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| author | Dave Martin <Dave.Martin@arm.com> | 2017-06-30 18:56:59 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@armlinux.org.uk> | 2017-07-24 14:26:55 +0100 |
| commit | ce184a0dee92a0a333236a26478e304dca29a3df (patch) | |
| tree | 32c4e3474394c37813bce1b2e6274894af240a3f /arch/arm/include | |
| parent | 269583559cdd8ab1203210893590ed4cc6af8171 (diff) | |
| download | linux-ce184a0dee92a0a333236a26478e304dca29a3df.tar.gz linux-ce184a0dee92a0a333236a26478e304dca29a3df.tar.bz2 linux-ce184a0dee92a0a333236a26478e304dca29a3df.zip | |
ARM: 8687/1: signal: Fix unparseable iwmmxt_sigframe in uc_regspace[]
In kernels with CONFIG_IWMMXT=y running on non-iWMMXt hardware, the
signal frame can be left partially uninitialised in such a way
that userspace cannot parse uc_regspace[] safely. In particular,
this means that the VFP registers cannot be located reliably in the
signal frame when a multi_v7_defconfig kernel is run on the
majority of platforms.
The cause is that the uc_regspace[] is laid out statically based on
the kernel config, but the decision of whether to save/restore the
iWMMXt registers must be a runtime decision.
To minimise breakage of software that may assume a fixed layout,
this patch emits a dummy block of the same size as iwmmxt_sigframe,
for non-iWMMXt threads. However, the magic and size of this block
are now filled in to help parsers skip over it. A new DUMMY_MAGIC
is defined for this purpose.
It is probably legitimate (if non-portable) for userspace to
manufacture its own sigframe for sigreturn, and there is no obvious
reason why userspace should be required to insert a DUMMY_MAGIC
block when running on non-iWMMXt hardware, when omitting it has
worked just fine forever in other configurations. So in this case,
sigreturn does not require this block to be present.
Reported-by: Edmund Grimley-Evans <Edmund.Grimley-Evans@arm.com>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Diffstat (limited to 'arch/arm/include')
| -rw-r--r-- | arch/arm/include/asm/ucontext.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/arm/include/asm/ucontext.h b/arch/arm/include/asm/ucontext.h index 14749aec94bf..921d8274855c 100644 --- a/arch/arm/include/asm/ucontext.h +++ b/arch/arm/include/asm/ucontext.h @@ -35,6 +35,12 @@ struct ucontext { * bytes, to prevent unpredictable padding in the signal frame. */ +/* + * Dummy padding block: if this magic is encountered, the block should + * be skipped using the corresponding size field. + */ +#define DUMMY_MAGIC 0xb0d9ed01 + #ifdef CONFIG_CRUNCH #define CRUNCH_MAGIC 0x5065cf03 #define CRUNCH_STORAGE_SIZE (CRUNCH_SIZE + 8) |