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linux/arch/arm64/mm/proc.S
Mark Rutland 8286824789 arm64: kasan: mte: use a constant kernel GCR_EL1 value 
When KASAN_HW_TAGS is selected, KASAN is enabled at boot time, and the
hardware supports MTE, we'll initialize `kernel_gcr_excl` with a value
dependent on KASAN_TAG_MAX. While the resulting value is a constant
which depends on KASAN_TAG_MAX, we have to perform some runtime work to
generate the value, and have to read the value from memory during the
exception entry path. It would be better if we could generate this as a
constant at compile-time, and use it as such directly.

Early in boot within __cpu_setup(), we initialize GCR_EL1 to a safe
value, and later override this with the value required by KASAN. If
CONFIG_KASAN_HW_TAGS is not selected, or if KASAN is disabeld at boot
time, the kernel will not use IRG instructions, and so the initial value
of GCR_EL1 is does not matter to the kernel. Thus, we can instead have
__cpu_setup() initialize GCR_EL1 to a value consistent with
KASAN_TAG_MAX, and avoid the need to re-initialize it during hotplug and
resume form suspend.

This patch makes arem64 use a compile-time constant KERNEL_GCR_EL1
value, which is compatible with KASAN_HW_TAGS when this is selected.
This removes the need to re-initialize GCR_EL1 dynamically, and acts as
an optimization to the entry assembly, which no longer needs to load
this value from memory. The redundant initialization hooks are removed.

In order to do this, KASAN_TAG_MAX needs to be visible outside of the
core KASAN code. To do this, I've moved the KASAN_TAG_* values into
<linux/kasan-tags.h>.

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

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Tested-by: Andrey Konovalov <andreyknvl@gmail.com>
Link: https://lore.kernel.org/r/20210714143843.56537-3-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2021-08-02 18:14:21 +01:00

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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Based on arch/arm/mm/proc.S
*
* Copyright (C) 2001 Deep Blue Solutions Ltd.
* Copyright (C) 2012 ARM Ltd.
* Author: Catalin Marinas <catalin.marinas@arm.com>
*/
#include <linux/init.h>
#include <linux/linkage.h>
#include <linux/pgtable.h>
#include <asm/assembler.h>
#include <asm/asm-offsets.h>
#include <asm/asm_pointer_auth.h>
#include <asm/hwcap.h>
#include <asm/pgtable-hwdef.h>
#include <asm/cpufeature.h>
#include <asm/alternative.h>
#include <asm/smp.h>
#include <asm/sysreg.h>
#ifdef CONFIG_ARM64_64K_PAGES
#define TCR_TG_FLAGS TCR_TG0_64K | TCR_TG1_64K
#elif defined(CONFIG_ARM64_16K_PAGES)
#define TCR_TG_FLAGS TCR_TG0_16K | TCR_TG1_16K
#else /* CONFIG_ARM64_4K_PAGES */
#define TCR_TG_FLAGS TCR_TG0_4K | TCR_TG1_4K
#endif
#ifdef CONFIG_RANDOMIZE_BASE
#define TCR_KASLR_FLAGS TCR_NFD1
#else
#define TCR_KASLR_FLAGS 0
#endif
#define TCR_SMP_FLAGS TCR_SHARED
/* PTWs cacheable, inner/outer WBWA */
#define TCR_CACHE_FLAGS TCR_IRGN_WBWA | TCR_ORGN_WBWA
#ifdef CONFIG_KASAN_SW_TAGS
#define TCR_KASAN_SW_FLAGS TCR_TBI1 | TCR_TBID1
#else
#define TCR_KASAN_SW_FLAGS 0
#endif
#ifdef CONFIG_KASAN_HW_TAGS
#define TCR_MTE_FLAGS SYS_TCR_EL1_TCMA1 | TCR_TBI1 | TCR_TBID1
#else
/*
* The mte_zero_clear_page_tags() implementation uses DC GZVA, which relies on
* TBI being enabled at EL1.
