() after init finishes, so they don't technically implement "always read-only". parisc, tile, powerpc, others have "always read-only", but disable read-only-after-init since they don't use mark_rodata_ro(). I think s390 has recently implemented both, but I have to double-check... -Kees > --- > arch/tile/include/asm/cache.h | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/tile/include/asm/cache.h b/arch/tile/include/asm/cache.h > index 6160761d5f61..4810e48dbbbf 100644 > --- a/arch/tile/include/asm/cache.h > +++ b/arch/tile/include/asm/cache.h > @@ -61,4 +61,7 @@ > */ > #define __write_once __read_mostly > > +/* __ro_after_init is the generic name for the tile arch __write_once. */ > +#define __ro_after_init __read_mostly > + > #endif /* _ASM_TILE_CACHE_H */ > -- > 2.7.2 > -- Kees Cook Nexus Security
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| From | Heiko Carstens <heiko.carstens@de.ibm.com> |
|---|---|
| Date | 2016-11-15 08:50 +0100 |
| Message-ID | <sDGFb-1YS-7@gated-at.bofh.it> |
| In reply to | #1522091 |
On Mon, Nov 14, 2016 at 01:12:05PM -0800, Kees Cook wrote: > At some point here, I want to collect all the arch maintainers and > discuss the options for correctly reflecting the three data > memory-protection needs we have: > > - always read-only > - read-only after init > - read-only except during rare updates > > (The latter one doesn't exist all yet...) > > x86, arm, and arm64 use mark_rodata_ro() after init finishes, so they > don't technically implement "always read-only". parisc, tile, powerpc, > others have "always read-only", but disable read-only-after-init since > they don't use mark_rodata_ro(). I think s390 has recently implemented > both, but I have to double-check... Yes, s390 has both: an early always read-only support, which is effective as soon as paging_init() has set up and enabled page tables. Our mark_rodata_ro() implementation only makes the ro_after_init section read-only.
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