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authorKees Cook <keescook@chromium.org>2017-07-10 15:52:51 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-07-10 16:32:36 -0700
commita73dc5370e153ac63718d850bddf0c9aa9d871e6 (patch)
tree7466025ac85a15dfe00ad32057aa6e365da3ad6b /arch/s390
parent47ebb09d54856500c5a5e14824781902b3bb738e (diff)
s390: reduce ELF_ET_DYN_BASE
Now that explicitly executed loaders are loaded in the mmap region, we have more freedom to decide where we position PIE binaries 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. On 32-bit use 4MB, which is the traditional x86 minimum load location, likely to avoid historically requiring a 4MB page table entry when only a portion of the first 4MB would be used (since the NULL address is avoided). For s390 the position could be 0x10000, but that is needlessly close to the NULL address. Link: http://lkml.kernel.org/r/1498154792-49952-5-git-send-email-keescook@chromium.org Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: James Hogan <james.hogan@imgtec.com> Cc: Pratyush Anand <panand@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/include/asm/elf.h15
1 files changed, 7 insertions, 8 deletions
diff --git a/arch/s390/include/asm/elf.h b/arch/s390/include/asm/elf.h
index ec024c08dabe..c92ed0170be2 100644
--- a/arch/s390/include/asm/elf.h
+++ b/arch/s390/include/asm/elf.h
@@ -193,14 +193,13 @@ struct arch_elf_state {
#define CORE_DUMP_USE_REGSET
#define ELF_EXEC_PAGESIZE 4096
-/* 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. 64-bit
- tasks are aligned to 4GB. */
-#define ELF_ET_DYN_BASE (is_compat_task() ? \
- (STACK_TOP / 3 * 2) : \
- (STACK_TOP / 3 * 2) & ~((1UL << 32) - 1))
+/*
+ * 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_compat_task() ? 0x000400000UL : \
+ 0x100000000UL)
/* This yields a mask that user programs can use to figure out what
instruction set this CPU supports. */