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linux/arch/arm64/kernel/entry.S
Mark Rutland da59f1d051 arm64: entry: simplify kernel_exit logic 
For historical reasons, the non-KPTI exception return path is duplicated for
EL1 and EL0, with the structure:

	.if \el == 0
	[ KPTI handling ]
	ldr     lr, [sp, #S_LR]
 	add	sp, sp, #PT_REGS_SIZE		// restore sp
	[ EL0 exception return workaround ]
	eret
	.else
	ldr     lr, [sp, #S_LR]
 	add	sp, sp, #PT_REGS_SIZE		// restore sp
	[ EL1 exception return workaround ]
	eret
	.endif
	sb

This would be simpler and clearer with the common portions factored out,
e.g.

	.if \el == 0
	[ KPTI handling ]
	.endif

	ldr     lr, [sp, #S_LR]
 	add	sp, sp, #PT_REGS_SIZE		// restore sp

	.if \el == 0
	[ EL0 exception return workaround ]
	.else
	[ EL1 exception return workaround ]
	.endif

	eret
	sb

This expands to the same code, but is simpler for a human to follow as
it avoids duplicates the restore of LR+SP, and makes it clear that the
ERET is associated with the SB.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20240116110221.420467-3-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
2024-01-18 11:00:09 +00:00

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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Low-level exception handling code
*
* Copyright (C) 2012 ARM Ltd.
* Authors: Catalin Marinas <catalin.marinas@arm.com>
* Will Deacon <will.deacon@arm.com>
*/
#include <linux/arm-smccc.h>
#include <linux/init.h>
#include <linux/linkage.h>
#include <asm/alternative.h>
#include <asm/assembler.h>
#include <asm/asm-offsets.h>
#include <asm/asm_pointer_auth.h>
#include <asm/bug.h>
#include <asm/cpufeature.h>
#include <asm/errno.h>
#include <asm/esr.h>
#include <asm/irq.h>
#include <asm/memory.h>
#include <asm/mmu.h>
#include <asm/processor.h>
#include <asm/ptrace.h>
#include <asm/scs.h>
#include <asm/thread_info.h>
#include <asm/asm-uaccess.h>
#include <asm/unistd.h>
.macro clear_gp_regs
.irp n,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29
mov x\n, xzr
.endr
.endm
.macro kernel_ventry, el:req, ht:req, regsize:req, label:req
.align 7
.Lventry_start\@:
.if \el == 0
/*
* This must be the first instruction of the EL0 vector entries. It is
* skipped by the trampoline vectors, to trigger the cleanup.
*/
b .Lskip_tramp_vectors_cleanup\@
.if \regsize == 64
mrs x30, tpidrro_el0
msr tpidrro_el0, xzr
.else
mov x30, xzr
.endif
.Lskip_tramp_vectors_cleanup\@:
.endif
sub sp, sp, #PT_REGS_SIZE
#ifdef CONFIG_VMAP_STACK
/*
* Test whether the SP has overflowed, without corrupting a GPR.
* Task and IRQ stacks are aligned so that SP & (1 << THREAD_SHIFT)
* should always be zero.
*/
add sp, sp, x0 // sp' = sp + x0
sub x0, sp, x0 // x0' = sp' - x0 = (sp + x0) - x0 = sp
tbnz x0, #THREAD_SHIFT, 0f
sub x0, sp, x0 // x0'' = sp' - x0' = (sp + x0) - sp = x0
sub sp, sp, x0 // sp'' = sp' - x0 = (sp + x0) - x0 = sp
b el\el\ht\()_\regsize\()_\label
0:
/*
* Either we've just detected an overflow, or we've taken an exception
* while on the overflow stack. Either way, we won't return to
* userspace, and can clobber EL0 registers to free up GPRs.
*/
/* Stash the original SP (minus PT_REGS_SIZE) in tpidr_el0. */
msr tpidr_el0, x0
/* Recover the original x0 value and stash it in tpidrro_el0 */
sub x0, sp, x0
msr tpidrro_el0, x0
/* Switch to the overflow stack */
adr_this_cpu sp, overflow_stack + OVERFLOW_STACK_SIZE, x0
/*
* Check whether we were already on the overflow stack. This may happen
* after panic() re-enables interrupts.
*/
mrs x0, tpidr_el0 // sp of interrupted context
sub x0, sp, x0 // delta with top of overflow stack
tst x0, #~(OVERFLOW_STACK_SIZE - 1) // within range?
b.ne __bad_stack // no? -> bad stack pointer
/* We were already on the overflow stack. Restore sp/x0 and carry on. */
sub sp, sp, x0
mrs x0, tpidrro_el0
#endif
b el\el\ht\()_\regsize\()_\label
.org .Lventry_start\@ + 128 // Did we overflow the ventry slot?
.endm
.macro tramp_alias, dst, sym
.set .Lalias\@, TRAMP_VALIAS + \sym - .entry.tramp.text
movz \dst, :abs_g2_s:.Lalias\@
movk \dst, :abs_g1_nc:.Lalias\@
movk \dst, :abs_g0_nc:.Lalias\@
.endm
/*
* This macro corrupts x0-x3. It is the caller's duty to save/restore
* them if required.
