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linux-bl808/arch/arm64/kernel/entry-common.c
Dave Martin 8ef8f360cf arm64: Basic Branch Target Identification support 
This patch adds the bare minimum required to expose the ARMv8.5
Branch Target Identification feature to userspace.

By itself, this does _not_ automatically enable BTI for any initial
executable pages mapped by execve().  This will come later, but for
now it should be possible to enable BTI manually on those pages by
using mprotect() from within the target process.

Other arches already using the generic mman.h are already using
0x10 for arch-specific prot flags, so we use that for PROT_BTI
here.

For consistency, signal handler entry points in BTI guarded pages
are required to be annotated as such, just like any other function.
This blocks a relatively minor attack vector, but comforming
userspace will have the annotations anyway, so we may as well
enforce them.

Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2020-03-16 17:19:48 +00:00

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// SPDX-License-Identifier: GPL-2.0
/*
* Exception handling code
*
* Copyright (C) 2019 ARM Ltd.
*/
#include <linux/context_tracking.h>
#include <linux/ptrace.h>
#include <linux/thread_info.h>
#include <asm/cpufeature.h>
#include <asm/daifflags.h>
#include <asm/esr.h>
#include <asm/exception.h>
#include <asm/kprobes.h>
#include <asm/mmu.h>
#include <asm/sysreg.h>
static void notrace el1_abort(struct pt_regs *regs, unsigned long esr)
{
unsigned long far = read_sysreg(far_el1);
local_daif_inherit(regs);
far = untagged_addr(far);
do_mem_abort(far, esr, regs);
}
NOKPROBE_SYMBOL(el1_abort);
static void notrace el1_pc(struct pt_regs *regs, unsigned long esr)
{
unsigned long far = read_sysreg(far_el1);
local_daif_inherit(regs);
do_sp_pc_abort(far, esr, regs);
}
NOKPROBE_SYMBOL(el1_pc);
static void notrace el1_undef(struct pt_regs *regs)
{
local_daif_inherit(regs);
do_undefinstr(regs);
}
NOKPROBE_SYMBOL(el1_undef);
static void notrace el1_inv(struct pt_regs *regs, unsigned long esr)
{
local_daif_inherit(regs);
bad_mode(regs, 0, esr);
}
NOKPROBE_SYMBOL(el1_inv);
static void notrace el1_dbg(struct pt_regs *regs, unsigned long esr)
{
unsigned long far = read_sysreg(far_el1);
/*
* The CPU masked interrupts, and we are leaving them masked during
* do_debug_exception(). Update PMR as if we had called
* local_mask_daif().
*/
if (system_uses_irq_prio_masking())
gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);
do_debug_exception(far, esr, regs);
}
NOKPROBE_SYMBOL(el1_dbg);
asmlinkage void notrace el1_sync_handler(struct pt_regs *regs)
{
unsigned long esr = read_sysreg(esr_el1);
switch (ESR_ELx_EC(esr)) {
case ESR_ELx_EC_DABT_CUR:
case ESR_ELx_EC_IABT_CUR:
el1_abort(regs, esr);
break;
/*
* We don't handle ESR_ELx_EC_SP_ALIGN, since we will have hit a
* recursive exception when trying to push the initial pt_regs.
*/
case ESR_ELx_EC_PC_ALIGN:
el1_pc(regs, esr);
break;
case ESR_ELx_EC_SYS64:
case ESR_ELx_EC_UNKNOWN:
el1_undef(regs);
break;
case ESR_ELx_EC_BREAKPT_CUR:
case ESR_ELx_EC_SOFTSTP_CUR:
case ESR_ELx_EC_WATCHPT_CUR:
case ESR_ELx_EC_BRK64:
el1_dbg(regs, esr);
break;
default:
el1_inv(regs, esr);
};
}
NOKPROBE_SYMBOL(el1_sync_handler);
static void notrace el0_da(struct pt_regs *regs, unsigned long esr)
{
unsigned long far = read_sysreg(far_el1);
user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
far = untagged_addr(far);
do_mem_abort(far, esr, regs);
}
NOKPROBE_SYMBOL(el0_da);
static void notrace el0_ia(struct pt_regs *regs, unsigned long esr)
{
unsigned long far = read_sysreg(far_el1);
/*
* We've taken an instruction abort from userspace and not yet
* re-enabled IRQs. If the address is a kernel address, apply
* BP hardening prior to enabling IRQs and pre-emption.
*/
if (!is_ttbr0_addr(far))
arm64_apply_bp_hardening();
user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
do_mem_abort(far, esr, regs);
}
NOKPROBE_SYMBOL(el0_ia);
static void notrace el0_fpsimd_acc(struct pt_regs *regs, unsigned long esr)
{
user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
do_fpsimd_acc(esr, regs);
}
NOKPROBE_SYMBOL(el0_fpsimd_acc);
static void notrace el0_sve_acc(struct pt_regs *regs, unsigned long esr)
{
user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
do_sve_acc(esr, regs);
