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Commit f01ad8d1 authored by Lijuan Gao's avatar Lijuan Gao
Browse files

arm: traps: emulate a MRRC instruction reading CNTVCT register 



Emulate CNTVCT access, so that userspace can get CNTVCT value,
if the direct counter read is disabled. Also, keep direct
access disabled by default for userspace.

Change-Id: I70263c129386314880cb28d1e561146ce62d52b8
Signed-off-by: default avatarNeeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: default avatarCong Zhang <congzhan@codeaurora.org>
Signed-off-by: default avatarShadab Naseem <snaseem@codeaurora.org>
Signed-off-by: default avatarLijuan Gao <lijuang@codeaurora.org>
parent dc9b4c45

arch/arm/include/asm/traps.h

+1 −0
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ static inline int __in_irqentry_text(unsigned long ptr) 
	       ptr < (unsigned long)&__irqentry_text_end;

}



extern void get_timer_count_hook_init(void);

extern void __init early_trap_init(void *);

extern void dump_backtrace_entry(unsigned long where, unsigned long from, unsigned long frame);

extern void ptrace_break(struct pt_regs *regs);

arch/arm/kernel/traps.c

+37 −0
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include <linux/irq.h>



#include <linux/atomic.h>

#include <asm/arch_timer.h>

#include <asm/cacheflush.h>

#include <asm/exception.h>

#include <asm/unistd.h>
@@ -711,6 +712,42 @@ late_initcall(arm_mrc_hook_init); 


#endif



static int get_timer_count_trap(struct pt_regs *regs, unsigned int instr)

{

	u64 cval;

	unsigned int res;

	int rd = (instr >> 12) & 0xF;

	int rn =  (instr >> 16) & 0xF;



	res = arm_check_condition(instr, regs->ARM_cpsr);

	if (res == ARM_OPCODE_CONDTEST_FAIL) {

		regs->ARM_pc += 4;

		return 0;

	}



	if (rd == 15 || rn == 15)

		return 1;

	cval = __arch_counter_get_cntvct();

	regs->uregs[rd] = cval;

	regs->uregs[rn] = cval >> 32;

	regs->ARM_pc += 4;

	return 0;

}



static struct undef_hook get_timer_count_hook = {

	.instr_mask	= 0x0ff00fff,

	.instr_val	= 0x0c500f1e,

	.cpsr_mask	= MODE_MASK,

	.cpsr_val	= USR_MODE,

	.fn		= get_timer_count_trap,

};



void get_timer_count_hook_init(void)

{

	register_undef_hook(&get_timer_count_hook);

}

EXPORT_SYMBOL(get_timer_count_hook_init);



/*

 * A data abort trap was taken, but we did not handle the instruction.

 * Try to abort the user program, or panic if it was the kernel.

arch/arm64/include/asm/traps.h

+1 −0
Original line number Diff line number Diff line
@@ -110,4 +110,5 @@ static inline u32 arm64_ras_serror_get_severity(u32 esr) 


bool arm64_is_fatal_ras_serror(struct pt_regs *regs, unsigned int esr);

void __noreturn arm64_serror_panic(struct pt_regs *regs, u32 esr);

static inline void get_timer_count_hook_init(void) {}

#endif

drivers/clocksource/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -387,7 +387,7 @@ config SUN50I_ERRATUM_UNKNOWN1 


config ARM_ARCH_TIMER_VCT_ACCESS

	bool "Support for ARM architected timer virtual counter access in userspace"

	default !ARM64

	default n

	depends on ARM_ARCH_TIMER

	help

	  This option enables support for reading the ARM architected timer's

drivers/clocksource/arm_arch_timer.c

+2 −0
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ 
#include <linux/acpi.h>



#include <asm/arch_timer.h>

#include <asm/traps.h>

#include <asm/virt.h>



#include <clocksource/arm_arch_timer.h>
@@ -1519,6 +1520,7 @@ static int __init arch_timer_mem_of_init(struct device_node *np) 
	ret = arch_timer_mem_frame_register(frame);

	if (!ret && !arch_timer_needs_of_probing())

		ret = arch_timer_common_init();

	get_timer_count_hook_init();

out:

	kfree(timer_mem);

	return ret;