*/
.macro apply_ssbd, state, tmp1, tmp2
alternative_cb ARM64_ALWAYS_SYSTEM, spectre_v4_patch_fw_mitigation_enable
b .L__asm_ssbd_skip\@ // Patched to NOP
alternative_cb_end
ldr_this_cpu \tmp2, arm64_ssbd_callback_required, \tmp1
cbz \tmp2, .L__asm_ssbd_skip\@
ldr \tmp2, [tsk, #TSK_TI_FLAGS]
tbnz \tmp2, #TIF_SSBD, .L__asm_ssbd_skip\@
mov w0, #ARM_SMCCC_ARCH_WORKAROUND_2
mov w1, #\state
alternative_cb ARM64_ALWAYS_SYSTEM, smccc_patch_fw_mitigation_conduit
nop // Patched to SMC/HVC #0
alternative_cb_end
.L__asm_ssbd_skip\@:
.endm
/* Check for MTE asynchronous tag check faults */
.macro check_mte_async_tcf, tmp, ti_flags, thread_sctlr
#ifdef CONFIG_ARM64_MTE
.arch_extension lse
alternative_if_not ARM64_MTE
b 1f
alternative_else_nop_endif
/*
* Asynchronous tag check faults are only possible in ASYNC (2) or
* ASYM (3) modes. In each of these modes bit 1 of SCTLR_EL1.TCF0 is
* set, so skip the check if it is unset.
*/
tbz \thread_sctlr, #(SCTLR_EL1_TCF0_SHIFT + 1), 1f
mrs_s \tmp, SYS_TFSRE0_EL1
tbz \tmp, #SYS_TFSR_EL1_TF0_SHIFT, 1f
/* Asynchronous TCF occurred for TTBR0 access, set the TI flag */
mov \tmp, #_TIF_MTE_ASYNC_FAULT
add \ti_flags, tsk, #TSK_TI_FLAGS
stset \tmp, [\ti_flags]
1:
#endif
.endm
/* Clear the MTE asynchronous tag check faults */
.macro clear_mte_async_tcf thread_sctlr
#ifdef CONFIG_ARM64_MTE
alternative_if ARM64_MTE
/* See comment in check_mte_async_tcf above. */
tbz \thread_sctlr, #(SCTLR_EL1_TCF0_SHIFT + 1), 1f
dsb ish
msr_s SYS_TFSRE0_EL1, xzr
1:
alternative_else_nop_endif
#endif
.endm
.macro mte_set_gcr, mte_ctrl, tmp
#ifdef CONFIG_ARM64_MTE
ubfx \tmp, \mte_ctrl, #MTE_CTRL_GCR_USER_EXCL_SHIFT, #16
orr \tmp, \tmp, #SYS_GCR_EL1_RRND
msr_s SYS_GCR_EL1, \tmp
#endif
.endm
.macro mte_set_kernel_gcr, tmp, tmp2
#ifdef CONFIG_KASAN_HW_TAGS
alternative_cb ARM64_ALWAYS_SYSTEM, kasan_hw_tags_enable
b 1f
alternative_cb_end
mov \tmp, KERNEL_GCR_EL1
msr_s SYS_GCR_EL1, \tmp
1:
#endif
.endm
.macro mte_set_user_gcr, tsk, tmp, tmp2
#ifdef CONFIG_KASAN_HW_TAGS
alternative_cb ARM64_ALWAYS_SYSTEM, kasan_hw_tags_enable
b 1f
alternative_cb_end
ldr \tmp, [\tsk, #THREAD_MTE_CTRL]
mte_set_gcr \tmp, \tmp2
1:
#endif
.endm
.macro kernel_entry, el, regsize = 64
.if \el == 0
alternative_insn nop, SET_PSTATE_DIT(1), ARM64_HAS_DIT
.endif
.if \regsize == 32
mov w0, w0 // zero upper 32 bits of x0
.endif
stp x0, x1, [sp, #16 * 0]
stp x2, x3, [sp, #16 * 1]
stp x4, x5, [sp, #16 * 2]
stp x6, x7, [sp, #16 * 3]
stp x8, x9, [sp, #16 * 4]
stp x10, x11, [sp, #16 * 5]
stp x12, x13, [sp, #16 * 6]
stp x14, x15, [sp, #16 * 7]
stp x16, x17, [sp, #16 * 8]
stp x18, x19, [sp, #16 * 9]
stp x20, x21, [sp, #16 * 10]
stp x22, x23, [sp, #16 * 11]
stp x24, x25, [sp, #16 * 12]
stp x26, x27, [sp, #16 * 13]
stp x28, x29, [sp, #16 * 14]
.if \el == 0
clear_gp_regs
mrs x21, sp_el0
ldr_this_cpu tsk, __entry_task, x20
msr sp_el0, tsk
/*
* Ensure MDSCR_EL1.SS is clear, since we can unmask debug exceptions
* when scheduling.
