[PATCH v5 00/21] arm64: refactor boot flow

[PATCH v5 00/21] arm64: refactor boot flow

[Ard Biesheuvel]

This series aims to streamline the boot flow with respect to cache
maintenance and redundant copying of data in memory.

Additionally, this series removes the little dance we do to create a
kernel mapping, relocate the kernel, run the KASLR init code, tear down
the old mapping and create a new one, relocate the kernel again, and
finally enter the kernel proper. Instead, it invokes a minimal C
function 'kaslr_early_init()' while running from the ID map which
includes a temporary mapping of the FDT. This change represents a
substantial chunk of the diffstat, as it requires some work to
instantiate code that can run safely from an arbitrary load address.

Changes since v4:
- drop all patches related to WXN support for the time being
- move assignment of vabits_actual earlier in the boot
- avoid TCR_T0SZ() macro as it is not quite appropriate for calculating
  the value of t0sz itself (as opposed to its representation in TCR)
- ensure that module randomization is done before modules may be loaded,
  which might we way before init runs (via request_module())

Changes since v3:
- drop changes for entering with the MMU enabled for now;
- reject mmap() and mprotect() calls with PROT_WRITE and PROT_EXEC flags
  passed when WXN is in effect; this essentially matches the behavior of
  both selinux and PaX, and most distros (including Android) can already
  deal with this just fine;
- defer KASLR initialization to an initcall() to the extent possible.
- add Anshuman's ack to a couple of patches

Changes since v2:
- create a separate, initial ID map that is discarded after boot, and
  create the permanent ID map from C code using the ordinary memory
  mapping code;
- refactor the extended ID map handling, and along with it, simplify the
  early memory mapping macros, so that we can deal with an extended ID
  map that requires multiple table entries at intermediate levels;
- eliminate all variable assignments with the MMU off from the happy
  flow;
- replace temporary FDT mapping in TTBR1 with a FDT mapping in the
  initial ID map;
- use read-only attributes for all code mappings, so we can boot with
  WXN enabled if we elect to do so.

Changes since v1:
- Remove the dodgy handling of the KASLR seed, which was necessary to
  avoid doing two iterations of the setup/teardown of the page tables.
  This is now dealt with by creating the TTBR1 page tables while
  executing from TTBR0, and so all memory manipulations are still done
  with the MMU and caches on.
- Only boot from EFI with the MMU and caches on if the image was not
  moved around in memory. Otherwise, we cannot rely on the firmware's ID
  map to have created an executable mapping for the copied code.

[0] https://lore.kernel.org/all/20220304175657.2744400-1-ardb@kernel.org/
[1] https://lore.kernel.org/all/20220330154205.2483167-1-ardb@kernel.org/
[2] https://lore.kernel.org/all/20220613144550.3760857-1-ardb@kernel.org/

Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>

Ard Biesheuvel (21):
  arm64: head: move kimage_vaddr variable into C file
  arm64: mm: make vabits_actual a build time constant if possible
  arm64: head: move assignment of idmap_t0sz to C code
  arm64: head: drop idmap_ptrs_per_pgd
  arm64: head: simplify page table mapping macros (slightly)
  arm64: head: switch to map_memory macro for the extended ID map
  arm64: head: split off idmap creation code
  arm64: kernel: drop unnecessary PoC cache clean+invalidate
  arm64: head: pass ID map root table address to __enable_mmu()
  arm64: mm: provide idmap pointer to cpu_replace_ttbr1()
  arm64: head: add helper function to remap regions in early page tables
  arm64: head: cover entire kernel image in initial ID map
  arm64: head: use relative references to the RELA and RELR tables
  arm64: head: create a temporary FDT mapping in the initial ID map
  arm64: idreg-override: use early FDT mapping in ID map
  arm64: head: factor out TTBR1 assignment into a macro
  arm64: head: populate kernel page tables with MMU and caches on
  arm64: head: record CPU boot mode after enabling the MMU
  arm64: kaslr: defer initialization to initcall where permitted
  arm64: head: avoid relocating the kernel twice for KASLR
  arm64: setup: drop early FDT pointer helpers

 arch/arm64/include/asm/assembler.h      |  31 +-
 arch/arm64/include/asm/kernel-pgtable.h |  18 +-
 arch/arm64/include/asm/memory.h         |   4 +
 arch/arm64/include/asm/mmu_context.h    |  16 +-
 arch/arm64/include/asm/setup.h          |   3 -
 arch/arm64/kernel/Makefile              |   2 +-
 arch/arm64/kernel/cpufeature.c          |   2 +-
 arch/arm64/kernel/head.S                | 458 ++++++++------------
 arch/arm64/kernel/hyp-stub.S            |   4 +-
 arch/arm64/kernel/idreg-override.c      |  17 +-
 arch/arm64/kernel/image-vars.h          |   4 +
 arch/arm64/kernel/kaslr.c               | 149 +------
 arch/arm64/kernel/pi/Makefile           |  33 ++
 arch/arm64/kernel/pi/kaslr_early.c      | 112 +++++
 arch/arm64/kernel/setup.c               |  15 -
 arch/arm64/kernel/sleep.S               |   1 +
 arch/arm64/kernel/suspend.c             |   2 +-
 arch/arm64/kernel/vmlinux.lds.S         |  19 +-
 arch/arm64/mm/init.c                    |  15 +-
 arch/arm64/mm/kasan_init.c              |   4 +-
 arch/arm64/mm/mmu.c                     |  55 ++-
 arch/arm64/mm/proc.S                    |  10 +-
 22 files changed, 505 insertions(+), 469 deletions(-)
 create mode 100644 arch/arm64/kernel/pi/Makefile
 create mode 100644 arch/arm64/kernel/pi/kaslr_early.c

-- 
2.35.1


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[PATCH v5 01/21] arm64: head: move kimage_vaddr variable into C file

[Ard Biesheuvel]

This variable definition does not need to be in head.S so move it out.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 arch/arm64/kernel/head.S | 7 -------
 arch/arm64/mm/mmu.c      | 3 +++
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 6a98f1a38c29..1cdecce552bb 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -469,13 +469,6 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 	ASM_BUG()
 SYM_FUNC_END(__primary_switched)
 
-	.pushsection ".rodata", "a"
-SYM_DATA_START(kimage_vaddr)
-	.quad		_text
-SYM_DATA_END(kimage_vaddr)
-EXPORT_SYMBOL(kimage_vaddr)
-	.popsection
-
 /*
  * end early head section, begin head code that is also used for
  * hotplug and needs to have the same protections as the text region
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index c5563ff990da..7148928e3932 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -49,6 +49,9 @@ u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
 u64 __section(".mmuoff.data.write") vabits_actual;
 EXPORT_SYMBOL(vabits_actual);
 
+u64 kimage_vaddr __ro_after_init = (u64)&_text;
+EXPORT_SYMBOL(kimage_vaddr);
+
 u64 kimage_voffset __ro_after_init;
 EXPORT_SYMBOL(kimage_voffset);
 
-- 
2.35.1


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[PATCH v5 02/21] arm64: mm: make vabits_actual a build time constant if possible

[Ard Biesheuvel]

Currently, we only support 52-bit virtual addressing on 64k pages
configurations, and in all other cases, vabits_actual is guaranteed to
equal VA_BITS (== VA_BITS_MIN). So get rid of the variable entirely in
that case.

While at it, move the assignment out of the asm entry code - it has no
need to be there.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/include/asm/memory.h |  4 ++++
 arch/arm64/kernel/head.S        | 15 +--------------
 arch/arm64/mm/init.c            | 15 ++++++++++++++-
 arch/arm64/mm/mmu.c             |  4 +++-
 4 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 0af70d9abede..c751cd9b94f8 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -174,7 +174,11 @@
 #include <linux/types.h>
 #include <asm/bug.h>
 
+#if VA_BITS > 48
 extern u64			vabits_actual;
+#else
+#define vabits_actual		((u64)VA_BITS)
+#endif
 
 extern s64			memstart_addr;
 /* PHYS_OFFSET - the physical address of the start of memory. */
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 1cdecce552bb..dc07858eb673 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -293,19 +293,6 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 	adrp	x0, idmap_pg_dir
 	adrp	x3, __idmap_text_start		// __pa(__idmap_text_start)
 
-#ifdef CONFIG_ARM64_VA_BITS_52
-	mrs_s	x6, SYS_ID_AA64MMFR2_EL1
-	and	x6, x6, #(0xf << ID_AA64MMFR2_LVA_SHIFT)
-	mov	x5, #52
-	cbnz	x6, 1f
-#endif
-	mov	x5, #VA_BITS_MIN
-1:
-	adr_l	x6, vabits_actual
-	str	x5, [x6]
-	dmb	sy
-	dc	ivac, x6		// Invalidate potentially stale cache line
-
 	/*
 	 * VA_BITS may be too small to allow for an ID mapping to be created
 	 * that covers system RAM if that is located sufficiently high in the
@@ -713,7 +700,7 @@ SYM_FUNC_START(__enable_mmu)
 SYM_FUNC_END(__enable_mmu)
 
 SYM_FUNC_START(__cpu_secondary_check52bitva)
-#ifdef CONFIG_ARM64_VA_BITS_52
+#if VA_BITS > 48
 	ldr_l	x0, vabits_actual
 	cmp	x0, #52
 	b.ne	2f
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 339ee84e5a61..1faa6760895e 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -265,7 +265,20 @@ early_param("mem", early_mem);
 
 void __init arm64_memblock_init(void)
 {
-	s64 linear_region_size = PAGE_END - _PAGE_OFFSET(vabits_actual);
+	s64 linear_region_size;
+
+#if VA_BITS > 48
+	if (cpuid_feature_extract_unsigned_field(
+				read_sysreg_s(SYS_ID_AA64MMFR2_EL1),
+				ID_AA64MMFR2_LVA_SHIFT))
+		vabits_actual = VA_BITS;
+
+	/* make the variable visible to secondaries with the MMU off */
+	dcache_clean_inval_poc((u64)&vabits_actual,
+			       (u64)&vabits_actual + sizeof(vabits_actual));
+#endif
+
+	linear_region_size = PAGE_END - _PAGE_OFFSET(vabits_actual);
 
 	/*
 	 * Corner case: 52-bit VA capable systems running KVM in nVHE mode may
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 7148928e3932..a6392656d589 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -46,8 +46,10 @@
 u64 idmap_t0sz = TCR_T0SZ(VA_BITS_MIN);
 u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
 
-u64 __section(".mmuoff.data.write") vabits_actual;
+#if VA_BITS > 48
+u64 vabits_actual __ro_after_init = VA_BITS_MIN;
 EXPORT_SYMBOL(vabits_actual);
+#endif
 
 u64 kimage_vaddr __ro_after_init = (u64)&_text;
 EXPORT_SYMBOL(kimage_vaddr);
-- 
2.35.1


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[PATCH v5 03/21] arm64: head: move assignment of idmap_t0sz to C code

[Ard Biesheuvel]

Setting idmap_t0sz involves fiddling with the caches if done with the
MMU off. Since we will be creating an initial ID map with the MMU and
caches off, and the permanent ID map with the MMU and caches on, let's
move this assignment of idmap_t0sz out of the startup code, and replace
it with a macro that simply issues the three instructions needed to
calculate the value wherever it is needed before the MMU is turned on.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/include/asm/assembler.h   | 14 ++++++++++++++
 arch/arm64/include/asm/mmu_context.h |  2 +-
 arch/arm64/kernel/head.S             | 13 +------------
 arch/arm64/mm/mmu.c                  |  4 +++-
 arch/arm64/mm/proc.S                 |  2 +-
 5 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 8c5a61aeaf8e..9468f45c07a6 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -359,6 +359,20 @@ alternative_cb_end
 	bfi	\valreg, \t1sz, #TCR_T1SZ_OFFSET, #TCR_TxSZ_WIDTH
 	.endm
 
+/*
+ * idmap_get_t0sz - get the T0SZ value needed to cover the ID map
+ *
+ * Calculate the maximum allowed value for TCR_EL1.T0SZ so that the
+ * entire ID map region can be mapped. As T0SZ == (64 - #bits used),
+ * this number conveniently equals the number of leading zeroes in
+ * the physical address of _end.
+ */
+	.macro	idmap_get_t0sz, reg
+	adrp	\reg, _end
+	orr	\reg, \reg, #(1 << VA_BITS_MIN) - 1
+	clz	\reg, \reg
+	.endm
+
 /*
  * tcr_compute_pa_size - set TCR.(I)PS to the highest supported
  * ID_AA64MMFR0_EL1.PARange value
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index 6770667b34a3..6ac0086ebb1a 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -60,7 +60,7 @@ static inline void cpu_switch_mm(pgd_t *pgd, struct mm_struct *mm)
  * TCR_T0SZ(VA_BITS), unless system RAM is positioned very high in
  * physical memory, in which case it will be smaller.
  */
-extern u64 idmap_t0sz;
+extern int idmap_t0sz;
 extern u64 idmap_ptrs_per_pgd;
 
 /*
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index dc07858eb673..7f361bc72d12 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -299,22 +299,11 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 	 * physical address space. So for the ID map, use an extended virtual
 	 * range in that case, and configure an additional translation level
 	 * if needed.
-	 *
-	 * Calculate the maximum allowed value for TCR_EL1.T0SZ so that the
-	 * entire ID map region can be mapped. As T0SZ == (64 - #bits used),
-	 * this number conveniently equals the number of leading zeroes in
-	 * the physical address of __idmap_text_end.
 	 */
-	adrp	x5, __idmap_text_end
-	clz	x5, x5
+	idmap_get_t0sz x5
 	cmp	x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough?
 	b.ge	1f			// .. then skip VA range extension
 
-	adr_l	x6, idmap_t0sz
-	str	x5, [x6]
-	dmb	sy
-	dc	ivac, x6		// Invalidate potentially stale cache line
-
 #if (VA_BITS < 48)
 #define EXTRA_SHIFT	(PGDIR_SHIFT + PAGE_SHIFT - 3)
 #define EXTRA_PTRS	(1 << (PHYS_MASK_SHIFT - EXTRA_SHIFT))
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index a6392656d589..f875c4954e22 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -43,7 +43,7 @@
 #define NO_CONT_MAPPINGS	BIT(1)
 #define NO_EXEC_MAPPINGS	BIT(2)	/* assumes FEAT_HPDS is not used */
 
-u64 idmap_t0sz = TCR_T0SZ(VA_BITS_MIN);
+int idmap_t0sz __ro_after_init;
 u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
 
 #if VA_BITS > 48
@@ -774,6 +774,8 @@ void __init paging_init(void)
 {
 	pgd_t *pgdp = pgd_set_fixmap(__pa_symbol(swapper_pg_dir));
 
+	idmap_t0sz = 63UL - __fls(__pa_symbol(_end) | GENMASK(VA_BITS_MIN - 1, 0));
+
 	map_kernel(pgdp);
 	map_mem(pgdp);
 
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 972ce8d7f2c5..97cd67697212 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -470,7 +470,7 @@ SYM_FUNC_START(__cpu_setup)
 	add		x9, x9, #64
 	tcr_set_t1sz	tcr, x9
 #else
-	ldr_l		x9, idmap_t0sz
+	idmap_get_t0sz	x9
 #endif
 	tcr_set_t0sz	tcr, x9
 
-- 
2.35.1


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[PATCH v5 04/21] arm64: head: drop idmap_ptrs_per_pgd

[Ard Biesheuvel]

The assignment of idmap_ptrs_per_pgd lacks any cache invalidation, even
though it is updated with the MMU and caches disabled. However, we never
bother to read the value again except in the very next instruction, and
so we can just drop the variable entirely.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 arch/arm64/include/asm/mmu_context.h | 1 -
 arch/arm64/kernel/head.S             | 7 +++----
 arch/arm64/mm/mmu.c                  | 1 -
 3 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index 6ac0086ebb1a..7b387c3b312a 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -61,7 +61,6 @@ static inline void cpu_switch_mm(pgd_t *pgd, struct mm_struct *mm)
  * physical memory, in which case it will be smaller.
  */
 extern int idmap_t0sz;
-extern u64 idmap_ptrs_per_pgd;
 
 /*
  * Ensure TCR.T0SZ is set to the provided value.
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 7f361bc72d12..53126a35d73c 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -300,6 +300,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 	 * range in that case, and configure an additional translation level
 	 * if needed.
 	 */
+	mov	x4, #PTRS_PER_PGD
 	idmap_get_t0sz x5
 	cmp	x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough?
 	b.ge	1f			// .. then skip VA range extension
@@ -319,18 +320,16 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 #error "Mismatch between VA_BITS and page size/number of translation levels"
 #endif
 
-	mov	x4, EXTRA_PTRS
-	create_table_entry x0, x3, EXTRA_SHIFT, x4, x5, x6
+	mov	x2, EXTRA_PTRS
+	create_table_entry x0, x3, EXTRA_SHIFT, x2, x5, x6
 #else
 	/*
 	 * If VA_BITS == 48, we don't have to configure an additional
 	 * translation level, but the top-level table has more entries.
 	 */
 	mov	x4, #1 << (PHYS_MASK_SHIFT - PGDIR_SHIFT)
-	str_l	x4, idmap_ptrs_per_pgd, x5
 #endif
 1:
-	ldr_l	x4, idmap_ptrs_per_pgd
 	adr_l	x6, __idmap_text_end		// __pa(__idmap_text_end)
 
 	map_memory x0, x1, x3, x6, x7, x3, x4, x10, x11, x12, x13, x14
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index f875c4954e22..3be0e9f69406 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -44,7 +44,6 @@
 #define NO_EXEC_MAPPINGS	BIT(2)	/* assumes FEAT_HPDS is not used */
 
 int idmap_t0sz __ro_after_init;
-u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
 
 #if VA_BITS > 48
 u64 vabits_actual __ro_after_init = VA_BITS_MIN;
-- 
2.35.1


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[PATCH v5 05/21] arm64: head: simplify page table mapping macros (slightly)

[Ard Biesheuvel]

Simplify the macros in head.S that are used to set up the early page
tables, by switching to immediates for the number of bits that are
interpreted as the table index at each level. This makes it much
easier to infer from the instruction stream what is going on, and
reduces the number of instructions emitted substantially.

