[PATCH] arm64: consistently use reserved_pg_dir
Mark Rutland
mark.rutland at arm.com
Tue Nov 3 05:22:29 EST 2020
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 at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
---
arch/arm64/include/asm/asm-uaccess.h | 4 ++--
arch/arm64/include/asm/kernel-pgtable.h | 6 ------
arch/arm64/include/asm/mmu_context.h | 6 +++---
arch/arm64/include/asm/pgtable.h | 1 +
arch/arm64/include/asm/uaccess.h | 4 ++--
arch/arm64/kernel/entry.S | 6 ++++--
arch/arm64/kernel/setup.c | 2 +-
arch/arm64/kernel/vmlinux.lds.S | 8 +++-----
arch/arm64/mm/proc.S | 2 +-
9 files changed, 17 insertions(+), 22 deletions(-)
diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h
index f68a0e64482a..5ef624fef44a 100644
--- a/arch/arm64/include/asm/asm-uaccess.h
+++ b/arch/arm64/include/asm/asm-uaccess.h
@@ -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
diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index 19ca76ea60d9..587c504a4c8b 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -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
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index 0672236e1aea..5c72c20bd300 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -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();
@@ -195,7 +195,7 @@ 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;
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 4ff12a7adcfd..74694e129f9a 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -519,6 +519,7 @@ 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);
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 991dd5f031e4..385a189f7d39 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -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);
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index f30007dff35f..eedea5306536 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -804,9 +804,10 @@ 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
@@ -823,9 +824,10 @@ 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
/*
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 133257ffd859..c28a9ec76b11 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -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]) {
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 6d78c041fdf6..fd56f4d56308 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -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 = .;
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 23c326a06b2d..0eaf16b0442a 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -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
--
2.11.0
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