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Commit 3eb5d588 authored by Anton Blanchard's avatar Anton Blanchard Committed by Michael Ellerman
Browse files

powerpc: Add ppc_strict_facility_enable boot option 



Add a boot option that strictly manages the MSR unavailable bits.
This catches kernel uses of FP/Altivec/SPE that would otherwise
corrupt user state.

Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent dc4fbba1

Documentation/kernel-parameters.txt

+6 −0
Original line number Diff line number Diff line
@@ -2978,6 +2978,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			may be specified.

			Format: <port>,<port>....



	ppc_strict_facility_enable

			[PPC] This option catches any kernel floating point,

			Altivec, VSX and SPE outside of regions specifically

			allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).

			There is some performance impact when enabling this.



	print-fatal-signals=

			[KNL] debug: print fatal signals

arch/powerpc/include/asm/reg.h

+9 −0
Original line number Diff line number Diff line
@@ -1214,6 +1214,15 @@ static inline void mtmsr_isync(unsigned long val) 
				     : "r" ((unsigned long)(v)) \

				     : "memory")



extern void msr_check_and_set(unsigned long bits);

extern bool strict_msr_control;

extern void __msr_check_and_clear(unsigned long bits);

static inline void msr_check_and_clear(unsigned long bits)

{

	if (strict_msr_control)

		__msr_check_and_clear(bits);

}



static inline unsigned long mfvtb (void)

{

#ifdef CONFIG_PPC_BOOK3S_64

arch/powerpc/include/asm/switch_to.h

+19 −5
Original line number Diff line number Diff line
@@ -4,6 +4,8 @@ 
#ifndef _ASM_POWERPC_SWITCH_TO_H

#define _ASM_POWERPC_SWITCH_TO_H



#include <asm/reg.h>



struct thread_struct;

struct task_struct;

struct pt_regs;
@@ -26,15 +28,15 @@ extern void enable_kernel_spe(void); 
extern void load_up_spe(struct task_struct *);

extern void switch_booke_debug_regs(struct debug_reg *new_debug);



static inline void disable_kernel_fp(void) { }

static inline void disable_kernel_altivec(void) { }

static inline void disable_kernel_spe(void) { }

static inline void disable_kernel_vsx(void) { }



#ifdef CONFIG_PPC_FPU

extern void flush_fp_to_thread(struct task_struct *);

extern void giveup_fpu(struct task_struct *);

extern void __giveup_fpu(struct task_struct *);

static inline void disable_kernel_fp(void)

{

	msr_check_and_clear(MSR_FP);

}



#else

static inline void flush_fp_to_thread(struct task_struct *t) { }

static inline void giveup_fpu(struct task_struct *t) { }
@@ -45,6 +47,10 @@ static inline void __giveup_fpu(struct task_struct *t) { } 
extern void flush_altivec_to_thread(struct task_struct *);

extern void giveup_altivec(struct task_struct *);

extern void __giveup_altivec(struct task_struct *);

static inline void disable_kernel_altivec(void)

{

	msr_check_and_clear(MSR_VEC);

}

#else

static inline void flush_altivec_to_thread(struct task_struct *t) { }

static inline void giveup_altivec(struct task_struct *t) { }
@@ -53,6 +59,10 @@ static inline void __giveup_altivec(struct task_struct *t) { } 


#ifdef CONFIG_VSX

extern void flush_vsx_to_thread(struct task_struct *);

static inline void disable_kernel_vsx(void)

{

	msr_check_and_clear(MSR_FP|MSR_VEC|MSR_VSX);

}

#else

static inline void flush_vsx_to_thread(struct task_struct *t)

{
@@ -63,6 +73,10 @@ static inline void flush_vsx_to_thread(struct task_struct *t) 
extern void flush_spe_to_thread(struct task_struct *);

extern void giveup_spe(struct task_struct *);

extern void __giveup_spe(struct task_struct *);

static inline void disable_kernel_spe(void)

{

	msr_check_and_clear(MSR_SPE);

}

#else

static inline void flush_spe_to_thread(struct task_struct *t) { }

static inline void giveup_spe(struct task_struct *t) { }

arch/powerpc/kernel/process.c

+15 −2
Original line number Diff line number Diff line
@@ -87,7 +87,19 @@ static void check_if_tm_restore_required(struct task_struct *tsk) 
static inline void check_if_tm_restore_required(struct task_struct *tsk) { }

#endif /* CONFIG_PPC_TRANSACTIONAL_MEM */



static void msr_check_and_set(unsigned long bits)

bool strict_msr_control;

EXPORT_SYMBOL(strict_msr_control);



static int __init enable_strict_msr_control(char *str)

{

	strict_msr_control = true;

	pr_info("Enabling strict facility control\n");



	return 0;

}

early_param("ppc_strict_facility_enable", enable_strict_msr_control);



void msr_check_and_set(unsigned long bits)

{

	unsigned long oldmsr = mfmsr();

	unsigned long newmsr;
@@ -103,7 +115,7 @@ static void msr_check_and_set(unsigned long bits) 
		mtmsr_isync(newmsr);

}



static void msr_check_and_clear(unsigned long bits)

void __msr_check_and_clear(unsigned long bits)

{

	unsigned long oldmsr = mfmsr();

	unsigned long newmsr;
@@ -118,6 +130,7 @@ static void msr_check_and_clear(unsigned long bits) 
	if (oldmsr != newmsr)

		mtmsr_isync(newmsr);

}

EXPORT_SYMBOL(__msr_check_and_clear);



#ifdef CONFIG_PPC_FPU

void giveup_fpu(struct task_struct *tsk)