[RFC PATCH v3 5/8] arm64: mm: Use HAVE_ARCH_COMPAT_MMAP_BASES

[Amanieu d'Antras]

This patch switches arm64 to use separate mmap_base for 32-bit and
64-bit mmaps. This is needed to ensure that compat syscalls
invoked by 64-bit tasks perform VM allocations in the low 4G of the
address space.

Signed-off-by: Amanieu d'Antras <amanieu at gmail.com>
Co-developed-by: Ryan Houdek <Houdek.Ryan at fex-emu.org>
Signed-off-by: Ryan Houdek <Houdek.Ryan at fex-emu.org>
---
 arch/arm64/Kconfig                 |  1 +
 arch/arm64/include/asm/elf.h       |  8 +++++---
 arch/arm64/include/asm/processor.h | 33 ++++++++++++++++++------------
 arch/arm64/mm/mmap.c               | 33 ++++++++++++++++++++++++++++++
 4 files changed, 59 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index dfdc3e0af5e1..d57b7bcbd758 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -133,6 +133,7 @@ config ARM64
 	select HAVE_ALIGNED_STRUCT_PAGE if SLUB
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_BITREVERSE
+	select HAVE_ARCH_COMPAT_MMAP_BASES if COMPAT
 	select HAVE_ARCH_COMPILER_H
 	select HAVE_ARCH_HUGE_VMAP
 	select HAVE_ARCH_JUMP_LABEL
diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 8d1c8dcb87fd..e21964898d06 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -187,12 +187,14 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm,
 				       int uses_interp);
 
 /* 1GB of VA */
+#define STACK_RND_MASK_64		(0x3ffff >> (PAGE_SHIFT - 12))
 #ifdef CONFIG_COMPAT
+#define STACK_RND_MASK_32		(0x7ff >> (PAGE_SHIFT - 12))
 #define STACK_RND_MASK			(test_thread_flag(TIF_32BIT) ? \
-						0x7ff >> (PAGE_SHIFT - 12) : \
-						0x3ffff >> (PAGE_SHIFT - 12))
+						STACK_RND_MASK_32 : \
+						STACK_RND_MASK_64)
 #else
-#define STACK_RND_MASK			(0x3ffff >> (PAGE_SHIFT - 12))
+#define STACK_RND_MASK			STACK_RND_MASK_64
 #endif
 
 #ifdef __AARCH64EB__
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index f47528aae321..f8309f8d0ece 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -70,29 +70,36 @@
 
 #ifdef CONFIG_ARM64_FORCE_52BIT
 #define STACK_TOP_MAX		TASK_SIZE_64
-#define TASK_UNMAPPED_BASE	(PAGE_ALIGN(TASK_SIZE / 4))
+#define TASK_UNMAPPED_BASE_64	(PAGE_ALIGN(TASK_SIZE_64 / 4))
 #else
 #define STACK_TOP_MAX		DEFAULT_MAP_WINDOW_64
-#define TASK_UNMAPPED_BASE	(PAGE_ALIGN(DEFAULT_MAP_WINDOW / 4))
+#define TASK_UNMAPPED_BASE_64	(PAGE_ALIGN(DEFAULT_MAP_WINDOW_64 / 4))
 #endif /* CONFIG_ARM64_FORCE_52BIT */
 
+#ifdef CONFIG_COMPAT
+#define TASK_UNMAPPED_BASE_32	(PAGE_ALIGN(TASK_SIZE_32 / 4))
+#define TASK_UNMAPPED_BASE	(test_thread_flag(TIF_32BIT) ? \
+				TASK_UNMAPPED_BASE_32 : TASK_UNMAPPED_BASE_64)
+#else
+#define TASK_UNMAPPED_BASE	TASK_UNMAPPED_BASE_64
+#endif /* CONFIG_COMPAT */
+
+#define STACK_TOP_64		STACK_TOP_MAX
 #ifdef CONFIG_COMPAT
 #define AARCH32_VECTORS_BASE	0xffff0000
+#define STACK_TOP_32		AARCH32_VECTORS_BASE
 #define STACK_TOP		(test_thread_flag(TIF_32BIT) ? \
-				AARCH32_VECTORS_BASE : STACK_TOP_MAX)
+				STACK_TOP_32 : STACK_TOP_64)
 #else
-#define STACK_TOP		STACK_TOP_MAX
+#define STACK_TOP		STACK_TOP_64
 #endif /* CONFIG_COMPAT */
 
-#ifndef CONFIG_ARM64_FORCE_52BIT
-#define arch_get_mmap_end(addr) ((addr > DEFAULT_MAP_WINDOW) ? TASK_SIZE :\
-				DEFAULT_MAP_WINDOW)
-
-#define arch_get_mmap_base_topdown(addr) \
-	((addr > DEFAULT_MAP_WINDOW) ? \
-	current->mm->mmap_base + TASK_SIZE - DEFAULT_MAP_WINDOW :\
-	current->mm->mmap_base)
-#endif /* CONFIG_ARM64_FORCE_52BIT */
+#define arch_get_mmap_end arch_get_mmap_end
+#define arch_get_mmap_base arch_get_mmap_base
+#define arch_get_mmap_base_topdown arch_get_mmap_base_topdown
+unsigned long arch_get_mmap_end(unsigned long addr);
+unsigned long arch_get_mmap_base(unsigned long addr);
+unsigned long arch_get_mmap_base_topdown(unsigned long addr);
 
 extern phys_addr_t arm64_dma_phys_limit;
 #define ARCH_LOW_ADDRESS_LIMIT	(arm64_dma_phys_limit - 1)
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index a38f54cd638c..956cab3ade11 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -38,3 +38,36 @@ int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
 {
 	return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK);
 }
+
+unsigned long arch_get_mmap_end(unsigned long addr)
+{
+#ifdef CONFIG_COMPAT
+	if (in_compat_syscall())
+		return TASK_SIZE_32;
+#endif /* CONFIG_COMPAT */
+#ifndef CONFIG_ARM64_FORCE_52BIT
+	if (addr > DEFAULT_MAP_WINDOW_64)
+		return TASK_SIZE_64;
+#endif /* CONFIG_ARM64_FORCE_52BIT */
+	return DEFAULT_MAP_WINDOW_64;
+}
+unsigned long arch_get_mmap_base(unsigned long addr)
+{
+#ifdef CONFIG_COMPAT
+	if (in_compat_syscall())
+		return current->mm->mmap_compat_base;
+#endif /* CONFIG_COMPAT */
+	return current->mm->mmap_base;
+}
+unsigned long arch_get_mmap_base_topdown(unsigned long addr)
+{
+#ifdef CONFIG_COMPAT
+	if (in_compat_syscall())
+		return current->mm->mmap_compat_base;
+#endif /* CONFIG_COMPAT */
+#ifndef CONFIG_ARM64_FORCE_52BIT
+	if (addr > DEFAULT_MAP_WINDOW_64)
+		return current->mm->mmap_base + TASK_SIZE - DEFAULT_MAP_WINDOW_64;
+#endif /* CONFIG_ARM64_FORCE_52BIT */
+	return current->mm->mmap_base;
+}
-- 
2.31.1