Note that the extended ID map for cases where no additional level needs
to be configured now uses a compile time size as well, which means that
we interpret up to 10 bits as the table index at the root level (for
52-bit physical addressing), without taking into account whether or not
this is supported on the current system.  However, those bits can only
be set if we are executing the image from an address that exceeds the
48-bit PA range, and are guaranteed to be cleared otherwise, and given
that we are dealing with a mapping in the lower TTBR0 range of the
address space, the result is therefore the same as if we'd mask off only
6 bits.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/head.S | 55 ++++++++------------
 1 file changed, 22 insertions(+), 33 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 53126a35d73c..9fdde2f9cc0f 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -179,31 +179,20 @@ SYM_CODE_END(preserve_boot_args)
  *	vstart:	virtual address of start of range
  *	vend:	virtual address of end of range - we map [vstart, vend]
  *	shift:	shift used to transform virtual address into index
- *	ptrs:	number of entries in page table
+ *	order:  #imm 2log(number of entries in page table)
  *	istart:	index in table corresponding to vstart
  *	iend:	index in table corresponding to vend
  *	count:	On entry: how many extra entries were required in previous level, scales
  *			  our end index.
  *		On exit: returns how many extra entries required for next page table level
  *
- * Preserves:	vstart, vend, shift, ptrs
+ * Preserves:	vstart, vend
  * Returns:	istart, iend, count
  */
-	.macro compute_indices, vstart, vend, shift, ptrs, istart, iend, count
-	lsr	\iend, \vend, \shift
-	mov	\istart, \ptrs
-	sub	\istart, \istart, #1
-	and	\iend, \iend, \istart	// iend = (vend >> shift) & (ptrs - 1)
-	mov	\istart, \ptrs
-	mul	\istart, \istart, \count
-	add	\iend, \iend, \istart	// iend += count * ptrs
-					// our entries span multiple tables
-
-	lsr	\istart, \vstart, \shift
-	mov	\count, \ptrs
-	sub	\count, \count, #1
-	and	\istart, \istart, \count
-
+	.macro compute_indices, vstart, vend, shift, order, istart, iend, count
+	ubfx	\istart, \vstart, \shift, \order
+	ubfx	\iend, \vend, \shift, \order
+	add	\iend, \iend, \count, lsl \order
 	sub	\count, \iend, \istart
 	.endm
 
@@ -218,38 +207,39 @@ SYM_CODE_END(preserve_boot_args)
  *	vend:	virtual address of end of range - we map [vstart, vend - 1]
  *	flags:	flags to use to map last level entries
  *	phys:	physical address corresponding to vstart - physical memory is contiguous
- *	pgds:	the number of pgd entries
+ *	order:  #imm 2log(number of entries in PGD table)
  *
  * Temporaries:	istart, iend, tmp, count, sv - these need to be different registers
  * Preserves:	vstart, flags
  * Corrupts:	tbl, rtbl, vend, istart, iend, tmp, count, sv
  */
-	.macro map_memory, tbl, rtbl, vstart, vend, flags, phys, pgds, istart, iend, tmp, count, sv
+	.macro map_memory, tbl, rtbl, vstart, vend, flags, phys, order, istart, iend, tmp, count, sv
 	sub \vend, \vend, #1
 	add \rtbl, \tbl, #PAGE_SIZE
-	mov \sv, \rtbl
 	mov \count, #0
-	compute_indices \vstart, \vend, #PGDIR_SHIFT, \pgds, \istart, \iend, \count
+
+	compute_indices \vstart, \vend, #PGDIR_SHIFT, #\order, \istart, \iend, \count
+	mov \sv, \rtbl
 	populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp
 	mov \tbl, \sv
-	mov \sv, \rtbl
 
 #if SWAPPER_PGTABLE_LEVELS > 3
-	compute_indices \vstart, \vend, #PUD_SHIFT, #PTRS_PER_PUD, \istart, \iend, \count
+	compute_indices \vstart, \vend, #PUD_SHIFT, #(PAGE_SHIFT - 3), \istart, \iend, \count
+	mov \sv, \rtbl
 	populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp
 	mov \tbl, \sv
-	mov \sv, \rtbl
 #endif
 
 #if SWAPPER_PGTABLE_LEVELS > 2
-	compute_indices \vstart, \vend, #SWAPPER_TABLE_SHIFT, #PTRS_PER_PMD, \istart, \iend, \count
+	compute_indices \vstart, \vend, #SWAPPER_TABLE_SHIFT, #(PAGE_SHIFT - 3), \istart, \iend, \count
+	mov \sv, \rtbl
 	populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp
 	mov \tbl, \sv
 #endif
 
-	compute_indices \vstart, \vend, #SWAPPER_BLOCK_SHIFT, #PTRS_PER_PTE, \istart, \iend, \count
-	bic \count, \phys, #SWAPPER_BLOCK_SIZE - 1
-	populate_entries \tbl, \count, \istart, \iend, \flags, #SWAPPER_BLOCK_SIZE, \tmp
+	compute_indices \vstart, \vend, #SWAPPER_BLOCK_SHIFT, #(PAGE_SHIFT - 3), \istart, \iend, \count
+	bic \rtbl, \phys, #SWAPPER_BLOCK_SIZE - 1
+	populate_entries \tbl, \rtbl, \istart, \iend, \flags, #SWAPPER_BLOCK_SIZE, \tmp
 	.endm
 
 /*
@@ -300,12 +290,12 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 	 * range in that case, and configure an additional translation level
 	 * if needed.
 	 */
-	mov	x4, #PTRS_PER_PGD
 	idmap_get_t0sz x5
 	cmp	x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough?
 	b.ge	1f			// .. then skip VA range extension
 
 #if (VA_BITS < 48)
+#define IDMAP_PGD_ORDER	(VA_BITS - PGDIR_SHIFT)
 #define EXTRA_SHIFT	(PGDIR_SHIFT + PAGE_SHIFT - 3)
 #define EXTRA_PTRS	(1 << (PHYS_MASK_SHIFT - EXTRA_SHIFT))
 
@@ -323,16 +313,16 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 	mov	x2, EXTRA_PTRS
 	create_table_entry x0, x3, EXTRA_SHIFT, x2, x5, x6
 #else
+#define IDMAP_PGD_ORDER	(PHYS_MASK_SHIFT - PGDIR_SHIFT)
 	/*
 	 * If VA_BITS == 48, we don't have to configure an additional
 	 * translation level, but the top-level table has more entries.
 	 */
-	mov	x4, #1 << (PHYS_MASK_SHIFT - PGDIR_SHIFT)
 #endif
 1:
 	adr_l	x6, __idmap_text_end		// __pa(__idmap_text_end)
 
-	map_memory x0, x1, x3, x6, x7, x3, x4, x10, x11, x12, x13, x14
+	map_memory x0, x1, x3, x6, x7, x3, IDMAP_PGD_ORDER, x10, x11, x12, x13, x14
 
 	/*
 	 * Map the kernel image (starting with PHYS_OFFSET).
@@ -340,13 +330,12 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 	adrp	x0, init_pg_dir
 	mov_q	x5, KIMAGE_VADDR		// compile time __va(_text)
 	add	x5, x5, x23			// add KASLR displacement
-	mov	x4, PTRS_PER_PGD
 	adrp	x6, _end			// runtime __pa(_end)
 	adrp	x3, _text			// runtime __pa(_text)
 	sub	x6, x6, x3			// _end - _text
 	add	x6, x6, x5			// runtime __va(_end)
 
-	map_memory x0, x1, x5, x6, x7, x3, x4, x10, x11, x12, x13, x14
+	map_memory x0, x1, x5, x6, x7, x3, (VA_BITS - PGDIR_SHIFT), x10, x11, x12, x13, x14
 
 	/*
 	 * Since the page tables have been populated with non-cacheable
-- 
2.35.1


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[PATCH v5 06/21] arm64: head: switch to map_memory macro for the extended ID map

[Ard Biesheuvel]

In a future patch, we will start using an ID map that covers the entire
image, rather than a single page. This means that we need to deal with
the pathological case of an extended ID map where the kernel image does
not fit neatly inside a single entry at the root level, which means we
will need to create additional table entries and map additional pages
for page tables.

The existing map_memory macro already takes care of most of that, so
let's just extend it to deal with this case as well. While at it, drop
the conditional branch on the value of T0SZ: we don't set the variable
anymore in the entry code, and so we can just let the map_memory macro
deal with the case where the output address exceeds VA_BITS.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/head.S | 76 ++++++++++----------
 1 file changed, 37 insertions(+), 39 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 9fdde2f9cc0f..eb54c0289c8a 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -122,29 +122,6 @@ SYM_CODE_START_LOCAL(preserve_boot_args)
 	b	dcache_inval_poc		// tail call
 SYM_CODE_END(preserve_boot_args)
 
-/*
- * Macro to create a table entry to the next page.
- *
- *	tbl:	page table address
- *	virt:	virtual address
- *	shift:	#imm page table shift
- *	ptrs:	#imm pointers per table page
- *
- * Preserves:	virt
- * Corrupts:	ptrs, tmp1, tmp2
- * Returns:	tbl -> next level table page address
- */
-	.macro	create_table_entry, tbl, virt, shift, ptrs, tmp1, tmp2
-	add	\tmp1, \tbl, #PAGE_SIZE
-	phys_to_pte \tmp2, \tmp1
-	orr	\tmp2, \tmp2, #PMD_TYPE_TABLE	// address of next table and entry type
-	lsr	\tmp1, \virt, #\shift
-	sub	\ptrs, \ptrs, #1
-	and	\tmp1, \tmp1, \ptrs		// table index
-	str	\tmp2, [\tbl, \tmp1, lsl #3]
-	add	\tbl, \tbl, #PAGE_SIZE		// next level table page
-	.endm
-
 /*
  * Macro to populate page table entries, these entries can be pointers to the next level
  * or last level entries pointing to physical memory.
@@ -209,15 +186,27 @@ SYM_CODE_END(preserve_boot_args)
  *	phys:	physical address corresponding to vstart - physical memory is contiguous
  *	order:  #imm 2log(number of entries in PGD table)
  *
+ * If extra_shift is set, an extra level will be populated if the end address does
+ * not fit in 'extra_shift' bits. This assumes vend is in the TTBR0 range.
+ *
  * Temporaries:	istart, iend, tmp, count, sv - these need to be different registers
  * Preserves:	vstart, flags
  * Corrupts:	tbl, rtbl, vend, istart, iend, tmp, count, sv
  */
-	.macro map_memory, tbl, rtbl, vstart, vend, flags, phys, order, istart, iend, tmp, count, sv
+	.macro map_memory, tbl, rtbl, vstart, vend, flags, phys, order, istart, iend, tmp, count, sv, extra_shift
 	sub \vend, \vend, #1
 	add \rtbl, \tbl, #PAGE_SIZE
 	mov \count, #0
 
+	.ifnb	\extra_shift
+	tst	\vend, #~((1 << (\extra_shift)) - 1)
+	b.eq	.L_\@
+	compute_indices \vstart, \vend, #\extra_shift, #(PAGE_SHIFT - 3), \istart, \iend, \count
+	mov \sv, \rtbl
+	populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp
+	mov \tbl, \sv
+	.endif
+.L_\@:
 	compute_indices \vstart, \vend, #PGDIR_SHIFT, #\order, \istart, \iend, \count
 	mov \sv, \rtbl
 	populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp
@@ -284,20 +273,32 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 	adrp	x3, __idmap_text_start		// __pa(__idmap_text_start)
 
 	/*
-	 * VA_BITS may be too small to allow for an ID mapping to be created
-	 * that covers system RAM if that is located sufficiently high in the
-	 * physical address space. So for the ID map, use an extended virtual
-	 * range in that case, and configure an additional translation level
-	 * if needed.
+	 * The ID map carries a 1:1 mapping of the physical address range
+	 * covered by the loaded image, which could be anywhere in DRAM. This
+	 * means that the required size of the VA (== PA) space is decided at
+	 * boot time, and could be more than the configured size of the VA
+	 * space for ordinary kernel and user space mappings.
+	 *
+	 * There are three cases to consider here:
+	 * - 39 <= VA_BITS < 48, and the ID map needs up to 48 VA bits to cover
+	 *   the placement of the image. In this case, we configure one extra
+	 *   level of translation on the fly for the ID map only. (This case
+	 *   also covers 42-bit VA/52-bit PA on 64k pages).
+	 *
+	 * - VA_BITS == 48, and the ID map needs more than 48 VA bits. This can
+	 *   only happen when using 64k pages, in which case we need to extend
+	 *   the root level table rather than add a level. Note that we can
+	 *   treat this case as 'always extended' as long as we take care not
+	 *   to program an unsupported T0SZ value into the TCR register.
+	 *
+	 * - Combinations that would require two additional levels of
+	 *   translation are not supported, e.g., VA_BITS==36 on 16k pages, or
+	 *   VA_BITS==39/4k pages with 5-level paging, where the input address
+	 *   requires more than 47 or 48 bits, respectively.
 	 */
-	idmap_get_t0sz x5
-	cmp	x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough?
-	b.ge	1f			// .. then skip VA range extension
-
 #if (VA_BITS < 48)
 #define IDMAP_PGD_ORDER	(VA_BITS - PGDIR_SHIFT)
 #define EXTRA_SHIFT	(PGDIR_SHIFT + PAGE_SHIFT - 3)
-#define EXTRA_PTRS	(1 << (PHYS_MASK_SHIFT - EXTRA_SHIFT))
 
 	/*
 	 * If VA_BITS < 48, we have to configure an additional table level.
@@ -309,20 +310,17 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 #if VA_BITS != EXTRA_SHIFT
 #error "Mismatch between VA_BITS and page size/number of translation levels"
 #endif
-
-	mov	x2, EXTRA_PTRS
-	create_table_entry x0, x3, EXTRA_SHIFT, x2, x5, x6
 #else
 #define IDMAP_PGD_ORDER	(PHYS_MASK_SHIFT - PGDIR_SHIFT)
+#define EXTRA_SHIFT
 	/*
 	 * If VA_BITS == 48, we don't have to configure an additional
 	 * translation level, but the top-level table has more entries.
 	 */
 #endif
-1:
 	adr_l	x6, __idmap_text_end		// __pa(__idmap_text_end)
 
-	map_memory x0, x1, x3, x6, x7, x3, IDMAP_PGD_ORDER, x10, x11, x12, x13, x14
+	map_memory x0, x1, x3, x6, x7, x3, IDMAP_PGD_ORDER, x10, x11, x12, x13, x14, EXTRA_SHIFT
 
 	/*
 	 * Map the kernel image (starting with PHYS_OFFSET).
-- 
2.35.1


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[PATCH v5 07/21] arm64: head: split off idmap creation code

[Ard Biesheuvel]

Split off the creation of the ID map page tables, so that we can avoid
running it again unnecessarily when KASLR is in effect (which only
randomizes the virtual placement). This will permit us to drop some
explicit cache maintenance to the PoC which was necessary because the
cache invalidation being performed on some global variables might
otherwise clobber unrelated variables that happen to share a cacheline.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/head.S | 101 ++++++++++----------
 1 file changed, 52 insertions(+), 49 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index eb54c0289c8a..1cbc52097bf9 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -84,7 +84,7 @@
 	 *  Register   Scope                      Purpose
 	 *  x21        primary_entry() .. start_kernel()        FDT pointer passed at boot in x0
 	 *  x23        primary_entry() .. start_kernel()        physical misalignment/KASLR offset
-	 *  x28        __create_page_tables()                   callee preserved temp register
+	 *  x28        clear_page_tables()                      callee preserved temp register
 	 *  x19/x20    __primary_switch()                       callee preserved temp registers
 	 *  x24        __primary_switch() .. relocate_kernel()  current RELR displacement
 	 */
@@ -94,7 +94,10 @@ SYM_CODE_START(primary_entry)
 	adrp	x23, __PHYS_OFFSET
 	and	x23, x23, MIN_KIMG_ALIGN - 1	// KASLR offset, defaults to 0
 	bl	set_cpu_boot_mode_flag
-	bl	__create_page_tables
+	bl	clear_page_tables
+	bl	create_idmap
+	bl	create_kernel_mapping
+
 	/*
 	 * The following calls CPU setup code, see arch/arm64/mm/proc.S for
 	 * details.
@@ -122,6 +125,35 @@ SYM_CODE_START_LOCAL(preserve_boot_args)
 	b	dcache_inval_poc		// tail call
 SYM_CODE_END(preserve_boot_args)
 
+SYM_FUNC_START_LOCAL(clear_page_tables)
+	mov	x28, lr
+
+	/*
+	 * Invalidate the init page tables to avoid potential dirty cache lines
+	 * being evicted. Other page tables are allocated in rodata as part of
+	 * the kernel image, and thus are clean to the PoC per the boot
+	 * protocol.
+	 */
+	adrp	x0, init_pg_dir
+	adrp	x1, init_pg_end
+	bl	dcache_inval_poc
+
+	/*
+	 * Clear the init page tables.
+	 */
+	adrp	x0, init_pg_dir
+	adrp	x1, init_pg_end
+	sub	x1, x1, x0
+1:	stp	xzr, xzr, [x0], #16
+	stp	xzr, xzr, [x0], #16
+	stp	xzr, xzr, [x0], #16
+	stp	xzr, xzr, [x0], #16
+	subs	x1, x1, #64
+	b.ne	1b
+
+	ret	x28
+SYM_FUNC_END(clear_page_tables)
+
 /*
  * Macro to populate page table entries, these entries can be pointers to the next level
  * or last level entries pointing to physical memory.
@@ -231,44 +263,8 @@ SYM_CODE_END(preserve_boot_args)
 	populate_entries \tbl, \rtbl, \istart, \iend, \flags, #SWAPPER_BLOCK_SIZE, \tmp
 	.endm
 
-/*
- * Setup the initial page tables. We only setup the barest amount which is
- * required to get the kernel running. The following sections are required:
- *   - identity mapping to enable the MMU (low address, TTBR0)
- *   - first few MB of the kernel linear mapping to jump to once the MMU has
- *     been enabled
- */
-SYM_FUNC_START_LOCAL(__create_page_tables)
-	mov	x28, lr
 
-	/*
-	 * Invalidate the init page tables to avoid potential dirty cache lines
-	 * being evicted. Other page tables are allocated in rodata as part of
-	 * the kernel image, and thus are clean to the PoC per the boot
-	 * protocol.
-	 */
-	adrp	x0, init_pg_dir
-	adrp	x1, init_pg_end
-	bl	dcache_inval_poc
-
-	/*
-	 * Clear the init page tables.
-	 */
-	adrp	x0, init_pg_dir
-	adrp	x1, init_pg_end
-	sub	x1, x1, x0
-1:	stp	xzr, xzr, [x0], #16
-	stp	xzr, xzr, [x0], #16
-	stp	xzr, xzr, [x0], #16
-	stp	xzr, xzr, [x0], #16
-	subs	x1, x1, #64
-	b.ne	1b
-
-	mov	x7, SWAPPER_MM_MMUFLAGS
-
-	/*
-	 * Create the identity mapping.
-	 */
+SYM_FUNC_START_LOCAL(create_idmap)
 	adrp	x0, idmap_pg_dir
 	adrp	x3, __idmap_text_start		// __pa(__idmap_text_start)
 
@@ -319,12 +315,23 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 	 */
 #endif
 	adr_l	x6, __idmap_text_end		// __pa(__idmap_text_end)
+	mov	x7, SWAPPER_MM_MMUFLAGS
 
 	map_memory x0, x1, x3, x6, x7, x3, IDMAP_PGD_ORDER, x10, x11, x12, x13, x14, EXTRA_SHIFT
 
 	/*
-	 * Map the kernel image (starting with PHYS_OFFSET).
+	 * Since the page tables have been populated with non-cacheable
+	 * accesses (MMU disabled), invalidate those tables again to
+	 * remove any speculatively loaded cache lines.
 	 */
+	dmb	sy
+
+	adrp	x0, idmap_pg_dir
+	adrp	x1, idmap_pg_end
+	b	dcache_inval_poc		// tail call
+SYM_FUNC_END(create_idmap)
+
+SYM_FUNC_START_LOCAL(create_kernel_mapping)
 	adrp	x0, init_pg_dir
 	mov_q	x5, KIMAGE_VADDR		// compile time __va(_text)
 	add	x5, x5, x23			// add KASLR displacement
@@ -332,6 +339,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 	adrp	x3, _text			// runtime __pa(_text)
 	sub	x6, x6, x3			// _end - _text
 	add	x6, x6, x5			// runtime __va(_end)
+	mov	x7, SWAPPER_MM_MMUFLAGS
 
 	map_memory x0, x1, x5, x6, x7, x3, (VA_BITS - PGDIR_SHIFT), x10, x11, x12, x13, x14
 
@@ -342,16 +350,10 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 	 */
 	dmb	sy
 
-	adrp	x0, idmap_pg_dir
-	adrp	x1, idmap_pg_end
-	bl	dcache_inval_poc
-
 	adrp	x0, init_pg_dir
 	adrp	x1, init_pg_end
-	bl	dcache_inval_poc
-
-	ret	x28
-SYM_FUNC_END(__create_page_tables)
+	b	dcache_inval_poc		// tail call
+SYM_FUNC_END(create_kernel_mapping)
 
 	/*
 	 * Initialize CPU registers with task-specific and cpu-specific context.
@@ -836,7 +838,8 @@ SYM_FUNC_START_LOCAL(__primary_switch)
 	pre_disable_mmu_workaround
 	msr	sctlr_el1, x20			// disable the MMU
 	isb
-	bl	__create_page_tables		// recreate kernel mapping
+	bl	clear_page_tables
+	bl	create_kernel_mapping		// Recreate kernel mapping
 
 	tlbi	vmalle1				// Remove any stale TLB entries
 	dsb	nsh
-- 
2.35.1


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[PATCH v5 08/21] arm64: kernel: drop unnecessary PoC cache clean+invalidate

[Ard Biesheuvel]

Some early boot code runs before the virtual placement of the kernel is
finalized, and we used to go back to the very start and recreate the ID
map along with the page tables describing the virtual kernel mapping,
and this involved setting some global variables with the caches off.

