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Diffstat (limited to '')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 1099 |
1 files changed, 1099 insertions, 0 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S new file mode 100644 index 0000000000..7fcbee0f6c --- /dev/null +++ b/arch/arm64/kernel/entry.S @@ -0,0 +1,1099 @@ +/* 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 + ldr lr, [sp, #S_LR] + add sp, sp, #PT_REGS_SIZE // restore sp + + /* 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 + eret + .else + ldr lr, [sp, #S_LR] + add sp, sp, #PT_REGS_SIZE // restore sp + + /* Ensure any device/NC reads complete */ + alternative_insn nop, "dmb sy", ARM64_WORKAROUND_1508412 + + eret + .endif + 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 */ |