Re: [PATCH v5 02/27] x86/fpu/xstate: Change names to separate XSAVES system and user states
From: Borislav Petkov <bp@alien8.de>
Date: 2018-10-15 17:03:37
Also in:
linux-api, linux-arch, linux-doc, linux-mm
On Thu, Oct 11, 2018 at 08:14:58AM -0700, Yu-cheng Yu wrote:
Control Flow Enforcement (CET) MSRs are XSAVES system/supervisor states. To support CET, we introduce XSAVES system states first. XSAVES is a "supervisor" instruction and, comparing to XSAVE, saves additional "supervisor" states that can be modified only from CPL 0. However, these states are per-task and not kernel's own. Rename "supervisor" states to "system" states to clearly separate them from "user" states. Signed-off-by: Yu-cheng Yu <redacted> --- arch/x86/include/asm/fpu/internal.h | 4 +- arch/x86/include/asm/fpu/xstate.h | 20 +++---- arch/x86/kernel/fpu/core.c | 4 +- arch/x86/kernel/fpu/init.c | 2 +- arch/x86/kernel/fpu/signal.c | 6 +-- arch/x86/kernel/fpu/xstate.c | 82 ++++++++++++++--------------- 6 files changed, 57 insertions(+), 61 deletions(-)
...
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diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 87a57b7642d3..e7cbaed12ef1 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c@@ -51,13 +51,14 @@ static short xsave_cpuid_features[] __initdata = { }; /* - * Mask of xstate features supported by the CPU and the kernel: + * Mask of supported 'user' xstate features derived from boot_cpu_has() and + * SUPPORTED_XFEATURES_MASK.
<--- This comment here looks like a good place to put some blurb about user and system states, what they are, what the distinction is and so on.
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*/ -u64 xfeatures_mask __read_mostly; +u64 xfeatures_mask_user __read_mostly; static unsigned int xstate_offsets[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1}; static unsigned int xstate_sizes[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1}; -static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8]; +static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask_user)*8]; /* * The XSAVE area of kernel can be in standard or compacted format;@@ -82,7 +83,7 @@ void fpu__xstate_clear_all_cpu_caps(void) */ int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name) { - u64 xfeatures_missing = xfeatures_needed & ~xfeatures_mask; + u64 xfeatures_missing = xfeatures_needed & ~xfeatures_mask_user; if (unlikely(feature_name)) { long xfeature_idx, max_idx;@@ -113,14 +114,11 @@ int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name) } EXPORT_SYMBOL_GPL(cpu_has_xfeatures); -static int xfeature_is_supervisor(int xfeature_nr) +static int xfeature_is_system(int xfeature_nr) { /* - * We currently do not support supervisor states, but if - * we did, we could find out like this. - * * SDM says: If state component 'i' is a user state component, - * ECX[0] return 0; if state component i is a supervisor + * ECX[0] return 0; if state component i is a system
is 0
* state component, ECX[0] returns 1.
is 1.
*/ u32 eax, ebx, ecx, edx;
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@@ -242,7 +238,7 @@ void fpu__init_cpu_xstate(void) */ static int xfeature_enabled(enum xfeature xfeature) { - return !!(xfeatures_mask & (1UL << xfeature)); + return !!(xfeatures_mask_user & BIT_ULL(xfeature)); } /*@@ -272,7 +268,7 @@ static void __init setup_xstate_features(void) cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx); /* - * If an xfeature is supervisor state, the offset + * If an xfeature is system state, the offset
is a system state, ...
* in EBX is invalid. We leave it to -1. */ if (xfeature_is_user(i))
--
Regards/Gruss,
Boris.
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