linux-kernel - [PATCH v1 8/8] powerpc/fsl_booke: Enable STRICT_KERNEL

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Date:   Fri, 15 Oct 2021 12:02:49 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v1 8/8] powerpc/fsl_booke: Enable STRICT_KERNEL_RWX

Enable STRICT_KERNEL_RWX on fsl_booke.

For that, we need additional TLBCAMs dedicated to linear mapping,
based on the alignment of _sinittext.

By default, up to 768 Mbytes of memory are mapped.
It uses 3 TLBCAMs of size 256 Mbytes.

With a data alignment of 16, we need up to 9 TLBCAMs:
  16/16/16/16/64/64/64/256/256

With a data alignment of 4, we need up to 12 TLBCAMs:
  4/4/4/4/16/16/16/64/64/64/256/256

With a data alignment of 1, we need up to 15 TLBCAMs:
  1/1/1/1/4/4/4/16/16/16/64/64/64/256/256

By default, set a 16 Mbytes alignment as a compromise between memory
usage and number of TLBCAMs. This can be adjusted manually when needed.

For the time being, it doens't work when the base is randomised.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/Kconfig | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 6b9f523882c5..939a47642a9c 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -139,6 +139,7 @@ config PPC
 	select ARCH_HAS_SCALED_CPUTIME		if VIRT_CPU_ACCOUNTING_NATIVE && PPC_BOOK3S_64
 	select ARCH_HAS_SET_MEMORY
 	select ARCH_HAS_STRICT_KERNEL_RWX	if (PPC_BOOK3S || PPC_8xx || 40x) && !HIBERNATION
+	select ARCH_HAS_STRICT_KERNEL_RWX	if FSL_BOOKE && !HIBERNATION && !RANDOMIZE_BASE
 	select ARCH_HAS_STRICT_MODULE_RWX	if ARCH_HAS_STRICT_KERNEL_RWX && !PPC_BOOK3S_32
 	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAS_UACCESS_FLUSHCACHE
@@ -778,7 +779,8 @@ config DATA_SHIFT_BOOL
 	bool "Set custom data alignment"
 	depends on ADVANCED_OPTIONS
 	depends on STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE
-	depends on PPC_BOOK3S_32 || (PPC_8xx && !PIN_TLB_DATA && !STRICT_KERNEL_RWX)
+	depends on PPC_BOOK3S_32 || (PPC_8xx && !PIN_TLB_DATA && !STRICT_KERNEL_RWX) || \
+		   FSL_BOOKE
 	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
@@ -791,11 +793,13 @@ config DATA_SHIFT
 	default 24 if STRICT_KERNEL_RWX && PPC64
 	range 17 28 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) && PPC_BOOK3S_32
 	range 19 23 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) && PPC_8xx
+	range 20 24 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) && PPC_FSL_BOOKE
 	default 22 if STRICT_KERNEL_RWX && PPC_BOOK3S_32
 	default 18 if (DEBUG_PAGEALLOC || KFENCE) && PPC_BOOK3S_32
 	default 23 if STRICT_KERNEL_RWX && PPC_8xx
 	default 23 if (DEBUG_PAGEALLOC || KFENCE) && PPC_8xx && PIN_TLB_DATA
 	default 19 if (DEBUG_PAGEALLOC || KFENCE) && PPC_8xx
+	default 24 if STRICT_KERNEL_RWX && FSL_BOOKE
 	default PPC_PAGE_SHIFT
 	help
 	  On Book3S 32 (603+), DBATs are used to map kernel text and rodata RO.
@@ -1123,7 +1127,10 @@ config LOWMEM_CAM_NUM_BOOL
 config LOWMEM_CAM_NUM
 	depends on FSL_BOOKE
 	int "Number of CAMs to use to map low memory" if LOWMEM_CAM_NUM_BOOL
-	default 3
+	default 3 if !STRICT_KERNEL_RWX
+	default 9 if DATA_SHIFT >= 24
+	default 12 if DATA_SHIFT >= 22
+	default 15
 
 config DYNAMIC_MEMSTART
 	bool "Enable page aligned dynamic load address for kernel"
-- 
2.31.1