From 969f5ea627570e91c9d54403287ee3ed657f58fe Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Mon, 29 Apr 2019 13:03:57 +0100 Subject: arm64: errata: Add workaround for Cortex-A76 erratum #1463225 Revisions of the Cortex-A76 CPU prior to r4p0 are affected by an erratum that can prevent interrupts from being taken when single-stepping. This patch implements a software workaround to prevent userspace from effectively being able to disable interrupts. Cc: Cc: Marc Zyngier Cc: Catalin Marinas Signed-off-by: Will Deacon --- arch/arm64/mm/fault.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) (limited to 'arch/arm64/mm') diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 0cb0e09995e1..9a84a4071561 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -810,6 +810,36 @@ void __init hook_debug_fault_code(int nr, debug_fault_info[nr].name = name; } +#ifdef CONFIG_ARM64_ERRATUM_1463225 +DECLARE_PER_CPU(int, __in_cortex_a76_erratum_1463225_wa); + +static int __exception +cortex_a76_erratum_1463225_debug_handler(struct pt_regs *regs) +{ + if (user_mode(regs)) + return 0; + + if (!__this_cpu_read(__in_cortex_a76_erratum_1463225_wa)) + return 0; + + /* + * We've taken a dummy step exception from the kernel to ensure + * that interrupts are re-enabled on the syscall path. Return back + * to cortex_a76_erratum_1463225_svc_handler() with debug exceptions + * masked so that we can safely restore the mdscr and get on with + * handling the syscall. + */ + regs->pstate |= PSR_D_BIT; + return 1; +} +#else +static int __exception +cortex_a76_erratum_1463225_debug_handler(struct pt_regs *regs) +{ + return 0; +} +#endif /* CONFIG_ARM64_ERRATUM_1463225 */ + asmlinkage void __exception do_debug_exception(unsigned long addr_if_watchpoint, unsigned int esr, struct pt_regs *regs) @@ -817,6 +847,9 @@ asmlinkage void __exception do_debug_exception(unsigned long addr_if_watchpoint, const struct fault_info *inf = esr_to_debug_fault_info(esr); unsigned long pc = instruction_pointer(regs); + if (cortex_a76_erratum_1463225_debug_handler(regs)) + return; + /* * Tell lockdep we disabled irqs in entry.S. Do nothing if they were * already disabled to preserve the last enabled/disabled addresses. -- cgit v1.2.1