Messages in this thread | | | Date | Tue, 28 Aug 2012 15:04:06 -0400 | From | Chris Metcalf <> | Subject | Re: [PATCH] [RFC] cross-arch: don't corrupt personality flags upon exec() |
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On 8/28/2012 2:49 PM, Jiri Kosina wrote: > On Tue, 28 Aug 2012, Chris Metcalf wrote: >>> On tile, the PER_LINUX_32BIT is always set for 32 bit compat tasks in a >>> 64 bit kernel, which is harmless but wrong anyway. Also this, tile never >>> calls set_personality, which is also harmless because it just means that >>> exec_domain switching on tile is broken, but the only non-bogus >>> exec_domain besides the default one is an experimental support for Acorn >>> RISC OS binaries that was last updated in 2002 for for linux-2.5.49. >> Arnd, thanks for the drive-by code review. Is this change the correct fix >> for your observation? >> >> diff --git a/arch/tile/include/asm/elf.h b/arch/tile/include/asm/elf.h >> index d16d006..fd31920 100644 >> --- a/arch/tile/include/asm/elf.h >> +++ b/arch/tile/include/asm/elf.h >> @@ -156,12 +156,12 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm, >> #undef SET_PERSONALITY >> #define SET_PERSONALITY(ex) \ >> do { \ >> - current->personality = PER_LINUX; \ >> + set_personality(PER_LINUX); \ >> current_thread_info()->status &= ~TS_COMPAT; \ >> } while (0) >> #define COMPAT_SET_PERSONALITY(ex) \ >> do { \ >> - current->personality = PER_LINUX_32BIT; \ >> + set_personality(PER_LINUX); \ >> current_thread_info()->status |= TS_COMPAT; \ >> } while (0) > Actually this is also wrong. You should be rather doing > > set_personality(PER_LINUX | (current->personality & (~PER_MASK))) > > otherwise you clobber the upper personality bits upon exec(). > > Something like the patch below. Either you can take it for tile, or I can > ask Andrew to fold it into my tree-wide fix currently waiting in -mm. Just > let me know.
It looks fine for tile, except that your change still uses PER_LINUX_32BIT, which Arnd points out is wrong; my proposed patch changed it to just PER_LINUX, though I'm not completely clear as to whether this is correct. The tilegx compat mode is an ILP32 mode where the compiler emits 32-bit Elf binaries and the compat layer is used to translate to and from 32-bit pointer and long, but nothing else. It sounds like PER_LINUX applies better than PER_LINUX_32BIT based on the fact that the extra 32-bit flag isn't actually used in any architecture-independent code (nor in tile code, which just checks whether something is a compat task per se, rather than looking at the personality bits).
Since you have a treewide fix going anyway, I'm happy for you to push this to Andrew. If it's OK with the one suggested change, you can add my
Acked-by: Chris Metcalf <cmetcalf@tilera.com>
-- Chris Metcalf, Tilera Corp. http://www.tilera.com
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