*/
ldr x19, [tsk, #TSK_TI_FLAGS]
disable_step_tsk x19, x20
/* Check for asynchronous tag check faults in user space */
ldr x0, [tsk, THREAD_SCTLR_USER]
check_mte_async_tcf x22, x23, x0
#ifdef CONFIG_ARM64_PTR_AUTH
alternative_if ARM64_HAS_ADDRESS_AUTH
/*
* Enable IA for in-kernel PAC if the task had it disabled. Although
* this could be implemented with an unconditional MRS which would avoid
* a load, this was measured to be slower on Cortex-A75 and Cortex-A76.
*
* Install the kernel IA key only if IA was enabled in the task. If IA
* was disabled on kernel exit then we would have left the kernel IA
* installed so there is no need to install it again.
*/
tbz x0, SCTLR_ELx_ENIA_SHIFT, 1f
__ptrauth_keys_install_kernel_nosync tsk, x20, x22, x23
b 2f
1:
mrs x0, sctlr_el1
orr x0, x0, SCTLR_ELx_ENIA
msr sctlr_el1, x0
2:
alternative_else_nop_endif
#endif
apply_ssbd 1, x22, x23
mte_set_kernel_gcr x22, x23
/*
* Any non-self-synchronizing system register updates required for
* kernel entry should be placed before this point.
*/
alternative_if ARM64_MTE
isb
b 1f
alternative_else_nop_endif
alternative_if ARM64_HAS_ADDRESS_AUTH
isb
alternative_else_nop_endif
1:
scs_load_current
.else
add x21, sp, #PT_REGS_SIZE
get_current_task tsk
.endif /* \el == 0 */
mrs x22, elr_el1
mrs x23, spsr_el1
stp lr, x21, [sp, #S_LR]
/*
* For exceptions from EL0, create a final frame record.
* For exceptions from EL1, create a synthetic frame record so the
* interrupted code shows up in the backtrace.
*/
.if \el == 0
stp xzr, xzr, [sp, #S_STACKFRAME]
.else
stp x29, x22, [sp, #S_STACKFRAME]
.endif
add x29, sp, #S_STACKFRAME
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
alternative_if_not ARM64_HAS_PAN
bl __swpan_entry_el\el
alternative_else_nop_endif
#endif
stp x22, x23, [sp, #S_PC]
/* Not in a syscall by default (el0_svc overwrites for real syscall) */
.if \el == 0
mov w21, #NO_SYSCALL
str w21, [sp, #S_SYSCALLNO]
.endif
#ifdef CONFIG_ARM64_PSEUDO_NMI
alternative_if_not ARM64_HAS_GIC_PRIO_MASKING
b .Lskip_pmr_save\@
alternative_else_nop_endif
mrs_s x20, SYS_ICC_PMR_EL1
str x20, [sp, #S_PMR_SAVE]
mov x20, #GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET
msr_s SYS_ICC_PMR_EL1, x20
.Lskip_pmr_save\@:
#endif
/*
* Registers that may be useful after this macro is invoked:
*
* x20 - ICC_PMR_EL1
* x21 - aborted SP
* x22 - aborted PC
* x23 - aborted PSTATE
*/
.endm
.macro kernel_exit, el
.if \el != 0
disable_daif
.endif
#ifdef CONFIG_ARM64_PSEUDO_NMI
alternative_if_not ARM64_HAS_GIC_PRIO_MASKING
b .Lskip_pmr_restore\@
alternative_else_nop_endif
ldr x20, [sp, #S_PMR_SAVE]
msr_s SYS_ICC_PMR_EL1, x20
/* Ensure priority change is seen by redistributor */
alternative_if_not ARM64_HAS_GIC_PRIO_RELAXED_SYNC
dsb sy
alternative_else_nop_endif
.Lskip_pmr_restore\@:
#endif
ldp x21, x22, [sp, #S_PC] // load ELR, SPSR
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
alternative_if_not ARM64_HAS_PAN
bl __swpan_exit_el\el
alternative_else_nop_endif
#endif
.if \el == 0
ldr x23, [sp, #S_SP] // load return stack pointer
msr sp_el0, x23
tst x22, #PSR_MODE32_BIT // native task?
b.eq 3f
#ifdef CONFIG_ARM64_ERRATUM_845719
alternative_if ARM64_WORKAROUND_845719
#ifdef CONFIG_PID_IN_CONTEXTIDR
mrs x29, contextidr_el1
msr contextidr_el1, x29
#else
msr contextidr_el1, xzr
#endif
alternative_else_nop_endif
#endif
3:
scs_save tsk
/* Ignore asynchronous tag check faults in the uaccess routines */
ldr x0, [tsk, THREAD_SCTLR_USER]
clear_mte_async_tcf x0
#ifdef CONFIG_ARM64_PTR_AUTH
alternative_if ARM64_HAS_ADDRESS_AUTH
/*
* IA was enabled for in-kernel PAC. Disable it now if needed, or
* alternatively install the user's IA. All other per-task keys and
* SCTLR bits were updated on task switch.
*
* No kernel C function calls after this.
