BACKPORT: arm64: Add CNTFRQ_EL0 trap handler

We now trap accesses to CNTVCT_EL0 when the counter is broken
enough to require the kernel to mediate the access. But it
turns out that some existing userspace (such as OpenMPI) do
probe for the counter frequency, leading to an UNDEF exception
as CNTVCT_EL0 and CNTFRQ_EL0 share the same control bit.

The fix is to handle the exception the same way we do for CNTVCT_EL0.

Fixes: a86bd139f2ae ("arm64: arch_timer: Enable CNTVCT_EL0 trap if workaround is enabled")
Reported-by: Hanjun Guo <guohanjun@huawei.com>
Tested-by: Hanjun Guo <guohanjun@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit 9842119a238bfb92cbab63258dabb54f0e7b111b)

Change-Id: I2f163e2511bab6225f319c0a9e732735cbd108a0
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index f40f2f4a4e847c2614c52abfc2af9f87557e147a..2d4e9c26f8f6e47de3b35ca8ae8c1f7b2fdcf887 100644 (file)
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -146,6 +146,9 @@
 #define ESR_ELx_SYS64_ISS_SYS_CNTVCT   (ESR_ELx_SYS64_ISS_SYS_VAL(3, 3, 2, 14, 0) | \
                                         ESR_ELx_SYS64_ISS_DIR_READ)
 
+#define ESR_ELx_SYS64_ISS_SYS_CNTFRQ   (ESR_ELx_SYS64_ISS_SYS_VAL(3, 3, 0, 14, 0) | \
+                                        ESR_ELx_SYS64_ISS_DIR_READ)
+
 #ifndef __ASSEMBLY__
 #include <asm/types.h>
 

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 42615da5b2e97700f16cb878795306e2f04c0b23..ef77a5f4f0750c7ee9583ff3c2f41433ca21fd38 100644 (file)
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -418,11 +418,23 @@ static void cntvct_read_handler(unsigned int esr, struct pt_regs *regs)
        regs->pc += 4;
 }
 
+static void cntfrq_read_handler(unsigned int esr, struct pt_regs *regs)
+{
+       int rt = (esr & ESR_ELx_SYS64_ISS_RT_MASK) >> ESR_ELx_SYS64_ISS_RT_SHIFT;
+
+       if (rt != 31)
+               regs->regs[rt] = read_sysreg(cntfrq_el0);
+       regs->pc += 4;
+}
+
 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) {
                cntvct_read_handler(esr, regs);
                return;
+       } else if ((esr & ESR_ELx_SYS64_ISS_SYS_OP_MASK) == ESR_ELx_SYS64_ISS_SYS_CNTFRQ) {
+               cntfrq_read_handler(esr, regs);
+               return;
        }
 
        do_undefinstr(regs);