In order to ensure that global state created by the KASLR code is not
corrupted by the cache invalidation that occurs in that case, we needed
to clean those global variables to the PoC explicitly.

This is no longer needed now that the ID map is created only once (and
the associated global variable updates are no longer repeated). So drop
the cache maintenance that is no longer necessary.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 arch/arm64/kernel/kaslr.c | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index 418b2bba1521..d5542666182f 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -13,7 +13,6 @@
 #include <linux/pgtable.h>
 #include <linux/random.h>
 
-#include <asm/cacheflush.h>
 #include <asm/fixmap.h>
 #include <asm/kernel-pgtable.h>
 #include <asm/memory.h>
@@ -72,9 +71,6 @@ u64 __init kaslr_early_init(void)
 	 * we end up running with module randomization disabled.
 	 */
 	module_alloc_base = (u64)_etext - MODULES_VSIZE;
-	dcache_clean_inval_poc((unsigned long)&module_alloc_base,
-			    (unsigned long)&module_alloc_base +
-				    sizeof(module_alloc_base));
 
 	/*
 	 * Try to map the FDT early. If this fails, we simply bail,
@@ -174,13 +170,6 @@ u64 __init kaslr_early_init(void)
 	module_alloc_base += (module_range * (seed & ((1 << 21) - 1))) >> 21;
 	module_alloc_base &= PAGE_MASK;
 
-	dcache_clean_inval_poc((unsigned long)&module_alloc_base,
-			    (unsigned long)&module_alloc_base +
-				    sizeof(module_alloc_base));
-	dcache_clean_inval_poc((unsigned long)&memstart_offset_seed,
-			    (unsigned long)&memstart_offset_seed +
-				    sizeof(memstart_offset_seed));
-
 	return offset;
 }
 
-- 
2.35.1


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[PATCH v5 09/21] arm64: head: pass ID map root table address to __enable_mmu()

[Ard Biesheuvel]

We will be adding an initial ID map that covers the entire kernel image,
so we will pass the actual ID map root table to use to __enable_mmu(),
rather than hard code it.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/head.S  | 14 ++++++++------
 arch/arm64/kernel/sleep.S |  1 +
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 1cbc52097bf9..70c462bbd6bf 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -595,6 +595,7 @@ SYM_FUNC_START_LOCAL(secondary_startup)
 	bl	__cpu_secondary_check52bitva
 	bl	__cpu_setup			// initialise processor
 	adrp	x1, swapper_pg_dir
+	adrp	x2, idmap_pg_dir
 	bl	__enable_mmu
 	ldr	x8, =__secondary_switched
 	br	x8
@@ -648,6 +649,7 @@ SYM_FUNC_END(__secondary_too_slow)
  *
  *  x0  = SCTLR_EL1 value for turning on the MMU.
  *  x1  = TTBR1_EL1 value
+ *  x2  = ID map root table address
  *
  * Returns to the caller via x30/lr. This requires the caller to be covered
  * by the .idmap.text section.
@@ -656,14 +658,13 @@ SYM_FUNC_END(__secondary_too_slow)
  * If it isn't, park the CPU
  */
 SYM_FUNC_START(__enable_mmu)
-	mrs	x2, ID_AA64MMFR0_EL1
-	ubfx	x2, x2, #ID_AA64MMFR0_TGRAN_SHIFT, 4
-	cmp     x2, #ID_AA64MMFR0_TGRAN_SUPPORTED_MIN
+	mrs	x3, ID_AA64MMFR0_EL1
+	ubfx	x3, x3, #ID_AA64MMFR0_TGRAN_SHIFT, 4
+	cmp     x3, #ID_AA64MMFR0_TGRAN_SUPPORTED_MIN
 	b.lt    __no_granule_support
-	cmp     x2, #ID_AA64MMFR0_TGRAN_SUPPORTED_MAX
+	cmp     x3, #ID_AA64MMFR0_TGRAN_SUPPORTED_MAX
 	b.gt    __no_granule_support
-	update_early_cpu_boot_status 0, x2, x3
-	adrp	x2, idmap_pg_dir
+	update_early_cpu_boot_status 0, x3, x4
 	phys_to_ttbr x1, x1
 	phys_to_ttbr x2, x2
 	msr	ttbr0_el1, x2			// load TTBR0
@@ -819,6 +820,7 @@ SYM_FUNC_START_LOCAL(__primary_switch)
 #endif
 
 	adrp	x1, init_pg_dir
+	adrp	x2, idmap_pg_dir
 	bl	__enable_mmu
 #ifdef CONFIG_RELOCATABLE
 #ifdef CONFIG_RELR
diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
index 4ea9392f86e0..e36b09d942f7 100644
--- a/arch/arm64/kernel/sleep.S
+++ b/arch/arm64/kernel/sleep.S
@@ -104,6 +104,7 @@ SYM_CODE_START(cpu_resume)
 	bl	__cpu_setup
 	/* enable the MMU early - so we can access sleep_save_stash by va */
 	adrp	x1, swapper_pg_dir
+	adrp	x2, idmap_pg_dir
 	bl	__enable_mmu
 	ldr	x8, =_cpu_resume
 	br	x8
-- 
2.35.1


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[PATCH v5 10/21] arm64: mm: provide idmap pointer to cpu_replace_ttbr1()

[Ard Biesheuvel]

In preparation for changing the way we initialize the permanent ID map,
update cpu_replace_ttbr1() so we can use it with the initial ID map as
well.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/include/asm/mmu_context.h | 13 +++++++++----
 arch/arm64/kernel/cpufeature.c       |  2 +-
 arch/arm64/kernel/suspend.c          |  2 +-
 arch/arm64/mm/kasan_init.c           |  4 ++--
 arch/arm64/mm/mmu.c                  |  2 +-
 5 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index 7b387c3b312a..c7ccd82db1d2 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -105,13 +105,18 @@ static inline void cpu_uninstall_idmap(void)
 		cpu_switch_mm(mm->pgd, mm);
 }
 
-static inline void cpu_install_idmap(void)
+static inline void __cpu_install_idmap(pgd_t *idmap)
 {
 	cpu_set_reserved_ttbr0();
 	local_flush_tlb_all();
 	cpu_set_idmap_tcr_t0sz();
 
-	cpu_switch_mm(lm_alias(idmap_pg_dir), &init_mm);
+	cpu_switch_mm(lm_alias(idmap), &init_mm);
+}
+
+static inline void cpu_install_idmap(void)
+{
+	__cpu_install_idmap(idmap_pg_dir);
 }
 
 /*
@@ -142,7 +147,7 @@ static inline void cpu_install_ttbr0(phys_addr_t ttbr0, unsigned long t0sz)
  * Atomically replaces the active TTBR1_EL1 PGD with a new VA-compatible PGD,
  * avoiding the possibility of conflicting TLB entries being allocated.
  */
-static inline void __nocfi cpu_replace_ttbr1(pgd_t *pgdp)
+static inline void __nocfi cpu_replace_ttbr1(pgd_t *pgdp, pgd_t *idmap)
 {
 	typedef void (ttbr_replace_func)(phys_addr_t);
 	extern ttbr_replace_func idmap_cpu_replace_ttbr1;
@@ -165,7 +170,7 @@ static inline void __nocfi cpu_replace_ttbr1(pgd_t *pgdp)
 
 	replace_phys = (void *)__pa_symbol(function_nocfi(idmap_cpu_replace_ttbr1));
 
-	cpu_install_idmap();
+	__cpu_install_idmap(idmap);
 	replace_phys(ttbr1);
 	cpu_uninstall_idmap();
 }
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 145b43c6c651..98b48d9069a7 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -3266,7 +3266,7 @@ subsys_initcall_sync(init_32bit_el0_mask);
 
 static void __maybe_unused cpu_enable_cnp(struct arm64_cpu_capabilities const *cap)
 {
-	cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
+	cpu_replace_ttbr1(lm_alias(swapper_pg_dir), idmap_pg_dir);
 }
 
 /*
diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
index 2b0887e58a7c..9135fe0f3df5 100644
--- a/arch/arm64/kernel/suspend.c
+++ b/arch/arm64/kernel/suspend.c
@@ -52,7 +52,7 @@ void notrace __cpu_suspend_exit(void)
 
 	/* Restore CnP bit in TTBR1_EL1 */
 	if (system_supports_cnp())
-		cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
+		cpu_replace_ttbr1(lm_alias(swapper_pg_dir), idmap_pg_dir);
 
 	/*
 	 * PSTATE was not saved over suspend/resume, re-enable any detected
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index c12cd700598f..e969e68de005 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -236,7 +236,7 @@ static void __init kasan_init_shadow(void)
 	 */
 	memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
 	dsb(ishst);
-	cpu_replace_ttbr1(lm_alias(tmp_pg_dir));
+	cpu_replace_ttbr1(lm_alias(tmp_pg_dir), idmap_pg_dir);
 
 	clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 
@@ -280,7 +280,7 @@ static void __init kasan_init_shadow(void)
 				PAGE_KERNEL_RO));
 
 	memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE);
-	cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
+	cpu_replace_ttbr1(lm_alias(swapper_pg_dir), idmap_pg_dir);
 }
 
 static void __init kasan_init_depth(void)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 3be0e9f69406..488628f07b89 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -780,7 +780,7 @@ void __init paging_init(void)
 
 	pgd_clear_fixmap();
 
-	cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
+	cpu_replace_ttbr1(lm_alias(swapper_pg_dir), idmap_pg_dir);
 	init_mm.pgd = swapper_pg_dir;
 
 	memblock_phys_free(__pa_symbol(init_pg_dir),
-- 
2.35.1


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[PATCH v5 11/21] arm64: head: add helper function to remap regions in early page tables

[Ard Biesheuvel]

The asm macros used to create the initial ID map and kernel mappings
don't support randomly remapping parts of the address space after it has
been populated. What we can do, however, given that all block or page
mappings are created at the final level, is take a subset of the mapped
range and update its attributes or output address. This will permit us
to make parts of these page tables read-only, or remap a part of it to
cover the device tree.

So add a helper that encapsulates this.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/head.S | 33 ++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 70c462bbd6bf..7397555f8437 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -263,6 +263,39 @@ SYM_FUNC_END(clear_page_tables)
 	populate_entries \tbl, \rtbl, \istart, \iend, \flags, #SWAPPER_BLOCK_SIZE, \tmp
 	.endm
 
+/*
+ * Remap a subregion created with the map_memory macro with modified attributes
+ * or output address. The entire remapped region must have been covered in the
+ * invocation of map_memory.
+ *
+ * x0: last level table address (returned in first argument to map_memory)
+ * x1: start VA of the existing mapping
+ * x2: start VA of the region to update
+ * x3: end VA of the region to update (exclusive)
+ * x4: start PA associated with the region to update
+ * x5: attributes to set on the updated region
+ * x6: order of the last level mappings
+ */
+SYM_FUNC_START_LOCAL(remap_region)
+	sub	x3, x3, #1		// make end inclusive
+
+	// Get the index offset for the start of the last level table
+	lsr	x1, x1, x6
+	bfi	x1, xzr, #0, #PAGE_SHIFT - 3
+
+	// Derive the start and end indexes into the last level table
+	// associated with the provided region
+	lsr	x2, x2, x6
+	lsr	x3, x3, x6
+	sub	x2, x2, x1
+	sub	x3, x3, x1
+
+	mov	x1, #1
+	lsl	x6, x1, x6		// block size at this level
+
+	populate_entries x0, x4, x2, x3, x5, x6, x7
+	ret
+SYM_FUNC_END(remap_region)
 
 SYM_FUNC_START_LOCAL(create_idmap)
 	adrp	x0, idmap_pg_dir
-- 
2.35.1


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[PATCH v5 12/21] arm64: head: cover entire kernel image in initial ID map

[Ard Biesheuvel]

As a first step towards avoiding the need to create, tear down and
recreate the kernel virtual mapping with MMU and caches disabled, start
by expanding the ID map so it covers the page tables as well as all
executable code. This will allow us to populate the page tables with the
MMU and caches on, and call KASLR init code before setting up the
virtual mapping.

Since this ID map is only needed at boot, create it as a temporary set
of page tables, and populate the permanent ID map after enabling the MMU
and caches. While at it, switch to read-only attributes for the where
possible, as writable permissions are only needed for the initial kernel
page tables. Note that on 4k granule configurations, the permanent ID
map will now be reduced to a single page rather than a 2M block mapping.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/include/asm/kernel-pgtable.h | 16 ++++++---
 arch/arm64/kernel/head.S                | 31 +++++++++++------
 arch/arm64/kernel/vmlinux.lds.S         |  7 ++--
 arch/arm64/mm/mmu.c                     | 35 +++++++++++++++++++-
 arch/arm64/mm/proc.S                    |  8 +++--
 5 files changed, 76 insertions(+), 21 deletions(-)

diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index 96dc0f7da258..5395e5a04f35 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -35,10 +35,8 @@
  */
 #if ARM64_KERNEL_USES_PMD_MAPS
 #define SWAPPER_PGTABLE_LEVELS	(CONFIG_PGTABLE_LEVELS - 1)
-#define IDMAP_PGTABLE_LEVELS	(ARM64_HW_PGTABLE_LEVELS(PHYS_MASK_SHIFT) - 1)
 #else
 #define SWAPPER_PGTABLE_LEVELS	(CONFIG_PGTABLE_LEVELS)
-#define IDMAP_PGTABLE_LEVELS	(ARM64_HW_PGTABLE_LEVELS(PHYS_MASK_SHIFT))
 #endif
 
 
@@ -87,7 +85,13 @@
 			+ EARLY_PUDS((vstart), (vend))	/* each PUD needs a next level page table */	\
 			+ EARLY_PMDS((vstart), (vend)))	/* each PMD needs a next level page table */
 #define INIT_DIR_SIZE (PAGE_SIZE * EARLY_PAGES(KIMAGE_VADDR, _end))
-#define IDMAP_DIR_SIZE		(IDMAP_PGTABLE_LEVELS * PAGE_SIZE)
+
+/* the initial ID map may need two extra pages if it needs to be extended */
+#if VA_BITS < 48
+#define INIT_IDMAP_DIR_SIZE	(INIT_DIR_SIZE + (2 * PAGE_SIZE))
+#else
+#define INIT_IDMAP_DIR_SIZE	INIT_DIR_SIZE
+#endif
 
 /* Initial memory map size */
 #if ARM64_KERNEL_USES_PMD_MAPS
@@ -107,9 +111,11 @@
 #define SWAPPER_PMD_FLAGS	(PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S)
 
 #if ARM64_KERNEL_USES_PMD_MAPS
-#define SWAPPER_MM_MMUFLAGS	(PMD_ATTRINDX(MT_NORMAL) | SWAPPER_PMD_FLAGS)
+#define SWAPPER_RW_MMUFLAGS	(PMD_ATTRINDX(MT_NORMAL) | SWAPPER_PMD_FLAGS)
+#define SWAPPER_RX_MMUFLAGS	(SWAPPER_RW_MMUFLAGS | PMD_SECT_RDONLY)
 #else
-#define SWAPPER_MM_MMUFLAGS	(PTE_ATTRINDX(MT_NORMAL) | SWAPPER_PTE_FLAGS)
+#define SWAPPER_RW_MMUFLAGS	(PTE_ATTRINDX(MT_NORMAL) | SWAPPER_PTE_FLAGS)
+#define SWAPPER_RX_MMUFLAGS	(SWAPPER_RW_MMUFLAGS | PTE_RDONLY)
 #endif
 
 /*
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 7397555f8437..93734c91a29a 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -87,6 +87,7 @@
 	 *  x28        clear_page_tables()                      callee preserved temp register
 	 *  x19/x20    __primary_switch()                       callee preserved temp registers
 	 *  x24        __primary_switch() .. relocate_kernel()  current RELR displacement
+	 *  x28        create_idmap()                           callee preserved temp register
 	 */
 SYM_CODE_START(primary_entry)
 	bl	preserve_boot_args
@@ -298,9 +299,7 @@ SYM_FUNC_START_LOCAL(remap_region)
 SYM_FUNC_END(remap_region)
 
