[RFC PATCH v6 03/26] x86/fpu/xstate: Change names to separate XSAVES system and user states

Yu-cheng Yu
2018-11-20T08:19:56Z

Control-flow Enforcement (CET) MSR contents are XSAVES system states.
To support CET, 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 <yu-cheng.yu@intel.com>
---
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 | 86 ++++++++++++++---------------
6 files changed, 60 insertions(+), 62 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 5f7290e6e954..540ef09d4b6e 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -93,7 +93,7 @@ static inline void fpstate_init_xstate(struct xregs_state *xsave)
* XRSTORS requires these bits set in xcomp_bv, or it will
* trigger #GP:
*/
- xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT | xfeatures_mask;
+ xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT | xfeatures_mask_user;
}

static inline void fpstate_init_fxstate(struct fxregs_state *fx)
@@ -233,7 +233,7 @@ static inline void copy_fxregs_to_kernel(struct fpu *fpu)

/*
* If XSAVES is enabled, it replaces XSAVEOPT because it supports a compact
- * format and supervisor states in addition to modified optimization in
+ * format and system states in addition to modified optimization in
* XSAVEOPT.
*
* Otherwise, if XSAVEOPT is enabled, XSAVEOPT replaces XSAVE because XSAVEOPT
diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index 48581988d78c..76f83d2ac10e 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -23,15 +23,15 @@
#define XFEATURE_MASK_SUPERVISOR (XFEATURE_MASK_PT)

/* All currently supported features */
-#define XCNTXT_MASK (XFEATURE_MASK_FP | \
- XFEATURE_MASK_SSE | \
- XFEATURE_MASK_YMM | \
- XFEATURE_MASK_OPMASK | \
- XFEATURE_MASK_ZMM_Hi256 | \
- XFEATURE_MASK_Hi16_ZMM | \
- XFEATURE_MASK_PKRU | \
- XFEATURE_MASK_BNDREGS | \
- XFEATURE_MASK_BNDCSR)
+#define SUPPORTED_XFEATURES_MASK (XFEATURE_MASK_FP | \
+ XFEATURE_MASK_SSE | \
+ XFEATURE_MASK_YMM | \
+ XFEATURE_MASK_OPMASK | \
+ XFEATURE_MASK_ZMM_Hi256 | \
+ XFEATURE_MASK_Hi16_ZMM | \
+ XFEATURE_MASK_PKRU | \
+ XFEATURE_MASK_BNDREGS | \
+ XFEATURE_MASK_BNDCSR)

#ifdef CONFIG_X86_64
#define REX_PREFIX "0x48, "
@@ -39,7 +39,7 @@
#define REX_PREFIX
#endif

-extern u64 xfeatures_mask;
+extern u64 xfeatures_mask_user;
extern u64 xstate_fx_sw_bytes[USER_XSTATE_FX_SW_WORDS];

extern void __init update_regset_xstate_info(unsigned int size,
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 2ea85b32421a..4bd56079048f 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -363,7 +363,7 @@ void fpu__drop(struct fpu *fpu)
* Clear FPU registers by setting them up from
* the init fpstate:
*/
-static inline void copy_init_fpstate_to_fpregs(void)
+static inline void copy_init_user_fpstate_to_fpregs(void)
{
if (use_xsave())
copy_kernel_to_xregs(&init_fpstate.xsave, -1);
@@ -395,7 +395,7 @@ void fpu__clear(struct fpu *fpu)
preempt_disable();
fpu__initialize(fpu);
user_fpu_begin();
- copy_init_fpstate_to_fpregs();
+ copy_init_user_fpstate_to_fpregs();
preempt_enable();
}
}
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 6abd83572b01..761c3a5a9e07 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -229,7 +229,7 @@ static void __init fpu__init_system_xstate_size_legacy(void)
*/
u64 __init fpu__get_supported_xfeatures_mask(void)
{
- return XCNTXT_MASK;
+ return SUPPORTED_XFEATURES_MASK;
}

