[PATCHv6 4/8] arm64: Move some head.text functions to executable section

[lauraa@codeaurora.org (Laura Abbott)]

The head.text section is intended to be run at early bootup
before any of the regular kernel mappings have been setup.
Parts of head.text may be freed back into the buddy allocator
due to TEXT_OFFSET so for security requirements this memory
must not be executable. The suspend/resume/hotplug code path
requires some of these head.S functions to run however which
means they need to be executable. Support these conflicting
requirements by moving the few head.text functions that need
to be executable to the text section which has the appropriate
page table permissions.

Tested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
---
v6: Dropped the latehead.text bit and just moved everything to the regular
text section
---
 arch/arm64/kernel/head.S | 407 ++++++++++++++++++++++++-----------------------
 1 file changed, 210 insertions(+), 197 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 10f5cc0..4b63d7a 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -238,7 +238,13 @@ ENTRY(stext)
 	mov	x0, x22
 	bl	lookup_processor_type
 	mov	x23, x0				// x23=current cpu_table
-	cbz	x23, __error_p			// invalid processor (x23=0)?
+	/*
+	 *	__error_p may end up out of range for cbz if text areas
+	 *	are aligned up to section sizes
+	 */
+	cbnz	x23, 1f				// invalid processor (x23=0)?
+	b	__error_p
+1:
 	bl	__vet_fdt
 	bl	__create_page_tables		// x25=TTBR0, x26=TTBR1
 	/*
@@ -250,13 +256,214 @@ ENTRY(stext)
 	 */
 	ldr	x27, __switch_data		// address to jump to after
 						// MMU has been enabled
-	adr	lr, __enable_mmu		// return (PIC) address
+	adrp	lr, __enable_mmu		// return (PIC) address
+	add	lr, lr, #:lo12:__enable_mmu
 	ldr	x12, [x23, #CPU_INFO_SETUP]
 	add	x12, x12, x28			// __virt_to_phys
 	br	x12				// initialise processor
 ENDPROC(stext)
 
 /*
+ * Determine validity of the x21 FDT pointer.
+ * The dtb must be 8-byte aligned and live in the first 512M of memory.
+ */
+__vet_fdt:
+	tst	x21, #0x7
+	b.ne	1f
+	cmp	x21, x24
+	b.lt	1f
+	mov	x0, #(1 << 29)
+	add	x0, x0, x24
+	cmp	x21, x0
+	b.ge	1f
+	ret
+1:
+	mov	x21, #0
+	ret
+ENDPROC(__vet_fdt)
+/*
+ * 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:	tmp1, tmp2
+ * Returns:	tbl -> next level table page address
+ */
+	.macro	create_table_entry, tbl, virt, shift, ptrs, tmp1, tmp2
+	lsr	\tmp1, \virt, #\shift
+	and	\tmp1, \tmp1, #\ptrs - 1	// table index
+	add	\tmp2, \tbl, #PAGE_SIZE
+	orr	\tmp2, \tmp2, #PMD_TYPE_TABLE	// address of next table and entry type
+	str	\tmp2, [\tbl, \tmp1, lsl #3]
+	add	\tbl, \tbl, #PAGE_SIZE		// next level table page
+	.endm
+
+/*
+ * Macro to populate the PGD (and possibily PUD) for the corresponding
+ * block entry in the next level (tbl) for the given virtual address.
+ *
+ * Preserves:	tbl, next, virt
+ * Corrupts:	tmp1, tmp2
+ */
+	.macro	create_pgd_entry, tbl, virt, tmp1, tmp2
+	create_table_entry \tbl, \virt, PGDIR_SHIFT, PTRS_PER_PGD, \tmp1, \tmp2
+#if SWAPPER_PGTABLE_LEVELS == 3
+	create_table_entry \tbl, \virt, TABLE_SHIFT, PTRS_PER_PTE, \tmp1, \tmp2
+#endif
+	.endm
+
+/*
+ * Macro to populate block entries in the page table for the start..end
+ * virtual range (inclusive).
