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.
From: Jiri Kosina <jkos...@suse.cz>
Subject: [PATCH] tile: Don't corrupt personality flags upon exec()
Historically, the top three bytes of personality have been used for things
such as ADDR_NO_RANDOMIZE, which made sense only for specific
architectures.
We now however have a flag there that is general no matter the
architecture (UNAME26); generally we have to be careful to preserve the
personality flags across exec().
This patch fixes tile architecture not to forcefully overwrite
personality flags during exec().
Plus it fixes exec_domain switching -- set_personality() should always be
used instead of directly assigning to current->personality.
Signed-off-by: Jiri Kosina <jkos...@suse.cz>
---
arch/tile/include/asm/elf.h | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/tile/include/asm/elf.h b/arch/tile/include/asm/elf.h
index d16d006..cf7f3bd 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->personality & (~PER_MASK))); \
current_thread_info()->status &= ~TS_COMPAT; \
} while (0)
#define COMPAT_SET_PERSONALITY(ex) \
do { \
- current->personality = PER_LINUX_32BIT; \
+ set_personality(PER_LINUX_32BIT | (current->personality &
(~PER_MASK))); \
current_thread_info()->status |= TS_COMPAT; \
} while (0)
--
Jiri Kosina
SUSE Labs
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