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linux/arch/arm64/mm/proc.S
Will Deacon 2ce77f6d8a arm64: proc: Set PTE_NG for table entries to avoid traversing them twice 
When KASAN is enabled, the swapper page table contains many identical
mappings of the zero page, which can lead to a stall during boot whilst
the G -> nG code continually walks the same page table entries looking
for global mappings.

This patch sets the nG bit (bit 11, which is IGNORED) in table entries
after processing the subtree so we can easily skip them if we see them
a second time.

Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2018-02-14 18:58:20 +00:00

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/*
* 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>
*
* 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.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/init.h>
#include <linux/linkage.h>
#include <asm/assembler.h>
#include <asm/asm-offsets.h>
#include <asm/hwcap.h>
#include <asm/pgtable.h>
#include <asm/pgtable-hwdef.h>
#include <asm/cpufeature.h>
#include <asm/alternative.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
#define TCR_SMP_FLAGS TCR_SHARED
/* PTWs cacheable, inner/outer WBWA */
#define TCR_CACHE_FLAGS TCR_IRGN_WBWA | TCR_ORGN_WBWA
#define MAIR(attr, mt) ((attr) << ((mt) * 8))
/*
* cpu_do_idle()
*
* Idle the processor (wait for interrupt).
*/
ENTRY(cpu_do_idle)
dsb sy // WFI may enter a low-power mode
wfi
ret
ENDPROC(cpu_do_idle)
#ifdef CONFIG_CPU_PM
/**
* cpu_do_suspend - save CPU registers context
*
* x0: virtual address of context pointer
*/
ENTRY(cpu_do_suspend)
mrs x2, tpidr_el0
mrs x3, tpidrro_el0
mrs x4, contextidr_el1
mrs x5, cpacr_el1
mrs x6, tcr_el1
mrs x7, vbar_el1
mrs x8, mdscr_el1
mrs x9, oslsr_el1
mrs x10, sctlr_el1
alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
mrs x11, tpidr_el1
alternative_else
mrs x11, tpidr_el2
alternative_endif
mrs x12, sp_el0
stp x2, x3, [x0]
stp x4, xzr, [x0, #16]
stp x5, x6, [x0, #32]
stp x7, x8, [x0, #48]
stp x9, x10, [x0, #64]
stp x11, x12, [x0, #80]
ret
ENDPROC(cpu_do_suspend)
/**
* cpu_do_resume - restore CPU register context
*
* x0: Address of context pointer
*/
.pushsection ".idmap.text", "awx"
ENTRY(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]
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 x5, tcr_el1
bfi x8, x5, 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
alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
msr tpidr_el1, x13
alternative_else
msr tpidr_el2, x13
alternative_endif
msr sp_el0, x14
/*
* Restore oslsr_el1 by writing oslar_el1
*/
ubfx x11, x11, #1, #1
msr oslar_el1, x11
reset_pmuserenr_el0 x0 // Disable PMU access from EL0
alternative_if ARM64_HAS_RAS_EXTN
msr_s SYS_DISR_EL1, xzr
alternative_else_nop_endif
isb
ret
ENDPROC(cpu_do_resume)
.popsection
#endif
/*
* cpu_do_switch_mm(pgd_phys, tsk)
*
* Set the translation table base pointer to be pgd_phys.
*
* - pgd_phys - physical address of new TTB
*/
ENTRY(cpu_do_switch_mm)
mrs x2, ttbr1_el1
mmid x1, x1 // get mm->context.id
phys_to_ttbr x3, x0
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
bfi x3, x1, #48, #16 // set the ASID field in TTBR0
#endif
bfi x2, x1, #48, #16 // set the ASID
msr ttbr1_el1, x2 // in TTBR1 (since TCR.A1 is set)
isb
msr ttbr0_el1, x3 // now update TTBR0
isb
b post_ttbr_update_workaround // Back to C code...
ENDPROC(cpu_do_switch_mm)
.pushsection ".idmap.text", "awx"
