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ARM: 6384/1: Remove the domain switching on ARMv6k/v7 CPUs

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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>
This commit is contained in:
Catalin Marinas
2010-09-13 16:03:21 +01:00
committed by Russell King
parent ff8b16d7e1
commit 247055aa21
15 changed files with 153 additions and 92 deletions
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13
arch/arm/include/asm/assembler.h
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@@ -18,6 +18,7 @@
#endif
#include <asm/ptrace.h>
#include <asm/domain.h>
/*
* Endian independent macros for shifting bytes within registers.
@@ -206,12 +207,12 @@
*/
#ifdef CONFIG_THUMB2_KERNEL
.macro usraccoff, instr, reg, ptr, inc, off, cond, abort
.macro usraccoff, instr, reg, ptr, inc, off, cond, abort, t=T()
9999:
.if \inc == 1
\instr\cond\()bt \reg, [\ptr, #\off]
\instr\cond\()b\()\t\().w \reg, [\ptr, #\off]
.elseif \inc == 4
\instr\cond\()t \reg, [\ptr, #\off]
\instr\cond\()\t\().w \reg, [\ptr, #\off]
.else
.error "Unsupported inc macro argument"
.endif
@@ -246,13 +247,13 @@
#else /* !CONFIG_THUMB2_KERNEL */
.macro usracc, instr, reg, ptr, inc, cond, rept, abort
.macro usracc, instr, reg, ptr, inc, cond, rept, abort, t=T()
.rept \rept
9999:
.if \inc == 1
\instr\cond\()bt \reg, [\ptr], #\inc
\instr\cond\()b\()\t \reg, [\ptr], #\inc
.elseif \inc == 4
\instr\cond\()t \reg, [\ptr], #\inc
\instr\cond\()\t \reg, [\ptr], #\inc
.else
.error "Unsupported inc macro argument"
.endif