 SYM_FUNC_START_LOCAL(create_idmap)
-	adrp	x0, idmap_pg_dir
-	adrp	x3, __idmap_text_start		// __pa(__idmap_text_start)
-
+	mov	x28, lr
 	/*
 	 * The ID map carries a 1:1 mapping of the physical address range
 	 * covered by the loaded image, which could be anywhere in DRAM. This
@@ -347,11 +346,22 @@ SYM_FUNC_START_LOCAL(create_idmap)
 	 * translation level, but the top-level table has more entries.
 	 */
 #endif
-	adr_l	x6, __idmap_text_end		// __pa(__idmap_text_end)
-	mov	x7, SWAPPER_MM_MMUFLAGS
+	adrp	x0, init_idmap_pg_dir
+	adrp	x3, _text
+	adrp	x6, _end
+	mov	x7, SWAPPER_RX_MMUFLAGS
 
 	map_memory x0, x1, x3, x6, x7, x3, IDMAP_PGD_ORDER, x10, x11, x12, x13, x14, EXTRA_SHIFT
 
+	/* Remap the kernel page tables r/w in the ID map */
+	adrp	x1, _text
+	adrp	x2, init_pg_dir
+	adrp	x3, init_pg_end
+	bic	x4, x2, #SWAPPER_BLOCK_SIZE - 1
+	mov	x5, SWAPPER_RW_MMUFLAGS
+	mov	x6, #SWAPPER_BLOCK_SHIFT
+	bl	remap_region
+
 	/*
 	 * Since the page tables have been populated with non-cacheable
 	 * accesses (MMU disabled), invalidate those tables again to
@@ -359,9 +369,10 @@ SYM_FUNC_START_LOCAL(create_idmap)
 	 */
 	dmb	sy
 
-	adrp	x0, idmap_pg_dir
-	adrp	x1, idmap_pg_end
-	b	dcache_inval_poc		// tail call
+	adrp	x0, init_idmap_pg_dir
+	adrp	x1, init_idmap_pg_end
+	bl	dcache_inval_poc
+	ret	x28
 SYM_FUNC_END(create_idmap)
 
 SYM_FUNC_START_LOCAL(create_kernel_mapping)
@@ -372,7 +383,7 @@ SYM_FUNC_START_LOCAL(create_kernel_mapping)
 	adrp	x3, _text			// runtime __pa(_text)
 	sub	x6, x6, x3			// _end - _text
 	add	x6, x6, x5			// runtime __va(_end)
-	mov	x7, SWAPPER_MM_MMUFLAGS
+	mov	x7, SWAPPER_RW_MMUFLAGS
 
 	map_memory x0, x1, x5, x6, x7, x3, (VA_BITS - PGDIR_SHIFT), x10, x11, x12, x13, x14
 
@@ -853,7 +864,7 @@ SYM_FUNC_START_LOCAL(__primary_switch)
 #endif
 
 	adrp	x1, init_pg_dir
-	adrp	x2, idmap_pg_dir
+	adrp	x2, init_idmap_pg_dir
 	bl	__enable_mmu
 #ifdef CONFIG_RELOCATABLE
 #ifdef CONFIG_RELR
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 8a078c0ee140..0ce3a7c9f8c4 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -199,8 +199,7 @@ SECTIONS
 	}
 
 	idmap_pg_dir = .;
-	. += IDMAP_DIR_SIZE;
-	idmap_pg_end = .;
+	. += PAGE_SIZE;
 
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
 	tramp_pg_dir = .;
@@ -236,6 +235,10 @@ SECTIONS
 	__inittext_end = .;
 	__initdata_begin = .;
 
+	init_idmap_pg_dir = .;
+	. += INIT_IDMAP_DIR_SIZE;
+	init_idmap_pg_end = .;
+
 	.init.data : {
 		INIT_DATA
 		INIT_SETUP(16)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 488628f07b89..e17eacfa048c 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -769,9 +769,40 @@ static void __init map_kernel(pgd_t *pgdp)
 	kasan_copy_shadow(pgdp);
 }
 
+static void __init create_idmap(void)
+{
+	u64 start = __pa_symbol(__idmap_text_start);
+	u64 size = __pa_symbol(__idmap_text_end) - start;
+	pgd_t *pgd = idmap_pg_dir;
+	u64 pgd_phys;
+
+	/* check if we need an additional level of translation */
+	if (VA_BITS < 48 && idmap_t0sz < (64 - VA_BITS_MIN)) {
+		pgd_phys = early_pgtable_alloc(PAGE_SHIFT);
+		set_pgd(&idmap_pg_dir[start >> VA_BITS],
+			__pgd(pgd_phys | P4D_TYPE_TABLE));
+		pgd = __va(pgd_phys);
+	}
+	__create_pgd_mapping(pgd, start, start, size, PAGE_KERNEL_ROX,
+			     early_pgtable_alloc, 0);
+
+	if (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0)) {
+		extern u32 __idmap_kpti_flag;
+		u64 pa = __pa_symbol(&__idmap_kpti_flag);
+
+		/*
+		 * The KPTI G-to-nG conversion code needs a read-write mapping
+		 * of its synchronization flag in the ID map.
+		 */
+		__create_pgd_mapping(pgd, pa, pa, sizeof(u32), PAGE_KERNEL,
+				     early_pgtable_alloc, 0);
+	}
+}
+
 void __init paging_init(void)
 {
 	pgd_t *pgdp = pgd_set_fixmap(__pa_symbol(swapper_pg_dir));
+	extern pgd_t init_idmap_pg_dir[];
 
 	idmap_t0sz = 63UL - __fls(__pa_symbol(_end) | GENMASK(VA_BITS_MIN - 1, 0));
 
@@ -780,13 +811,15 @@ void __init paging_init(void)
 
 	pgd_clear_fixmap();
 
-	cpu_replace_ttbr1(lm_alias(swapper_pg_dir), idmap_pg_dir);
+	cpu_replace_ttbr1(lm_alias(swapper_pg_dir), init_idmap_pg_dir);
 	init_mm.pgd = swapper_pg_dir;
 
 	memblock_phys_free(__pa_symbol(init_pg_dir),
 			   __pa_symbol(init_pg_end) - __pa_symbol(init_pg_dir));
 
 	memblock_allow_resize();
+
+	create_idmap();
 }
 
 /*
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 97cd67697212..493b8ffc9be5 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -249,8 +249,10 @@ SYM_FUNC_END(idmap_cpu_replace_ttbr1)
  *
  * Called exactly once from stop_machine context by each CPU found during boot.
  */
-__idmap_kpti_flag:
-	.long	1
+	.pushsection	".data", "aw", %progbits
+SYM_DATA(__idmap_kpti_flag, .long 1)
+	.popsection
+
 SYM_FUNC_START(idmap_kpti_install_ng_mappings)
 	cpu		.req	w0
 	temp_pte	.req	x0
@@ -273,7 +275,7 @@ SYM_FUNC_START(idmap_kpti_install_ng_mappings)
 
 	mov	x5, x3				// preserve temp_pte arg
 	mrs	swapper_ttb, ttbr1_el1
-	adr	flag_ptr, __idmap_kpti_flag
+	adr_l	flag_ptr, __idmap_kpti_flag
 
 	cbnz	cpu, __idmap_kpti_secondary
 
-- 
2.35.1


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[PATCH v5 13/21] arm64: head: use relative references to the RELA and RELR tables

[Ard Biesheuvel]

Formerly, we had to access the RELA and RELR tables via the kernel
mapping that was being relocated, and so deriving the start and end
addresses using ADRP/ADD references was not possible, as the relocation
code runs from the ID map.

Now that we map the entire kernel image via the ID map, we can simplify
this, and just load the entries via the ID map as well.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/head.S        | 13 ++++---------
 arch/arm64/kernel/vmlinux.lds.S | 12 ++++--------
 2 files changed, 8 insertions(+), 17 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 93734c91a29a..f1497f7b4da0 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -757,13 +757,10 @@ SYM_FUNC_START_LOCAL(__relocate_kernel)
 	 * Iterate over each entry in the relocation table, and apply the
 	 * relocations in place.
 	 */
-	ldr	w9, =__rela_offset		// offset to reloc table
-	ldr	w10, =__rela_size		// size of reloc table
-
+	adr_l	x9, __rela_start
+	adr_l	x10, __rela_end
 	mov_q	x11, KIMAGE_VADDR		// default virtual offset
 	add	x11, x11, x23			// actual virtual offset
-	add	x9, x9, x11			// __va(.rela)
-	add	x10, x9, x10			// __va(.rela) + sizeof(.rela)
 
 0:	cmp	x9, x10
 	b.hs	1f
@@ -813,10 +810,8 @@ SYM_FUNC_START_LOCAL(__relocate_kernel)
 	 * __relocate_kernel is called twice with non-zero displacements (i.e.
 	 * if there is both a physical misalignment and a KASLR displacement).
 	 */
-	ldr	w9, =__relr_offset		// offset to reloc table
-	ldr	w10, =__relr_size		// size of reloc table
-	add	x9, x9, x11			// __va(.relr)
-	add	x10, x9, x10			// __va(.relr) + sizeof(.relr)
+	adr_l	x9, __relr_start
+	adr_l	x10, __relr_end
 
 	sub	x15, x23, x24			// delta from previous offset
 	cbz	x15, 7f				// nothing to do if unchanged
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 0ce3a7c9f8c4..45131e354e27 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -257,21 +257,17 @@ SECTIONS
 	HYPERVISOR_RELOC_SECTION
 
 	.rela.dyn : ALIGN(8) {
+		__rela_start = .;
 		*(.rela .rela*)
+		__rela_end = .;
 	}
 
-	__rela_offset	= ABSOLUTE(ADDR(.rela.dyn) - KIMAGE_VADDR);
-	__rela_size	= SIZEOF(.rela.dyn);
-
-#ifdef CONFIG_RELR
 	.relr.dyn : ALIGN(8) {
+		__relr_start = .;
 		*(.relr.dyn)
+		__relr_end = .;
 	}
 
-	__relr_offset	= ABSOLUTE(ADDR(.relr.dyn) - KIMAGE_VADDR);
-	__relr_size	= SIZEOF(.relr.dyn);
-#endif
-
 	. = ALIGN(SEGMENT_ALIGN);
 	__initdata_end = .;
 	__init_end = .;
-- 
2.35.1


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[PATCH v5 14/21] arm64: head: create a temporary FDT mapping in the initial ID map

[Ard Biesheuvel]

We need to access the DT very early to get at the command line and the
KASLR seed, which currently means we rely on some hacks to call into the
kernel before really calling into the kernel, which is undesirable.

So instead, let's create a mapping for the FDT in the initial ID map,
which is feasible now that it has been extended to cover more than a
single page or block, and can be updated in place to remap other output
addresses.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/include/asm/kernel-pgtable.h |  6 ++++--
 arch/arm64/kernel/head.S                | 14 +++++++++++++-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index 5395e5a04f35..02e59fa8f293 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -8,6 +8,7 @@
 #ifndef __ASM_KERNEL_PGTABLE_H
 #define __ASM_KERNEL_PGTABLE_H
 
+#include <asm/boot.h>
 #include <asm/pgtable-hwdef.h>
 #include <asm/sparsemem.h>
 
@@ -88,10 +89,11 @@
 
 /* the initial ID map may need two extra pages if it needs to be extended */
 #if VA_BITS < 48
-#define INIT_IDMAP_DIR_SIZE	(INIT_DIR_SIZE + (2 * PAGE_SIZE))
+#define INIT_IDMAP_DIR_SIZE	((INIT_IDMAP_DIR_PAGES + 2) * PAGE_SIZE)
 #else
-#define INIT_IDMAP_DIR_SIZE	INIT_DIR_SIZE
+#define INIT_IDMAP_DIR_SIZE	(INIT_IDMAP_DIR_PAGES * PAGE_SIZE)
 #endif
+#define INIT_IDMAP_DIR_PAGES	EARLY_PAGES(KIMAGE_VADDR, _end + MAX_FDT_SIZE + SWAPPER_BLOCK_SIZE)
 
 /* Initial memory map size */
 #if ARM64_KERNEL_USES_PMD_MAPS
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index f1497f7b4da0..8283ff848328 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -83,6 +83,7 @@
 	 *
 	 *  Register   Scope                      Purpose
 	 *  x21        primary_entry() .. start_kernel()        FDT pointer passed at boot in x0
+	 *  x22        create_idmap() .. start_kernel()         ID map VA of the DT blob
 	 *  x23        primary_entry() .. start_kernel()        physical misalignment/KASLR offset
 	 *  x28        clear_page_tables()                      callee preserved temp register
 	 *  x19/x20    __primary_switch()                       callee preserved temp registers
@@ -348,7 +349,7 @@ SYM_FUNC_START_LOCAL(create_idmap)
 #endif
 	adrp	x0, init_idmap_pg_dir
 	adrp	x3, _text
-	adrp	x6, _end
+	adrp	x6, _end + MAX_FDT_SIZE + SWAPPER_BLOCK_SIZE
 	mov	x7, SWAPPER_RX_MMUFLAGS
 
 	map_memory x0, x1, x3, x6, x7, x3, IDMAP_PGD_ORDER, x10, x11, x12, x13, x14, EXTRA_SHIFT
@@ -362,6 +363,17 @@ SYM_FUNC_START_LOCAL(create_idmap)
 	mov	x6, #SWAPPER_BLOCK_SHIFT
 	bl	remap_region
 
+	/* Remap the FDT after the kernel image */
+	adrp	x1, _text
+	adrp	x22, _end + SWAPPER_BLOCK_SIZE
+	bic	x2, x22, #SWAPPER_BLOCK_SIZE - 1
+	bfi	x22, x21, #0, #SWAPPER_BLOCK_SHIFT		// remapped FDT address
+	add	x3, x2, #MAX_FDT_SIZE + SWAPPER_BLOCK_SIZE
+	bic	x4, x21, #SWAPPER_BLOCK_SIZE - 1
+	mov	x5, SWAPPER_RW_MMUFLAGS
+	mov	x6, #SWAPPER_BLOCK_SHIFT
+	bl	remap_region
+
 	/*
 	 * Since the page tables have been populated with non-cacheable
 	 * accesses (MMU disabled), invalidate those tables again to
-- 
2.35.1


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[PATCH v5 15/21] arm64: idreg-override: use early FDT mapping in ID map

[Ard Biesheuvel]

Instead of calling into the kernel to map the FDT into the kernel page
tables before even calling start_kernel(), let's switch to the initial,
temporary mapping of the device tree that has been added to the ID map.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/head.S           |  1 +
 arch/arm64/kernel/idreg-override.c | 17 ++++++-----------
 2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 8283ff848328..64ebff634b83 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -472,6 +472,7 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 #endif
 	mov	x0, x21				// pass FDT address in x0
 	bl	early_fdt_map			// Try mapping the FDT early
+	mov	x0, x22				// pass FDT address in x0
 	bl	init_feature_override		// Parse cpu feature overrides
 #ifdef CONFIG_RANDOMIZE_BASE
 	tst	x23, ~(MIN_KIMG_ALIGN - 1)	// already running randomized?
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 8a2ceb591686..f92836e196e5 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -201,16 +201,11 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
 	} while (1);
 }
 
-static __init const u8 *get_bootargs_cmdline(void)
+static __init const u8 *get_bootargs_cmdline(const void *fdt)
 {
 	const u8 *prop;
-	void *fdt;
 	int node;
 
-	fdt = get_early_fdt_ptr();
-	if (!fdt)
-		return NULL;
-
 	node = fdt_path_offset(fdt, "/chosen");
 	if (node < 0)
 		return NULL;
@@ -222,9 +217,9 @@ static __init const u8 *get_bootargs_cmdline(void)
 	return strlen(prop) ? prop : NULL;
 }
 
-static __init void parse_cmdline(void)
+static __init void parse_cmdline(const void *fdt)
 {
-	const u8 *prop = get_bootargs_cmdline();
+	const u8 *prop = get_bootargs_cmdline(fdt);
 
 	if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
 		__parse_cmdline(CONFIG_CMDLINE, true);
@@ -234,9 +229,9 @@ static __init void parse_cmdline(void)
 }
 
 /* Keep checkers quiet */
-void init_feature_override(void);
+void init_feature_override(const void *fdt);
 
-asmlinkage void __init init_feature_override(void)
+asmlinkage void __init init_feature_override(const void *fdt)
 {
 	int i;
 
@@ -247,7 +242,7 @@ asmlinkage void __init init_feature_override(void)
 		}
 	}
 
-	parse_cmdline();
+	parse_cmdline(fdt);
 
 	for (i = 0; i < ARRAY_SIZE(regs); i++) {
 		if (regs[i]->override)
-- 
2.35.1


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[PATCH v5 16/21] arm64: head: factor out TTBR1 assignment into a macro

[Ard Biesheuvel]

Create a macro load_ttbr1 to avoid having to repeat the same instruction
sequence 3 times in a subsequent patch. No functional change intended.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/include/asm/assembler.h | 17 +++++++++++++----
 arch/arm64/kernel/head.S           |  5 +----
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 9468f45c07a6..b2584709c332 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -479,6 +479,18 @@ alternative_endif
 	_cond_extable .Licache_op\@, \fixup
 	.endm
 
+/*
+ * load_ttbr1 - install @pgtbl as a TTBR1 page table
+ * pgtbl preserved
+ * tmp1/tmp2 clobbered, either may overlap with pgtbl
+ */
+	.macro		load_ttbr1, pgtbl, tmp1, tmp2
+	phys_to_ttbr	\tmp1, \pgtbl
+	offset_ttbr1 	\tmp1, \tmp2
+	msr		ttbr1_el1, \tmp1
+	isb
+	.endm
+
 /*
  * To prevent the possibility of old and new partial table walks being visible
  * in the tlb, switch the ttbr to a zero page when we invalidate the old
@@ -492,10 +504,7 @@ alternative_endif
 	isb
 	tlbi	vmalle1
 	dsb	nsh
-	phys_to_ttbr \tmp, \page_table
-	offset_ttbr1 \tmp, \tmp2
-	msr	ttbr1_el1, \tmp
-	isb
+	load_ttbr1 \page_table, \tmp, \tmp2
 	.endm
 
 /*
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 64ebff634b83..d704d0bd8ffc 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -722,12 +722,9 @@ SYM_FUNC_START(__enable_mmu)
 	cmp     x3, #ID_AA64MMFR0_TGRAN_SUPPORTED_MAX
 	b.gt    __no_granule_support
 	update_early_cpu_boot_status 0, x3, x4
-	phys_to_ttbr x1, x1
 	phys_to_ttbr x2, x2
 	msr	ttbr0_el1, x2			// load TTBR0
-	offset_ttbr1 x1, x3
-	msr	ttbr1_el1, x1			// load TTBR1
-	isb
+	load_ttbr1 x1, x1, x3
 
 	set_sctlr_el1	x0
 
-- 
2.35.1


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[PATCH v5 17/21] arm64: head: populate kernel page tables with MMU and caches on

[Ard Biesheuvel]