/* Legacy code to initialize eager fpu mode. */
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 61a949d84dfa..1e20c2272e84 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -249,11 +249,11 @@ static inline int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_
{
if (use_xsave()) {
if ((unsigned long)buf % 64 || fx_only) {
- u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
+ u64 init_bv = xfeatures_mask_user & ~XFEATURE_MASK_FPSSE;
copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
return copy_user_to_fxregs(buf);
} else {
- u64 init_bv = xfeatures_mask & ~xbv;
+ u64 init_bv = xfeatures_mask_user & ~xbv;
if (unlikely(init_bv))
copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
return copy_user_to_xregs(buf, xbv);
@@ -416,7 +416,7 @@ void fpu__init_prepare_fx_sw_frame(void)

fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
fx_sw_reserved.extended_size = size;
- fx_sw_reserved.xfeatures = xfeatures_mask;
+ fx_sw_reserved.xfeatures = xfeatures_mask_user;
fx_sw_reserved.xstate_size = fpu_user_xstate_size;

if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 87a57b7642d3..326b64a61fc9 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -51,13 +51,16 @@ static short xsave_cpuid_features[] __initdata = {
};

/*
- * Mask of xstate features supported by the CPU and the kernel:
+ * XSAVES system states can only be modified from CPL 0 and saved by
+ * XSAVES. The rest are user states. The following is a mask of
+ * supported user state features derived from boot_cpu_has() and
+ * SUPPORTED_XFEATURES_MASK.
*/
-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 +85,7 @@ 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;
@@ -113,15 +116,12 @@ 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
- * state component, ECX[0] returns 1.
+ * ECX[0] is 0; if state component i is a system state component,
+ * ECX[0] is 1.
*/
u32 eax, ebx, ecx, edx;

@@ -131,7 +131,7 @@ static int xfeature_is_supervisor(int xfeature_nr)

static int xfeature_is_user(int xfeature_nr)
{
- return !xfeature_is_supervisor(xfeature_nr);
+ return !xfeature_is_system(xfeature_nr);
}

/*
@@ -164,7 +164,7 @@ void fpstate_sanitize_xstate(struct fpu *fpu)
* None of the feature bits are in init state. So nothing else
* to do for us, as the memory layout is up to date.
*/
- if ((xfeatures & xfeatures_mask) == xfeatures_mask)
+ if ((xfeatures & xfeatures_mask_user) == xfeatures_mask_user)
return;

/*
@@ -191,7 +191,7 @@ void fpstate_sanitize_xstate(struct fpu *fpu)
* in a special way already:
*/
feature_bit = 0x2;
- xfeatures = (xfeatures_mask & ~xfeatures) >> 2;
+ xfeatures = (xfeatures_mask_user & ~xfeatures) >> 2;

/*
* Update all the remaining memory layouts according to their
@@ -219,20 +219,18 @@ void fpstate_sanitize_xstate(struct fpu *fpu)
*/
void fpu__init_cpu_xstate(void)
{
- if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask)
+ if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask_user)
return;
/*
- * Make it clear that XSAVES supervisor states are not yet
- * implemented should anyone expect it to work by changing
- * bits in XFEATURE_MASK_* macros and XCR0.
+ * XCR_XFEATURE_ENABLED_MASK sets the features that are managed
+ * by XSAVE{C, OPT} and XRSTOR. Only XSAVE user states can be
+ * set here.
*/
- WARN_ONCE((xfeatures_mask & XFEATURE_MASK_SUPERVISOR),
- "x86/fpu: XSAVES supervisor states are not yet implemented.\n");

- xfeatures_mask &= ~XFEATURE_MASK_SUPERVISOR;
+ xfeatures_mask_user &= ~XFEATURE_MASK_SUPERVISOR;

cr4_set_bits(X86_CR4_OSXSAVE);
- xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
+ xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_user);
}

/*
@@ -242,7 +240,7 @@ 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 +270,7 @@ 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 a system state, the offset
* in EBX is invalid. We leave it to -1.
*/
if (xfeature_is_user(i))
@@ -348,7 +346,7 @@ static int xfeature_is_aligned(int xfeature_nr)
*/
static void __init setup_xstate_comp(void)
{
- unsigned int xstate_comp_sizes[sizeof(xfeatures_mask)*8];
+ unsigned int xstate_comp_sizes[sizeof(xfeatures_mask_user)*8];
int i;

/*
@@ -421,7 +419,7 @@ static void __init setup_init_fpu_buf(void)
print_xstate_features();

if (boot_cpu_has(X86_FEATURE_XSAVES))
- init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
+ init_fpstate.xsave.header.xcomp_bv = BIT_ULL(63) | xfeatures_mask_user;

/*
* Init all the features state with header.xfeatures being 0x0
@@ -440,8 +438,8 @@ static int xfeature_uncompacted_offset(int xfeature_nr)
u32 eax, ebx, ecx, edx;