*/
#define TCR_MTE_FLAGS TCR_TBI1 | TCR_TBID1
#endif
/*
* Default MAIR_EL1. MT_NORMAL_TAGGED is initially mapped as Normal memory and
* changed during __cpu_setup to Normal Tagged if the system supports MTE.
*/
#define MAIR_EL1_SET \
(MAIR_ATTRIDX(MAIR_ATTR_DEVICE_nGnRnE, MT_DEVICE_nGnRnE) | \
MAIR_ATTRIDX(MAIR_ATTR_DEVICE_nGnRE, MT_DEVICE_nGnRE) | \
MAIR_ATTRIDX(MAIR_ATTR_NORMAL_NC, MT_NORMAL_NC) | \
MAIR_ATTRIDX(MAIR_ATTR_NORMAL, MT_NORMAL) | \
MAIR_ATTRIDX(MAIR_ATTR_NORMAL, MT_NORMAL_TAGGED))
#ifdef CONFIG_CPU_PM
/**
* cpu_do_suspend - save CPU registers context
*
* x0: virtual address of context pointer
*
* This must be kept in sync with struct cpu_suspend_ctx in <asm/suspend.h>.
*/
SYM_FUNC_START(cpu_do_suspend)
mrs x2, tpidr_el0
mrs x3, tpidrro_el0
mrs x4, contextidr_el1
mrs x5, osdlr_el1
mrs x6, cpacr_el1
mrs x7, tcr_el1
mrs x8, vbar_el1
mrs x9, mdscr_el1
mrs x10, oslsr_el1
mrs x11, sctlr_el1
get_this_cpu_offset x12
mrs x13, sp_el0
stp x2, x3, [x0]
stp x4, x5, [x0, #16]
stp x6, x7, [x0, #32]
stp x8, x9, [x0, #48]
stp x10, x11, [x0, #64]
stp x12, x13, [x0, #80]
/*
* Save x18 as it may be used as a platform register, e.g. by shadow
* call stack.
*/
str x18, [x0, #96]
ret
SYM_FUNC_END(cpu_do_suspend)
/**
* cpu_do_resume - restore CPU register context
*
* x0: Address of context pointer
*/
.pushsection ".idmap.text", "awx"
SYM_FUNC_START(cpu_do_resume)
ldp x2, x3, [x0]
ldp x4, x5, [x0, #16]
ldp x6, x8, [x0, #32]
ldp x9, x10, [x0, #48]
ldp x11, x12, [x0, #64]
ldp x13, x14, [x0, #80]
/*
* Restore x18, as it may be used as a platform register, and clear
* the buffer to minimize the risk of exposure when used for shadow
* call stack.
*/
ldr x18, [x0, #96]
str xzr, [x0, #96]
msr tpidr_el0, x2
msr tpidrro_el0, x3
msr contextidr_el1, x4
msr cpacr_el1, x6
/* Don't change t0sz here, mask those bits when restoring */
mrs x7, tcr_el1
bfi x8, x7, TCR_T0SZ_OFFSET, TCR_TxSZ_WIDTH
msr tcr_el1, x8
msr vbar_el1, x9
/*
* __cpu_setup() cleared MDSCR_EL1.MDE and friends, before unmasking
* debug exceptions. By restoring MDSCR_EL1 here, we may take a debug
* exception. Mask them until local_daif_restore() in cpu_suspend()
* resets them.
