Re: [PATCH] Fix offset2lib issue for x86*, ARM*, PowerPC and MIPS

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 27 Feb 2015 10:21:36 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:

> > +/* Not all architectures implement mmap_rnd() */
> > +unsigned long __weak mmap_rnd(void)
> > +{
> > +}
> > +
> > +/*
> > + * Not all architectures use randomize_et_dyn(), so use __weak to let the
> > + * linker omit it from vmlinux
> > + */
> > +unsigned long __weak randomize_et_dyn(unsigned long base)
> > +{
> > +	unsigned long ret;
> > +
> > +	if ((current->personality & ADDR_NO_RANDOMIZE) ||
> > +		!(current->flags & PF_RANDOMIZE))
> > +		return base;
> > +	ret = base + mmap_rnd();
> > +	return max(ret, base);
> > +}
> > +
> 
> Didn't we have some trouble with some compilers when the weak function
> (mmap_rnd) was defined and used in the same file i.e. the wrong one was
> used?

I have vague memories, but I forget the details.

This sucks anyway - let's do it properly.

I'm just flinging together trollpatches here.  Someone please review,
test and fix this stuff.  Kees?

diff -puN arch/arm/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2 arch/arm/Kconfig
--- a/arch/arm/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2
+++ a/arch/arm/Kconfig
@@ -5,6 +5,7 @@ config ARM
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAVE_CUSTOM_GPIO_H
 	select ARCH_HAS_GCOV_PROFILE_ALL
+	select ARCH_HAVE_ELF_ASLR
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_USE_BUILTIN_BSWAP
diff -puN arch/arm64/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2 arch/arm64/Kconfig
--- a/arch/arm64/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2
+++ a/arch/arm64/Kconfig
@@ -9,6 +9,7 @@ config ARM64
 	select ARCH_WANT_OPTIONAL_GPIOLIB
 	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 	select ARCH_WANT_FRAME_POINTERS
+	select ARCH_HAVE_ELF_ASLR
 	select ARM_AMBA
 	select ARM_ARCH_TIMER
 	select ARM_GIC
diff -puN arch/mips/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2 arch/mips/Kconfig
--- a/arch/mips/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2
+++ a/arch/mips/Kconfig
@@ -39,6 +39,7 @@ config MIPS
 	select HAVE_MEMBLOCK
 	select HAVE_MEMBLOCK_NODE_MAP
 	select ARCH_DISCARD_MEMBLOCK
+	select ARCH_HAVE_ELF_ASLR
 	select GENERIC_SMP_IDLE_THREAD
 	select BUILDTIME_EXTABLE_SORT
 	select GENERIC_CLOCKEVENTS
diff -puN arch/powerpc/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2 arch/powerpc/Kconfig
--- a/arch/powerpc/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2
+++ a/arch/powerpc/Kconfig
@@ -97,6 +97,7 @@ config PPC
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select SYSCTL_EXCEPTION_TRACE
 	select ARCH_WANT_OPTIONAL_GPIOLIB
+	select ARCH_HAVE_ELF_ASLR
 	select VIRT_TO_BUS if !PPC64
 	select HAVE_IDE
 	select HAVE_IOREMAP_PROT
diff -puN arch/x86/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2 arch/x86/Kconfig
--- a/arch/x86/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2
+++ a/arch/x86/Kconfig
@@ -28,6 +28,7 @@ config X86
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_MIGHT_HAVE_PC_SERIO
+	select ARCH_HAVE_ELF_ASLR
 	select HAVE_AOUT if X86_32
 	select HAVE_UNSTABLE_SCHED_CLOCK
 	select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
diff -puN fs/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2 fs/Kconfig
--- a/fs/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2
+++ a/fs/Kconfig
@@ -50,6 +50,9 @@ config FS_DAX
 
 endif # BLOCK
 
+config ARCH_HAVE_ELF_ASLR
+	bool
+
 # Posix ACL utility routines
 #
 # Note: Posix ACLs can be implemented without these helpers.  Never use
diff -puN fs/binfmt_elf.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2 fs/binfmt_elf.c
--- a/fs/binfmt_elf.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix-fix-2
+++ a/fs/binfmt_elf.c
@@ -2301,15 +2301,7 @@ out:
 
 #endif		/* CONFIG_ELF_CORE */
 
-/* Not all architectures implement mmap_rnd() */
-unsigned long __weak mmap_rnd(void)
-{
-}
-
-/*
- * Not all architectures use randomize_et_dyn(), but there doesn't seem to be
- * a compile-time way of avoiding its generation.
- */
+#ifdef ARCH_HAVE_ELF_ASLR
 unsigned long randomize_et_dyn(unsigned long base)
 {
 	unsigned long ret;
@@ -2320,6 +2312,7 @@ unsigned long randomize_et_dyn(unsigned
 	ret = base + mmap_rnd();
 	return max(ret, base);
 }
+#endif
 
 static int __init init_elf_binfmt(void)
 {
_