arm64: kernel: move identity map out of .text mapping

Reorganize the ID map slightly so that only code that is executed with
the MMU off or via the 1:1 mapping remains. This allows us to move the
identity map out of the .text segment, as it will no longer need
executable permissions via the kernel mapping.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20230111102236.1430401-3-ardb@kernel.orgSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/head.S

@@ -543,19 +543,6 @@ SYM_INNER_LABEL(init_el2, SYM_L_LOCAL)
 	eret
 SYM_FUNC_END(init_kernel_el)
 
-/*
- * Sets the __boot_cpu_mode flag depending on the CPU boot mode passed
- * in w0. See arch/arm64/include/asm/virt.h for more info.
- */
-SYM_FUNC_START_LOCAL(set_cpu_boot_mode_flag)
-	adr_l	x1, __boot_cpu_mode
-	cmp	w0, #BOOT_CPU_MODE_EL2
-	b.ne	1f
-	add	x1, x1, #4
-1:	str	w0, [x1]			// Save CPU boot mode
-	ret
-SYM_FUNC_END(set_cpu_boot_mode_flag)
-
 	/*
 	 * This provides a "holding pen" for platforms to hold all secondary
 	 * cores are held until we're ready for them to initialise.
@@ -599,6 +586,7 @@ SYM_FUNC_START_LOCAL(secondary_startup)
 	br	x8
 SYM_FUNC_END(secondary_startup)
 
+	.text
 SYM_FUNC_START_LOCAL(__secondary_switched)
 	mov	x0, x20
 	bl	set_cpu_boot_mode_flag
@@ -631,6 +619,19 @@ SYM_FUNC_START_LOCAL(__secondary_too_slow)
 	b	__secondary_too_slow
 SYM_FUNC_END(__secondary_too_slow)
 
+/*
+ * Sets the __boot_cpu_mode flag depending on the CPU boot mode passed
+ * in w0. See arch/arm64/include/asm/virt.h for more info.
+ */
+SYM_FUNC_START_LOCAL(set_cpu_boot_mode_flag)
+	adr_l	x1, __boot_cpu_mode
+	cmp	w0, #BOOT_CPU_MODE_EL2
+	b.ne	1f
+	add	x1, x1, #4
+1:	str	w0, [x1]			// Save CPU boot mode
+	ret
+SYM_FUNC_END(set_cpu_boot_mode_flag)
+
 /*
  * The booting CPU updates the failed status @__early_cpu_boot_status,
  * with MMU turned off.
@@ -662,6 +663,7 @@ SYM_FUNC_END(__secondary_too_slow)
  * Checks if the selected granule size is supported by the CPU.
  * If it isn't, park the CPU
  */
+	.section ".idmap.text","awx"
 SYM_FUNC_START(__enable_mmu)
 	mrs	x3, ID_AA64MMFR0_EL1
 	ubfx	x3, x3, #ID_AA64MMFR0_EL1_TGRAN_SHIFT, 4

arch/arm64/kernel/vmlinux.lds.S

@@ -179,7 +179,6 @@ SECTIONS
 			LOCK_TEXT
 			KPROBES_TEXT
 			HYPERVISOR_TEXT
-			IDMAP_TEXT
 			*(.gnu.warning)
 		. = ALIGN(16);
 		*(.got)			/* Global offset table		*/
@@ -206,6 +205,7 @@ SECTIONS
 		TRAMP_TEXT
 		HIBERNATE_TEXT
 		KEXEC_TEXT
+		IDMAP_TEXT
 		. = ALIGN(PAGE_SIZE);
 	}
 

arch/arm64/mm/proc.S

@@ -110,7 +110,6 @@ SYM_FUNC_END(cpu_do_suspend)
  *
  * x0: Address of context pointer
  */
-	.pushsection ".idmap.text", "awx"
 SYM_FUNC_START(cpu_do_resume)
 	ldp	x2, x3, [x0]
 	ldp	x4, x5, [x0, #16]
@@ -166,7 +165,6 @@ alternative_else_nop_endif
 	isb
 	ret
 SYM_FUNC_END(cpu_do_resume)
-	.popsection
 #endif
 
 	.pushsection ".idmap.text", "awx"