*/
tbz x0, SCTLR_ELx_ENIA_SHIFT, 1f
__ptrauth_keys_install_user tsk, x0, x1, x2
b 2f
1:
mrs x0, sctlr_el1
bic x0, x0, SCTLR_ELx_ENIA
msr sctlr_el1, x0
2:
alternative_else_nop_endif
#endif
mte_set_user_gcr tsk, x0, x1
apply_ssbd 0, x0, x1
.endif
msr elr_el1, x21 // set up the return data
msr spsr_el1, x22
ldp x0, x1, [sp, #16 * 0]
ldp x2, x3, [sp, #16 * 1]
ldp x4, x5, [sp, #16 * 2]
ldp x6, x7, [sp, #16 * 3]
ldp x8, x9, [sp, #16 * 4]
ldp x10, x11, [sp, #16 * 5]
ldp x12, x13, [sp, #16 * 6]
ldp x14, x15, [sp, #16 * 7]
ldp x16, x17, [sp, #16 * 8]
ldp x18, x19, [sp, #16 * 9]
ldp x20, x21, [sp, #16 * 10]
ldp x22, x23, [sp, #16 * 11]
ldp x24, x25, [sp, #16 * 12]
ldp x26, x27, [sp, #16 * 13]
ldp x28, x29, [sp, #16 * 14]
.if \el == 0
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
alternative_insn "b .L_skip_tramp_exit_\@", nop, ARM64_UNMAP_KERNEL_AT_EL0
msr far_el1, x29
ldr_this_cpu x30, this_cpu_vector, x29
tramp_alias x29, tramp_exit
msr vbar_el1, x30 // install vector table
ldr lr, [sp, #S_LR] // restore x30
add sp, sp, #PT_REGS_SIZE // restore sp
br x29
.L_skip_tramp_exit_\@:
#endif
.endif
ldr lr, [sp, #S_LR]
add sp, sp, #PT_REGS_SIZE // restore sp
.if \el == 0
/* This must be after the last explicit memory access */
alternative_if ARM64_WORKAROUND_SPECULATIVE_UNPRIV_LOAD
tlbi vale1, xzr
dsb nsh
alternative_else_nop_endif
.else
/* Ensure any device/NC reads complete */
alternative_insn nop, "dmb sy", ARM64_WORKAROUND_1508412
.endif
eret
sb
.endm
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
/*
* Set the TTBR0 PAN bit in SPSR. When the exception is taken from
* EL0, there is no need to check the state of TTBR0_EL1 since
* accesses are always enabled.
* Note that the meaning of this bit differs from the ARMv8.1 PAN
* feature as all TTBR0_EL1 accesses are disabled, not just those to
* user mappings.
*/
SYM_CODE_START_LOCAL(__swpan_entry_el1)
mrs x21, ttbr0_el1
tst x21, #TTBR_ASID_MASK // Check for the reserved ASID
orr x23, x23, #PSR_PAN_BIT // Set the emulated PAN in the saved SPSR
b.eq 1f // TTBR0 access already disabled
and x23, x23, #~PSR_PAN_BIT // Clear the emulated PAN in the saved SPSR
SYM_INNER_LABEL(__swpan_entry_el0, SYM_L_LOCAL)
__uaccess_ttbr0_disable x21
1: ret
SYM_CODE_END(__swpan_entry_el1)
/*
* Restore access to TTBR0_EL1. If returning to EL0, no need for SPSR
* PAN bit checking.
*/
SYM_CODE_START_LOCAL(__swpan_exit_el1)
tbnz x22, #22, 1f // Skip re-enabling TTBR0 access if the PSR_PAN_BIT is set
__uaccess_ttbr0_enable x0, x1
1: and x22, x22, #~PSR_PAN_BIT // ARMv8.0 CPUs do not understand this bit
ret
SYM_CODE_END(__swpan_exit_el1)
SYM_CODE_START_LOCAL(__swpan_exit_el0)
__uaccess_ttbr0_enable x0, x1
/*
* Enable errata workarounds only if returning to user. The only
* workaround currently required for TTBR0_EL1 changes are for the
* Cavium erratum 27456 (broadcast TLBI instructions may cause I-cache
* corruption).
*/
b post_ttbr_update_workaround
SYM_CODE_END(__swpan_exit_el0)
#endif
/* GPRs used by entry code */
tsk .req x28 // current thread_info
.text
/*
* Exception vectors.
*/
.pushsection ".entry.text", "ax"
.align 11
SYM_CODE_START(vectors)
kernel_ventry 1, t, 64, sync // Synchronous EL1t
kernel_ventry 1, t, 64, irq // IRQ EL1t
kernel_ventry 1, t, 64, fiq // FIQ EL1t
kernel_ventry 1, t, 64, error // Error EL1t
kernel_ventry 1, h, 64, sync // Synchronous EL1h
kernel_ventry 1, h, 64, irq // IRQ EL1h
kernel_ventry 1, h, 64, fiq // FIQ EL1h
kernel_ventry 1, h, 64, error // Error EL1h
kernel_ventry 0, t, 64, sync // Synchronous 64-bit EL0
kernel_ventry 0, t, 64, irq // IRQ 64-bit EL0
kernel_ventry 0, t, 64, fiq // FIQ 64-bit EL0
kernel_ventry 0, t, 64, error // Error 64-bit EL0
kernel_ventry 0, t, 32, sync // Synchronous 32-bit EL0
kernel_ventry 0, t, 32, irq // IRQ 32-bit EL0
kernel_ventry 0, t, 32, fiq // FIQ 32-bit EL0
kernel_ventry 0, t, 32, error // Error 32-bit EL0
SYM_CODE_END(vectors)
#ifdef CONFIG_VMAP_STACK
SYM_CODE_START_LOCAL(__bad_stack)
/*
* We detected an overflow in kernel_ventry, which switched to the
* overflow stack. Stash the exception regs, and head to our overflow
* handler.
