xref: /openbmc/linux/arch/arm64/include/asm/daifflags.h (revision 4d6a38da)
1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * Copyright (C) 2017 ARM Ltd.
4  */
5 #ifndef __ASM_DAIFFLAGS_H
6 #define __ASM_DAIFFLAGS_H
7 
8 #include <linux/irqflags.h>
9 
10 #include <asm/arch_gicv3.h>
11 #include <asm/barrier.h>
12 #include <asm/cpufeature.h>
13 #include <asm/ptrace.h>
14 
15 #define DAIF_PROCCTX		0
16 #define DAIF_PROCCTX_NOIRQ	(PSR_I_BIT | PSR_F_BIT)
17 #define DAIF_ERRCTX		(PSR_A_BIT | PSR_I_BIT | PSR_F_BIT)
18 #define DAIF_MASK		(PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT)
19 
20 
21 /* mask/save/unmask/restore all exceptions, including interrupts. */
local_daif_mask(void)22 static inline void local_daif_mask(void)
23 {
24 	WARN_ON(system_has_prio_mask_debugging() &&
25 		(read_sysreg_s(SYS_ICC_PMR_EL1) == (GIC_PRIO_IRQOFF |
26 						    GIC_PRIO_PSR_I_SET)));
27 
28 	asm volatile(
29 		"msr	daifset, #0xf		// local_daif_mask\n"
30 		:
31 		:
32 		: "memory");
33 
34 	/* Don't really care for a dsb here, we don't intend to enable IRQs */
35 	if (system_uses_irq_prio_masking())
36 		gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);
37 
38 	trace_hardirqs_off();
39 }
40 
local_daif_save_flags(void)41 static inline unsigned long local_daif_save_flags(void)
42 {
43 	unsigned long flags;
44 
45 	flags = read_sysreg(daif);
46 
47 	if (system_uses_irq_prio_masking()) {
48 		/* If IRQs are masked with PMR, reflect it in the flags */
49 		if (read_sysreg_s(SYS_ICC_PMR_EL1) != GIC_PRIO_IRQON)
50 			flags |= PSR_I_BIT | PSR_F_BIT;
51 	}
52 
53 	return flags;
54 }
55 
local_daif_save(void)56 static inline unsigned long local_daif_save(void)
57 {
58 	unsigned long flags;
59 
60 	flags = local_daif_save_flags();
61 
62 	local_daif_mask();
63 
64 	return flags;
65 }
66 
local_daif_restore(unsigned long flags)67 static inline void local_daif_restore(unsigned long flags)
68 {
69 	bool irq_disabled = flags & PSR_I_BIT;
70 
71 	WARN_ON(system_has_prio_mask_debugging() &&
72 		(read_sysreg(daif) & (PSR_I_BIT | PSR_F_BIT)) != (PSR_I_BIT | PSR_F_BIT));
73 
74 	if (!irq_disabled) {
75 		trace_hardirqs_on();
76 
77 		if (system_uses_irq_prio_masking()) {
78 			gic_write_pmr(GIC_PRIO_IRQON);
79 			pmr_sync();
80 		}
81 	} else if (system_uses_irq_prio_masking()) {
82 		u64 pmr;
83 
84 		if (!(flags & PSR_A_BIT)) {
85 			/*
86 			 * If interrupts are disabled but we can take
87 			 * asynchronous errors, we can take NMIs
88 			 */
89 			flags &= ~(PSR_I_BIT | PSR_F_BIT);
90 			pmr = GIC_PRIO_IRQOFF;
91 		} else {
92 			pmr = GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET;
93 		}
94 
95 		/*
96 		 * There has been concern that the write to daif
97 		 * might be reordered before this write to PMR.
98 		 * From the ARM ARM DDI 0487D.a, section D1.7.1
99 		 * "Accessing PSTATE fields":
100 		 *   Writes to the PSTATE fields have side-effects on
101 		 *   various aspects of the PE operation. All of these
102 		 *   side-effects are guaranteed:
103 		 *     - Not to be visible to earlier instructions in
104 		 *       the execution stream.
105 		 *     - To be visible to later instructions in the
106 		 *       execution stream
107 		 *
108 		 * Also, writes to PMR are self-synchronizing, so no
109 		 * interrupts with a lower priority than PMR is signaled
110 		 * to the PE after the write.
111 		 *
112 		 * So we don't need additional synchronization here.
113 		 */
114 		gic_write_pmr(pmr);
115 	}
116 
117 	write_sysreg(flags, daif);
118 
119 	if (irq_disabled)
120 		trace_hardirqs_off();
121 }
122 
123 /*
124  * Called by synchronous exception handlers to restore the DAIF bits that were
125  * modified by taking an exception.
126  */
local_daif_inherit(struct pt_regs * regs)127 static inline void local_daif_inherit(struct pt_regs *regs)
128 {
129 	unsigned long flags = regs->pstate & DAIF_MASK;
130 
131 	if (interrupts_enabled(regs))
132 		trace_hardirqs_on();
133 
134 	if (system_uses_irq_prio_masking())
135 		gic_write_pmr(regs->pmr_save);
136 
137 	/*
138 	 * We can't use local_daif_restore(regs->pstate) here as
139 	 * system_has_prio_mask_debugging() won't restore the I bit if it can
140 	 * use the pmr instead.
141 	 */
142 	write_sysreg(flags, daif);
143 }
144 #endif
145