*/
disable_daif
msr mdscr_el1, x10
msr sctlr_el1, x12
set_this_cpu_offset x13
msr sp_el0, x14
/*
* Restore oslsr_el1 by writing oslar_el1
*/
msr osdlr_el1, x5
ubfx x11, x11, #1, #1
msr oslar_el1, x11
reset_pmuserenr_el0 x0 // Disable PMU access from EL0
reset_amuserenr_el0 x0 // Disable AMU access from EL0
alternative_if ARM64_HAS_RAS_EXTN
msr_s SYS_DISR_EL1, xzr
alternative_else_nop_endif
ptrauth_keys_install_kernel_nosync x14, x1, x2, x3
isb
ret
SYM_FUNC_END(cpu_do_resume)
.popsection
#endif
.pushsection ".idmap.text", "awx"
.macro __idmap_cpu_set_reserved_ttbr1, tmp1, tmp2
adrp \tmp1, reserved_pg_dir
phys_to_ttbr \tmp2, \tmp1
offset_ttbr1 \tmp2, \tmp1
msr ttbr1_el1, \tmp2
isb
tlbi vmalle1
dsb nsh
isb
.endm
/*
* void idmap_cpu_replace_ttbr1(phys_addr_t ttbr1)
*
* This is the low-level counterpart to cpu_replace_ttbr1, and should not be
* called by anything else. It can only be executed from a TTBR0 mapping.
*/
SYM_FUNC_START(idmap_cpu_replace_ttbr1)
save_and_disable_daif flags=x2
__idmap_cpu_set_reserved_ttbr1 x1, x3
offset_ttbr1 x0, x3
msr ttbr1_el1, x0
isb
restore_daif x2
ret
SYM_FUNC_END(idmap_cpu_replace_ttbr1)
.popsection
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
.pushsection ".idmap.text", "awx"
.macro __idmap_kpti_get_pgtable_ent, type
dc cvac, cur_\()\type\()p // Ensure any existing dirty
dmb sy // lines are written back before
ldr \type, [cur_\()\type\()p] // loading the entry
tbz \type, #0, skip_\()\type // Skip invalid and
tbnz \type, #11, skip_\()\type // non-global entries
.endm
.macro __idmap_kpti_put_pgtable_ent_ng, type
orr \type, \type, #PTE_NG // Same bit for blocks and pages
str \type, [cur_\()\type\()p] // Update the entry and ensure
dmb sy // that it is visible to all
dc civac, cur_\()\type\()p // CPUs.
.endm
/*
* void __kpti_install_ng_mappings(int cpu, int num_cpus, phys_addr_t swapper)
*
* Called exactly once from stop_machine context by each CPU found during boot.
*/
__idmap_kpti_flag:
.long 1
SYM_FUNC_START(idmap_kpti_install_ng_mappings)
cpu .req w0
num_cpus .req w1
swapper_pa .req x2
swapper_ttb .req x3
flag_ptr .req x4
cur_pgdp .req x5
end_pgdp .req x6
pgd .req x7
cur_pudp .req x8
end_pudp .req x9
pud .req x10
cur_pmdp .req x11
end_pmdp .req x12
pmd .req x13
cur_ptep .req x14
end_ptep .req x15
pte .req x16
mrs swapper_ttb, ttbr1_el1
restore_ttbr1 swapper_ttb
adr flag_ptr, __idmap_kpti_flag
cbnz cpu, __idmap_kpti_secondary
/* We're the boot CPU. Wait for the others to catch up */
sevl
1: wfe
ldaxr w17, [flag_ptr]
eor w17, w17, num_cpus
cbnz w17, 1b
/* We need to walk swapper, so turn off the MMU. */
pre_disable_mmu_workaround
mrs x17, sctlr_el1
bic x17, x17, #SCTLR_ELx_M