}
NOKPROBE_SYMBOL(el0_sve_acc);
static void notrace el0_fpsimd_exc(struct pt_regs *regs, unsigned long esr)
{
user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
do_fpsimd_exc(esr, regs);
}
NOKPROBE_SYMBOL(el0_fpsimd_exc);
static void notrace el0_sys(struct pt_regs *regs, unsigned long esr)
{
user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
do_sysinstr(esr, regs);
}
NOKPROBE_SYMBOL(el0_sys);
static void notrace el0_pc(struct pt_regs *regs, unsigned long esr)
{
unsigned long far = read_sysreg(far_el1);
if (!is_ttbr0_addr(instruction_pointer(regs)))
arm64_apply_bp_hardening();
user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
do_sp_pc_abort(far, esr, regs);
}
NOKPROBE_SYMBOL(el0_pc);
static void notrace el0_sp(struct pt_regs *regs, unsigned long esr)
{
user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX_NOIRQ);
do_sp_pc_abort(regs->sp, esr, regs);
}
NOKPROBE_SYMBOL(el0_sp);
static void notrace el0_undef(struct pt_regs *regs)
{
user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
do_undefinstr(regs);
}
NOKPROBE_SYMBOL(el0_undef);
static void notrace el0_bti(struct pt_regs *regs)
{
user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
do_bti(regs);
}
NOKPROBE_SYMBOL(el0_bti);
static void notrace el0_inv(struct pt_regs *regs, unsigned long esr)
{
user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
bad_el0_sync(regs, 0, esr);
}
NOKPROBE_SYMBOL(el0_inv);
static void notrace el0_dbg(struct pt_regs *regs, unsigned long esr)
{
/* Only watchpoints write FAR_EL1, otherwise its UNKNOWN */
unsigned long far = read_sysreg(far_el1);
if (system_uses_irq_prio_masking())
gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);
user_exit_irqoff();
do_debug_exception(far, esr, regs);
local_daif_restore(DAIF_PROCCTX_NOIRQ);
}
NOKPROBE_SYMBOL(el0_dbg);
static void notrace el0_svc(struct pt_regs *regs)
{
if (system_uses_irq_prio_masking())
gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);
do_el0_svc(regs);
}
NOKPROBE_SYMBOL(el0_svc);
asmlinkage void notrace el0_sync_handler(struct pt_regs *regs)
{
unsigned long esr = read_sysreg(esr_el1);
switch (ESR_ELx_EC(esr)) {
case ESR_ELx_EC_SVC64:
el0_svc(regs);
break;
case ESR_ELx_EC_DABT_LOW:
el0_da(regs, esr);
break;
case ESR_ELx_EC_IABT_LOW:
el0_ia(regs, esr);
break;
case ESR_ELx_EC_FP_ASIMD:
el0_fpsimd_acc(regs, esr);
break;
case ESR_ELx_EC_SVE:
el0_sve_acc(regs, esr);
break;
case ESR_ELx_EC_FP_EXC64:
el0_fpsimd_exc(regs, esr);
break;
case ESR_ELx_EC_SYS64:
case ESR_ELx_EC_WFx:
el0_sys(regs, esr);
break;
case ESR_ELx_EC_SP_ALIGN:
el0_sp(regs, esr);
break;
case ESR_ELx_EC_PC_ALIGN:
el0_pc(regs, esr);
break;
case ESR_ELx_EC_UNKNOWN:
el0_undef(regs);
break;
case ESR_ELx_EC_BTI:
el0_bti(regs);
break;
case ESR_ELx_EC_BREAKPT_LOW:
case ESR_ELx_EC_SOFTSTP_LOW:
case ESR_ELx_EC_WATCHPT_LOW:
case ESR_ELx_EC_BRK64:
el0_dbg(regs, esr);
break;
default:
el0_inv(regs, esr);
}
}
NOKPROBE_SYMBOL(el0_sync_handler);
#ifdef CONFIG_COMPAT
static void notrace el0_cp15(struct pt_regs *regs, unsigned long esr)
{
user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
do_cp15instr(esr, regs);
}
NOKPROBE_SYMBOL(el0_cp15);
static void notrace el0_svc_compat(struct pt_regs *regs)
{
if (system_uses_irq_prio_masking())
gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);
do_el0_svc_compat(regs);
}
NOKPROBE_SYMBOL(el0_svc_compat);
asmlinkage void notrace el0_sync_compat_handler(struct pt_regs *regs)
{
unsigned long esr = read_sysreg(esr_el1);
switch (ESR_ELx_EC(esr)) {
case ESR_ELx_EC_SVC32:
el0_svc_compat(regs);
break;
case ESR_ELx_EC_DABT_LOW:
el0_da(regs, esr);
break;
case ESR_ELx_EC_IABT_LOW:
el0_ia(regs, esr);
break;
case ESR_ELx_EC_FP_ASIMD:
el0_fpsimd_acc(regs, esr);
break;
case ESR_ELx_EC_FP_EXC32:
el0_fpsimd_exc(regs, esr);
break;
case ESR_ELx_EC_PC_ALIGN:
el0_pc(regs, esr);
break;
case ESR_ELx_EC_UNKNOWN:
case ESR_ELx_EC_CP14_MR:
case ESR_ELx_EC_CP14_LS:
case ESR_ELx_EC_CP14_64:
el0_undef(regs);
break;
case ESR_ELx_EC_CP15_32:
case ESR_ELx_EC_CP15_64:
el0_cp15(regs, esr);
break;
case ESR_ELx_EC_BREAKPT_LOW:
case ESR_ELx_EC_SOFTSTP_LOW:
case ESR_ELx_EC_WATCHPT_LOW:
case ESR_ELx_EC_BKPT32:
el0_dbg(regs, esr);
break;
default:
el0_inv(regs, esr);
}
}
NOKPROBE_SYMBOL(el0_sync_compat_handler);
#endif /* CONFIG_COMPAT */
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