+ *
+ * Preserves:	tbl, flags
+ * Corrupts:	phys, start, end, pstate
+ */
+	.macro	create_block_map, tbl, flags, phys, start, end
+	lsr	\phys, \phys, #BLOCK_SHIFT
+	lsr	\start, \start, #BLOCK_SHIFT
+	and	\start, \start, #PTRS_PER_PTE - 1	// table index
+	orr	\phys, \flags, \phys, lsl #BLOCK_SHIFT	// table entry
+	lsr	\end, \end, #BLOCK_SHIFT
+	and	\end, \end, #PTRS_PER_PTE - 1		// table end index
+9999:	str	\phys, [\tbl, \start, lsl #3]		// store the entry
+	add	\start, \start, #1			// next entry
+	add	\phys, \phys, #BLOCK_SIZE		// next block
+	cmp	\start, \end
+	b.ls	9999b
+	.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, including the FDT blob (TTBR1)
+ *   - pgd entry for fixed mappings (TTBR1)
+ */
+__create_page_tables:
+	pgtbl	x25, x26, x28			// idmap_pg_dir and swapper_pg_dir addresses
+	mov	x27, lr
+
+	/*
+	 * Invalidate the idmap and swapper page tables to avoid potential
+	 * dirty cache lines being evicted.
+	 */
+	mov	x0, x25
+	add	x1, x26, #SWAPPER_DIR_SIZE
+	bl	__inval_cache_range
+
+	/*
+	 * Clear the idmap and swapper page tables.
+	 */
+	mov	x0, x25
+	add	x6, x26, #SWAPPER_DIR_SIZE
+1:	stp	xzr, xzr, [x0], #16
+	stp	xzr, xzr, [x0], #16
+	stp	xzr, xzr, [x0], #16
+	stp	xzr, xzr, [x0], #16
+	cmp	x0, x6
+	b.lo	1b
+
+	ldr	x7, =MM_MMUFLAGS
+
+	/*
+	 * Create the identity mapping.
+	 */
+	mov	x0, x25				// idmap_pg_dir
+	ldr	x3, =KERNEL_START
+	add	x3, x3, x28			// __pa(KERNEL_START)
+	create_pgd_entry x0, x3, x5, x6
+	ldr	x6, =KERNEL_END
+	mov	x5, x3				// __pa(KERNEL_START)
+	add	x6, x6, x28			// __pa(KERNEL_END)
+	create_block_map x0, x7, x3, x5, x6
+
+	/*
+	 * Map the kernel image (starting with PHYS_OFFSET).
+	 */
+	mov	x0, x26				// swapper_pg_dir
+	mov	x5, #PAGE_OFFSET
+	create_pgd_entry x0, x5, x3, x6
+	ldr	x6, =KERNEL_END
+	mov	x3, x24				// phys offset
+	create_block_map x0, x7, x3, x5, x6
+
+	/*
+	 * Map the FDT blob (maximum 2MB; must be within 512MB of
+	 * PHYS_OFFSET).
+	 */
+	mov	x3, x21				// FDT phys address
+	and	x3, x3, #~((1 << 21) - 1)	// 2MB aligned
+	mov	x6, #PAGE_OFFSET
+	sub	x5, x3, x24			// subtract PHYS_OFFSET
+	tst	x5, #~((1 << 29) - 1)		// within 512MB?
+	csel	x21, xzr, x21, ne		// zero the FDT pointer
+	b.ne	1f
+	add	x5, x5, x6			// __va(FDT blob)
+	add	x6, x5, #1 << 21		// 2MB for the FDT blob
+	sub	x6, x6, #1			// inclusive range
+	create_block_map x0, x7, x3, x5, x6
+1:
+	/*
+	 * Since the page tables have been populated with non-cacheable
+	 * accesses (MMU disabled), invalidate the idmap and swapper page
+	 * tables again to remove any speculatively loaded cache lines.
+	 */
+	mov	x0, x25
+	add	x1, x26, #SWAPPER_DIR_SIZE
+	bl	__inval_cache_range
+
+	mov	lr, x27
+	ret
+ENDPROC(__create_page_tables)
+	.ltorg
+
+	.align	3
+	.type	__switch_data, %object
+__switch_data:
+	.quad	__mmap_switched
+	.quad	__bss_start			// x6
+	.quad	__bss_stop			// x7
+	.quad	processor_id			// x4
+	.quad	__fdt_pointer			// x5
+	.quad	memstart_addr			// x6
+	.quad	init_thread_union + THREAD_START_SP // sp
+
+/*
+ * The following fragment of code is executed with the MMU on in MMU mode, and
+ * uses absolute addresses; this is not position independent.
