diff options
| -rw-r--r-- | Documentation/arm64/legacy_instructions.txt | 33 | ||||
| -rw-r--r-- | arch/arm64/Kconfig | 18 | ||||
| -rw-r--r-- | arch/arm64/kernel/Makefile | 1 | ||||
| -rw-r--r-- | arch/arm64/kernel/armv8_deprecated.c | 216 |
4 files changed, 268 insertions, 0 deletions
diff --git a/Documentation/arm64/legacy_instructions.txt b/Documentation/arm64/legacy_instructions.txt new file mode 100644 index 000000000000..49d4867c0c09 --- /dev/null +++ b/Documentation/arm64/legacy_instructions.txt @@ -0,0 +1,33 @@ +The arm64 port of the Linux kernel provides infrastructure to support +emulation of instructions which have been deprecated, or obsoleted in +the architecture. The infrastructure code uses undefined instruction +hooks to support emulation. Where available it also allows turning on +the instruction execution in hardware. + +The emulation mode can be controlled by writing to sysctl nodes +(/proc/sys/abi). The following explains the different execution +behaviours and the corresponding values of the sysctl nodes - + +* Undef + Value: 0 + Generates undefined instruction abort. Default for instructions that + have been obsoleted in the architecture, e.g., SWP + +* Emulate + Value: 1 + Uses software emulation. To aid migration of software, in this mode + usage of emulated instruction is traced as well as rate limited + warnings are issued. This is the default for deprecated + instructions, .e.g., CP15 barriers + +* Hardware Execution + Value: 2 + Although marked as deprecated, some implementations may support the + enabling/disabling of hardware support for the execution of these + instructions. Using hardware execution generally provides better + performance, but at the loss of ability to gather runtime statistics + about the use of the deprecated instructions. + +The default mode depends on the status of the instruction in the +architecture. Deprecated instructions should default to emulation +while obsolete instructions must be undefined by default. diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 1e0e4671dd25..aa8f4bea3738 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -164,6 +164,24 @@ config ARCH_XGENE help This enables support for AppliedMicro X-Gene SOC Family +comment "Processor Features" + +menuconfig ARMV8_DEPRECATED + bool "Emulate deprecated/obsolete ARMv8 instructions" + depends on COMPAT + help + Legacy software support may require certain instructions + that have been deprecated or obsoleted in the architecture. + + Enable this config to enable selective emulation of these + features. + + If unsure, say Y + +if ARMV8_DEPRECATED + +endif + endmenu menu "Bus support" diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index a4d8671d6d11..84e9e5153efe 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -32,6 +32,7 @@ arm64-obj-$(CONFIG_JUMP_LABEL) += jump_label.o arm64-obj-$(CONFIG_KGDB) += kgdb.o arm64-obj-$(CONFIG_EFI) += efi.o efi-stub.o efi-entry.o arm64-obj-$(CONFIG_PCI) += pci.o +arm64-obj-$(CONFIG_ARMV8_DEPRECATED) += armv8_deprecated.o obj-y += $(arm64-obj-y) vdso/ obj-m += $(arm64-obj-m) diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c new file mode 100644 index 000000000000..db3b79da6a48 --- /dev/null +++ b/arch/arm64/kernel/armv8_deprecated.c @@ -0,0 +1,216 @@ +/* + * Copyright (C) 2014 ARM Limited + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include <linux/init.h> +#include <linux/list.h> +#include <linux/slab.h> +#include <linux/sysctl.h> + +#include <asm/traps.h> + +/* + * The runtime support for deprecated instruction support can be in one of + * following three states - + * + * 0 = undef + * 1 = emulate (software emulation) + * 2 = hw (supported in hardware) + */ +enum insn_emulation_mode { + INSN_UNDEF, + INSN_EMULATE, + INSN_HW, +}; + +enum legacy_insn_status { + INSN_DEPRECATED, + INSN_OBSOLETE, +}; + +struct insn_emulation_ops { + const char *name; + enum legacy_insn_status status; + struct undef_hook *hooks; + int (*set_hw_mode)(bool enable); +}; + +struct