kernel.git/arch/powerpc/include/asm/thread_info.h, branch linux-3.17.y

powerpc: Don't corrupt transactional state when using FP/VMX in kernel

2014-01-15T02:59:11Z

Currently, when we have a process using the transactional memory facilities on POWER8 (that is, the processor is in transactional or suspended state), and the process enters the kernel and the kernel then uses the floating-point or vector (VMX/Altivec) facility, we end up corrupting the user-visible FP/VMX/VSX state. This happens, for example, if a page fault causes a copy-on-write operation, because the copy_page function will use VMX to do the copy on POWER8. The test program below demonstrates the bug. The bug happens because when FP/VMX state for a transactional process is stored in the thread_struct, we store the checkpointed state in .fp_state/.vr_state and the transactional (current) state in .transact_fp/.transact_vr. However, when the kernel wants to use FP/VMX, it calls enable_kernel_fp() or enable_kernel_altivec(), which saves the current state in .fp_state/.vr_state. Furthermore, when we return to the user process we return with FP/VMX/VSX disabled. The next time the process uses FP/VMX/VSX, we don't know which set of state (the current register values, .fp_state/.vr_state, or .transact_fp/.transact_vr) we should be using, since we have no way to tell if we are still in the same transaction, and if not, whether the previous transaction succeeded or failed. Thus it is necessary to strictly adhere to the rule that if FP has been enabled at any point in a transaction, we must keep FP enabled for the user process with the current transactional state in the FP registers, until we detect that it is no longer in a transaction. Similarly for VMX; once enabled it must stay enabled until the process is no longer transactional. In order to keep this rule, we add a new thread_info flag which we test when returning from the kernel to userspace, called TIF_RESTORE_TM. This flag indicates that there is FP/VMX/VSX state to be restored before entering userspace, and when it is set the .tm_orig_msr field in the thread_struct indicates what state needs to be restored. The restoration is done by restore_tm_state(). The TIF_RESTORE_TM bit is set by new giveup_fpu/altivec_maybe_transactional helpers, which are called from enable_kernel_fp/altivec, giveup_vsx, and flush_fp/altivec_to_thread instead of giveup_fpu/altivec. The other thing to be done is to get the transactional FP/VMX/VSX state from .fp_state/.vr_state when doing reclaim, if that state has been saved there by giveup_fpu/altivec_maybe_transactional. Having done this, we set the FP/VMX bit in the thread's MSR after reclaim to indicate that that part of the state is now valid (having been reclaimed from the processor's checkpointed state). Finally, in the signal handling code, we move the clearing of the transactional state bits in the thread's MSR a bit earlier, before calling flush_fp_to_thread(), so that we don't unnecessarily set the TIF_RESTORE_TM bit. This is the test program: /* Michael Neuling 4/12/2013 * * See if the altivec state is leaked out of an aborted transaction due to * kernel vmx copy loops. * * gcc -m64 htm_vmxcopy.c -o htm_vmxcopy * */ /* We don't use all of these, but for reference: */ int main(int argc, char *argv[]) { long double vecin = 1.3; long double vecout; unsigned long pgsize = getpagesize(); int i; int fd; int size = pgsize*16; char tmpfile[] = "/tmp/page_faultXXXXXX"; char buf[pgsize]; char *a; uint64_t aborted = 0; fd = mkstemp(tmpfile); assert(fd >= 0); memset(buf, 0, pgsize); for (i = 0; i < size; i += pgsize) assert(write(fd, buf, pgsize) == pgsize); unlink(tmpfile); a = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0); assert(a != MAP_FAILED); asm __volatile__( "lxvd2x 40,0,%[vecinptr] ; " // set 40 to initial value TBEGIN "beq 3f ;" TSUSPEND "xxlxor 40,40,40 ; " // set 40 to 0 "std 5, 0(%[map]) ;" // cause kernel vmx copy page TABORT TRESUME TEND "li %[res], 0 ;" "b 5f ;" "3: ;" // Abort handler "li %[res], 1 ;" "5: ;" "stxvd2x 40,0,%[vecoutptr] ; " : [res]"=r"(aborted) : [vecinptr]"r"(&vecin), [vecoutptr]"r"(&vecout), [map]"r"(a) : "memory", "r0", "r3", "r4", "r5", "r6", "r7"); if (aborted && (vecin != vecout)){ printf("FAILED: vector state leaked on abort %f != %f\n", (double)vecin, (double)vecout); exit(1); } munmap(a, size); close(fd); printf("PASSED!\n"); return 0; } Signed-off-by: Paul Mackerras Signed-off-by: Benjamin Herrenschmidt

powerpc: Reclaim two unused thread_info flag bits

2014-01-15T02:59:07Z

TIF_PERFMON_WORK and TIF_PERFMON_CTXSW are completely unused. They appear to be related to the old perfmon2 code, which has been superseded by the perf_event infrastructure. This removes their definitions so that the bits can be used for other purposes. Signed-off-by: Paul Mackerras Signed-off-by: Benjamin Herrenschmidt

Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc

2013-11-20T23:13:47Z

Pull powerpc LE updates from Ben Herrenschmidt: "With my previous pull request I mentioned some remaining Little Endian patches, notably support for our new ABI, which I was sitting on making sure it was all finalized. The toolchain folks confirmed it now, the new ABI is stable and merged with gcc, so we are all good. Oh and we actually missed the actual Kconfig switch for LE so here it is, along with a couple more bug fixes. I have more fixes but not related to LE so I'll send them as a separate pull request tomorrow, let's get this one out of the way. Note that this supports running user space binaries using the new ABI, but the kernel itself still needs to be built with the old one. We'll bring fixes for that after -rc1. Here's Anton log that goes with this series: This patch series adds support for the new ABI, LPAR support for H_SET_MODE and finally adds a kconfig option and defconfig. ABIv2 support was recently committed to binutils and gcc, and should be merged into glibc soon. There are a number of very nice improvements including the removal of function descriptors. Rusty's kernel patches allow binaries of either ABI to work, easing the transition" * 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc: powerpc: Wrong DWARF CFI in the kernel vdso for little-endian / ELFv2 powerpc: Add pseries_le_defconfig powerpc: Add CONFIG_CPU_LITTLE_ENDIAN kernel config option. powerpc: Don't use ELFv2 ABI to build the kernel powerpc: ELF2 binaries signal handling powerpc: ELF2 binaries launched directly. powerpc: Set eflags correctly for ELF ABIv2 core dumps. powerpc: Add TIF_ELF2ABI flag. pseries: Add H_SET_MODE to change exception endianness powerpc/pseries: Fix endian issues in pseries EEH code

powerpc: Add TIF_ELF2ABI flag.

2013-11-20T22:19:17Z

Little endian ppc64 is getting an exciting new ABI. This is reflected by the bottom two bits of e_flags in the ELF header: 0 == legacy binaries (v1 ABI) 1 == binaries using the old ABI (compiled with a new toolchain) 2 == binaries using the new ABI. We store this in a thread flag, because we need to set it in core dumps and for signal delivery. Our chief concern is that it doesn't use function descriptors. Signed-off-by: Rusty Russell Signed-off-by: Anton Blanchard Signed-off-by: Benjamin Herrenschmidt

preempt: Make PREEMPT_ACTIVE generic

2013-11-13T19:21:47Z

No point in having this bit defined by architecture. Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20130917183629.090698799@linutronix.de

powerpc: Syscall hooks for context tracking subsystem

2013-05-14T06:00:19Z

This is the syscall slow path hooks for context tracking subsystem, corresponding to [PATCH] x86: Syscall hooks for userspace RCU extended QS commit bf5a3c13b939813d28ce26c01425054c740d6731 TIF_MEMDIE is moved to the second 16-bits (with value 17), as it seems there is no asm code using it. TIF_NOHZ is added to _TIF_SYCALL_T_OR_A, so it is better for it to be in the same 16 bits with others in the group, so in the asm code, andi. with this group could work. Signed-off-by: Li Zhong Acked-by: Frederic Weisbecker Signed-off-by: Benjamin Herrenschmidt

arch: Consolidate tsk_is_polling()

2013-04-08T15:39:22Z

Move it to a common place. Preparatory patch for implementing set/clear for the idle need_resched poll implementation. Signed-off-by: Thomas Gleixner Cc: Linus Torvalds Cc: Rusty Russell Cc: Paul McKenney Cc: Peter Zijlstra Reviewed-by: Cc: Srivatsa S. Bhat Cc: Magnus Damm Link: http://lkml.kernel.org/r/20130321215233.446034505@linutronix.de Signed-off-by: Thomas Gleixner

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal

2012-10-12T01:49:08Z

Pull pile 2 of execve and kernel_thread unification work from Al Viro: "Stuff in there: kernel_thread/kernel_execve/sys_execve conversions for several more architectures plus assorted signal fixes and cleanups. There'll be more (in particular, real fixes for the alpha do_notify_resume() irq mess)..." * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal: (43 commits) alpha: don't open-code trace_report_syscall_{enter,exit} Uninclude linux/freezer.h m32r: trim masks avr32: trim masks tile: don't bother with SIGTRAP in setup_frame microblaze: don't bother with SIGTRAP in setup_rt_frame() mn10300: don't bother with SIGTRAP in setup_frame() frv: no need to raise SIGTRAP in setup_frame() x86: get rid of duplicate code in case of CONFIG_VM86 unicore32: remove pointless test h8300: trim _TIF_WORK_MASK parisc: decide whether to go to slow path (tracesys) based on thread flags parisc: don't bother looping in do_signal() parisc: fix double restarts bury the rest of TIF_IRET sanitize tsk_is_polling() bury _TIF_RESTORE_SIGMASK unicore32: unobfuscate _TIF_WORK_MASK mips: NOTIFY_RESUME is not needed in TIF masks mips: merge the identical "return from syscall" per-ABI code ... Conflicts: arch/arm/include/asm/thread_info.h

sanitize tsk_is_polling()

2012-10-01T13:58:13Z

Make default just return 0. The current default (checking TIF_POLLING_NRFLAG) is taken to architectures that need it; ones that don't do polling in their idle threads don't need to defined TIF_POLLING_NRFLAG at all. ia64 defined both TS_POLLING (used by its tsk_is_polling()) and TIF_POLLING_NRFLAG (not used at all). Killed the latter... Signed-off-by: Al Viro

powerpc/kprobe: Introduce a new thread flag

2012-09-18T05:32:39Z

We need to add a new thread flag, TIF_EMULATE_STACK_STORE, for emulating stack store operation while exiting exception. Signed-off-by: Tiejun Chen Signed-off-by: Benjamin Herrenschmidt