*/
/* Restore the original x0 value */
mrs x0, tpidrro_el0
/*
* Store the original GPRs to the new stack. The orginal SP (minus
* PT_REGS_SIZE) was stashed in tpidr_el0 by kernel_ventry.
*/
sub sp, sp, #PT_REGS_SIZE
kernel_entry 1
mrs x0, tpidr_el0
add x0, x0, #PT_REGS_SIZE
str x0, [sp, #S_SP]
/* Stash the regs for handle_bad_stack */
mov x0, sp
/* Time to die */
bl handle_bad_stack
ASM_BUG()
SYM_CODE_END(__bad_stack)
#endif /* CONFIG_VMAP_STACK */
.macro entry_handler el:req, ht:req, regsize:req, label:req
SYM_CODE_START_LOCAL(el\el\ht\()_\regsize\()_\label)
kernel_entry \el, \regsize
mov x0, sp
bl el\el\ht\()_\regsize\()_\label\()_handler
.if \el == 0
b ret_to_user
.else
b ret_to_kernel
.endif
SYM_CODE_END(el\el\ht\()_\regsize\()_\label)
.endm
/*
* Early exception handlers
*/
entry_handler 1, t, 64, sync
entry_handler 1, t, 64, irq
entry_handler 1, t, 64, fiq
entry_handler 1, t, 64, error
entry_handler 1, h, 64, sync
entry_handler 1, h, 64, irq
entry_handler 1, h, 64, fiq
entry_handler 1, h, 64, error
entry_handler 0, t, 64, sync
entry_handler 0, t, 64, irq
entry_handler 0, t, 64, fiq
entry_handler 0, t, 64, error
entry_handler 0, t, 32, sync
entry_handler 0, t, 32, irq
entry_handler 0, t, 32, fiq
entry_handler 0, t, 32, error
SYM_CODE_START_LOCAL(ret_to_kernel)
kernel_exit 1
SYM_CODE_END(ret_to_kernel)
SYM_CODE_START_LOCAL(ret_to_user)
ldr x19, [tsk, #TSK_TI_FLAGS] // re-check for single-step
enable_step_tsk x19, x2
#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
bl stackleak_erase_on_task_stack
#endif
kernel_exit 0
SYM_CODE_END(ret_to_user)
.popsection // .entry.text
// Move from tramp_pg_dir to swapper_pg_dir
.macro tramp_map_kernel, tmp
mrs \tmp, ttbr1_el1
add \tmp, \tmp, #TRAMP_SWAPPER_OFFSET
bic \tmp, \tmp, #USER_ASID_FLAG
msr ttbr1_el1, \tmp
#ifdef CONFIG_QCOM_FALKOR_ERRATUM_1003
alternative_if ARM64_WORKAROUND_QCOM_FALKOR_E1003
/* ASID already in \tmp[63:48] */
movk \tmp, #:abs_g2_nc:(TRAMP_VALIAS >> 12)
movk \tmp, #:abs_g1_nc:(TRAMP_VALIAS >> 12)
/* 2MB boundary containing the vectors, so we nobble the walk cache */
movk \tmp, #:abs_g0_nc:((TRAMP_VALIAS & ~(SZ_2M - 1)) >> 12)
isb
tlbi vae1, \tmp
dsb nsh
alternative_else_nop_endif
#endif /* CONFIG_QCOM_FALKOR_ERRATUM_1003 */
.endm
// Move from swapper_pg_dir to tramp_pg_dir
.macro tramp_unmap_kernel, tmp
mrs \tmp, ttbr1_el1
sub \tmp, \tmp, #TRAMP_SWAPPER_OFFSET
orr \tmp, \tmp, #USER_ASID_FLAG
msr ttbr1_el1, \tmp
/*
* We avoid running the post_ttbr_update_workaround here because
* it's only needed by Cavium ThunderX, which requires KPTI to be
* disabled.
*/
.endm
.macro tramp_data_read_var dst, var
#ifdef CONFIG_RELOCATABLE
ldr \dst, .L__tramp_data_\var
.ifndef .L__tramp_data_\var
.pushsection ".entry.tramp.rodata", "a", %progbits
.align 3
.L__tramp_data_\var:
.quad \var
.popsection
.endif
#else
/*
* As !RELOCATABLE implies !RANDOMIZE_BASE the address is always a
* compile time constant (and hence not secret and not worth hiding).
*
* As statically allocated kernel code and data always live in the top
* 47 bits of the address space we can sign-extend bit 47 and avoid an
* instruction to load the upper 16 bits (which must be 0xFFFF).