.macro __idmap_cpu_set_reserved_ttbr1, tmp1, tmp2
adrp \tmp1, empty_zero_page
phys_to_ttbr \tmp2, \tmp1
msr ttbr1_el1, \tmp2
isb
tlbi vmalle1
dsb nsh
isb
.endm
/*
* void idmap_cpu_replace_ttbr1(phys_addr_t new_pgd)
*
* 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.
*/
ENTRY(idmap_cpu_replace_ttbr1)
save_and_disable_daif flags=x2
__idmap_cpu_set_reserved_ttbr1 x1, x3
phys_to_ttbr x3, x0
msr ttbr1_el1, x3
isb
restore_daif x2
ret
ENDPROC(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 it
dc civac, cur_\()\type\()p // is visible to all 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
ENTRY(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
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 w18, [flag_ptr]
eor w18, w18, num_cpus
cbnz w18, 1b
/* We need to walk swapper, so turn off the MMU. */
pre_disable_mmu_workaround
mrs x18, sctlr_el1
bic x18, x18, #SCTLR_ELx_M
msr sctlr_el1, x18
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 x18, sctlr_el1
orr x18, x18, #SCTLR_ELx_M
msr sctlr_el1, x18
isb
/* 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
/* Secondary CPUs end up here */
__idmap_kpti_secondary:
/* Uninstall swapper before surgery begins */
__idmap_cpu_set_reserved_ttbr1 x18, x17
/* Increment the flag to let the boot CPU we're ready */
1: ldxr w18, [flag_ptr]
add w18, w18, #1
stxr w17, w18, [flag_ptr]
cbnz w17, 1b
/* Wait for the boot CPU to finish messing around with swapper */
sevl
1: wfe
ldxr w18, [flag_ptr]
cbnz w18, 1b
/* All done, act like nothing happened */
msr ttbr1_el1, swapper_ttb
isb
ret
.unreq cpu
.unreq num_cpus
.unreq swapper_pa
.unreq swapper_ttb
.unreq flag_ptr
.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
ENDPROC(idmap_kpti_install_ng_mappings)
.popsection
#endif
/*
* __cpu_setup
*
* Initialise the processor for turning the MMU on. Return in x0 the
* value of the SCTLR_EL1 register.
*/
.pushsection ".idmap.text", "awx"
ENTRY(__cpu_setup)
tlbi vmalle1 // Invalidate local TLB
dsb nsh
mov x0, #3 << 20
msr cpacr_el1, x0 // Enable FP/ASIMD
mov x0, #1 << 12 // Reset mdscr_el1 and disable
msr mdscr_el1, x0 // access to the DCC from EL0
isb // Unmask debug exceptions now,
enable_dbg // since this is per-cpu
reset_pmuserenr_el0 x0 // Disable PMU access from EL0
/*
* Memory region attributes for LPAE:
*
* n = AttrIndx[2:0]
* n MAIR
* DEVICE_nGnRnE 000 00000000
* DEVICE_nGnRE 001 00000100
* DEVICE_GRE 010 00001100
* NORMAL_NC 011 01000100
* NORMAL 100 11111111
* NORMAL_WT 101 10111011
*/
ldr x5, =MAIR(0x00, MT_DEVICE_nGnRnE) | \
MAIR(0x04, MT_DEVICE_nGnRE) | \
MAIR(0x0c, MT_DEVICE_GRE) | \
MAIR(0x44, MT_NORMAL_NC) | \
MAIR(0xff, MT_NORMAL) | \
MAIR(0xbb, MT_NORMAL_WT)
msr mair_el1, x5
/*
* Prepare SCTLR
*/
mov_q x0, SCTLR_EL1_SET
/*
* Set/prepare TCR and TTBR. We use 512GB (39-bit) address range for
* both user and kernel.
*/
ldr x10, =TCR_TxSZ(VA_BITS) | TCR_CACHE_FLAGS | TCR_SMP_FLAGS | \
TCR_TG_FLAGS | TCR_ASID16 | TCR_TBI0 | TCR_A1
tcr_set_idmap_t0sz x10, x9
/*
* Set the IPS bits in TCR_EL1.
*/
tcr_compute_pa_size x10, #TCR_IPS_SHIFT, x5, x6
#ifdef CONFIG_ARM64_HW_AFDBM
/*
* Hardware update of the Access and Dirty bits.
*/
mrs x9, ID_AA64MMFR1_EL1
and x9, x9, #0xf
cbz x9, 2f
cmp x9, #2
b.lt 1f
orr x10, x10, #TCR_HD // hardware Dirty flag update
1: orr x10, x10, #TCR_HA // hardware Access flag update
2:
#endif /* CONFIG_ARM64_HW_AFDBM */
msr tcr_el1, x10
ret // return to head.S
ENDPROC(__cpu_setup)
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