Commit 4b0e07a5 authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Russell King
Browse files

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



Patch from Nicolas Pitre

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

Signed-off-by: Nicolas Pitre
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent f7e68bbf

arch/arm/kernel/entry-armv.S

+3 −7
Original line number Diff line number Diff line
@@ -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

arch/arm/kernel/traps.c

+7 −4
Original line number Diff line number Diff line
@@ -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)

arch/arm/mm/Kconfig

+15 −9
Original line number Diff line number Diff line
@@ -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.