linux-kernel - [PATCH v2 6/6] powerpc/32s: Use dedicated segment for modules with STRICT_KERNEL

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Message-Id: <eb8faba9148b6cf17c696ba776b4e8ee2f6313bf.1593428200.git.christophe.leroy@csgroup.eu>
Date:   Mon, 29 Jun 2020 11:15:26 +0000 (UTC)
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:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2 6/6] powerpc/32s: Use dedicated segment for modules with
 STRICT_KERNEL_RWX

When STRICT_KERNEL_RWX is set, we want to set NX bit on vmalloc
segments. But modules require exec.

Use a dedicated segment for modules. There is not much space
above kernel, and we don't waste vmalloc space to do alignment.
Therefore, we take the segment before PAGE_OFFSET for modules.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/Kconfig                         |  1 +
 arch/powerpc/include/asm/book3s/32/pgtable.h | 15 +++++----------
 arch/powerpc/mm/ptdump/ptdump.c              |  8 ++++++++
 3 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 51abc59c3334..963b3bc7d969 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -1194,6 +1194,7 @@ config TASK_SIZE_BOOL
 config TASK_SIZE
 	hex "Size of user task space" if TASK_SIZE_BOOL
 	default "0x80000000" if PPC_8xx
+	default "0xb0000000" if PPC_BOOK3S_32 && STRICT_KERNEL_RWX
 	default "0xc0000000"
 endmenu
 
diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
index 224912432821..36443cda8dcf 100644
--- a/arch/powerpc/include/asm/book3s/32/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
@@ -184,17 +184,7 @@ int map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot);
  */
 #define VMALLOC_OFFSET (0x1000000) /* 16M */
 
-/*
- * With CONFIG_STRICT_KERNEL_RWX, kernel segments are set NX. But when modules
- * are used, NX cannot be set on VMALLOC space. So vmalloc VM space and linear
- * memory shall not share segments.
- */
-#if defined(CONFIG_STRICT_KERNEL_RWX) && defined(CONFIG_MODULES)
-#define VMALLOC_START ((ALIGN((long)high_memory, 256L << 20) + VMALLOC_OFFSET) & \
-		       ~(VMALLOC_OFFSET - 1))
-#else
 #define VMALLOC_START ((((long)high_memory + VMALLOC_OFFSET) & ~(VMALLOC_OFFSET-1)))
-#endif
 
 #ifdef CONFIG_KASAN_VMALLOC
 #define VMALLOC_END	ALIGN_DOWN(ioremap_bot, PAGE_SIZE << KASAN_SHADOW_SCALE_SHIFT)
@@ -202,6 +192,11 @@ int map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot);
 #define VMALLOC_END	ioremap_bot
 #endif
 
+#ifdef CONFIG_STRICT_KERNEL_RWX
+#define MODULES_END	ALIGN_DOWN(PAGE_OFFSET, SZ_256M)
+#define MODULES_VADDR	(MODULES_END - SZ_256M)
+#endif
+
 #ifndef __ASSEMBLY__
 #include <linux/sched.h>
 #include <linux/threads.h>
diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
index 9d942136c7be..b2ed1ca4f254 100644
--- a/arch/powerpc/mm/ptdump/ptdump.c
+++ b/arch/powerpc/mm/ptdump/ptdump.c
@@ -74,6 +74,10 @@ struct addr_marker {
 
 static struct addr_marker address_markers[] = {
 	{ 0,	"Start of kernel VM" },
+#ifdef MODULES_VADDR
+	{ 0,	"modules start" },
+	{ 0,	"modules end" },
+#endif
 	{ 0,	"vmalloc() Area" },
 	{ 0,	"vmalloc() End" },
 #ifdef CONFIG_PPC64
@@ -352,6 +356,10 @@ static void populate_markers(void)
 	address_markers[i++].start_address = PAGE_OFFSET;
 #else
 	address_markers[i++].start_address = TASK_SIZE;
+#endif
+#ifdef MODULES_VADDR
+	address_markers[i++].start_address = MODULES_VADDR;
+	address_markers[i++].start_address = MODULES_END;
 #endif
 	address_markers[i++].start_address = VMALLOC_START;
 	address_markers[i++].start_address = VMALLOC_END;
-- 
2.25.0