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Now that explicitly executed loaders are loaded in the mmap region,
position PIE binaries lower in the address space to avoid possible
collisions with mmap or stack regions. For 64-bit, align to 4GB to
allow runtimes to use the entire 32-bit address space for 32-bit
pointers.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/arm64/include/asm/elf.h | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 5d1700425efe..f742af8f7c42 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -113,12 +113,13 @@
#define ELF_EXEC_PAGESIZE PAGE_SIZE

/*
- * This is the location that an ET_DYN program is loaded if exec'ed. Typical
- * use of this is to invoke "./ld.so someprog" to test out a new version of
- * the loader. We need to make sure that it is out of the way of the program
- * that it will "exec", and that there is sufficient room for the brk.
+ * This is the base location for PIE (ET_DYN with INTERP) loads. On
+ * 64-bit, this is raised to 4GB to leave the entire 32-bit address
+ * space open for things that want to use the area for 32-bit pointers.
*/
-#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3)
+#define ELF_ET_DYN_BASE (test_thread_flag(TIF_32BIT) ? \
+ 0x000400000UL : \
+ 0x100000000UL)

#ifndef __ASSEMBLY__

@@ -173,8 +174,6 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm,

#ifdef CONFIG_COMPAT

-#define COMPAT_ELF_ET_DYN_BASE (2 * TASK_SIZE_32 / 3)
-
/* AArch32 registers. */
#define COMPAT_ELF_NGREG 18
typedef unsigned int compat_elf_greg_t;
--
2.7.4
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