Now that we can access the entire kernel image via the ID map, we can
execute the page table population code with the MMU and caches enabled.
The only thing we need to ensure is that translations via TTBR1 remain
disabled while we are updating the page tables the second time around,
in case KASLR wants them to be randomized.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/head.S | 62 +++++---------------
 1 file changed, 16 insertions(+), 46 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index d704d0bd8ffc..583cbea865e1 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -85,8 +85,6 @@
 	 *  x21        primary_entry() .. start_kernel()        FDT pointer passed at boot in x0
 	 *  x22        create_idmap() .. start_kernel()         ID map VA of the DT blob
 	 *  x23        primary_entry() .. start_kernel()        physical misalignment/KASLR offset
-	 *  x28        clear_page_tables()                      callee preserved temp register
-	 *  x19/x20    __primary_switch()                       callee preserved temp registers
 	 *  x24        __primary_switch() .. relocate_kernel()  current RELR displacement
 	 *  x28        create_idmap()                           callee preserved temp register
 	 */
@@ -96,9 +94,7 @@ SYM_CODE_START(primary_entry)
 	adrp	x23, __PHYS_OFFSET
 	and	x23, x23, MIN_KIMG_ALIGN - 1	// KASLR offset, defaults to 0
 	bl	set_cpu_boot_mode_flag
-	bl	clear_page_tables
 	bl	create_idmap
-	bl	create_kernel_mapping
 
 	/*
 	 * The following calls CPU setup code, see arch/arm64/mm/proc.S for
@@ -128,32 +124,14 @@ SYM_CODE_START_LOCAL(preserve_boot_args)
 SYM_CODE_END(preserve_boot_args)
 
 SYM_FUNC_START_LOCAL(clear_page_tables)
-	mov	x28, lr
-
-	/*
-	 * Invalidate the init page tables to avoid potential dirty cache lines
-	 * being evicted. Other page tables are allocated in rodata as part of
-	 * the kernel image, and thus are clean to the PoC per the boot
-	 * protocol.
-	 */
-	adrp	x0, init_pg_dir
-	adrp	x1, init_pg_end
-	bl	dcache_inval_poc
-
 	/*
 	 * Clear the init page tables.
 	 */
 	adrp	x0, init_pg_dir
 	adrp	x1, init_pg_end
-	sub	x1, x1, x0
-1:	stp	xzr, xzr, [x0], #16
-	stp	xzr, xzr, [x0], #16
-	stp	xzr, xzr, [x0], #16
-	stp	xzr, xzr, [x0], #16
-	subs	x1, x1, #64
-	b.ne	1b
-
-	ret	x28
+	sub	x2, x1, x0
+	mov	x1, xzr
+	b	__pi_memset			// tail call
 SYM_FUNC_END(clear_page_tables)
 
 /*
@@ -399,16 +377,8 @@ SYM_FUNC_START_LOCAL(create_kernel_mapping)
 
 	map_memory x0, x1, x5, x6, x7, x3, (VA_BITS - PGDIR_SHIFT), x10, x11, x12, x13, x14
 
-	/*
-	 * Since the page tables have been populated with non-cacheable
-	 * accesses (MMU disabled), invalidate those tables again to
-	 * remove any speculatively loaded cache lines.
-	 */
-	dmb	sy
-
-	adrp	x0, init_pg_dir
-	adrp	x1, init_pg_end
-	b	dcache_inval_poc		// tail call
+	dsb	ishst				// sync with page table walker
+	ret
 SYM_FUNC_END(create_kernel_mapping)
 
 	/*
@@ -863,14 +833,15 @@ SYM_FUNC_END(__relocate_kernel)
 #endif
 
 SYM_FUNC_START_LOCAL(__primary_switch)
-#ifdef CONFIG_RANDOMIZE_BASE
-	mov	x19, x0				// preserve new SCTLR_EL1 value
-	mrs	x20, sctlr_el1			// preserve old SCTLR_EL1 value
-#endif
-
-	adrp	x1, init_pg_dir
+	adrp	x1, reserved_pg_dir
 	adrp	x2, init_idmap_pg_dir
 	bl	__enable_mmu
+
+	bl	clear_page_tables
+	bl	create_kernel_mapping
+
+	adrp	x1, init_pg_dir
+	load_ttbr1 x1, x1, x2
 #ifdef CONFIG_RELOCATABLE
 #ifdef CONFIG_RELR
 	mov	x24, #0				// no RELR displacement yet
@@ -886,9 +857,8 @@ SYM_FUNC_START_LOCAL(__primary_switch)
 	 * to take into account by discarding the current kernel mapping and
 	 * creating a new one.
 	 */
-	pre_disable_mmu_workaround
-	msr	sctlr_el1, x20			// disable the MMU
-	isb
+	adrp	x1, reserved_pg_dir		// Disable translations via TTBR1
+	load_ttbr1 x1, x1, x2
 	bl	clear_page_tables
 	bl	create_kernel_mapping		// Recreate kernel mapping
 
@@ -896,8 +866,8 @@ SYM_FUNC_START_LOCAL(__primary_switch)
 	dsb	nsh
 	isb
 
-	set_sctlr_el1	x19			// re-enable the MMU
-
+	adrp	x1, init_pg_dir			// Re-enable translations via TTBR1
+	load_ttbr1 x1, x1, x2
 	bl	__relocate_kernel
 #endif
 #endif
-- 
2.35.1


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[PATCH v5 18/21] arm64: head: record CPU boot mode after enabling the MMU

[Ard Biesheuvel]

In order to avoid having to touch memory with the MMU and caches
disabled, and therefore having to invalidate it from the caches
explicitly, just defer storing the value until after the MMU has been
turned on, unless we are giving up with an error.

While at it, move the associated variable definitions into C code.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/head.S     | 50 +++++---------------
 arch/arm64/kernel/hyp-stub.S |  4 +-
 arch/arm64/mm/mmu.c          |  8 ++++
 3 files changed, 23 insertions(+), 39 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 583cbea865e1..8de346dd4470 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -82,6 +82,7 @@
 	 * primary lowlevel boot path:
 	 *
 	 *  Register   Scope                      Purpose
+	 *  x20        primary_entry() .. __primary_switch()    CPU boot mode
 	 *  x21        primary_entry() .. start_kernel()        FDT pointer passed at boot in x0
 	 *  x22        create_idmap() .. start_kernel()         ID map VA of the DT blob
 	 *  x23        primary_entry() .. start_kernel()        physical misalignment/KASLR offset
@@ -91,9 +92,9 @@
 SYM_CODE_START(primary_entry)
 	bl	preserve_boot_args
 	bl	init_kernel_el			// w0=cpu_boot_mode
+	mov	x20, x0
 	adrp	x23, __PHYS_OFFSET
 	and	x23, x23, MIN_KIMG_ALIGN - 1	// KASLR offset, defaults to 0
-	bl	set_cpu_boot_mode_flag
 	bl	create_idmap
 
 	/*
@@ -429,6 +430,9 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 	sub	x4, x4, x0			// the kernel virtual and
 	str_l	x4, kimage_voffset, x5		// physical mappings
 
+	mov	x0, x20
+	bl	set_cpu_boot_mode_flag
+
 	// Clear BSS
 	adr_l	x0, __bss_start
 	mov	x1, xzr
@@ -454,6 +458,7 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 	ret					// to __primary_switch()
 0:
 #endif
+	mov	x0, x20
 	bl	switch_to_vhe			// Prefer VHE if possible
 	ldp	x29, x30, [sp], #16
 	bl	start_kernel
@@ -553,52 +558,21 @@ SYM_FUNC_START_LOCAL(set_cpu_boot_mode_flag)
 	b.ne	1f
 	add	x1, x1, #4
 1:	str	w0, [x1]			// Save CPU boot mode
-	dmb	sy
-	dc	ivac, x1			// Invalidate potentially stale cache line
 	ret
 SYM_FUNC_END(set_cpu_boot_mode_flag)
 
-/*
- * These values are written with the MMU off, but read with the MMU on.
- * Writers will invalidate the corresponding address, discarding up to a
- * 'Cache Writeback Granule' (CWG) worth of data. The linker script ensures
- * sufficient alignment that the CWG doesn't overlap another section.
- */
-	.pushsection ".mmuoff.data.write", "aw"
-/*
- * We need to find out the CPU boot mode long after boot, so we need to
- * store it in a writable variable.
- *
- * This is not in .bss, because we set it sufficiently early that the boot-time
- * zeroing of .bss would clobber it.
- */
-SYM_DATA_START(__boot_cpu_mode)
-	.long	BOOT_CPU_MODE_EL2
-	.long	BOOT_CPU_MODE_EL1
-SYM_DATA_END(__boot_cpu_mode)
-/*
- * The booting CPU updates the failed status @__early_cpu_boot_status,
- * with MMU turned off.
- */
-SYM_DATA_START(__early_cpu_boot_status)
-	.quad 	0
-SYM_DATA_END(__early_cpu_boot_status)
-
-	.popsection
-
 	/*
 	 * This provides a "holding pen" for platforms to hold all secondary
 	 * cores are held until we're ready for them to initialise.
 	 */
 SYM_FUNC_START(secondary_holding_pen)
 	bl	init_kernel_el			// w0=cpu_boot_mode
-	bl	set_cpu_boot_mode_flag
-	mrs	x0, mpidr_el1
+	mrs	x2, mpidr_el1
 	mov_q	x1, MPIDR_HWID_BITMASK
-	and	x0, x0, x1
+	and	x2, x2, x1
 	adr_l	x3, secondary_holding_pen_release
 pen:	ldr	x4, [x3]
-	cmp	x4, x0
+	cmp	x4, x2
 	b.eq	secondary_startup
 	wfe
 	b	pen
@@ -610,7 +584,6 @@ SYM_FUNC_END(secondary_holding_pen)
 	 */
 SYM_FUNC_START(secondary_entry)
 	bl	init_kernel_el			// w0=cpu_boot_mode
-	bl	set_cpu_boot_mode_flag
 	b	secondary_startup
 SYM_FUNC_END(secondary_entry)
 
@@ -618,6 +591,7 @@ SYM_FUNC_START_LOCAL(secondary_startup)
 	/*
 	 * Common entry point for secondary CPUs.
 	 */
+	mov	x20, x0				// preserve boot mode
 	bl	switch_to_vhe
 	bl	__cpu_secondary_check52bitva
 	bl	__cpu_setup			// initialise processor
@@ -629,6 +603,9 @@ SYM_FUNC_START_LOCAL(secondary_startup)
 SYM_FUNC_END(secondary_startup)
 
 SYM_FUNC_START_LOCAL(__secondary_switched)
+	mov	x0, x20
+	bl	set_cpu_boot_mode_flag
+	str_l	xzr, __early_cpu_boot_status, x3
 	adr_l	x5, vectors
 	msr	vbar_el1, x5
 	isb
@@ -691,7 +668,6 @@ SYM_FUNC_START(__enable_mmu)
 	b.lt    __no_granule_support
 	cmp     x3, #ID_AA64MMFR0_TGRAN_SUPPORTED_MAX
 	b.gt    __no_granule_support
-	update_early_cpu_boot_status 0, x3, x4
 	phys_to_ttbr x2, x2
 	msr	ttbr0_el1, x2			// load TTBR0
 	load_ttbr1 x1, x1, x3
diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
index 43d212618834..5bafb53fafb4 100644
--- a/arch/arm64/kernel/hyp-stub.S
+++ b/arch/arm64/kernel/hyp-stub.S
@@ -223,11 +223,11 @@ SYM_FUNC_END(__hyp_reset_vectors)
 
 /*
  * Entry point to switch to VHE if deemed capable
+ *
+ * w0: boot mode, as returned by init_kernel_el()
  */
 SYM_FUNC_START(switch_to_vhe)
 	// Need to have booted at EL2
-	adr_l	x1, __boot_cpu_mode
-	ldr	w0, [x1]
 	cmp	w0, #BOOT_CPU_MODE_EL2
 	b.ne	1f
 
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index e17eacfa048c..a723bd2cfc27 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -56,6 +56,14 @@ EXPORT_SYMBOL(kimage_vaddr);
 u64 kimage_voffset __ro_after_init;
 EXPORT_SYMBOL(kimage_voffset);
 
+u32 __boot_cpu_mode[] = { BOOT_CPU_MODE_EL2, BOOT_CPU_MODE_EL1 };
+
+/*
+ * The booting CPU updates the failed status @__early_cpu_boot_status,
+ * with MMU turned off.
+ */
+long __section(".mmuoff.data.write") __early_cpu_boot_status;
+
 /*
  * Empty_zero_page is a special page that is used for zero-initialized data
  * and COW.
-- 
2.35.1


_______________________________________________
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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v5 19/21] arm64: kaslr: defer initialization to initcall where permitted

[Ard Biesheuvel]

The early KASLR init code runs extremely early, and anything that could
be deferred until later should be. So let's defer the randomization of
the module region until much later - this also simplifies the
arithmetic, given that we no longer have to reason about the link time
vs load time placement of the core kernel explicitly. Also get rid of
the global status variable, and infer the status reported by the
diagnostic print from other KASLR related context.

While at it, get rid of the special case for KASAN without
KASAN_VMALLOC, which never occurs in practice.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/kaslr.c | 95 +++++++++-----------
 1 file changed, 40 insertions(+), 55 deletions(-)

diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index d5542666182f..3edee81d8ea7 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -20,14 +20,6 @@
 #include <asm/sections.h>
 #include <asm/setup.h>
 
-enum kaslr_status {
-	KASLR_ENABLED,
-	KASLR_DISABLED_CMDLINE,
-	KASLR_DISABLED_NO_SEED,
-	KASLR_DISABLED_FDT_REMAP,
-};
-
-static enum kaslr_status __initdata kaslr_status;
 u64 __ro_after_init module_alloc_base;
 u16 __initdata memstart_offset_seed;
 
@@ -63,15 +55,9 @@ struct arm64_ftr_override kaslr_feature_override __initdata;
 u64 __init kaslr_early_init(void)
 {
 	void *fdt;
-	u64 seed, offset, mask, module_range;
+	u64 seed, offset, mask;
 	unsigned long raw;
 
-	/*
-	 * Set a reasonable default for module_alloc_base in case
-	 * we end up running with module randomization disabled.
-	 */
-	module_alloc_base = (u64)_etext - MODULES_VSIZE;
-
 	/*
 	 * Try to map the FDT early. If this fails, we simply bail,
 	 * and proceed with KASLR disabled. We will make another
@@ -79,7 +65,6 @@ u64 __init kaslr_early_init(void)
 	 */
 	fdt = get_early_fdt_ptr();
 	if (!fdt) {
-		kaslr_status = KASLR_DISABLED_FDT_REMAP;
 		return 0;
 	}
 
@@ -93,7 +78,6 @@ u64 __init kaslr_early_init(void)
 	 * return 0 if that is the case.
 	 */
 	if (kaslr_feature_override.val & kaslr_feature_override.mask & 0xf) {
-		kaslr_status = KASLR_DISABLED_CMDLINE;
 		return 0;
 	}
 
@@ -106,7 +90,6 @@ u64 __init kaslr_early_init(void)
 		seed ^= raw;
 
 	if (!seed) {
-		kaslr_status = KASLR_DISABLED_NO_SEED;
 		return 0;
 	}
 
@@ -126,19 +109,43 @@ u64 __init kaslr_early_init(void)
 	/* use the top 16 bits to randomize the linear region */
 	memstart_offset_seed = seed >> 48;
 
-	if (!IS_ENABLED(CONFIG_KASAN_VMALLOC) &&
-	    (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
-	     IS_ENABLED(CONFIG_KASAN_SW_TAGS)))
-		/*
-		 * KASAN without KASAN_VMALLOC does not expect the module region
-		 * to intersect the vmalloc region, since shadow memory is
-		 * allocated for each module at load time, whereas the vmalloc
-		 * region is shadowed by KASAN zero pages. So keep modules
-		 * out of the vmalloc region if KASAN is enabled without
-		 * KASAN_VMALLOC, and put the kernel well within 4 GB of the
-		 * module region.
-		 */
-		return offset % SZ_2G;
+	return offset;
+}
+
+static int __init kaslr_init(void)
+{
+	u64 module_range;
+	u32 seed;
+
+	/*
+	 * Set a reasonable default for module_alloc_base in case
+	 * we end up running with module randomization disabled.
+	 */
+	module_alloc_base = (u64)_etext - MODULES_VSIZE;
+
+	if (kaslr_feature_override.val & kaslr_feature_override.mask & 0xf) {
+		pr_info("KASLR disabled on command line\n");
+		return 0;
+	}
+
+	if (!kaslr_offset()) {
+		pr_warn("KASLR disabled due to lack of seed\n");
+		return 0;
+	}
+
+	pr_info("KASLR enabled\n");
+
+	/*
+	 * KASAN without KASAN_VMALLOC does not expect the module region to
+	 * intersect the vmalloc region, since shadow memory is allocated for
+	 * each module at load time, whereas the vmalloc region will already be
+	 * shadowed by KASAN zero pages.
+	 */
+	BUILD_BUG_ON((IS_ENABLED(CONFIG_KASAN_GENERIC) ||
+	              IS_ENABLED(CONFIG_KASAN_SW_TAGS)) &&
+		     !IS_ENABLED(CONFIG_KASAN_VMALLOC));
+
+	seed = get_random_u32();
 
 	if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) {
 		/*
@@ -150,8 +157,7 @@ u64 __init kaslr_early_init(void)
 		 * resolved normally.)
 		 */
 		module_range = SZ_2G - (u64)(_end - _stext);
-		module_alloc_base = max((u64)_end + offset - SZ_2G,
-					(u64)MODULES_VADDR);
+		module_alloc_base = max((u64)_end - SZ_2G, (u64)MODULES_VADDR);
 	} else {
 		/*
 		 * Randomize the module region by setting module_alloc_base to
@@ -163,33 +169,12 @@ u64 __init kaslr_early_init(void)
 		 * when ARM64_MODULE_PLTS is enabled.
 		 */
 		module_range = MODULES_VSIZE - (u64)(_etext - _stext);
-		module_alloc_base = (u64)_etext + offset - MODULES_VSIZE;
 	}
 
 	/* use the lower 21 bits to randomize the base of the module region */
 	module_alloc_base += (module_range * (seed & ((1 << 21) - 1))) >> 21;
 	module_alloc_base &= PAGE_MASK;
 
-	return offset;
-}
-
-static int __init kaslr_init(void)
-{
-	switch (kaslr_status) {
-	case KASLR_ENABLED:
-		pr_info("KASLR enabled\n");
-		break;
-	case KASLR_DISABLED_CMDLINE:
-		pr_info("KASLR disabled on command line\n");
-		break;
-	case KASLR_DISABLED_NO_SEED:
-		pr_warn("KASLR disabled due to lack of seed\n");
-		break;
-	case KASLR_DISABLED_FDT_REMAP:
-		pr_warn("KASLR disabled due to FDT remapping failure\n");
-		break;
-	}
-
 	return 0;
 }
-core_initcall(kaslr_init)
+subsys_initcall(kaslr_init)
-- 
2.35.1


_______________________________________________
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v5 20/21] arm64: head: avoid relocating the kernel twice for KASLR

[Ard Biesheuvel]

Currently, when KASLR is in effect, we set up the kernel virtual address
space twice: the first time, the KASLR seed is looked up in the device
tree, and the kernel virtual mapping is torn down and recreated again,
after which the relocations are applied a second time. The latter step
means that statically initialized global pointer variables will be reset
to their initial values, and to ensure that BSS variables are not set to
values based on the initial translation, they are cleared again as well.