*/
movz \dst, :abs_g2_s:\var
movk \dst, :abs_g1_nc:\var
movk \dst, :abs_g0_nc:\var
#endif
.endm
#define BHB_MITIGATION_NONE 0
#define BHB_MITIGATION_LOOP 1
#define BHB_MITIGATION_FW 2
#define BHB_MITIGATION_INSN 3
.macro tramp_ventry, vector_start, regsize, kpti, bhb
.align 7
1:
.if \regsize == 64
msr tpidrro_el0, x30 // Restored in kernel_ventry
.endif
.if \bhb == BHB_MITIGATION_LOOP
/*
* This sequence must appear before the first indirect branch. i.e. the
* ret out of tramp_ventry. It appears here because x30 is free.
*/
__mitigate_spectre_bhb_loop x30
.endif // \bhb == BHB_MITIGATION_LOOP
.if \bhb == BHB_MITIGATION_INSN
clearbhb
isb
.endif // \bhb == BHB_MITIGATION_INSN
.if \kpti == 1
/*
* Defend against branch aliasing attacks by pushing a dummy
* entry onto the return stack and using a RET instruction to
* enter the full-fat kernel vectors.
*/
bl 2f
b .
2:
tramp_map_kernel x30
alternative_insn isb, nop, ARM64_WORKAROUND_QCOM_FALKOR_E1003
tramp_data_read_var x30, vectors
alternative_if_not ARM64_WORKAROUND_CAVIUM_TX2_219_PRFM
prfm plil1strm, [x30, #(1b - \vector_start)]
alternative_else_nop_endif
msr vbar_el1, x30
isb
.else
adr_l x30, vectors
.endif // \kpti == 1
.if \bhb == BHB_MITIGATION_FW
/*
* The firmware sequence must appear before the first indirect branch.
* i.e. the ret out of tramp_ventry. But it also needs the stack to be
* mapped to save/restore the registers the SMC clobbers.
*/
__mitigate_spectre_bhb_fw
.endif // \bhb == BHB_MITIGATION_FW
add x30, x30, #(1b - \vector_start + 4)
ret
.org 1b + 128 // Did we overflow the ventry slot?
.endm
.macro generate_tramp_vector, kpti, bhb
.Lvector_start\@:
.space 0x400
.rept 4
tramp_ventry .Lvector_start\@, 64, \kpti, \bhb
.endr
.rept 4
tramp_ventry .Lvector_start\@, 32, \kpti, \bhb
.endr
.endm
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
/*
* Exception vectors trampoline.
* The order must match __bp_harden_el1_vectors and the
* arm64_bp_harden_el1_vectors enum.
*/
.pushsection ".entry.tramp.text", "ax"
.align 11
SYM_CODE_START_LOCAL_NOALIGN(tramp_vectors)
#ifdef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
generate_tramp_vector kpti=1, bhb=BHB_MITIGATION_LOOP
generate_tramp_vector kpti=1, bhb=BHB_MITIGATION_FW
generate_tramp_vector kpti=1, bhb=BHB_MITIGATION_INSN
#endif /* CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY */
generate_tramp_vector kpti=1, bhb=BHB_MITIGATION_NONE
SYM_CODE_END(tramp_vectors)
SYM_CODE_START_LOCAL(tramp_exit)
tramp_unmap_kernel x29
mrs x29, far_el1 // restore x29
eret
sb
SYM_CODE_END(tramp_exit)
.popsection // .entry.tramp.text
#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
/*
* Exception vectors for spectre mitigations on entry from EL1 when
* kpti is not in use.
*/
.macro generate_el1_vector, bhb
.Lvector_start\@:
kernel_ventry 1, t, 64, sync // Synchronous EL1t
kernel_ventry 1, t, 64, irq // IRQ EL1t
kernel_ventry 1, t, 64, fiq // FIQ EL1h
kernel_ventry 1, t, 64, error // Error EL1t
kernel_ventry 1, h, 64, sync // Synchronous EL1h
kernel_ventry 1, h, 64, irq // IRQ EL1h
kernel_ventry 1, h, 64, fiq // FIQ EL1h
kernel_ventry 1, h, 64, error // Error EL1h
.rept 4
tramp_ventry .Lvector_start\@, 64, 0, \bhb
.endr
.rept 4
tramp_ventry .Lvector_start\@, 32, 0, \bhb
.endr
.endm
/* The order must match tramp_vecs and the arm64_bp_harden_el1_vectors enum. */
.pushsection ".entry.text", "ax"
.align 11
SYM_CODE_START(__bp_harden_el1_vectors)
#ifdef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
generate_el1_vector bhb=BHB_MITIGATION_LOOP
generate_el1_vector bhb=BHB_MITIGATION_FW
generate_el1_vector bhb=BHB_MITIGATION_INSN
#endif /* CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY */
SYM_CODE_END(__bp_harden_el1_vectors)
.popsection
/*
* Register switch for AArch64. The callee-saved registers need to be saved
* and restored. On entry:
* x0 = previous task_struct (must be preserved across the switch)
* x1 = next task_struct
* Previous and next are guaranteed not to be the same.