+ */
+__mmap_switched:
+	adr	x3, __switch_data + 8
+
+	ldp	x6, x7, [x3], #16
+1:	cmp	x6, x7
+	b.hs	2f
+	str	xzr, [x6], #8			// Clear BSS
+	b	1b
+2:
+	ldp	x4, x5, [x3], #16
+	ldr	x6, [x3], #8
+	ldr	x16, [x3]
+	mov	sp, x16
+	str	x22, [x4]			// Save processor ID
+	str	x21, [x5]			// Save FDT pointer
+	str	x24, [x6]			// Save PHYS_OFFSET
+	mov	x29, #0
+	b	start_kernel
+ENDPROC(__mmap_switched)
+
+/*
+ * end early head section, begin head code that is also used for
+ * hotplug and needs to have the same protections as the text region
+ */
+	.section ".text","ax"
+/*
  * If we're fortunate enough to boot@EL2, ensure that the world is
  * sane before dropping to EL1.
  *
@@ -493,183 +700,6 @@ ENDPROC(__calc_phys_offset)
 	.quad	PAGE_OFFSET
 
 /*
- * 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:	tmp1, tmp2
- * Returns:	tbl -> next level table page address
- */
-	.macro	create_table_entry, tbl, virt, shift, ptrs, tmp1, tmp2
-	lsr	\tmp1, \virt, #\shift
-	and	\tmp1, \tmp1, #\ptrs - 1	// table index
-	add	\tmp2, \tbl, #PAGE_SIZE
-	orr	\tmp2, \tmp2, #PMD_TYPE_TABLE	// address of next table and entry type
-	str	\tmp2, [\tbl, \tmp1, lsl #3]
-	add	\tbl, \tbl, #PAGE_SIZE		// next level table page
-	.endm
-
-/*
- * Macro to populate the PGD (and possibily PUD) for the corresponding
- * block entry in the next level (tbl) for the given virtual address.
- *
- * Preserves:	tbl, next, virt
- * Corrupts:	tmp1, tmp2
- */
-	.macro	create_pgd_entry, tbl, virt, tmp1, tmp2
-	create_table_entry \tbl, \virt, PGDIR_SHIFT, PTRS_PER_PGD, \tmp1, \tmp2
-#if SWAPPER_PGTABLE_LEVELS == 3
-	create_table_entry \tbl, \virt, TABLE_SHIFT, PTRS_PER_PTE, \tmp1, \tmp2
-#endif
-	.endm
-
-/*
- * Macro to populate block entries in the page table for the start..end
- * virtual range (inclusive).
- *
- * Preserves:	tbl, flags
- * Corrupts:	phys, start, end, pstate
- */
-	.macro	create_block_map, tbl, flags, phys, start, end
-	lsr	\phys, \phys, #BLOCK_SHIFT
-	lsr	\start, \start, #BLOCK_SHIFT
-	and	\start, \start, #PTRS_PER_PTE - 1	// table index
-	orr	\phys, \flags, \phys, lsl #BLOCK_SHIFT	// table entry
-	lsr	\end, \end, #BLOCK_SHIFT
-	and	\end, \end, #PTRS_PER_PTE - 1		// table end index
-9999:	str	\phys, [\tbl, \start, lsl #3]		// store the entry
-	add	\start, \start, #1			// next entry
-	add	\phys, \phys, #BLOCK_SIZE		// next block
-	cmp	\start, \end
-	b.ls	9999b
-	.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, including the FDT blob (TTBR1)
- *   - pgd entry for fixed mappings (TTBR1)
- */
-__create_page_tables:
-	pgtbl	x25, x26, x28			// idmap_pg_dir and swapper_pg_dir addresses
-	mov	x27, lr
-
-	/*
-	 * Invalidate the idmap and swapper page tables to avoid potential
-	 * dirty cache lines being evicted.
-	 */
-	mov	x0, x25
-	add	x1, x26, #SWAPPER_DIR_SIZE
-	bl	__inval_cache_range
-
-	/*
-	 * Clear the idmap and swapper page tables.
-	 */
-	mov	x0, x25
-	add	x6, x26, #SWAPPER_DIR_SIZE
-1:	stp	xzr, xzr, [x0], #16
-	stp	xzr, xzr, [x0], #16
-	stp	xzr, xzr, [x0], #16
-	stp	xzr, xzr, [x0], #16
-	cmp	x0, x6
-	b.lo	1b
-
-	ldr	x7, =MM_MMUFLAGS
-
-	/*
-	 * Create the identity mapping.