All of this is needed because we need the command line (taken from the
DT) to tell us whether or not to randomize the virtual address space
before entering the kernel proper. However, this code has expanded
little by little and now creates global state unrelated to the virtual
randomization of the kernel before the mapping is torn down and set up
again, and the BSS cleared for a second time. This has created some
issues in the past, and it would be better to avoid this little dance if
possible.

So instead, let's use the temporary mapping of the device tree, and
execute the bare minimum of code to decide whether or not KASLR should
be enabled, and what the seed is. Only then, create the virtual kernel
mapping, clear BSS, etc and proceed as normal.  This avoids the issues
around inconsistent global state due to BSS being cleared twice, and is
generally more maintainable, as it permits us to defer all the remaining
DT parsing and KASLR initialization to a later time.

This means the relocation fixup code runs only a single time as well,
allowing us to simplify the RELR handling code too, which is not
idempotent and was therefore required to keep track of the offset that
was applied the first time around.

Note that this means we have to clone a pair of FDT library objects, so
that we can control how they are built - we need the stack protector
and other instrumentation disabled so that the code can tolerate being
called this early. Note that only the kernel page tables and the
temporary stack are mapped read-write at this point, which ensures that
the early code does not modify any global state inadvertently.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/Makefile         |   2 +-
 arch/arm64/kernel/head.S           |  73 ++++---------
 arch/arm64/kernel/image-vars.h     |   4 +
 arch/arm64/kernel/kaslr.c          |  87 ---------------
 arch/arm64/kernel/pi/Makefile      |  33 ++++++
 arch/arm64/kernel/pi/kaslr_early.c | 112 ++++++++++++++++++++
 6 files changed, 171 insertions(+), 140 deletions(-)

diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index fa7981d0d917..88a96511580e 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -59,7 +59,7 @@ obj-$(CONFIG_ACPI)			+= acpi.o
 obj-$(CONFIG_ACPI_NUMA)			+= acpi_numa.o
 obj-$(CONFIG_ARM64_ACPI_PARKING_PROTOCOL)	+= acpi_parking_protocol.o
 obj-$(CONFIG_PARAVIRT)			+= paravirt.o
-obj-$(CONFIG_RANDOMIZE_BASE)		+= kaslr.o
+obj-$(CONFIG_RANDOMIZE_BASE)		+= kaslr.o pi/
 obj-$(CONFIG_HIBERNATION)		+= hibernate.o hibernate-asm.o
 obj-$(CONFIG_ELF_CORE)			+= elfcore.o
 obj-$(CONFIG_KEXEC_CORE)		+= machine_kexec.o relocate_kernel.o	\
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 8de346dd4470..5a2ff6466b6b 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -86,15 +86,13 @@
 	 *  x21        primary_entry() .. start_kernel()        FDT pointer passed at boot in x0
 	 *  x22        create_idmap() .. start_kernel()         ID map VA of the DT blob
 	 *  x23        primary_entry() .. start_kernel()        physical misalignment/KASLR offset
-	 *  x24        __primary_switch() .. relocate_kernel()  current RELR displacement
+	 *  x24        __primary_switch()                       linear map KASLR seed
 	 *  x28        create_idmap()                           callee preserved temp register
 	 */
 SYM_CODE_START(primary_entry)
 	bl	preserve_boot_args
 	bl	init_kernel_el			// w0=cpu_boot_mode
 	mov	x20, x0
-	adrp	x23, __PHYS_OFFSET
-	and	x23, x23, MIN_KIMG_ALIGN - 1	// KASLR offset, defaults to 0
 	bl	create_idmap
 
 	/*
@@ -441,6 +439,10 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 	bl	__pi_memset
 	dsb	ishst				// Make zero page visible to PTW
 
+#ifdef CONFIG_RANDOMIZE_BASE
+	adrp	x5, memstart_offset_seed	// Save KASLR linear map seed
+	strh	w24, [x5, :lo12:memstart_offset_seed]
+#endif
 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 	bl	kasan_early_init
 #endif
@@ -448,16 +450,6 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 	bl	early_fdt_map			// Try mapping the FDT early
 	mov	x0, x22				// pass FDT address in x0
 	bl	init_feature_override		// Parse cpu feature overrides
-#ifdef CONFIG_RANDOMIZE_BASE
-	tst	x23, ~(MIN_KIMG_ALIGN - 1)	// already running randomized?
-	b.ne	0f
-	bl	kaslr_early_init		// parse FDT for KASLR options
-	cbz	x0, 0f				// KASLR disabled? just proceed
-	orr	x23, x23, x0			// record KASLR offset
-	ldp	x29, x30, [sp], #16		// we must enable KASLR, return
-	ret					// to __primary_switch()
-0:
-#endif
 	mov	x0, x20
 	bl	switch_to_vhe			// Prefer VHE if possible
 	ldp	x29, x30, [sp], #16
@@ -759,27 +751,17 @@ SYM_FUNC_START_LOCAL(__relocate_kernel)
 	 * entry in x9, the address being relocated by the current address or
 	 * bitmap entry in x13 and the address being relocated by the current
 	 * bit in x14.
-	 *
-	 * Because addends are stored in place in the binary, RELR relocations
-	 * cannot be applied idempotently. We use x24 to keep track of the
-	 * currently applied displacement so that we can correctly relocate if
-	 * __relocate_kernel is called twice with non-zero displacements (i.e.
-	 * if there is both a physical misalignment and a KASLR displacement).
 	 */
 	adr_l	x9, __relr_start
 	adr_l	x10, __relr_end
 
-	sub	x15, x23, x24			// delta from previous offset
-	cbz	x15, 7f				// nothing to do if unchanged
-	mov	x24, x23			// save new offset
-
 2:	cmp	x9, x10
 	b.hs	7f
 	ldr	x11, [x9], #8
 	tbnz	x11, #0, 3f			// branch to handle bitmaps
 	add	x13, x11, x23
 	ldr	x12, [x13]			// relocate address entry
-	add	x12, x12, x15
+	add	x12, x12, x23
 	str	x12, [x13], #8			// adjust to start of bitmap
 	b	2b
 
@@ -788,7 +770,7 @@ SYM_FUNC_START_LOCAL(__relocate_kernel)
 	cbz	x11, 6f
 	tbz	x11, #0, 5f			// skip bit if not set
 	ldr	x12, [x14]			// relocate bit
-	add	x12, x12, x15
+	add	x12, x12, x23
 	str	x12, [x14]
 
 5:	add	x14, x14, #8			// move to next bit's address
@@ -812,40 +794,27 @@ SYM_FUNC_START_LOCAL(__primary_switch)
 	adrp	x1, reserved_pg_dir
 	adrp	x2, init_idmap_pg_dir
 	bl	__enable_mmu
-
+#ifdef CONFIG_RELOCATABLE
+	adrp	x23, __PHYS_OFFSET
+	and	x23, x23, MIN_KIMG_ALIGN - 1
+#ifdef CONFIG_RANDOMIZE_BASE
+	mov	x0, x22
+	adrp	x1, init_pg_end
+	mov	sp, x1
+	mov	x29, xzr
+	bl	__pi_kaslr_early_init
+	and	x24, x0, #SZ_2M - 1		// capture memstart offset seed
+	bic	x0, x0, #SZ_2M - 1
+	orr	x23, x23, x0			// record kernel offset
+#endif
+#endif
 	bl	clear_page_tables
 	bl	create_kernel_mapping
 
 	adrp	x1, init_pg_dir
 	load_ttbr1 x1, x1, x2
 #ifdef CONFIG_RELOCATABLE
-#ifdef CONFIG_RELR
-	mov	x24, #0				// no RELR displacement yet
-#endif
 	bl	__relocate_kernel
-#ifdef CONFIG_RANDOMIZE_BASE
-	ldr	x8, =__primary_switched
-	adrp	x0, __PHYS_OFFSET
-	blr	x8
-
-	/*
-	 * If we return here, we have a KASLR displacement in x23 which we need
-	 * to take into account by discarding the current kernel mapping and
-	 * creating a new one.
-	 */
-	adrp	x1, reserved_pg_dir		// Disable translations via TTBR1
-	load_ttbr1 x1, x1, x2
-	bl	clear_page_tables
-	bl	create_kernel_mapping		// Recreate kernel mapping
-
-	tlbi	vmalle1				// Remove any stale TLB entries
-	dsb	nsh
-	isb
-
-	adrp	x1, init_pg_dir			// Re-enable translations via TTBR1
-	load_ttbr1 x1, x1, x2
-	bl	__relocate_kernel
-#endif
 #endif
 	ldr	x8, =__primary_switched
 	adrp	x0, __PHYS_OFFSET
diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index 241c86b67d01..0c381a405bf0 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -41,6 +41,10 @@ __efistub_dcache_clean_poc = __pi_dcache_clean_poc;
 __efistub___memcpy		= __pi_memcpy;
 __efistub___memmove		= __pi_memmove;
 __efistub___memset		= __pi_memset;
+
+__pi___memcpy			= __pi_memcpy;
+__pi___memmove			= __pi_memmove;
+__pi___memset			= __pi_memset;
 #endif
 
 __efistub__text			= _text;
diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index 3edee81d8ea7..325455d16dbc 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -23,95 +23,8 @@
 u64 __ro_after_init module_alloc_base;
 u16 __initdata memstart_offset_seed;
 
-static __init u64 get_kaslr_seed(void *fdt)
-{
-	int node, len;
-	fdt64_t *prop;
-	u64 ret;
-
-	node = fdt_path_offset(fdt, "/chosen");
-	if (node < 0)
-		return 0;
-
-	prop = fdt_getprop_w(fdt, node, "kaslr-seed", &len);
-	if (!prop || len != sizeof(u64))
-		return 0;
-
-	ret = fdt64_to_cpu(*prop);
-	*prop = 0;
-	return ret;
-}
-
 struct arm64_ftr_override kaslr_feature_override __initdata;
 
-/*
- * This routine will be executed with the kernel mapped at its default virtual
- * address, and if it returns successfully, the kernel will be remapped, and
- * start_kernel() will be executed from a randomized virtual offset. The
- * relocation will result in all absolute references (e.g., static variables
- * containing function pointers) to be reinitialized, and zero-initialized
- * .bss variables will be reset to 0.
- */
-u64 __init kaslr_early_init(void)
-{
-	void *fdt;
-	u64 seed, offset, mask;
-	unsigned long raw;
-
-	/*
-	 * Try to map the FDT early. If this fails, we simply bail,
-	 * and proceed with KASLR disabled. We will make another
-	 * attempt at mapping the FDT in setup_machine()
-	 */
-	fdt = get_early_fdt_ptr();
-	if (!fdt) {
-		return 0;
-	}
-
-	/*
-	 * Retrieve (and wipe) the seed from the FDT
-	 */
-	seed = get_kaslr_seed(fdt);
-
-	/*
-	 * Check if 'nokaslr' appears on the command line, and
-	 * return 0 if that is the case.
-	 */
-	if (kaslr_feature_override.val & kaslr_feature_override.mask & 0xf) {
-		return 0;
-	}
-
-	/*
-	 * Mix in any entropy obtainable architecturally if enabled
-	 * and supported.
-	 */
-
-	if (arch_get_random_seed_long_early(&raw))
-		seed ^= raw;
-
-	if (!seed) {
-		return 0;
-	}
-
-	/*
-	 * OK, so we are proceeding with KASLR enabled. Calculate a suitable
-	 * kernel image offset from the seed. Let's place the kernel in the
-	 * middle half of the VMALLOC area (VA_BITS_MIN - 2), and stay clear of
-	 * the lower and upper quarters to avoid colliding with other
-	 * allocations.
-	 * Even if we could randomize at page granularity for 16k and 64k pages,
-	 * let's always round to 2 MB so we don't interfere with the ability to
-	 * map using contiguous PTEs
-	 */
-	mask = ((1UL << (VA_BITS_MIN - 2)) - 1) & ~(SZ_2M - 1);
-	offset = BIT(VA_BITS_MIN - 3) + (seed & mask);
-
-	/* use the top 16 bits to randomize the linear region */
-	memstart_offset_seed = seed >> 48;
-
-	return offset;
-}
-
 static int __init kaslr_init(void)
 {
 	u64 module_range;
diff --git a/arch/arm64/kernel/pi/Makefile b/arch/arm64/kernel/pi/Makefile
new file mode 100644
index 000000000000..839291430cb3
--- /dev/null
+++ b/arch/arm64/kernel/pi/Makefile
@@ -0,0 +1,33 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright 2022 Google LLC
+
+KBUILD_CFLAGS	:= $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) -fpie \
+		   -Os -DDISABLE_BRANCH_PROFILING $(DISABLE_STACKLEAK_PLUGIN) \
+		   $(call cc-option,-mbranch-protection=none) \
+		   -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \
+		   -include $(srctree)/include/linux/hidden.h \
+		   -D__DISABLE_EXPORTS -ffreestanding -D__NO_FORTIFY \
+		   $(call cc-option,-fno-addrsig)
+
+# remove SCS flags from all objects in this directory
+KBUILD_CFLAGS	:= $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
+# disable LTO
+KBUILD_CFLAGS	:= $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))
+
+GCOV_PROFILE	:= n
+KASAN_SANITIZE	:= n
+KCSAN_SANITIZE	:= n
+UBSAN_SANITIZE	:= n
+KCOV_INSTRUMENT	:= n
+
+$(obj)/%.pi.o: OBJCOPYFLAGS := --prefix-symbols=__pi_ \
+			       --remove-section=.note.gnu.property \
+			       --prefix-alloc-sections=.init
+$(obj)/%.pi.o: $(obj)/%.o FORCE
+	$(call if_changed,objcopy)
+
+$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
+	$(call if_changed_rule,cc_o_c)
+
+obj-y		:= kaslr_early.pi.o lib-fdt.pi.o lib-fdt_ro.pi.o
+extra-y		:= $(patsubst %.pi.o,%.o,$(obj-y))
diff --git a/arch/arm64/kernel/pi/kaslr_early.c b/arch/arm64/kernel/pi/kaslr_early.c
new file mode 100644
index 000000000000..6c3855e69395
--- /dev/null
+++ b/arch/arm64/kernel/pi/kaslr_early.c
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright 2022 Google LLC
+// Author: Ard Biesheuvel <ardb@google.com>
+
+// NOTE: code in this file runs *very* early, and is not permitted to use
+// global variables or anything that relies on absolute addressing.
+
+#include <linux/libfdt.h>
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <linux/types.h>
+#include <linux/sizes.h>
+#include <linux/string.h>
+
+#include <asm/archrandom.h>
+#include <asm/memory.h>
+
+/* taken from lib/string.c */
+static char *__strstr(const char *s1, const char *s2)
+{
+	size_t l1, l2;
+
+	l2 = strlen(s2);
+	if (!l2)
+		return (char *)s1;
+	l1 = strlen(s1);
+	while (l1 >= l2) {
+		l1--;
+		if (!memcmp(s1, s2, l2))
+			return (char *)s1;
+		s1++;
+	}
+	return NULL;
+}
+static bool cmdline_contains_nokaslr(const u8 *cmdline)
+{
+	const u8 *str;
+
+	str = __strstr(cmdline, "nokaslr");
+	return str == cmdline || (str > cmdline && *(str - 1) == ' ');
+}
+
+static bool is_kaslr_disabled_cmdline(void *fdt)
+{
+	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
+		int node;
+		const u8 *prop;
+
+		node = fdt_path_offset(fdt, "/chosen");
+		if (node < 0)
+			goto out;
+
+		prop = fdt_getprop(fdt, node, "bootargs", NULL);
+		if (!prop)
+			goto out;
+
+		if (cmdline_contains_nokaslr(prop))
+			return true;
+
+		if (IS_ENABLED(CONFIG_CMDLINE_EXTEND))
+			goto out;
+
+		return false;
+	}
+out:
+	return cmdline_contains_nokaslr(CONFIG_CMDLINE);
+}
+
+static u64 get_kaslr_seed(void *fdt)
+{
+	int node, len;
+	fdt64_t *prop;
+	u64 ret;
+
+	node = fdt_path_offset(fdt, "/chosen");
+	if (node < 0)
+		return 0;
+
+	prop = fdt_getprop_w(fdt, node, "kaslr-seed", &len);
+	if (!prop || len != sizeof(u64))
+		return 0;
+
+	ret = fdt64_to_cpu(*prop);
+	*prop = 0;
+	return ret;
+}
+
+asmlinkage u64 kaslr_early_init(void *fdt)
+{
+	u64 seed;
+
+	if (is_kaslr_disabled_cmdline(fdt))
+		return 0;
+
+	seed = get_kaslr_seed(fdt);
+	if (!seed) {
+#ifdef CONFIG_ARCH_RANDOM
+		 if (!__early_cpu_has_rndr() ||
+		     !__arm64_rndr((unsigned long *)&seed))
+#endif
+		return 0;
+	}
+
+	/*
+	 * OK, so we are proceeding with KASLR enabled. Calculate a suitable
+	 * kernel image offset from the seed. Let's place the kernel in the
+	 * middle half of the VMALLOC area (VA_BITS_MIN - 2), and stay clear of
+	 * the lower and upper quarters to avoid colliding with other
+	 * allocations.
+	 */
+	return BIT(VA_BITS_MIN - 3) + (seed & GENMASK(VA_BITS_MIN - 3, 0));
+}
-- 
2.35.1


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[PATCH v5 21/21] arm64: setup: drop early FDT pointer helpers

[Ard Biesheuvel]

We no longer need to call into the kernel to map the FDT before calling
into the kernel so let's drop the helpers we added for this.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/include/asm/setup.h |  3 ---
 arch/arm64/kernel/head.S       |  2 --
 arch/arm64/kernel/setup.c      | 15 ---------------
 3 files changed, 20 deletions(-)

diff --git a/arch/arm64/include/asm/setup.h b/arch/arm64/include/asm/setup.h
index 6437df661700..5f147a418281 100644
--- a/arch/arm64/include/asm/setup.h
+++ b/arch/arm64/include/asm/setup.h
@@ -5,9 +5,6 @@
 
 #include <uapi/asm/setup.h>
 
-void *get_early_fdt_ptr(void);
-void early_fdt_map(u64 dt_phys);
-
 /*
  * These two variables are used in the head.S file.
  */
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 5a2ff6466b6b..6bf685f988f1 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -446,8 +446,6 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 	bl	kasan_early_init
 #endif
-	mov	x0, x21				// pass FDT address in x0
-	bl	early_fdt_map			// Try mapping the FDT early
 	mov	x0, x22				// pass FDT address in x0
 	bl	init_feature_override		// Parse cpu feature overrides
 	mov	x0, x20
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index fea3223704b6..d0e6c7a291da 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -163,21 +163,6 @@ static void __init smp_build_mpidr_hash(void)
 		pr_warn("Large number of MPIDR hash buckets detected\n");
 }
 
-static void *early_fdt_ptr __initdata;
-
-void __init *get_early_fdt_ptr(void)
-{
-	return early_fdt_ptr;
-}
-
-asmlinkage void __init early_fdt_map(u64 dt_phys)
-{
-	int fdt_size;
-
-	early_fixmap_init();
-	early_fdt_ptr = fixmap_remap_fdt(dt_phys, &fdt_size, PAGE_KERNEL);
-}
-
 static void __init setup_machine_fdt(phys_addr_t dt_phys)
 {
 	int size;
-- 
2.35.1


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Re: [PATCH v5 00/21] arm64: refactor boot flow

[Will Deacon]

On Fri, 24 Jun 2022 17:06:30 +0200, Ard Biesheuvel wrote:
> This series aims to streamline the boot flow with respect to cache
> maintenance and redundant copying of data in memory.
> 
> Additionally, this series removes the little dance we do to create a
> kernel mapping, relocate the kernel, run the KASLR init code, tear down
> the old mapping and create a new one, relocate the kernel again, and
> finally enter the kernel proper. Instead, it invokes a minimal C
> function 'kaslr_early_init()' while running from the ID map which
> includes a temporary mapping of the FDT. This change represents a
> substantial chunk of the diffstat, as it requires some work to
> instantiate code that can run safely from an arbitrary load address.
> 
> [...]