/*
- * Only XSAVES supports supervisor states and it uses compacted
- * format. Checking a supervisor state's uncompacted offset is
+ * Only XSAVES supports system states and it uses compacted
+ * format. Checking a system state's uncompacted offset is
* an error.
*/
if (XFEATURE_MASK_SUPERVISOR & (1 << xfeature_nr)) {
@@ -465,7 +463,7 @@ static int xfeature_size(int xfeature_nr)

/*
* 'XSAVES' implies two different things:
- * 1. saving of supervisor/system state
+ * 1. saving of system state
* 2. using the compacted format
*
* Use this function when dealing with the compacted format so
@@ -480,8 +478,8 @@ int using_compacted_format(void)
/* Validate an xstate header supplied by userspace (ptrace or sigreturn) */
int validate_xstate_header(const struct xstate_header *hdr)
{
- /* No unknown or supervisor features may be set */
- if (hdr->xfeatures & (~xfeatures_mask | XFEATURE_MASK_SUPERVISOR))
+ /* No unknown or system features may be set */
+ if (hdr->xfeatures & ~xfeatures_mask_user)
return -EINVAL;

/* Userspace must use the uncompacted format */
@@ -588,11 +586,11 @@ static void do_extra_xstate_size_checks(void)

check_xstate_against_struct(i);
/*
- * Supervisor state components can be managed only by
+ * System state components can be managed only by
* XSAVES, which is compacted-format only.
*/
if (!using_compacted_format())
- XSTATE_WARN_ON(xfeature_is_supervisor(i));
+ XSTATE_WARN_ON(xfeature_is_system(i));

/* Align from the end of the previous feature */
if (xfeature_is_aligned(i))
@@ -616,7 +614,7 @@ static void do_extra_xstate_size_checks(void)

/*
- * Get total size of enabled xstates in XCR0/xfeatures_mask.
+ * Get total size of enabled xstates in XCR0/xfeatures_mask_user.
*
* Note the SDM's wording here. "sub-function 0" only enumerates
* the size of the *user* states. If we use it to size a buffer
@@ -706,7 +704,7 @@ static int init_xstate_size(void)
*/
static void fpu__init_disable_system_xstate(void)
{
- xfeatures_mask = 0;
+ xfeatures_mask_user = 0;
cr4_clear_bits(X86_CR4_OSXSAVE);
fpu__xstate_clear_all_cpu_caps();
}
@@ -742,15 +740,15 @@ void __init fpu__init_system_xstate(void)
}

cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
- xfeatures_mask = eax + ((u64)edx << 32);
+ xfeatures_mask_user = eax + ((u64)edx << 32);

- if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
+ if ((xfeatures_mask_user & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
/*
* This indicates that something really unexpected happened
* with the enumeration. Disable XSAVE and try to continue
* booting without it. This is too early to BUG().
*/
- pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask);
+ pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask_user);
goto out_disable;
}

@@ -759,10 +757,10 @@ void __init fpu__init_system_xstate(void)
*/
for (i = 0; i < ARRAY_SIZE(xsave_cpuid_features); i++) {
if (!boot_cpu_has(xsave_cpuid_features[i]))
- xfeatures_mask &= ~BIT(i);
+ xfeatures_mask_user &= ~BIT_ULL(i);
}

- xfeatures_mask &= fpu__get_supported_xfeatures_mask();
+ xfeatures_mask_user &= fpu__get_supported_xfeatures_mask();

/* Enable xstate instructions to be able to continue with initialization: */
fpu__init_cpu_xstate();
@@ -772,9 +770,9 @@ void __init fpu__init_system_xstate(void)

/*
* Update info used for ptrace frames; use standard-format size and no
- * supervisor xstates:
+ * system xstates:
*/
- update_regset_xstate_info(fpu_user_xstate_size, xfeatures_mask & ~XFEATURE_MASK_SUPERVISOR);
+ update_regset_xstate_info(fpu_user_xstate_size, xfeatures_mask_user & ~XFEATURE_MASK_SUPERVISOR);

fpu__init_prepare_fx_sw_frame();
setup_init_fpu_buf();
@@ -782,7 +780,7 @@ void __init fpu__init_system_xstate(void)
print_xstate_offset_size();

pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
- xfeatures_mask,
+ xfeatures_mask_user,
fpu_kernel_xstate_size,
boot_cpu_has(X86_FEATURE_XSAVES) ? "compacted" : "standard");
return;
@@ -801,7 +799,7 @@ void fpu__resume_cpu(void)
* