[PATCH 3/4] powerpc: Reduce ELF_ET_DYN_BASE

From	Kees Cook <keescook@chromium.org>
Newsgroups	linux.kernel
Subject	[PATCH 3/4] powerpc: Reduce ELF_ET_DYN_BASE
Date	2017-06-22 20:10 +0200
Message-ID	<tVeIi-8fG-9@gated-at.bofh.it> (permalink)
References	<tVeIi-8fG-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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/powerpc/include/asm/elf.h | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
index 09bde6e34f5d..548d9a411a0d 100644
--- a/arch/powerpc/include/asm/elf.h
+++ b/arch/powerpc/include/asm/elf.h
@@ -23,12 +23,13 @@
 #define CORE_DUMP_USE_REGSET
 #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.  */
-
-#define ELF_ET_DYN_BASE	0x20000000
+/*
+ * 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		(is_32bit_task() ? 0x000400000UL : \
+						   0x100000000UL)
 
 #define ELF_CORE_EFLAGS (is_elf2_task() ? 2 : 0)
 
-- 
2.7.4

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[PATCH 3/4] powerpc: Reduce ELF_ET_DYN_BASE Kees Cook <keescook@chromium.org> - 2017-06-22 20:10 +0200
  Re: [PATCH 3/4] powerpc: Reduce ELF_ET_DYN_BASE Michael Ellerman <mpe@ellerman.id.au> - 2017-06-23 09:10 +0200
    Re: [PATCH 3/4] powerpc: Reduce ELF_ET_DYN_BASE Kees Cook <keescook@chromium.org> - 2017-06-23 22:10 +0200
      Re: [PATCH 3/4] powerpc: Reduce ELF_ET_DYN_BASE Michael Ellerman <mpe@ellerman.id.au> - 2017-06-26 15:10 +0200
        Re: [PATCH 3/4] powerpc: Reduce ELF_ET_DYN_BASE Kees Cook <keescook@chromium.org> - 2017-06-26 20:30 +0200

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