msr sctlr_el1, x17
isb
/* Everybody is enjoying the idmap, so we can rewrite swapper. */
/* PGD */
mov cur_pgdp, swapper_pa
add end_pgdp, cur_pgdp, #(PTRS_PER_PGD * 8)
do_pgd: __idmap_kpti_get_pgtable_ent pgd
tbnz pgd, #1, walk_puds
next_pgd:
__idmap_kpti_put_pgtable_ent_ng pgd
skip_pgd:
add cur_pgdp, cur_pgdp, #8
cmp cur_pgdp, end_pgdp
b.ne do_pgd
/* Publish the updated tables and nuke all the TLBs */
dsb sy
tlbi vmalle1is
dsb ish
isb
/* We're done: fire up the MMU again */
mrs x17, sctlr_el1
orr x17, x17, #SCTLR_ELx_M
set_sctlr_el1 x17
/* Set the flag to zero to indicate that we're all done */
str wzr, [flag_ptr]
ret
/* PUD */
walk_puds:
.if CONFIG_PGTABLE_LEVELS > 3
pte_to_phys cur_pudp, pgd
add end_pudp, cur_pudp, #(PTRS_PER_PUD * 8)
do_pud: __idmap_kpti_get_pgtable_ent pud
tbnz pud, #1, walk_pmds
next_pud:
__idmap_kpti_put_pgtable_ent_ng pud
skip_pud:
add cur_pudp, cur_pudp, 8
cmp cur_pudp, end_pudp
b.ne do_pud
b next_pgd
.else /* CONFIG_PGTABLE_LEVELS <= 3 */
mov pud, pgd
b walk_pmds
next_pud:
b next_pgd
.endif
/* PMD */
walk_pmds:
.if CONFIG_PGTABLE_LEVELS > 2
pte_to_phys cur_pmdp, pud
add end_pmdp, cur_pmdp, #(PTRS_PER_PMD * 8)
do_pmd: __idmap_kpti_get_pgtable_ent pmd
tbnz pmd, #1, walk_ptes
next_pmd:
__idmap_kpti_put_pgtable_ent_ng pmd
skip_pmd:
add cur_pmdp, cur_pmdp, #8
cmp cur_pmdp, end_pmdp
b.ne do_pmd
b next_pud
.else /* CONFIG_PGTABLE_LEVELS <= 2 */
mov pmd, pud
b walk_ptes
next_pmd:
b next_pud
.endif
/* PTE */
walk_ptes:
pte_to_phys cur_ptep, pmd
add end_ptep, cur_ptep, #(PTRS_PER_PTE * 8)
do_pte: __idmap_kpti_get_pgtable_ent pte
__idmap_kpti_put_pgtable_ent_ng pte
skip_pte:
add cur_ptep, cur_ptep, #8
cmp cur_ptep, end_ptep
b.ne do_pte
b next_pmd
.unreq cpu
.unreq num_cpus
.unreq swapper_pa
.unreq cur_pgdp
.unreq end_pgdp
.unreq pgd
.unreq cur_pudp
.unreq end_pudp
.unreq pud
.unreq cur_pmdp
.unreq end_pmdp
.unreq pmd
.unreq cur_ptep
.unreq end_ptep
.unreq pte
/* Secondary CPUs end up here */
__idmap_kpti_secondary:
/* Uninstall swapper before surgery begins */
__idmap_cpu_set_reserved_ttbr1 x16, x17
/* Increment the flag to let the boot CPU we're ready */
1: ldxr w16, [flag_ptr]
add w16, w16, #1
stxr w17, w16, [flag_ptr]
cbnz w17, 1b
/* Wait for the boot CPU to finish messing around with swapper */
sevl
1: wfe
ldxr w16, [flag_ptr]
cbnz w16, 1b
/* All done, act like nothing happened */
offset_ttbr1 swapper_ttb, x16
msr ttbr1_el1, swapper_ttb
isb
ret
.unreq swapper_ttb
.unreq flag_ptr
SYM_FUNC_END(idmap_kpti_install_ng_mappings)
.popsection
#endif
/*
* __cpu_setup
*
* Initialise the processor for turning the MMU on.
*
* Output:
* Return in x0 the value of the SCTLR_EL1 register.
