powerpc/8xx: Allow STRICT_KERNEL_RwX with pinned TLB

Pinned TLB are 8M. Now that there is no strict boundary anymore
between text and RO data, it is possible to use 8M pinned executable
TLB that covers both text and RO data.

When PIN_TLB_DATA or PIN_TLB_TEXT is selected, enforce 8M RW data
alignment and allow STRICT_KERNEL_RWX.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c535fc97bf0dd8693192e25feeed8088701e00c6.1589866984.git.christophe.leroy@csgroup.eu

arch/powerpc/Kconfig

@@ -779,9 +779,10 @@ config THREAD_SHIFT
 	  want. Only change this if you know what you are doing.
 
 config DATA_SHIFT_BOOL
-	bool "Set custom data alignment" if STRICT_KERNEL_RWX && \
-					    (PPC_BOOK3S_32 || PPC_8xx)
+	bool "Set custom data alignment"
 	depends on ADVANCED_OPTIONS
+	depends on STRICT_KERNEL_RWX
+	depends on PPC_BOOK3S_32 || (PPC_8xx && !PIN_TLB_DATA && !PIN_TLB_TEXT)
 	help
 	  This option allows you to set the kernel data alignment. When
 	  RAM is mapped by blocks, the alignment needs to fit the size and
@@ -803,7 +804,8 @@ config DATA_SHIFT
 
 	  On 8xx, large pages (512kb or 8M) are used to map kernel linear
 	  memory. Aligning to 8M reduces TLB misses as only 8M pages are used
-	  in that case.
+	  in that case. If PIN_TLB is selected, it must be aligned to 8M as
+	  8M pages will be pinned.
 
 config FORCE_MAX_ZONEORDER
 	int "Maximum zone order"

arch/powerpc/mm/nohash/8xx.c

@@ -127,7 +127,7 @@ void __init mmu_mapin_immr(void)
 				    PAGE_KERNEL_NCG, MMU_PAGE_512K, true);
 }
 
-static void __init mmu_mapin_ram_chunk(unsigned long offset, unsigned long top,
+static void mmu_mapin_ram_chunk(unsigned long offset, unsigned long top,
 				pgprot_t prot, bool new)
 {
 	unsigned long v = PAGE_OFFSET + offset;
@@ -181,6 +181,9 @@ void mmu_mark_initmem_nx(void)
 
 	mmu_mapin_ram_chunk(0, boundary, PAGE_KERNEL_TEXT, false);
 	mmu_mapin_ram_chunk(boundary, einittext8, PAGE_KERNEL, false);
+
+	if (IS_ENABLED(CONFIG_PIN_TLB_TEXT))
+		mmu_pin_tlb(block_mapped_ram, false);
 }
 
 #ifdef CONFIG_STRICT_KERNEL_RWX
@@ -189,6 +192,8 @@ void mmu_mark_rodata_ro(void)
 	unsigned long sinittext = __pa(_sinittext);
 
 	mmu_mapin_ram_chunk(0, sinittext, PAGE_KERNEL_ROX, false);
+	if (IS_ENABLED(CONFIG_PIN_TLB_DATA))
+		mmu_pin_tlb(block_mapped_ram, true);
 }
 #endif
 

arch/powerpc/platforms/8xx/Kconfig

@@ -167,7 +167,7 @@ menu "8xx advanced setup"
 
 config PIN_TLB
 	bool "Pinned Kernel TLBs"
-	depends on ADVANCED_OPTIONS && !DEBUG_PAGEALLOC && !STRICT_KERNEL_RWX
+	depends on ADVANCED_OPTIONS && !DEBUG_PAGEALLOC
 	help
 	  On the 8xx, we have 32 instruction TLBs and 32 data TLBs. In each
 	  table 4 TLBs can be pinned.