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[PATCH] ARM: 2663/1: straightify TLS register emulation a bit more

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Patch from Nicolas Pitre

This better express things, and should cover RMK's weird SMP toys.

Signed-off-by: Nicolas Pitre
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Nicolas Pitre 2005-05-05 23:24:45 +01:00 committed by Russell King
parent f7e68bbf40
commit 4b0e07a556
3 changed files with 25 additions and 20 deletions
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10
arch/arm/kernel/entry-armv.S
View file

@ -505,9 +505,9 @@ ENTRY(__switch_to)
mra r4, r5, acc0
stmia ip, {r4, r5}
#endif
#ifdef CONFIG_HAS_TLS_REG
#if defined(CONFIG_HAS_TLS_REG)
mcr p15, 0, r3, c13, c0, 3 @ set TLS register
#else
#elif !defined(CONFIG_TLS_REG_EMUL)
mov r4, #0xffff0fff
str r3, [r4, #-15] @ TLS val at 0xffff0ff0
#endif
@ -690,11 +690,7 @@ __kuser_cmpxchg: @ 0xffff0fc0
__kuser_get_tls: @ 0xffff0fe0
#ifndef CONFIG_HAS_TLS_REG
#ifdef CONFIG_SMP /* sanity check */
#error "CONFIG_SMP without CONFIG_HAS_TLS_REG is wrong"
#endif
#if !defined(CONFIG_HAS_TLS_REG) && !defined(CONFIG_TLS_REG_EMUL)
ldr r0, [pc, #(16 - 8)] @ TLS stored at 0xffff0ff0
mov pc, lr

11
arch/arm/kernel/traps.c
View file

@ -451,9 +451,9 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
case NR(set_tls):
thread->tp_value = regs->ARM_r0;
#ifdef CONFIG_HAS_TLS_REG
#if defined(CONFIG_HAS_TLS_REG)
asm ("mcr p15, 0, %0, c13, c0, 3" : : "r" (regs->ARM_r0) );
#else
#elif !defined(CONFIG_TLS_REG_EMUL)
/*
* User space must never try to access this directly.
* Expect your app to break eventually if you do so.
@ -498,11 +498,14 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
return 0;
}
#if defined(CONFIG_CPU_32v6) && !defined(CONFIG_HAS_TLS_REG)
#ifdef CONFIG_TLS_REG_EMUL
/*
* We might be running on an ARMv6+ processor which should have the TLS
* register, but for some reason we can't use it and have to emulate it.
* register but for some reason we can't use it, or maybe an SMP system
* using a pre-ARMv6 processor (there are apparently a few prototypes like
* that in existence) and therefore access to that register must be
* emulated.
*/
static int get_tp_trap(struct pt_regs *regs, unsigned int instr)

24
arch/arm/mm/Kconfig
View file

@ -410,17 +410,23 @@ config CPU_BPREDICT_DISABLE
help
Say Y here to disable branch prediction. If unsure, say N.
config TLS_REG_EMUL
bool
default y if (SMP || CPU_32v6) && (CPU_32v5 || CPU_32v4 || CPU_32v3)
help
We might be running on an ARMv6+ processor which should have the TLS
register but for some reason we can't use it, or maybe an SMP system
using a pre-ARMv6 processor (there are apparently a few prototypes
like that in existence) and therefore access to that register must
be emulated.
config HAS_TLS_REG
bool
depends on CPU_32v6 && !CPU_32v5 && !CPU_32v4 && !CPU_32v3
default y
depends on CPU_32v6
default y if !TLS_REG_EMUL
help
This selects support for the CP15 thread register.
It is defined to be available on ARMv6 or later. However
if the kernel is configured to support multiple CPUs including
a pre-ARMv6 processors, or if a given ARMv6 processor doesn't
implement the thread register for some reason, then access to
this register from user space must be trapped and emulated.
If user space is relying on the __kuser_get_tls code then
there should not be any impact.
It is defined to be available on ARMv6 or later. If a particular
ARMv6 or later CPU doesn't support it then it must omc;ide "select
TLS_REG_EMUL" along with its other caracteristics.