*/
.pushsection ".idmap.text", "awx"
SYM_FUNC_START(__cpu_setup)
tlbi vmalle1 // Invalidate local TLB
dsb nsh
mov x1, #3 << 20
msr cpacr_el1, x1 // Enable FP/ASIMD
mov x1, #1 << 12 // Reset mdscr_el1 and disable
msr mdscr_el1, x1 // access to the DCC from EL0
isb // Unmask debug exceptions now,
enable_dbg // since this is per-cpu
reset_pmuserenr_el0 x1 // Disable PMU access from EL0
reset_amuserenr_el0 x1 // Disable AMU access from EL0
/*
* Default values for VMSA control registers. These will be adjusted
* below depending on detected CPU features.
*/
mair .req x17
tcr .req x16
mov_q mair, MAIR_EL1_SET
mov_q tcr, TCR_TxSZ(VA_BITS) | TCR_CACHE_FLAGS | TCR_SMP_FLAGS | \
TCR_TG_FLAGS | TCR_KASLR_FLAGS | TCR_ASID16 | \
TCR_TBI0 | TCR_A1 | TCR_KASAN_SW_FLAGS
#ifdef CONFIG_ARM64_MTE
/*
* Update MAIR_EL1, GCR_EL1 and TFSR*_EL1 if MTE is supported
* (ID_AA64PFR1_EL1[11:8] > 1).
*/
mrs x10, ID_AA64PFR1_EL1
ubfx x10, x10, #ID_AA64PFR1_MTE_SHIFT, #4
cmp x10, #ID_AA64PFR1_MTE
b.lt 1f
/* Normal Tagged memory type at the corresponding MAIR index */
mov x10, #MAIR_ATTR_NORMAL_TAGGED
bfi mair, x10, #(8 * MT_NORMAL_TAGGED), #8
mov x10, #KERNEL_GCR_EL1
msr_s SYS_GCR_EL1, x10
/*
* If GCR_EL1.RRND=1 is implemented the same way as RRND=0, then
* RGSR_EL1.SEED must be non-zero for IRG to produce
* pseudorandom numbers. As RGSR_EL1 is UNKNOWN out of reset, we
* must initialize it.
*/
mrs x10, CNTVCT_EL0
ands x10, x10, #SYS_RGSR_EL1_SEED_MASK
csinc x10, x10, xzr, ne
lsl x10, x10, #SYS_RGSR_EL1_SEED_SHIFT
msr_s SYS_RGSR_EL1, x10
/* clear any pending tag check faults in TFSR*_EL1 */
msr_s SYS_TFSR_EL1, xzr
msr_s SYS_TFSRE0_EL1, xzr
/* set the TCR_EL1 bits */
mov_q x10, TCR_MTE_FLAGS
orr tcr, tcr, x10
1:
#endif
tcr_clear_errata_bits tcr, x9, x5
#ifdef CONFIG_ARM64_VA_BITS_52
ldr_l x9, vabits_actual
sub x9, xzr, x9
add x9, x9, #64
tcr_set_t1sz tcr, x9
#else
ldr_l x9, idmap_t0sz
#endif
tcr_set_t0sz tcr, x9
/*
* Set the IPS bits in TCR_EL1.
*/
tcr_compute_pa_size tcr, #TCR_IPS_SHIFT, x5, x6
#ifdef CONFIG_ARM64_HW_AFDBM
/*
* Enable hardware update of the Access Flags bit.
* Hardware dirty bit management is enabled later,
* via capabilities.
*/
mrs x9, ID_AA64MMFR1_EL1
and x9, x9, #0xf
cbz x9, 1f
orr tcr, tcr, #TCR_HA // hardware Access flag update
1:
#endif /* CONFIG_ARM64_HW_AFDBM */
msr mair_el1, mair
msr tcr_el1, tcr
/*
* Prepare SCTLR
*/
mov_q x0, INIT_SCTLR_EL1_MMU_ON
ret // return to head.S
.unreq mair
.unreq tcr
SYM_FUNC_END(__cpu_setup)
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