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arm64: consistently use reserved_pg_dir

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[ Upstream commit 833be850f1cabd0e3b5337c0fcab20a6e936dd48 ]

Depending on configuration options and specific code paths, we either
use the empty_zero_page or the configuration-dependent reserved_ttbr0
as a reserved value for TTBR{0,1}_EL1.

To simplify this code, let's always allocate and use the same
reserved_pg_dir, replacing reserved_ttbr0. Note that this is allocated
(and hence pre-zeroed), and is also marked as read-only in the kernel
Image mapping.

Keeping this separate from the empty_zero_page potentially helps with
robustness as the empty_zero_page is used in a number of cases where a
failure to map it read-only could allow it to become corrupted.

The (presently unused) swapper_pg_end symbol is also removed, and
comments are added wherever we rely on the offsets between the
pre-allocated pg_dirs to keep these cases easily identifiable.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201103102229.8542-1-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Mark Rutland 2020-11-03 10:22:29 +00:00 committed by Greg Kroah-Hartman
parent f1f30b3373
commit 8d6acfe80d
9 changed files with 17 additions and 22 deletions
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4
arch/arm64/include/asm/asm-uaccess.h
View File

@ -15,10 +15,10 @@
.macro __uaccess_ttbr0_disable, tmp1
mrs \tmp1, ttbr1_el1 // swapper_pg_dir
bic \tmp1, \tmp1, #TTBR_ASID_MASK
sub \tmp1, \tmp1, #RESERVED_TTBR0_SIZE // reserved_ttbr0 just before swapper_pg_dir
sub \tmp1, \tmp1, #PAGE_SIZE // reserved_pg_dir just before swapper_pg_dir
msr ttbr0_el1, \tmp1 // set reserved TTBR0_EL1
isb
add \tmp1, \tmp1, #RESERVED_TTBR0_SIZE
add \tmp1, \tmp1, #PAGE_SIZE
msr ttbr1_el1, \tmp1 // set reserved ASID
isb
.endm

6
arch/arm64/include/asm/kernel-pgtable.h
View File

@ -89,12 +89,6 @@
#define INIT_DIR_SIZE (PAGE_SIZE * EARLY_PAGES(KIMAGE_VADDR, _end))
#define IDMAP_DIR_SIZE (IDMAP_PGTABLE_LEVELS * PAGE_SIZE)
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
#define RESERVED_TTBR0_SIZE (PAGE_SIZE)
#else
#define RESERVED_TTBR0_SIZE (0)
#endif
/* Initial memory map size */
#if ARM64_SWAPPER_USES_SECTION_MAPS
#define SWAPPER_BLOCK_SHIFT SECTION_SHIFT

6
arch/arm64/include/asm/mmu_context.h
View File

@ -36,11 +36,11 @@ static inline void contextidr_thread_switch(struct task_struct *next)
}
/*
* Set TTBR0 to empty_zero_page. No translations will be possible via TTBR0.
* Set TTBR0 to reserved_pg_dir. No translations will be possible via TTBR0.
*/
static inline void cpu_set_reserved_ttbr0(void)
{
unsigned long ttbr = phys_to_ttbr(__pa_symbol(empty_zero_page));
unsigned long ttbr = phys_to_ttbr(__pa_symbol(reserved_pg_dir));
write_sysreg(ttbr, ttbr0_el1);
isb();
@ -192,7 +192,7 @@ static inline void update_saved_ttbr0(struct task_struct *tsk,
return;
if (mm == &init_mm)
ttbr = __pa_symbol(empty_zero_page);
ttbr = __pa_symbol(reserved_pg_dir);
else
ttbr = virt_to_phys(mm->pgd) | ASID(mm) << 48;

1
arch/arm64/include/asm/pgtable.h
View File

@ -530,6 +530,7 @@ extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
extern pgd_t idmap_pg_dir[PTRS_PER_PGD];
extern pgd_t idmap_pg_end[];
extern pgd_t tramp_pg_dir[PTRS_PER_PGD];
extern pgd_t reserved_pg_dir[PTRS_PER_PGD];
extern void set_swapper_pgd(pgd_t *pgdp, pgd_t pgd);

4
arch/arm64/include/asm/uaccess.h
View File

@ -113,8 +113,8 @@ static inline void __uaccess_ttbr0_disable(void)
local_irq_save(flags);
ttbr = read_sysreg(ttbr1_el1);
ttbr &= ~TTBR_ASID_MASK;
/* reserved_ttbr0 placed before swapper_pg_dir */
write_sysreg(ttbr - RESERVED_TTBR0_SIZE, ttbr0_el1);
/* reserved_pg_dir placed before swapper_pg_dir */
write_sysreg(ttbr - PAGE_SIZE, ttbr0_el1);
isb();
/* Set reserved ASID */
write_sysreg(ttbr, ttbr1_el1);

6
arch/arm64/kernel/entry.S
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@ -770,9 +770,10 @@ SYM_CODE_END(ret_to_user)
*/
.pushsection ".entry.tramp.text", "ax"
// Move from tramp_pg_dir to swapper_pg_dir
.macro tramp_map_kernel, tmp
mrs \tmp, ttbr1_el1
add \tmp, \tmp, #(PAGE_SIZE + RESERVED_TTBR0_SIZE)
add \tmp, \tmp, #(2 * PAGE_SIZE)
bic \tmp, \tmp, #USER_ASID_FLAG
msr ttbr1_el1, \tmp
#ifdef CONFIG_QCOM_FALKOR_ERRATUM_1003
@ -789,9 +790,10 @@ 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, #(PAGE_SIZE + RESERVED_TTBR0_SIZE)
sub \tmp, \tmp, #(2 * PAGE_SIZE)
orr \tmp, \tmp, #USER_ASID_FLAG
msr ttbr1_el1, \tmp
/*

2
arch/arm64/kernel/setup.c
View File

@ -366,7 +366,7 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
* faults in case uaccess_enable() is inadvertently called by the init
* thread.
*/
init_task.thread_info.ttbr0 = __pa_symbol(empty_zero_page);
init_task.thread_info.ttbr0 = __pa_symbol(reserved_pg_dir);
#endif
if (boot_args[1] || boot_args[2] || boot_args[3]) {

8
arch/arm64/kernel/vmlinux.lds.S
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@ -164,13 +164,11 @@ SECTIONS
. += PAGE_SIZE;
#endif
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
reserved_ttbr0 = .;
. += RESERVED_TTBR0_SIZE;
#endif
reserved_pg_dir = .;
. += PAGE_SIZE;
swapper_pg_dir = .;
. += PAGE_SIZE;
swapper_pg_end = .;
. = ALIGN(SEGMENT_ALIGN);
__init_begin = .;

2
arch/arm64/mm/proc.S
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@ -168,7 +168,7 @@ SYM_FUNC_END(cpu_do_resume)
.pushsection ".idmap.text", "awx"
.macro __idmap_cpu_set_reserved_ttbr1, tmp1, tmp2
adrp \tmp1, empty_zero_page
adrp \tmp1, reserved_pg_dir
phys_to_ttbr \tmp2, \tmp1
offset_ttbr1 \tmp2, \tmp1
msr ttbr1_el1, \tmp2