Applied to arm64 (for-next/boot), thanks!

[01/21] arm64: head: move kimage_vaddr variable into C file
        https://git.kernel.org/arm64/c/475031b6ed43
[02/21] arm64: mm: make vabits_actual a build time constant if possible
        https://git.kernel.org/arm64/c/0d9b1ffefabe
[03/21] arm64: head: move assignment of idmap_t0sz to C code
        https://git.kernel.org/arm64/c/e8d13cced5c5
[04/21] arm64: head: drop idmap_ptrs_per_pgd
        https://git.kernel.org/arm64/c/ebd9aea1f27e
[05/21] arm64: head: simplify page table mapping macros (slightly)
        https://git.kernel.org/arm64/c/53519ddf5894
[06/21] arm64: head: switch to map_memory macro for the extended ID map
        https://git.kernel.org/arm64/c/50fcd39d24c2
[07/21] arm64: head: split off idmap creation code
        https://git.kernel.org/arm64/c/e42ade29e3bc
[08/21] arm64: kernel: drop unnecessary PoC cache clean+invalidate
        https://git.kernel.org/arm64/c/2e945851e268
[09/21] arm64: head: pass ID map root table address to __enable_mmu()
        https://git.kernel.org/arm64/c/723d3a8ed172
[10/21] arm64: mm: provide idmap pointer to cpu_replace_ttbr1()
        https://git.kernel.org/arm64/c/1682c45b9206
[11/21] arm64: head: add helper function to remap regions in early page tables
        https://git.kernel.org/arm64/c/b013c1e1c659
[12/21] arm64: head: cover entire kernel image in initial ID map
        https://git.kernel.org/arm64/c/c3cee924bd85
[13/21] arm64: head: use relative references to the RELA and RELR tables
        https://git.kernel.org/arm64/c/d7bea550279d
[14/21] arm64: head: create a temporary FDT mapping in the initial ID map
        https://git.kernel.org/arm64/c/f70b3a23324a
[15/21] arm64: idreg-override: use early FDT mapping in ID map
        https://git.kernel.org/arm64/c/a004393f45d9
[16/21] arm64: head: factor out TTBR1 assignment into a macro
        https://git.kernel.org/arm64/c/c0be8f18a3bf
[17/21] arm64: head: populate kernel page tables with MMU and caches on
        https://git.kernel.org/arm64/c/6495b9ba6271
[18/21] arm64: head: record CPU boot mode after enabling the MMU
        https://git.kernel.org/arm64/c/005e12676af0
[19/21] arm64: kaslr: defer initialization to initcall where permitted
        https://git.kernel.org/arm64/c/fc5a89f75d2a
[20/21] arm64: head: avoid relocating the kernel twice for KASLR
        https://git.kernel.org/arm64/c/aacd149b6238
[21/21] arm64: setup: drop early FDT pointer helpers
        https://git.kernel.org/arm64/c/7559d9f97581

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

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Re: [PATCH v5 01/21] arm64: head: move kimage_vaddr variable into C file

[Mark Rutland]

On Fri, Jun 24, 2022 at 05:06:31PM +0200, Ard Biesheuvel wrote:
> This variable definition does not need to be in head.S so move it out.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

Nice!

Acked-by: Mark Rutland <mar.rutland@arm.com>

> ---
>  arch/arm64/kernel/head.S | 7 -------
>  arch/arm64/mm/mmu.c      | 3 +++
>  2 files changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 6a98f1a38c29..1cdecce552bb 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -469,13 +469,6 @@ SYM_FUNC_START_LOCAL(__primary_switched)
>  	ASM_BUG()
>  SYM_FUNC_END(__primary_switched)
>  
> -	.pushsection ".rodata", "a"
> -SYM_DATA_START(kimage_vaddr)
> -	.quad		_text
> -SYM_DATA_END(kimage_vaddr)
> -EXPORT_SYMBOL(kimage_vaddr)
> -	.popsection
> -
>  /*
>   * end early head section, begin head code that is also used for
>   * hotplug and needs to have the same protections as the text region
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index c5563ff990da..7148928e3932 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -49,6 +49,9 @@ u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
>  u64 __section(".mmuoff.data.write") vabits_actual;
>  EXPORT_SYMBOL(vabits_actual);
>  
> +u64 kimage_vaddr __ro_after_init = (u64)&_text;
> +EXPORT_SYMBOL(kimage_vaddr);
> +
>  u64 kimage_voffset __ro_after_init;
>  EXPORT_SYMBOL(kimage_voffset);
>  
> -- 
> 2.35.1
> 

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Re: [PATCH v5 02/21] arm64: mm: make vabits_actual a build time constant if possible

[Mark Rutland]

On Fri, Jun 24, 2022 at 05:06:32PM +0200, Ard Biesheuvel wrote:
> Currently, we only support 52-bit virtual addressing on 64k pages
> configurations, and in all other cases, vabits_actual is guaranteed to
> equal VA_BITS (== VA_BITS_MIN). So get rid of the variable entirely in
> that case.
> 
> While at it, move the assignment out of the asm entry code - it has no
> need to be there.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

I see the patch itself checks VA_BITS rather than PAGE_SIZE, (and the former is
the right thing to for FEAT_LPA2), so FWIW:

Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
>  arch/arm64/include/asm/memory.h |  4 ++++
>  arch/arm64/kernel/head.S        | 15 +--------------
>  arch/arm64/mm/init.c            | 15 ++++++++++++++-
>  arch/arm64/mm/mmu.c             |  4 +++-
>  4 files changed, 22 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> index 0af70d9abede..c751cd9b94f8 100644
> --- a/arch/arm64/include/asm/memory.h
> +++ b/arch/arm64/include/asm/memory.h
> @@ -174,7 +174,11 @@
>  #include <linux/types.h>
>  #include <asm/bug.h>
>  
> +#if VA_BITS > 48
>  extern u64			vabits_actual;
> +#else
> +#define vabits_actual		((u64)VA_BITS)
> +#endif
>  
>  extern s64			memstart_addr;
>  /* PHYS_OFFSET - the physical address of the start of memory. */
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 1cdecce552bb..dc07858eb673 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -293,19 +293,6 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
>  	adrp	x0, idmap_pg_dir
>  	adrp	x3, __idmap_text_start		// __pa(__idmap_text_start)
>  
> -#ifdef CONFIG_ARM64_VA_BITS_52
> -	mrs_s	x6, SYS_ID_AA64MMFR2_EL1
> -	and	x6, x6, #(0xf << ID_AA64MMFR2_LVA_SHIFT)
> -	mov	x5, #52
> -	cbnz	x6, 1f
> -#endif
> -	mov	x5, #VA_BITS_MIN
> -1:
> -	adr_l	x6, vabits_actual
> -	str	x5, [x6]
> -	dmb	sy
> -	dc	ivac, x6		// Invalidate potentially stale cache line
> -
>  	/*
>  	 * VA_BITS may be too small to allow for an ID mapping to be created
>  	 * that covers system RAM if that is located sufficiently high in the
> @@ -713,7 +700,7 @@ SYM_FUNC_START(__enable_mmu)
>  SYM_FUNC_END(__enable_mmu)
>  
>  SYM_FUNC_START(__cpu_secondary_check52bitva)
> -#ifdef CONFIG_ARM64_VA_BITS_52
> +#if VA_BITS > 48
>  	ldr_l	x0, vabits_actual
>  	cmp	x0, #52
>  	b.ne	2f
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 339ee84e5a61..1faa6760895e 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -265,7 +265,20 @@ early_param("mem", early_mem);
>  
>  void __init arm64_memblock_init(void)
>  {
> -	s64 linear_region_size = PAGE_END - _PAGE_OFFSET(vabits_actual);
> +	s64 linear_region_size;
> +
> +#if VA_BITS > 48
> +	if (cpuid_feature_extract_unsigned_field(
> +				read_sysreg_s(SYS_ID_AA64MMFR2_EL1),
> +				ID_AA64MMFR2_LVA_SHIFT))
> +		vabits_actual = VA_BITS;
> +
> +	/* make the variable visible to secondaries with the MMU off */
> +	dcache_clean_inval_poc((u64)&vabits_actual,
> +			       (u64)&vabits_actual + sizeof(vabits_actual));
> +#endif
> +
> +	linear_region_size = PAGE_END - _PAGE_OFFSET(vabits_actual);
>  
>  	/*
>  	 * Corner case: 52-bit VA capable systems running KVM in nVHE mode may
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 7148928e3932..a6392656d589 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -46,8 +46,10 @@
>  u64 idmap_t0sz = TCR_T0SZ(VA_BITS_MIN);
>  u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
>  
> -u64 __section(".mmuoff.data.write") vabits_actual;
> +#if VA_BITS > 48
> +u64 vabits_actual __ro_after_init = VA_BITS_MIN;
>  EXPORT_SYMBOL(vabits_actual);
> +#endif
>  
>  u64 kimage_vaddr __ro_after_init = (u64)&_text;
>  EXPORT_SYMBOL(kimage_vaddr);
> -- 
> 2.35.1
> 

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Re: [PATCH v5 03/21] arm64: head: move assignment of idmap_t0sz to C code

[Mark Rutland]

On Fri, Jun 24, 2022 at 05:06:33PM +0200, Ard Biesheuvel wrote:
> Setting idmap_t0sz involves fiddling with the caches if done with the
> MMU off. Since we will be creating an initial ID map with the MMU and
> caches off, and the permanent ID map with the MMU and caches on, let's
> move this assignment of idmap_t0sz out of the startup code, and replace
> it with a macro that simply issues the three instructions needed to
> calculate the value wherever it is needed before the MMU is turned on.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  arch/arm64/include/asm/assembler.h   | 14 ++++++++++++++
>  arch/arm64/include/asm/mmu_context.h |  2 +-
>  arch/arm64/kernel/head.S             | 13 +------------
>  arch/arm64/mm/mmu.c                  |  4 +++-
>  arch/arm64/mm/proc.S                 |  2 +-
>  5 files changed, 20 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
> index 8c5a61aeaf8e..9468f45c07a6 100644
> --- a/arch/arm64/include/asm/assembler.h
> +++ b/arch/arm64/include/asm/assembler.h
> @@ -359,6 +359,20 @@ alternative_cb_end
>  	bfi	\valreg, \t1sz, #TCR_T1SZ_OFFSET, #TCR_TxSZ_WIDTH
>  	.endm
>  
> +/*
> + * idmap_get_t0sz - get the T0SZ value needed to cover the ID map
> + *
> + * Calculate the maximum allowed value for TCR_EL1.T0SZ so that the
> + * entire ID map region can be mapped. As T0SZ == (64 - #bits used),
> + * this number conveniently equals the number of leading zeroes in
> + * the physical address of _end.
> + */
> +	.macro	idmap_get_t0sz, reg
> +	adrp	\reg, _end
> +	orr	\reg, \reg, #(1 << VA_BITS_MIN) - 1
> +	clz	\reg, \reg
> +	.endm

I understand we ORR in the VA_BITS_MIN case so that we don't calculate a
smaller size than we'll create tables for. That might be worht a comment, but either way:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> +
>  /*
>   * tcr_compute_pa_size - set TCR.(I)PS to the highest supported
>   * ID_AA64MMFR0_EL1.PARange value
> diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
> index 6770667b34a3..6ac0086ebb1a 100644
> --- a/arch/arm64/include/asm/mmu_context.h
> +++ b/arch/arm64/include/asm/mmu_context.h
> @@ -60,7 +60,7 @@ static inline void cpu_switch_mm(pgd_t *pgd, struct mm_struct *mm)
>   * TCR_T0SZ(VA_BITS), unless system RAM is positioned very high in
>   * physical memory, in which case it will be smaller.
>   */
> -extern u64 idmap_t0sz;
> +extern int idmap_t0sz;
>  extern u64 idmap_ptrs_per_pgd;
>  
>  /*
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index dc07858eb673..7f361bc72d12 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -299,22 +299,11 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
>  	 * physical address space. So for the ID map, use an extended virtual
>  	 * range in that case, and configure an additional translation level
>  	 * if needed.
> -	 *
> -	 * Calculate the maximum allowed value for TCR_EL1.T0SZ so that the
> -	 * entire ID map region can be mapped. As T0SZ == (64 - #bits used),
> -	 * this number conveniently equals the number of leading zeroes in
> -	 * the physical address of __idmap_text_end.
>  	 */
> -	adrp	x5, __idmap_text_end
> -	clz	x5, x5
> +	idmap_get_t0sz x5
>  	cmp	x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough?
>  	b.ge	1f			// .. then skip VA range extension
>  
> -	adr_l	x6, idmap_t0sz
> -	str	x5, [x6]
> -	dmb	sy
> -	dc	ivac, x6		// Invalidate potentially stale cache line
> -
>  #if (VA_BITS < 48)
>  #define EXTRA_SHIFT	(PGDIR_SHIFT + PAGE_SHIFT - 3)
>  #define EXTRA_PTRS	(1 << (PHYS_MASK_SHIFT - EXTRA_SHIFT))
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index a6392656d589..f875c4954e22 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -43,7 +43,7 @@
>  #define NO_CONT_MAPPINGS	BIT(1)
>  #define NO_EXEC_MAPPINGS	BIT(2)	/* assumes FEAT_HPDS is not used */
>  
> -u64 idmap_t0sz = TCR_T0SZ(VA_BITS_MIN);
> +int idmap_t0sz __ro_after_init;
>  u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
>  
>  #if VA_BITS > 48
> @@ -774,6 +774,8 @@ void __init paging_init(void)
>  {
>  	pgd_t *pgdp = pgd_set_fixmap(__pa_symbol(swapper_pg_dir));
>  
> +	idmap_t0sz = 63UL - __fls(__pa_symbol(_end) | GENMASK(VA_BITS_MIN - 1, 0));
> +
>  	map_kernel(pgdp);
>  	map_mem(pgdp);
>  
> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> index 972ce8d7f2c5..97cd67697212 100644
> --- a/arch/arm64/mm/proc.S
> +++ b/arch/arm64/mm/proc.S
> @@ -470,7 +470,7 @@ SYM_FUNC_START(__cpu_setup)
>  	add		x9, x9, #64
>  	tcr_set_t1sz	tcr, x9
>  #else
> -	ldr_l		x9, idmap_t0sz
> +	idmap_get_t0sz	x9
>  #endif
>  	tcr_set_t0sz	tcr, x9
>  
> -- 
> 2.35.1
> 

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Re: [PATCH v5 04/21] arm64: head: drop idmap_ptrs_per_pgd

[Mark Rutland]

On Fri, Jun 24, 2022 at 05:06:34PM +0200, Ard Biesheuvel wrote:
> The assignment of idmap_ptrs_per_pgd lacks any cache invalidation, even
> though it is updated with the MMU and caches disabled. However, we never
> bother to read the value again except in the very next instruction, and
> so we can just drop the variable entirely.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
>  arch/arm64/include/asm/mmu_context.h | 1 -
>  arch/arm64/kernel/head.S             | 7 +++----
>  arch/arm64/mm/mmu.c                  | 1 -
>  3 files changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
> index 6ac0086ebb1a..7b387c3b312a 100644
> --- a/arch/arm64/include/asm/mmu_context.h
> +++ b/arch/arm64/include/asm/mmu_context.h
> @@ -61,7 +61,6 @@ static inline void cpu_switch_mm(pgd_t *pgd, struct mm_struct *mm)
>   * physical memory, in which case it will be smaller.
>   */
>  extern int idmap_t0sz;
> -extern u64 idmap_ptrs_per_pgd;
>  
>  /*
>   * Ensure TCR.T0SZ is set to the provided value.
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 7f361bc72d12..53126a35d73c 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -300,6 +300,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
>  	 * range in that case, and configure an additional translation level
>  	 * if needed.
>  	 */
> +	mov	x4, #PTRS_PER_PGD
>  	idmap_get_t0sz x5
>  	cmp	x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough?
>  	b.ge	1f			// .. then skip VA range extension
> @@ -319,18 +320,16 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
>  #error "Mismatch between VA_BITS and page size/number of translation levels"
>  #endif
>  
> -	mov	x4, EXTRA_PTRS
> -	create_table_entry x0, x3, EXTRA_SHIFT, x4, x5, x6
> +	mov	x2, EXTRA_PTRS
> +	create_table_entry x0, x3, EXTRA_SHIFT, x2, x5, x6
>  #else
>  	/*
>  	 * If VA_BITS == 48, we don't have to configure an additional
>  	 * translation level, but the top-level table has more entries.
>  	 */
>  	mov	x4, #1 << (PHYS_MASK_SHIFT - PGDIR_SHIFT)
> -	str_l	x4, idmap_ptrs_per_pgd, x5
>  #endif
>  1:
> -	ldr_l	x4, idmap_ptrs_per_pgd
>  	adr_l	x6, __idmap_text_end		// __pa(__idmap_text_end)
>  
>  	map_memory x0, x1, x3, x6, x7, x3, x4, x10, x11, x12, x13, x14
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index f875c4954e22..3be0e9f69406 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -44,7 +44,6 @@
>  #define NO_EXEC_MAPPINGS	BIT(2)	/* assumes FEAT_HPDS is not used */
>  
>  int idmap_t0sz __ro_after_init;
> -u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
>  
>  #if VA_BITS > 48
>  u64 vabits_actual __ro_after_init = VA_BITS_MIN;
> -- 
> 2.35.1
> 

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Re: [PATCH v5 05/21] arm64: head: simplify page table mapping macros (slightly)

[Mark Rutland]

On Fri, Jun 24, 2022 at 05:06:35PM +0200, Ard Biesheuvel wrote:
> Simplify the macros in head.S that are used to set up the early page
> tables, by switching to immediates for the number of bits that are
> interpreted as the table index at each level. This makes it much
> easier to infer from the instruction stream what is going on, and
> reduces the number of instructions emitted substantially.