*
*/
SYM_FUNC_START(cpu_switch_to)
mov x10, #THREAD_CPU_CONTEXT
add x8, x0, x10
mov x9, sp
stp x19, x20, [x8], #16 // store callee-saved registers
stp x21, x22, [x8], #16
stp x23, x24, [x8], #16
stp x25, x26, [x8], #16
stp x27, x28, [x8], #16
stp x29, x9, [x8], #16
str lr, [x8]
add x8, x1, x10
ldp x19, x20, [x8], #16 // restore callee-saved registers
ldp x21, x22, [x8], #16
ldp x23, x24, [x8], #16
ldp x25, x26, [x8], #16
ldp x27, x28, [x8], #16
ldp x29, x9, [x8], #16
ldr lr, [x8]
mov sp, x9
msr sp_el0, x1
ptrauth_keys_install_kernel x1, x8, x9, x10
scs_save x0
scs_load_current
ret
SYM_FUNC_END(cpu_switch_to)
NOKPROBE(cpu_switch_to)
/*
* This is how we return from a fork.
*/
SYM_CODE_START(ret_from_fork)
bl schedule_tail
cbz x19, 1f // not a kernel thread
mov x0, x20
blr x19
1: get_current_task tsk
mov x0, sp
bl asm_exit_to_user_mode
b ret_to_user
SYM_CODE_END(ret_from_fork)
NOKPROBE(ret_from_fork)
/*
* void call_on_irq_stack(struct pt_regs *regs,
* void (*func)(struct pt_regs *));
*
* Calls func(regs) using this CPU's irq stack and shadow irq stack.
*/
SYM_FUNC_START(call_on_irq_stack)
#ifdef CONFIG_SHADOW_CALL_STACK
get_current_task x16
scs_save x16
ldr_this_cpu scs_sp, irq_shadow_call_stack_ptr, x17
#endif
/* Create a frame record to save our LR and SP (implicit in FP) */
stp x29, x30, [sp, #-16]!
mov x29, sp
ldr_this_cpu x16, irq_stack_ptr, x17
/* Move to the new stack and call the function there */
add sp, x16, #IRQ_STACK_SIZE
blr x1
/*
* Restore the SP from the FP, and restore the FP and LR from the frame
* record.
*/
mov sp, x29
ldp x29, x30, [sp], #16
scs_load_current
ret
SYM_FUNC_END(call_on_irq_stack)
NOKPROBE(call_on_irq_stack)
#ifdef CONFIG_ARM_SDE_INTERFACE
#include <asm/sdei.h>
#include <uapi/linux/arm_sdei.h>
.macro sdei_handler_exit exit_mode
/* On success, this call never returns... */
cmp \exit_mode, #SDEI_EXIT_SMC
b.ne 99f
smc #0
b .
99: hvc #0
b .
.endm
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
/*
* The regular SDEI entry point may have been unmapped along with the rest of
* the kernel. This trampoline restores the kernel mapping to make the x1 memory
* argument accessible.
*
* This clobbers x4, __sdei_handler() will restore this from firmware's
* copy.
*/
.pushsection ".entry.tramp.text", "ax"
SYM_CODE_START(__sdei_asm_entry_trampoline)
mrs x4, ttbr1_el1
tbz x4, #USER_ASID_BIT, 1f
tramp_map_kernel tmp=x4
isb
mov x4, xzr
/*
* Remember whether to unmap the kernel on exit.
*/
1: str x4, [x1, #(SDEI_EVENT_INTREGS + S_SDEI_TTBR1)]
tramp_data_read_var x4, __sdei_asm_handler
br x4
SYM_CODE_END(__sdei_asm_entry_trampoline)
NOKPROBE(__sdei_asm_entry_trampoline)
/*
* Make the exit call and restore the original ttbr1_el1
*
* x0 & x1: setup for the exit API call
* x2: exit_mode
* x4: struct sdei_registered_event argument from registration time.
*/
SYM_CODE_START(__sdei_asm_exit_trampoline)
ldr x4, [x4, #(SDEI_EVENT_INTREGS + S_SDEI_TTBR1)]
cbnz x4, 1f
tramp_unmap_kernel tmp=x4
1: sdei_handler_exit exit_mode=x2
SYM_CODE_END(__sdei_asm_exit_trampoline)
NOKPROBE(__sdei_asm_exit_trampoline)
.popsection // .entry.tramp.text
#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
/*
* Software Delegated Exception entry point.
*
* x0: Event number
* x1: struct sdei_registered_event argument from registration time.
* x2: interrupted PC
* x3: interrupted PSTATE
* x4: maybe clobbered by the trampoline
*
* Firmware has preserved x0->x17 for us, we must save/restore the rest to
* follow SMC-CC. We save (or retrieve) all the registers as the handler may
* want them.
