These targets are marked as PHONY. No need to add FORCE to their dependency. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Signed-off-by: Michal Marek <mmarek@suse.com>
Although the ARM vDSO is cleanly separated by code/data with the code being read-only in userspace mappings, the code page is still writable from the kernel. There have been exploits (such as http://itszn.com/blog/?p=21) that take advantage of this on x86 to go from a bad kernel write to full root. Prevent this specific exploit class on ARM as well by putting the vDSO code page in post-init read-only memory as well. Before: vdso: 1 text pages at base 80927000 root@Vexpress:/ cat /sys/kernel/debug/kernel_page_tables ---[ Modules ]--- ---[ Kernel Mapping ]--- 0x80000000-0x80100000 1M RW NX SHD 0x80100000-0x80600000 5M ro x SHD 0x80600000-0x80800000 2M ro NX SHD 0x80800000-0xbe000000 984M RW NX SHD After: vdso: 1 text pages at base 8072b000 root@Vexpress:/ cat /sys/kernel/debug/kernel_page_tables ---[ Modules ]--- ---[ Kernel Mapping ]--- 0x80000000-0x80100000 1M RW NX SHD 0x80100000-0x80600000 5M ro x SHD 0x80600000-0x80800000 2M ro NX SHD 0x80800000-0xbe000000 984M RW NX SHD Inspired by https://lkml.org/lkml/2016/1/19/494 based on work by the PaX Team, Brad Spengler, and Kees Cook. Signed-off-by: David Brown <david.brown@linaro.org> Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Borislav Petkov <bp@alien8.de> Cc: Brad Spengler <spender@grsecurity.net> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Emese Revfy <re.emese@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mathias Krause <minipli@googlemail.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Nathan Lynch <nathan_lynch@mentor.com> Cc: PaX Team <pageexec@freemail.hu> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Russell King <linux@arm.linux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kernel-hardening@lists.openwall.com Cc: linux-arch <linux-arch@vger.kernel.org> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1455748879-21872-8-git-send-email-keescook@chromium.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Commit 8a603f91cc48 ("ARM: 8445/1: fix vdsomunge not to depend on
glibc specific byteswap.h") unfortunately introduced a bug created but
not found during discussion and patch simplification.
Reported-by: Efraim Yawitz <efraim.yawitz@gmail.com>
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Fixes: 8a603f91cc48 ("ARM: 8445/1: fix vdsomunge not to depend on glibc specific byteswap.h")
Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
If the host toolchain is not glibc based then the arm kernel build fails with HOSTCC arch/arm/vdso/vdsomunge arch/arm/vdso/vdsomunge.c:48:22: fatal error: byteswap.h: No such file or directory Observed: with omap2plus_defconfig and compile on Mac OS X with arm ELF cross-compiler. Reason: byteswap.h is a glibc only header. Solution: replace by private byte-swapping macros (taken from arch/mips/boot/elf2ecoff.c and kindly improved by Russell King) Tested to compile on Mac OS X 10.9.5 host. Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com> Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
The Sourcery CodeBench Lite 2014.05 toolchain (gcc 4.8.3, binutils
2.24.51) has a GCC which implements -fuse-ld, and it doesn't include
the gold linker, but it lacks an ld.bfd executable in its
installation. This means that passing -fuse-ld=bfd fails with:
VDSO arch/arm/vdso/vdso.so.raw
collect2: fatal error: cannot find 'ld'
Arguably this is a deficiency in the toolchain, but I suspect it's
commonly used enough that it's worth accommodating: just use
cc-ldoption (to cause a link attempt) instead of cc-option to test
whether we can use -fuse-ld. So -fuse-ld=bfd won't be used with this
toolchain, but the build will rightly succeed, just as it does for
toolchains which don't implement -fuse-ld (and don't use gold as the
default linker).
Note: this will change the failure mode for a corner case I was trying
to handle in d2b30cd4b722, where the toolchain defaults to the gold
linker and the BFD linker is not found in PATH, from:
VDSO arch/arm/vdso/vdso.so.raw
collect2: fatal error: cannot find 'ld'
i.e. the BFD linker is not found, to:
OBJCOPY arch/arm/vdso/vdso.so
BFD: arch/arm/vdso/vdso.so: Not enough room for program headers, try
linking with -N
that is, we fail to prevent gold from being used as the linker, and it
produces an object that objcopy can't digest.
Reported-by: Baruch Siach <baruch@tkos.co.il>
Tested-by: Baruch Siach <baruch@tkos.co.il>
Tested-by: Raphaël Poggi <poggi.raph@gmail.com>
Fixes: d2b30cd4b722 ("ARM: 8384/1: VDSO: force use of BFD linker")
Cc: stable@vger.kernel.org
Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
If the host toolchain is not glibc based then the arm kernel build
fails with
arch/arm/vdso/vdsomunge.c:53:19: fatal error: error.h: No such file or directory
error.h is a glibc only header (ie not available in musl, newlib and
bsd libcs). Changed the error reporting to standard conforming code
to avoid depending on specific C implementations.
Signed-off-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Fixes: 8512287a8165 ("ARM: 8330/1: add VDSO user-space code")
Cc: stable@vger.kernel.org
Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
When using a toolchain with gold as the default linker, the VDSO build fails: VDSO arch/arm/vdso/vdso.so.raw HOSTCC arch/arm/vdso/vdsomunge MUNGE arch/arm/vdso/vdso.so.dbg OBJCOPY arch/arm/vdso/vdso.so BFD: arch/arm/vdso/vdso.so: Not enough room for program headers, try linking with -N For whatever reason, ld.gold is omitting an exidx program header that ld.bfd emits, and even when I work around that, I don't get a working VDSO. For now, instead of supporting gold (which will fail to link the kernel anyway since it does not implement --pic-veneer), direct the compiler to use the traditional bfd linker. This is accomplished by using -fuse-ld, which is implemented in GCC 4.8 and later. Note: one limitation of this is that if the toolchain is configured to use gold by default, and the bfd linker is not in $PATH, the VDSO build will fail: VDSO arch/arm/vdso/vdso.so.raw collect2: fatal error: cannot find 'ld' This will happen if CROSS_COMPILE begins with a path such as /opt/bin/arm-linux-gnu- but /opt/bin is not in $PATH. This is considered an acceptable corner-case limitation and is easily worked around. Additonal note: we use cc-option instead of cc-ldoption so that -fuse-ld=bfd is placed in the command line if the compiler recognizes the option. Using cc-ldoption results in an attempt to link, which fails in the situation just described, causing -fuse-ld=bfd to be omitted and gold to be used for the VDSO link, which is what we're trying to prevent. Reported-by: Stefan Agner <stefan@agner.ch> Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Currently the VDSO's link options are kind of a mess spread between ccflags-y and cmd_vdsold. Collect linker directives into one variable, VDSO_LDFLAGS, and use that in cmd_vdsold. Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
When CONFIG_VDSO=n, the build normally does not enter arch/arm/vdso/ because arch/arm/Makefile does not add it to core-y. However, if the user runs 'make arch/arm/vdso/' the VDSO targets will get visited. This is because the VDSO Makefile itself does not consider the value of CONFIG_VDSO. It is arguably better and more consistent behavior to generate an empty built-in.o when CONFIG_VDSO=n and the user attempts to build arch/arm/vdso/. It's nicer because it doesn't try to build things that Kconfig dependencies are there to prevent (e.g. the dependency on AEABI), and it's less confusing than building objects that won't be used in the final image. Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>