Nice!

> Note that the extended ID map for cases where no additional level needs
> to be configured now uses a compile time size as well, which means that
> we interpret up to 10 bits as the table index at the root level (for
> 52-bit physical addressing), without taking into account whether or not
> this is supported on the current system.  However, those bits can only
> be set if we are executing the image from an address that exceeds the
> 48-bit PA range, and are guaranteed to be cleared otherwise, and given
> that we are dealing with a mapping in the lower TTBR0 range of the
> address space, the result is therefore the same as if we'd mask off only
> 6 bits.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Aside from one trivial comment below, this looks good to me, so either way:

Acked-by: Mark Rutland <mark.rutland@arm.com>

> ---
>  arch/arm64/kernel/head.S | 55 ++++++++------------
>  1 file changed, 22 insertions(+), 33 deletions(-)
> 
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 53126a35d73c..9fdde2f9cc0f 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -179,31 +179,20 @@ SYM_CODE_END(preserve_boot_args)
>   *	vstart:	virtual address of start of range
>   *	vend:	virtual address of end of range - we map [vstart, vend]
>   *	shift:	shift used to transform virtual address into index
> - *	ptrs:	number of entries in page table
> + *	order:  #imm 2log(number of entries in page table)
>   *	istart:	index in table corresponding to vstart
>   *	iend:	index in table corresponding to vend
>   *	count:	On entry: how many extra entries were required in previous level, scales
>   *			  our end index.
>   *		On exit: returns how many extra entries required for next page table level
>   *
> - * Preserves:	vstart, vend, shift, ptrs
> + * Preserves:	vstart, vend
>   * Returns:	istart, iend, count
>   */
> -	.macro compute_indices, vstart, vend, shift, ptrs, istart, iend, count
> -	lsr	\iend, \vend, \shift
> -	mov	\istart, \ptrs
> -	sub	\istart, \istart, #1
> -	and	\iend, \iend, \istart	// iend = (vend >> shift) & (ptrs - 1)
> -	mov	\istart, \ptrs
> -	mul	\istart, \istart, \count
> -	add	\iend, \iend, \istart	// iend += count * ptrs
> -					// our entries span multiple tables
> -
> -	lsr	\istart, \vstart, \shift
> -	mov	\count, \ptrs
> -	sub	\count, \count, #1
> -	and	\istart, \istart, \count
> -
> +	.macro compute_indices, vstart, vend, shift, order, istart, iend, count
> +	ubfx	\istart, \vstart, \shift, \order
> +	ubfx	\iend, \vend, \shift, \order
> +	add	\iend, \iend, \count, lsl \order
>  	sub	\count, \iend, \istart
>  	.endm
>  
> @@ -218,38 +207,39 @@ SYM_CODE_END(preserve_boot_args)
>   *	vend:	virtual address of end of range - we map [vstart, vend - 1]
>   *	flags:	flags to use to map last level entries
>   *	phys:	physical address corresponding to vstart - physical memory is contiguous
> - *	pgds:	the number of pgd entries
> + *	order:  #imm 2log(number of entries in PGD table)

For clarity, perhaps: s/2log/ilog2/ ? The latter is used much more commonly
throughot the kernel.

>   *
>   * Temporaries:	istart, iend, tmp, count, sv - these need to be different registers
>   * Preserves:	vstart, flags
>   * Corrupts:	tbl, rtbl, vend, istart, iend, tmp, count, sv
>   */
> -	.macro map_memory, tbl, rtbl, vstart, vend, flags, phys, pgds, istart, iend, tmp, count, sv
> +	.macro map_memory, tbl, rtbl, vstart, vend, flags, phys, order, istart, iend, tmp, count, sv
>  	sub \vend, \vend, #1
>  	add \rtbl, \tbl, #PAGE_SIZE
> -	mov \sv, \rtbl
>  	mov \count, #0
> -	compute_indices \vstart, \vend, #PGDIR_SHIFT, \pgds, \istart, \iend, \count
> +
> +	compute_indices \vstart, \vend, #PGDIR_SHIFT, #\order, \istart, \iend, \count
> +	mov \sv, \rtbl
>  	populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp
>  	mov \tbl, \sv
> -	mov \sv, \rtbl

FWIW, moving the temporary save of (r)tbl immediately around populate_entries
is *much* clearer!

Mark.

>  
>  #if SWAPPER_PGTABLE_LEVELS > 3
> -	compute_indices \vstart, \vend, #PUD_SHIFT, #PTRS_PER_PUD, \istart, \iend, \count
> +	compute_indices \vstart, \vend, #PUD_SHIFT, #(PAGE_SHIFT - 3), \istart, \iend, \count
> +	mov \sv, \rtbl
>  	populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp
>  	mov \tbl, \sv
> -	mov \sv, \rtbl
>  #endif
>  
>  #if SWAPPER_PGTABLE_LEVELS > 2
> -	compute_indices \vstart, \vend, #SWAPPER_TABLE_SHIFT, #PTRS_PER_PMD, \istart, \iend, \count
> +	compute_indices \vstart, \vend, #SWAPPER_TABLE_SHIFT, #(PAGE_SHIFT - 3), \istart, \iend, \count
> +	mov \sv, \rtbl
>  	populate_entries \tbl, \rtbl, \istart, \iend, #PMD_TYPE_TABLE, #PAGE_SIZE, \tmp
>  	mov \tbl, \sv
>  #endif
>  
> -	compute_indices \vstart, \vend, #SWAPPER_BLOCK_SHIFT, #PTRS_PER_PTE, \istart, \iend, \count
> -	bic \count, \phys, #SWAPPER_BLOCK_SIZE - 1
> -	populate_entries \tbl, \count, \istart, \iend, \flags, #SWAPPER_BLOCK_SIZE, \tmp
> +	compute_indices \vstart, \vend, #SWAPPER_BLOCK_SHIFT, #(PAGE_SHIFT - 3), \istart, \iend, \count
> +	bic \rtbl, \phys, #SWAPPER_BLOCK_SIZE - 1
> +	populate_entries \tbl, \rtbl, \istart, \iend, \flags, #SWAPPER_BLOCK_SIZE, \tmp
>  	.endm
>  
>  /*
> @@ -300,12 +290,12 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
>  	 * range in that case, and configure an additional translation level
>  	 * if needed.
>  	 */
> -	mov	x4, #PTRS_PER_PGD
>  	idmap_get_t0sz x5
>  	cmp	x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough?
>  	b.ge	1f			// .. then skip VA range extension
>  
>  #if (VA_BITS < 48)
> +#define IDMAP_PGD_ORDER	(VA_BITS - PGDIR_SHIFT)
>  #define EXTRA_SHIFT	(PGDIR_SHIFT + PAGE_SHIFT - 3)
>  #define EXTRA_PTRS	(1 << (PHYS_MASK_SHIFT - EXTRA_SHIFT))
>  
> @@ -323,16 +313,16 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
>  	mov	x2, EXTRA_PTRS
>  	create_table_entry x0, x3, EXTRA_SHIFT, x2, x5, x6
>  #else
> +#define IDMAP_PGD_ORDER	(PHYS_MASK_SHIFT - PGDIR_SHIFT)
>  	/*
>  	 * If VA_BITS == 48, we don't have to configure an additional
>  	 * translation level, but the top-level table has more entries.
>  	 */
> -	mov	x4, #1 << (PHYS_MASK_SHIFT - PGDIR_SHIFT)
>  #endif
>  1:
>  	adr_l	x6, __idmap_text_end		// __pa(__idmap_text_end)
>  
> -	map_memory x0, x1, x3, x6, x7, x3, x4, x10, x11, x12, x13, x14
> +	map_memory x0, x1, x3, x6, x7, x3, IDMAP_PGD_ORDER, x10, x11, x12, x13, x14
>  
>  	/*
>  	 * Map the kernel image (starting with PHYS_OFFSET).
> @@ -340,13 +330,12 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
>  	adrp	x0, init_pg_dir
>  	mov_q	x5, KIMAGE_VADDR		// compile time __va(_text)
>  	add	x5, x5, x23			// add KASLR displacement
> -	mov	x4, PTRS_PER_PGD
>  	adrp	x6, _end			// runtime __pa(_end)
>  	adrp	x3, _text			// runtime __pa(_text)
>  	sub	x6, x6, x3			// _end - _text
>  	add	x6, x6, x5			// runtime __va(_end)
>  
> -	map_memory x0, x1, x5, x6, x7, x3, x4, x10, x11, x12, x13, x14
> +	map_memory x0, x1, x5, x6, x7, x3, (VA_BITS - PGDIR_SHIFT), x10, x11, x12, x13, x14
>  
>  	/*
>  	 * Since the page tables have been populated with non-cacheable
> -- 
> 2.35.1
> 

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Re: [PATCH v5 15/21] arm64: idreg-override: use early FDT mapping in ID map

[Mark Rutland]

Hi Ard,

On Fri, Jun 24, 2022 at 05:06:45PM +0200, Ard Biesheuvel wrote:
> Instead of calling into the kernel to map the FDT into the kernel page
> tables before even calling start_kernel(), let's switch to the initial,
> temporary mapping of the device tree that has been added to the ID map.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Unfortunately, this patch breaks KASAN_INLINE=y, as the accesses to the idmap
alias of the FDT get a poison check, which faults, resulting in a panic()
before any of the command line is parsed.

It's a bit painful to fix this; I had hoped it would be simple to fix by
adding:

	KASAN_SANITIZE_idreg-override.o := n

... to arch/arm64/kernel/Makefile, but there are a bunch of calls to
out-of-line functions that end up being instrumented (e.g. strncpy() and some
fdt_*() functions), and it doesn't look like it'll be simple to go fix those.

Can we revert this? IIUC this patch is an optimization rather being necessary
for later changes.

Thanks,
Mark.

> ---
>  arch/arm64/kernel/head.S           |  1 +
>  arch/arm64/kernel/idreg-override.c | 17 ++++++-----------
>  2 files changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 8283ff848328..64ebff634b83 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -472,6 +472,7 @@ SYM_FUNC_START_LOCAL(__primary_switched)
>  #endif
>  	mov	x0, x21				// pass FDT address in x0
>  	bl	early_fdt_map			// Try mapping the FDT early
> +	mov	x0, x22				// pass FDT address in x0
>  	bl	init_feature_override		// Parse cpu feature overrides
>  #ifdef CONFIG_RANDOMIZE_BASE
>  	tst	x23, ~(MIN_KIMG_ALIGN - 1)	// already running randomized?
> diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
> index 8a2ceb591686..f92836e196e5 100644
> --- a/arch/arm64/kernel/idreg-override.c
> +++ b/arch/arm64/kernel/idreg-override.c
> @@ -201,16 +201,11 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
>  	} while (1);
>  }
>  
> -static __init const u8 *get_bootargs_cmdline(void)
> +static __init const u8 *get_bootargs_cmdline(const void *fdt)
>  {
>  	const u8 *prop;
> -	void *fdt;
>  	int node;
>  
> -	fdt = get_early_fdt_ptr();
> -	if (!fdt)
> -		return NULL;
> -
>  	node = fdt_path_offset(fdt, "/chosen");
>  	if (node < 0)
>  		return NULL;
> @@ -222,9 +217,9 @@ static __init const u8 *get_bootargs_cmdline(void)
>  	return strlen(prop) ? prop : NULL;
>  }
>  
> -static __init void parse_cmdline(void)
> +static __init void parse_cmdline(const void *fdt)
>  {
> -	const u8 *prop = get_bootargs_cmdline();
> +	const u8 *prop = get_bootargs_cmdline(fdt);
>  
>  	if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
>  		__parse_cmdline(CONFIG_CMDLINE, true);
> @@ -234,9 +229,9 @@ static __init void parse_cmdline(void)
>  }
>  
>  /* Keep checkers quiet */
> -void init_feature_override(void);
> +void init_feature_override(const void *fdt);
>  
> -asmlinkage void __init init_feature_override(void)
> +asmlinkage void __init init_feature_override(const void *fdt)
>  {
>  	int i;
>  
> @@ -247,7 +242,7 @@ asmlinkage void __init init_feature_override(void)
>  		}
>  	}
>  
> -	parse_cmdline();
> +	parse_cmdline(fdt);
>  
>  	for (i = 0; i < ARRAY_SIZE(regs); i++) {
>  		if (regs[i]->override)
> -- 
> 2.35.1
> 
> 
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> 

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Re: [PATCH v5 15/21] arm64: idreg-override: use early FDT mapping in ID map

[Ard Biesheuvel]

On Mon, 11 Jul 2022 at 17:39, Mark Rutland <mark.rutland@arm.com> wrote:
>
> Hi Ard,
>
> On Fri, Jun 24, 2022 at 05:06:45PM +0200, Ard Biesheuvel wrote:
> > Instead of calling into the kernel to map the FDT into the kernel page
> > tables before even calling start_kernel(), let's switch to the initial,
> > temporary mapping of the device tree that has been added to the ID map.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>
> Unfortunately, this patch breaks KASAN_INLINE=y, as the accesses to the idmap
> alias of the FDT get a poison check, which faults, resulting in a panic()
> before any of the command line is parsed.
>
> It's a bit painful to fix this; I had hoped it would be simple to fix by
> adding:
>
>         KASAN_SANITIZE_idreg-override.o := n
>
> ... to arch/arm64/kernel/Makefile, but there are a bunch of calls to
> out-of-line functions that end up being instrumented (e.g. strncpy() and some
> fdt_*() functions), and it doesn't look like it'll be simple to go fix those.
>

Ugh. I suppose the KASAN projection produces invalid shadow addresses
for the TTBR0 range, so there is no way we can map some zero shadow
for the FDT?

> Can we revert this? IIUC this patch is an optimization rather being necessary
> for later changes.
>

Indeed, let's revert this for now, along with the follow-up patch that
removes the early FDT fixmap remap hack.

>
> > ---
> >  arch/arm64/kernel/head.S           |  1 +
> >  arch/arm64/kernel/idreg-override.c | 17 ++++++-----------
> >  2 files changed, 7 insertions(+), 11 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> > index 8283ff848328..64ebff634b83 100644
> > --- a/arch/arm64/kernel/head.S
> > +++ b/arch/arm64/kernel/head.S
> > @@ -472,6 +472,7 @@ SYM_FUNC_START_LOCAL(__primary_switched)
> >  #endif
> >       mov     x0, x21                         // pass FDT address in x0
> >       bl      early_fdt_map                   // Try mapping the FDT early
> > +     mov     x0, x22                         // pass FDT address in x0
> >       bl      init_feature_override           // Parse cpu feature overrides
> >  #ifdef CONFIG_RANDOMIZE_BASE
> >       tst     x23, ~(MIN_KIMG_ALIGN - 1)      // already running randomized?
> > diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
> > index 8a2ceb591686..f92836e196e5 100644
> > --- a/arch/arm64/kernel/idreg-override.c
> > +++ b/arch/arm64/kernel/idreg-override.c
> > @@ -201,16 +201,11 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
> >       } while (1);
> >  }
> >
> > -static __init const u8 *get_bootargs_cmdline(void)
> > +static __init const u8 *get_bootargs_cmdline(const void *fdt)
> >  {
> >       const u8 *prop;
> > -     void *fdt;
> >       int node;
> >
> > -     fdt = get_early_fdt_ptr();
> > -     if (!fdt)
> > -             return NULL;
> > -
> >       node = fdt_path_offset(fdt, "/chosen");
> >       if (node < 0)
> >               return NULL;
> > @@ -222,9 +217,9 @@ static __init const u8 *get_bootargs_cmdline(void)
> >       return strlen(prop) ? prop : NULL;
> >  }
> >
> > -static __init void parse_cmdline(void)
> > +static __init void parse_cmdline(const void *fdt)
> >  {
> > -     const u8 *prop = get_bootargs_cmdline();
> > +     const u8 *prop = get_bootargs_cmdline(fdt);
> >
> >       if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
> >               __parse_cmdline(CONFIG_CMDLINE, true);
> > @@ -234,9 +229,9 @@ static __init void parse_cmdline(void)
> >  }
> >
> >  /* Keep checkers quiet */
> > -void init_feature_override(void);
> > +void init_feature_override(const void *fdt);
> >
> > -asmlinkage void __init init_feature_override(void)
> > +asmlinkage void __init init_feature_override(const void *fdt)
> >  {
> >       int i;
> >
> > @@ -247,7 +242,7 @@ asmlinkage void __init init_feature_override(void)
> >               }
> >       }
> >
> > -     parse_cmdline();
> > +     parse_cmdline(fdt);
> >
> >       for (i = 0; i < ARRAY_SIZE(regs); i++) {
> >               if (regs[i]->override)
> > --
> > 2.35.1
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> >

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Re: [PATCH v5 15/21] arm64: idreg-override: use early FDT mapping in ID map

[Mark Rutland]

On Tue, Jul 12, 2022 at 07:03:56PM +0200, Ard Biesheuvel wrote:
> On Mon, 11 Jul 2022 at 17:39, Mark Rutland <mark.rutland@arm.com> wrote:
> >
> > Hi Ard,
> >
> > On Fri, Jun 24, 2022 at 05:06:45PM +0200, Ard Biesheuvel wrote:
> > > Instead of calling into the kernel to map the FDT into the kernel page
> > > tables before even calling start_kernel(), let's switch to the initial,
> > > temporary mapping of the device tree that has been added to the ID map.
> > >
> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> >
> > Unfortunately, this patch breaks KASAN_INLINE=y, as the accesses to the idmap
> > alias of the FDT get a poison check, which faults, resulting in a panic()
> > before any of the command line is parsed.
> >
> > It's a bit painful to fix this; I had hoped it would be simple to fix by
> > adding:
> >
> >         KASAN_SANITIZE_idreg-override.o := n
> >
> > ... to arch/arm64/kernel/Makefile, but there are a bunch of calls to
> > out-of-line functions that end up being instrumented (e.g. strncpy() and some
> > fdt_*() functions), and it doesn't look like it'll be simple to go fix those.
> 
> Ugh. I suppose the KASAN projection produces invalid shadow addresses
> for the TTBR0 range, so there is no way we can map some zero shadow
> for the FDT?

Yup, exactly.

> > Can we revert this? IIUC this patch is an optimization rather being necessary
> > for later changes.
> 
> Indeed, let's revert this for now, along with the follow-up patch that
> removes the early FDT fixmap remap hack.

I'll send a patch shortly.

Thanks,
Mark.

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