*/
SYM_CODE_START(__sdei_asm_handler)
stp x2, x3, [x1, #SDEI_EVENT_INTREGS + S_PC]
stp x4, x5, [x1, #SDEI_EVENT_INTREGS + 16 * 2]
stp x6, x7, [x1, #SDEI_EVENT_INTREGS + 16 * 3]
stp x8, x9, [x1, #SDEI_EVENT_INTREGS + 16 * 4]
stp x10, x11, [x1, #SDEI_EVENT_INTREGS + 16 * 5]
stp x12, x13, [x1, #SDEI_EVENT_INTREGS + 16 * 6]
stp x14, x15, [x1, #SDEI_EVENT_INTREGS + 16 * 7]
stp x16, x17, [x1, #SDEI_EVENT_INTREGS + 16 * 8]
stp x18, x19, [x1, #SDEI_EVENT_INTREGS + 16 * 9]
stp x20, x21, [x1, #SDEI_EVENT_INTREGS + 16 * 10]
stp x22, x23, [x1, #SDEI_EVENT_INTREGS + 16 * 11]
stp x24, x25, [x1, #SDEI_EVENT_INTREGS + 16 * 12]
stp x26, x27, [x1, #SDEI_EVENT_INTREGS + 16 * 13]
stp x28, x29, [x1, #SDEI_EVENT_INTREGS + 16 * 14]
mov x4, sp
stp lr, x4, [x1, #SDEI_EVENT_INTREGS + S_LR]
mov x19, x1
/* Store the registered-event for crash_smp_send_stop() */
ldrb w4, [x19, #SDEI_EVENT_PRIORITY]
cbnz w4, 1f
adr_this_cpu dst=x5, sym=sdei_active_normal_event, tmp=x6
b 2f
1: adr_this_cpu dst=x5, sym=sdei_active_critical_event, tmp=x6
2: str x19, [x5]
#ifdef CONFIG_VMAP_STACK
/*
* entry.S may have been using sp as a scratch register, find whether
* this is a normal or critical event and switch to the appropriate
* stack for this CPU.
*/
cbnz w4, 1f
ldr_this_cpu dst=x5, sym=sdei_stack_normal_ptr, tmp=x6
b 2f
1: ldr_this_cpu dst=x5, sym=sdei_stack_critical_ptr, tmp=x6
2: mov x6, #SDEI_STACK_SIZE
add x5, x5, x6
mov sp, x5
#endif
#ifdef CONFIG_SHADOW_CALL_STACK
/* Use a separate shadow call stack for normal and critical events */
cbnz w4, 3f
ldr_this_cpu dst=scs_sp, sym=sdei_shadow_call_stack_normal_ptr, tmp=x6
b 4f
3: ldr_this_cpu dst=scs_sp, sym=sdei_shadow_call_stack_critical_ptr, tmp=x6
4:
#endif
/*
* We may have interrupted userspace, or a guest, or exit-from or
* return-to either of these. We can't trust sp_el0, restore it.
*/
mrs x28, sp_el0
ldr_this_cpu dst=x0, sym=__entry_task, tmp=x1
msr sp_el0, x0
/* If we interrupted the kernel point to the previous stack/frame. */
and x0, x3, #0xc
mrs x1, CurrentEL
cmp x0, x1
csel x29, x29, xzr, eq // fp, or zero
csel x4, x2, xzr, eq // elr, or zero
stp x29, x4, [sp, #-16]!
mov x29, sp
add x0, x19, #SDEI_EVENT_INTREGS
mov x1, x19
bl __sdei_handler
msr sp_el0, x28
/* restore regs >x17 that we clobbered */
mov x4, x19 // keep x4 for __sdei_asm_exit_trampoline
ldp x28, x29, [x4, #SDEI_EVENT_INTREGS + 16 * 14]
ldp x18, x19, [x4, #SDEI_EVENT_INTREGS + 16 * 9]
ldp lr, x1, [x4, #SDEI_EVENT_INTREGS + S_LR]
mov sp, x1
mov x1, x0 // address to complete_and_resume
/* x0 = (x0 <= SDEI_EV_FAILED) ?
* EVENT_COMPLETE:EVENT_COMPLETE_AND_RESUME
*/
cmp x0, #SDEI_EV_FAILED
mov_q x2, SDEI_1_0_FN_SDEI_EVENT_COMPLETE
mov_q x3, SDEI_1_0_FN_SDEI_EVENT_COMPLETE_AND_RESUME
csel x0, x2, x3, ls
ldr_l x2, sdei_exit_mode
/* Clear the registered-event seen by crash_smp_send_stop() */
ldrb w3, [x4, #SDEI_EVENT_PRIORITY]
cbnz w3, 1f
adr_this_cpu dst=x5, sym=sdei_active_normal_event, tmp=x6
b 2f
1: adr_this_cpu dst=x5, sym=sdei_active_critical_event, tmp=x6
2: str xzr, [x5]
alternative_if_not ARM64_UNMAP_KERNEL_AT_EL0
sdei_handler_exit exit_mode=x2
alternative_else_nop_endif
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
tramp_alias dst=x5, sym=__sdei_asm_exit_trampoline
br x5
#endif
SYM_CODE_END(__sdei_asm_handler)
NOKPROBE(__sdei_asm_handler)
SYM_CODE_START(__sdei_handler_abort)
mov_q x0, SDEI_1_0_FN_SDEI_EVENT_COMPLETE_AND_RESUME
adr x1, 1f
ldr_l x2, sdei_exit_mode
sdei_handler_exit exit_mode=x2
// exit the handler and jump to the next instruction.
// Exit will stomp x0-x17, PSTATE, ELR_ELx, and SPSR_ELx.
1: ret
SYM_CODE_END(__sdei_handler_abort)
NOKPROBE(__sdei_handler_abort)
#endif /* CONFIG_ARM_SDE_INTERFACE */
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