-	 */
-	mov	x0, x25				// idmap_pg_dir
-	ldr	x3, =KERNEL_START
-	add	x3, x3, x28			// __pa(KERNEL_START)
-	create_pgd_entry x0, x3, x5, x6
-	ldr	x6, =KERNEL_END
-	mov	x5, x3				// __pa(KERNEL_START)
-	add	x6, x6, x28			// __pa(KERNEL_END)
-	create_block_map x0, x7, x3, x5, x6
-
-	/*
-	 * Map the kernel image (starting with PHYS_OFFSET).
-	 */
-	mov	x0, x26				// swapper_pg_dir
-	mov	x5, #PAGE_OFFSET
-	create_pgd_entry x0, x5, x3, x6
-	ldr	x6, =KERNEL_END
-	mov	x3, x24				// phys offset
-	create_block_map x0, x7, x3, x5, x6
-
-	/*
-	 * Map the FDT blob (maximum 2MB; must be within 512MB of
-	 * PHYS_OFFSET).
-	 */
-	mov	x3, x21				// FDT phys address
-	and	x3, x3, #~((1 << 21) - 1)	// 2MB aligned
-	mov	x6, #PAGE_OFFSET
-	sub	x5, x3, x24			// subtract PHYS_OFFSET
-	tst	x5, #~((1 << 29) - 1)		// within 512MB?
-	csel	x21, xzr, x21, ne		// zero the FDT pointer
-	b.ne	1f
-	add	x5, x5, x6			// __va(FDT blob)
-	add	x6, x5, #1 << 21		// 2MB for the FDT blob
-	sub	x6, x6, #1			// inclusive range
-	create_block_map x0, x7, x3, x5, x6
-1:
-	/*
-	 * Since the page tables have been populated with non-cacheable
-	 * accesses (MMU disabled), invalidate the idmap and swapper page
-	 * tables again to remove any speculatively loaded cache lines.
-	 */
-	mov	x0, x25
-	add	x1, x26, #SWAPPER_DIR_SIZE
-	bl	__inval_cache_range
-
-	mov	lr, x27
-	ret
-ENDPROC(__create_page_tables)
-	.ltorg
-
-	.align	3
-	.type	__switch_data, %object
-__switch_data:
-	.quad	__mmap_switched
-	.quad	__bss_start			// x6
-	.quad	__bss_stop			// x7
-	.quad	processor_id			// x4
-	.quad	__fdt_pointer			// x5
-	.quad	memstart_addr			// x6
-	.quad	init_thread_union + THREAD_START_SP // sp
-
-/*
- * The following fragment of code is executed with the MMU on in MMU mode, and
- * uses absolute addresses; this is not position independent.
- */
-__mmap_switched:
-	adr	x3, __switch_data + 8
-
-	ldp	x6, x7, [x3], #16
-1:	cmp	x6, x7
-	b.hs	2f
-	str	xzr, [x6], #8			// Clear BSS
-	b	1b
-2:
-	ldp	x4, x5, [x3], #16
-	ldr	x6, [x3], #8
-	ldr	x16, [x3]
-	mov	sp, x16
-	str	x22, [x4]			// Save processor ID
-	str	x21, [x5]			// Save FDT pointer
-	str	x24, [x6]			// Save PHYS_OFFSET
-	mov	x29, #0
-	b	start_kernel
-ENDPROC(__mmap_switched)
-
-/*
  * Exception handling. Something went wrong and we can't proceed. We ought to
  * tell the user, but since we don't have any guarantee that we're even
  * running on the right architecture, we do virtually nothing.
@@ -717,21 +747,4 @@ __lookup_processor_type_data:
 	.quad	cpu_table
 	.size	__lookup_processor_type_data, . - __lookup_processor_type_data
 
-/*
- * Determine validity of the x21 FDT pointer.
- * The dtb must be 8-byte aligned and live in the first 512M of memory.
- */
-__vet_fdt:
-	tst	x21, #0x7
-	b.ne	1f
-	cmp	x21, x24
-	b.lt	1f
-	mov	x0, #(1 << 29)
-	add	x0, x0, x24
-	cmp	x21, x0
-	b.ge	1f
-	ret
-1:
-	mov	x21, #0
-	ret
-ENDPROC(__vet_fdt)
+
-- 
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