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Building kernels before linux-4.7 with gcc-8 results in many build failures
when gcc triggers a check that was meant to catch broken compilers:
/tmp/ccCGMQmS.s:648: Error: .err encountered
According to the discussion in the gcc bugzilla, a local "register
asm()" variable is still supposed to be the correct way to force an
inline assembly to use a particular register, but marking it 'const'
lets the compiler do optimizations that break that, i.e the compiler is
free to treat the variable as either 'const' or 'register' in that case.
Upstream commit 9f73bd8bb445 ("ARM: uaccess: remove put_user() code
duplication") fixed this problem in linux-4.8 as part of a larger change,
but seems a little too big to be backported to 4.4.
Let's take the simplest fix and change only the one broken line in the
same way as newer kernels.
Suggested-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85745
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86673
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 0ca85fc310e8c24cba10ed241a0188795e177683)
/tmp/ccmcXtfu.s: Assembler messages:
/tmp/ccmcXtfu.s:1441: Error: .err encountered
Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>
Conflicts:
arch/arm/include/asm/uaccess.h
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This patch removes the domain switching functionality via the set_fs and
__switch_to functions on cores that have a TLS register.
Currently, the ioremap and vmalloc areas share the same level 1 page
tables and therefore have the same domain (DOMAIN_KERNEL). When the
kernel domain is modified from Client to Manager (via the __set_fs or in
the __switch_to function), the XN (eXecute Never) bit is overridden and
newer CPUs can speculatively prefetch the ioremap'ed memory.
Linux performs the kernel domain switching to allow user-specific
functions (copy_to/from_user, get/put_user etc.) to access kernel
memory. In order for these functions to work with the kernel domain set
to Client, the patch modifies the LDRT/STRT and related instructions to
the LDR/STR ones.
The user pages access rights are also modified for kernel read-only
access rather than read/write so that the copy-on-write mechanism still
works. CPU_USE_DOMAINS gets disabled only if the hardware has a TLS register
(CPU_32v6K is defined) since writing the TLS value to the high vectors page
isn't possible.
The user addresses passed to the kernel are checked by the access_ok()
function so that they do not point to the kernel space.
Tested-by: Anton Vorontsov <cbouatmailru@gmail.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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/tmp/ccJ3ssZW.s: Assembler messages:
/tmp/ccJ3ssZW.s:1952: Error: can't resolve `.text' {.text section} - `.LFB1077'
This is caused because:
.section .data
.section .text
.section .text
.previous
does not return us to the .text section, but the .data section; this
makes use of .previous dangerous if the ordering of previous sections
is not known.
Fix up the other users of .previous; .pushsection and .popsection are
a safer pairing to use than .section and .previous.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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This patch adds the ARM/Thumb-2 unified support for the arch/arm/lib/*
files.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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This allows for optional alternative implementations of __copy_to_user
and __clear_user, with a possible runtime fallback to the standard
version when the alternative provides no gain over that standard
version. This is done by making the standard __copy_to_user into a weak
alias for the symbol __copy_to_user_std. Same thing for __clear_user.
Those two functions are particularly good candidates to have alternative
implementations for, since they rely on the STRT instruction which has
lower performances than STM instructions on some CPU cores such as
the ARM1176 and Marvell Feroceon.
Signed-off-by: Nicolas Pitre <nico@marvell.com>
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... and fix those drivers that were incorrectly relying upon
that include.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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As suggested by Andrew Morton, remove memzero() - it's not supported
on other architectures so use of it is a potential build breaking bug.
Since the compiler optimizes memset(x,0,n) to __memzero() perfectly
well, we don't miss out on the underlying benefits of memzero().
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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The post-index immediate value is optional if it is 0 and this patch
removes it. The reason is to allow such instructions to compile to
Thumb-2 where only pre-indexed LDRT/STRT instructions are allowed.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Move platform independent header files to arch/arm/include/asm, leaving
those in asm/arch* and asm/plat* alone.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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