insn_emulation { + struct list_head node; + struct insn_emulation_ops *ops; + int current_mode; + int min; + int max; +}; + +static LIST_HEAD(insn_emulation); +static int nr_insn_emulated; +static DEFINE_RAW_SPINLOCK(insn_emulation_lock); + +static void register_emulation_hooks(struct insn_emulation_ops *ops) +{ + struct undef_hook *hook; + + BUG_ON(!ops->hooks); + + for (hook = ops->hooks; hook->instr_mask; hook++) + register_undef_hook(hook); + + pr_notice("Registered %s emulation handler\n", ops->name); +} + +static void remove_emulation_hooks(struct insn_emulation_ops *ops) +{ + struct undef_hook *hook; + + BUG_ON(!ops->hooks); + + for (hook = ops->hooks; hook->instr_mask; hook++) + unregister_undef_hook(hook); + + pr_notice("Removed %s emulation handler\n", ops->name); +} + +static int update_insn_emulation_mode(struct insn_emulation *insn, + enum insn_emulation_mode prev) +{ + int ret = 0; + + switch (prev) { + case INSN_UNDEF: /* Nothing to be done */ + break; + case INSN_EMULATE: + remove_emulation_hooks(insn->ops); + break; + case INSN_HW: + if (insn->ops->set_hw_mode) { + insn->ops->set_hw_mode(false); + pr_notice("Disabled %s support\n", insn->ops->name); + } + break; + } + + switch (insn->current_mode) { + case INSN_UNDEF: + break; + case INSN_EMULATE: + register_emulation_hooks(insn->ops); + break; + case INSN_HW: + if (insn->ops->set_hw_mode && insn->ops->set_hw_mode(true)) + pr_notice("Enabled %s support\n", insn->ops->name); + else + ret = -EINVAL; + break; + } + + return ret; +} + +static void register_insn_emulation(struct insn_emulation_ops *ops) +{ + unsigned long flags; + struct insn_emulation *insn; + + insn = kzalloc(sizeof(*insn), GFP_KERNEL); + insn->ops = ops; + insn->min = INSN_UNDEF; + + switch (ops->status) { + case INSN_DEPRECATED: + insn->current_mode = INSN_EMULATE; + insn->max = INSN_HW; + break; + case INSN_OBSOLETE: + insn->current_mode = INSN_UNDEF; + insn->max = INSN_EMULATE; + break; + } + + raw_spin_lock_irqsave(&insn_emulation_lock, flags); + list_add(&insn->node, &insn_emulation); + nr_insn_emulated++; + raw_spin_unlock_irqrestore(&insn_emulation_lock, flags); + + /* Register any handlers if required */ + update_insn_emulation_mode(insn, INSN_UNDEF); +} + +static int emulation_proc_handler(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, + loff_t *ppos) +{ + int ret = 0; + struct insn_emulation *insn = (struct insn_emulation *) table->data; + enum insn_emulation_mode prev_mode = insn->current_mode; + + table->data = &insn->current_mode; + ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + + if (ret || !write || prev_mode == insn->current_mode) + goto ret; + + ret = update_insn_emulation_mode(insn, prev_mode); + if (!ret) { + /* Mode change failed, revert to previous mode. */ + insn->current_mode = prev_mode; + update_insn_emulation_mode(insn, INSN_UNDEF); + } +ret: + table->data = insn; + return ret; +} + +static struct ctl_table ctl_abi[] = { + { + .procname = "abi", + .mode = 0555, + }, + { } +}; + +static void register_insn_emulation_sysctl(struct ctl_table *table) +{ + unsigned long flags; + int i = 0; + struct insn_emulation *insn; + struct ctl_table *insns_sysctl, *sysctl; + + insns_sysctl = kzalloc(sizeof(*sysctl) * (nr_insn_emulated + 1), + GFP_KERNEL); + + raw_spin_lock_irqsave(&insn_emulation_lock, flags); + list_for_each_entry(insn, &insn_emulation, node) { + sysctl = &insns_sysctl[i]; + + sysctl->mode = 0644; + sysctl->maxlen = sizeof(int); + + sysctl->procname = insn->ops->name; + sysctl->data = insn; + sysctl->extra1 = &insn->min; + sysctl->extra2 = &insn->max; + sysctl->proc_handler = emulation_proc_handler; + i++; + } + raw_spin_unlock_irqrestore(&insn_emulation_lock, flags); + + table->child = insns_sysctl; + register_sysctl_table(table); +} + +/* + * Invoked as late_initcall, since not needed before init spawned. + */ +static int __init armv8_deprecated_init(void) +{ + register_insn_emulation_sysctl(ctl_abi); + + return 0; +} + +late_initcall(armv8_deprecated_init); |