kernel.git/arch/x86/kernel/fpu, branch linux-5.7.y

copy_xstate_to_kernel: Fix typo which caused GDB regression

2020-07-22T07:34:11Z

commit 5714ee50bb4375bd586858ad800b1d9772847452 upstream. This fixes a regression encountered while running the gdb.base/corefile.exp test in GDB's test suite. In my testing, the typo prevented the sw_reserved field of struct fxregs_state from being output to the kernel XSAVES area. Thus the correct mask corresponding to XCR0 was not present in the core file for GDB to interrogate, resulting in the following behavior: [kev@f32-1 gdb]$ ./gdb -q testsuite/outputs/gdb.base/corefile/corefile testsuite/outputs/gdb.base/corefile/corefile.core Reading symbols from testsuite/outputs/gdb.base/corefile/corefile... [New LWP 232880] warning: Unexpected size of section `.reg-xstate/232880' in core file. With the typo fixed, the test works again as expected. Signed-off-by: Kevin Buettner Fixes: 9e4636545933 ("copy_xstate_to_kernel(): don't leave parts of destination uninitialized") Cc: Al Viro Cc: Dave Airlie Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

x86/fpu: Reset MXCSR to default in kernel_fpu_begin()

2020-07-22T07:33:59Z

[ Upstream commit 7ad816762f9bf89e940e618ea40c43138b479e10 ] Previously, kernel floating point code would run with the MXCSR control register value last set by userland code by the thread that was active on the CPU core just before kernel call. This could affect calculation results if rounding mode was changed, or a crash if a FPU/SIMD exception was unmasked. Restore MXCSR to the kernel's default value. [ bp: Carve out from a bigger patch by Petteri, add feature check, add FNINIT call too (amluto). ] Signed-off-by: Petteri Aimonen Signed-off-by: Borislav Petkov Link: https://bugzilla.kernel.org/show_bug.cgi?id=207979 Link: https://lkml.kernel.org/r/20200624114646.28953-2-bp@alien8.de Signed-off-by: Sasha Levin

copy_xstate_to_kernel(): don't leave parts of destination uninitialized

2020-05-27T21:06:31Z

copy the corresponding pieces of init_fpstate into the gaps instead. Cc: stable@kernel.org Tested-by: Alexander Potapenko Acked-by: Borislav Petkov Signed-off-by: Al Viro

x86/pkeys: Add check for pkey "overflow"

2020-02-24T19:25:21Z

Alex Shi reported the pkey macros above arch_set_user_pkey_access() to be unused. They are unused, and even refer to a nonexistent CONFIG option. But, they might have served a good use, which was to ensure that the code does not try to set values that would not fit in the PKRU register. As it stands, a too-large 'pkey' value would be likely to silently overflow the u32 new_pkru_bits. Add a check to look for overflows. Also add a comment to remind any future developer to closely examine the types used to store pkey values if arch_max_pkey() ever changes. This boots and passes the x86 pkey selftests. Reported-by: Alex Shi Signed-off-by: Dave Hansen Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20200122165346.AD4DA150@viggo.jf.intel.com

x86/fpu/xstate: Warn when checking alignment of disabled xfeatures

2020-02-12T14:43:34Z

An XSAVES component's alignment/offset is meaningful only when the feature is enabled. Return zero and WARN_ONCE on checking alignment of disabled features. Signed-off-by: Yu-cheng Yu Signed-off-by: Borislav Petkov Reviewed-by: Dave Hansen Link: https://lkml.kernel.org/r/20200109211452.27369-4-yu-cheng.yu@intel.com

x86/fpu/xstate: Fix XSAVES offsets in setup_xstate_comp()

2020-02-12T14:43:31Z

In setup_xstate_comp(), each XSAVES component offset starts from the end of its preceding component plus alignment. A disabled feature does not take space and its offset should be set to the end of its preceding one with no alignment. However, in this case, alignment is incorrectly added to the offset, which can cause the next component to have a wrong offset. This problem has not been visible because currently there is no xfeature requiring alignment. Fix it by tracking the next starting offset only from enabled xfeatures. To make it clear, also change the function name to setup_xstate_comp_offsets(). [ bp: Fix a typo in the comment above it, while at it. ] Signed-off-by: Yu-cheng Yu Signed-off-by: Borislav Petkov Reviewed-by: Dave Hansen Link: https://lkml.kernel.org/r/20200109211452.27369-3-yu-cheng.yu@intel.com

x86/fpu/xstate: Fix last_good_offset in setup_xstate_features()

