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authorVineeth Vijayan <vvijayan@mvista.com>2014-11-14 14:42:05 +0530
committerMichael Ellerman <mpe@ellerman.id.au>2014-11-17 17:55:11 +1100
commit59994fb01a102a448ba758c9b824a29b4a99cc1b (patch)
tree3dfb16993c500822787ebc76098d2cd5525da0da
parentcf2b1e0eb0c281122b001cc879ca0118bff71255 (diff)
powerpc: Use generic PIE randomization
Back in 2009 we merged 501cb16d3cfd "Randomise PIEs", which added support for randomizing PIE (Position Independent Executable) binaries. That commit added randomize_et_dyn(), which correctly randomized the addresses, but failed to honor PF_RANDOMIZE. That means it was not possible to disable PIE randomization via the personality flag, or /proc/sys/kernel/randomize_va_space. Since then there has been generic support for PIE randomization added to binfmt_elf.c, selectable via ARCH_BINFMT_ELF_RANDOMIZE_PIE. Enabling that allows us to drop randomize_et_dyn(), which means we start honoring PF_RANDOMIZE correctly. It also causes a fairly major change to how we layout PIE binaries. Currently we will place the binary at 512MB-520MB for 32 bit binaries, or 512MB-1.5GB for 64 bit binaries, eg: $ cat /proc/$$/maps 4e550000-4e580000 r-xp 00000000 08:02 129813 /bin/dash 4e580000-4e590000 rw-p 00020000 08:02 129813 /bin/dash 10014110000-10014140000 rw-p 00000000 00:00 0 [heap] 3fffaa3f0000-3fffaa5a0000 r-xp 00000000 08:02 921 /lib/powerpc64le-linux-gnu/libc-2.19.so 3fffaa5a0000-3fffaa5b0000 rw-p 001a0000 08:02 921 /lib/powerpc64le-linux-gnu/libc-2.19.so 3fffaa5c0000-3fffaa5d0000 rw-p 00000000 00:00 0 3fffaa5d0000-3fffaa5f0000 r-xp 00000000 00:00 0 [vdso] 3fffaa5f0000-3fffaa620000 r-xp 00000000 08:02 1246 /lib/powerpc64le-linux-gnu/ld-2.19.so 3fffaa620000-3fffaa630000 rw-p 00020000 08:02 1246 /lib/powerpc64le-linux-gnu/ld-2.19.so 3ffffc340000-3ffffc370000 rw-p 00000000 00:00 0 [stack] With this commit applied we don't do any special randomisation for the binary, and instead rely on mmap randomisation. This means the binary ends up at high addresses, eg: $ cat /proc/$$/maps 3fff99820000-3fff999d0000 r-xp 00000000 08:02 921 /lib/powerpc64le-linux-gnu/libc-2.19.so 3fff999d0000-3fff999e0000 rw-p 001a0000 08:02 921 /lib/powerpc64le-linux-gnu/libc-2.19.so 3fff999f0000-3fff99a00000 rw-p 00000000 00:00 0 3fff99a00000-3fff99a20000 r-xp 00000000 00:00 0 [vdso] 3fff99a20000-3fff99a50000 r-xp 00000000 08:02 1246 /lib/powerpc64le-linux-gnu/ld-2.19.so 3fff99a50000-3fff99a60000 rw-p 00020000 08:02 1246 /lib/powerpc64le-linux-gnu/ld-2.19.so 3fff99a60000-3fff99a90000 r-xp 00000000 08:02 129813 /bin/dash 3fff99a90000-3fff99aa0000 rw-p 00020000 08:02 129813 /bin/dash 3fffc3de0000-3fffc3e10000 rw-p 00000000 00:00 0 [stack] 3fffc55e0000-3fffc5610000 rw-p 00000000 00:00 0 [heap] Although this should be OK, it's possible it might break badly written binaries that make assumptions about the address space layout. Signed-off-by: Vineeth Vijayan <vvijayan@mvista.com> [mpe: Rewrite changelog] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
-rw-r--r--arch/powerpc/Kconfig1
-rw-r--r--arch/powerpc/include/asm/elf.h3
-rw-r--r--arch/powerpc/kernel/process.c9
3 files changed, 2 insertions, 11 deletions
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 46227336aacb..421df5cc6d18 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -88,6 +88,7 @@ config PPC
select ARCH_MIGHT_HAVE_PC_PARPORT
select ARCH_MIGHT_HAVE_PC_SERIO
select BINFMT_ELF
+ select ARCH_BINFMT_ELF_RANDOMIZE_PIE
select OF
select OF_EARLY_FLATTREE
select OF_RESERVED_MEM
diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
index 888d8f3f2524..57d289acb803 100644
--- a/arch/powerpc/include/asm/elf.h
+++ b/arch/powerpc/include/asm/elf.h
@@ -28,8 +28,7 @@
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. */
-extern unsigned long randomize_et_dyn(unsigned long base);
-#define ELF_ET_DYN_BASE (randomize_et_dyn(0x20000000))
+#define ELF_ET_DYN_BASE 0x20000000
#define ELF_CORE_EFLAGS (is_elf2_task() ? 2 : 0)
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index f6b82152e7aa..b4cc7bef6b16 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1654,12 +1654,3 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
return ret;
}
-unsigned long randomize_et_dyn(unsigned long base)
-{
- unsigned long ret = PAGE_ALIGN(base + brk_rnd());
-
- if (ret < base)
- return base;
-
- return ret;
-}