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2016-04-20kbuild: drop FORCE from PHONY targetsMasahiro Yamada
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>
2016-02-22ARM/vdso: Mark the vDSO code read-only after initDavid Brown
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>
2015-10-29ARM: 8449/1: fix bug in vdsomunge swab32 macroH. Nikolaus Schaller
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>
2015-10-19ARM: 8445/1: fix vdsomunge not to depend on glibc specific byteswap.hH. Nikolaus Schaller
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>
2015-07-31ARM: 8405/1: VDSO: fix regression with toolchains lacking ld.bfd executableNathan Lynch
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: Raphaƫl 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>
2015-07-07Merge branches 'fixes' and 'ioremap' into for-linusRussell King
2015-07-03ARM: 8397/1: fix vdsomunge not to depend on glibc specific error.hSzabolcs Nagy
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>
2015-06-06ARM: 8384/1: VDSO: force use of BFD linkerNathan Lynch
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>
2015-06-06ARM: 8385/1: VDSO: group link optionsNathan Lynch
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>
2015-04-21ARM: 8344/1: VDSO: honor CONFIG_VDSO in MakefileNathan Lynch
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>
2015-04-21ARM: 8343/1: VDSO: add build artifacts to .gitignoreNathan Lynch
vdsomunge and vdso.so.raw are outputs that don't get matched by the normal ignore rules. Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2015-03-27ARM: 8330/1: add VDSO user-space codeNathan Lynch
Place VDSO-related user-space code in arch/arm/kernel/vdso/. It is almost completely written in C with some assembly helpers to load the data page address, sample the counter, and fall back to system calls when necessary. The VDSO can service gettimeofday and clock_gettime when CONFIG_ARM_ARCH_TIMER is enabled and the architected timer is present (and correctly configured). It reads the CP15-based virtual counter to compute high-resolution timestamps. Of particular note is that a post-processing step ("vdsomunge") is necessary to produce a shared object which is architecturally allowed to be used by both soft- and hard-float EABI programs. The 2012 edition of the ARM ABI defines Tag_ABI_VFP_args = 3 "Code is compatible with both the base and VFP variants; the user did not permit non-variadic functions to pass FP parameters/results." Unfortunately current toolchains do not support this tag, which is ideally what we would use. The best available option is to ensure that both EF_ARM_ABI_FLOAT_SOFT and EF_ARM_ABI_FLOAT_HARD are unset in the ELF header's e_flags, indicating that the shared object is "old" and should be accepted for backward compatibility's sake. While binutils < 2.24 appear to produce a vdso.so with both flags clear, 2.24 always sets EF_ARM_ABI_FLOAT_SOFT, with no way to inhibit this behavior. So we have to fix things up with a custom post-processing step. In fact, the VDSO code in glibc does much less validation (including checking these flags) than the code for handling conventional file-backed shared libraries, so this is a bit moot unless glibc's VDSO code becomes more strict. Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>