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Commit c371b355 authored by Razziell's avatar Razziell
Browse files

HACK: arm64: add CNTPCT_EL0 trap handler 

The upstream kernel deliberately blocks EL0 access to CNTPCT.  However
Qualcomm's time_daemon attempts to read from CNTPCT_EL0, and Qualcomm
has forked the ARM architectured timer driver to allow this to succeed.

As a workaround, add a trap handler for CNTPCT similar to the existing
one for CNTVCT.

Bug: 68266545
Change-Id: Id49b60ebdeca84fab655079c8c22afd3171371b0 (reverted from commit 5495a952) (reverted from commit 3c65698c)
parent 32acc26c

arch/arm64/kernel/traps.c

+16 −0
Original line number Diff line number Diff line
@@ -419,6 +419,19 @@ static void cntfrq_read_handler(unsigned int esr, struct pt_regs *regs) 
	regs->pc += 4;

}



static void cntpct_read_handler(unsigned int esr, struct pt_regs *regs)

{

	int rt = (esr & ESR_ELx_SYS64_ISS_RT_MASK) >> ESR_ELx_SYS64_ISS_RT_SHIFT;



	isb();

	if (rt != 31)

		regs->regs[rt] = arch_counter_get_cntpct();

	regs->pc += 4;

}



#define ESR_ELx_SYS64_ISS_SYS_CNTPCT    (ESR_ELx_SYS64_ISS_SYS_VAL(3, 3, 1, 14, 0) | \

                                         ESR_ELx_SYS64_ISS_DIR_READ)



asmlinkage void __exception do_sysinstr(unsigned int esr, struct pt_regs *regs)

{

	if ((esr & ESR_ELx_SYS64_ISS_SYS_OP_MASK) == ESR_ELx_SYS64_ISS_SYS_CNTVCT) {
@@ -427,6 +440,9 @@ asmlinkage void __exception do_sysinstr(unsigned int esr, struct pt_regs *regs) 
	} else if ((esr & ESR_ELx_SYS64_ISS_SYS_OP_MASK) == ESR_ELx_SYS64_ISS_SYS_CNTFRQ) {

		cntfrq_read_handler(esr, regs);

		return;

	} else if ((esr & ESR_ELx_SYS64_ISS_SYS_OP_MASK) == ESR_ELx_SYS64_ISS_SYS_CNTPCT) {

		cntpct_read_handler(esr, regs);

		return;

	}



	do_undefinstr(regs);