From 587064b610c703f259317d00dc37bf6d40f4fc74 Mon Sep 17 00:00:00 2001 From: Punit Agrawal Date: Tue, 18 Nov 2014 11:41:24 +0000 Subject: arm64: Add framework for legacy instruction emulation Typically, providing support for legacy instructions requires emulating the behaviour of instructions whose encodings have become undefined. If the instructions haven't been removed from the architecture, there maybe an option in the implementation to turn on/off the support for these instructions. Create common infrastructure to support legacy instruction emulation. In addition to emulation, also provide an option to support hardware execution when supported. The default execution mode (one of undef, emulate, hw exeuction) is dependent on the state of the instruction (deprecated or obsolete) in the architecture and can specified at the time of registering the instruction handlers. The runtime state of the emulation can be controlled by writing to individual nodes in sysctl. The expected default behaviour is documented as part of this patch. Reviewed-by: Catalin Marinas Signed-off-by: Punit Agrawal Signed-off-by: Will Deacon --- arch/arm64/kernel/Makefile | 1 + arch/arm64/kernel/armv8_deprecated.c | 216 +++++++++++++++++++++++++++++++++++ 2 files changed, 217 insertions(+) create mode 100644 arch/arm64/kernel/armv8_deprecated.c (limited to 'arch/arm64/kernel') 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 +#include +#include +#include + +#include + +/* + * 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); -- cgit v1.2.3