2020-02-11T18:54:04Z

The function setup_xstate_features() uses CPUID to find each xfeature's standard-format offset and size. Since XSAVES always uses the compacted format, supervisor xstates are *NEVER* in the standard-format and their offsets are left as -1's. However, they are still being tracked as last_good_offset. Fix it by tracking only user xstate offsets. [ bp: Use xfeature_is_supervisor() and save an indentation level. Drop now unused xfeature_is_user(). ] Signed-off-by: Yu-cheng Yu Signed-off-by: Borislav Petkov Reviewed-by: Dave Hansen Link: https://lkml.kernel.org/r/20200109211452.27369-2-yu-cheng.yu@intel.com

x86/fpu: Deactivate FPU state after failure during state load

2020-01-07T12:44:42Z

In __fpu__restore_sig(), fpu_fpregs_owner_ctx needs to be reset if the FPU state was not fully restored. Otherwise the following may happen (on the same CPU): Task A Task B fpu_fpregs_owner_ctx *active* A.fpu __fpu__restore_sig() ctx switch load B.fpu *active* B.fpu fpregs_lock() copy_user_to_fpregs_zeroing() copy_kernel_to_xregs() *modify* copy_user_to_xregs() *fails* fpregs_unlock() ctx switch skip loading B.fpu, *active* B.fpu In the success case, fpu_fpregs_owner_ctx is set to the current task. In the failure case, the FPU state might have been modified by loading the init state. In this case, fpu_fpregs_owner_ctx needs to be reset in order to ensure that the FPU state of the following task is loaded from saved state (and not skipped because it was the previous state). Reset fpu_fpregs_owner_ctx after a failure during restore occurred, to ensure that the FPU state for the next task is always loaded. The problem was debugged-by Yu-cheng Yu . [ bp: Massage commit message. ] Fixes: 5f409e20b7945 ("x86/fpu: Defer FPU state load until return to userspace") Reported-by: Yu-cheng Yu Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Borislav Petkov Cc: Andy Lutomirski Cc: Dave Hansen Cc: Fenghua Yu Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Jann Horn Cc: Peter Zijlstra Cc: "Ravi V. Shankar" Cc: Rik van Riel Cc: Thomas Gleixner Cc: Tony Luck Cc: x86-ml Link: https://lkml.kernel.org/r/20191220195906.plk6kpmsrikvbcfn@linutronix.de

x86/fpu/xstate: Make xfeature_is_supervisor()/xfeature_is_user() return bool

2020-01-06T18:08:40Z

Have both xfeature_is_supervisor()/xfeature_is_user() return bool because they are used only in boolean context. Suggested-by: Borislav Petkov Signed-off-by: Yu-cheng Yu Signed-off-by: Borislav Petkov Acked-by: Sebastian Andrzej Siewior Cc: Andy Lutomirski Cc: Dave Hansen Cc: Fenghua Yu Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Peter Zijlstra Cc: "Ravi V. Shankar" Cc: Rik van Riel Cc: Thomas Gleixner Cc: Tony Luck Cc: x86-ml Link: https://lkml.kernel.org/r/20191212210855.19260-3-yu-cheng.yu@intel.com

x86/fpu/xstate: Fix small issues

2020-01-06T16:31:11Z

In response to earlier comments, fix small issues before introducing XSAVES supervisor states: - Fix comments of xfeature_is_supervisor(). - Replace ((u64)1 << 63) with XCOMP_BV_COMPACTED_FORMAT. No functional changes. Signed-off-by: Yu-cheng Yu Signed-off-by: Borislav Petkov Reviewed-by: Dave Hansen Reviewed-by: Tony Luck Acked-by: Sebastian Andrzej Siewior Cc: Andy Lutomirski Cc: Dave Hansen Cc: Fenghua Yu Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Peter Zijlstra Cc: "Ravi V. Shankar" Cc: Rik van Riel Cc: Thomas Gleixner Cc: x86-ml Link: https://lkml.kernel.org/r/20191212210855.19260-2-yu-cheng.yu@intel.com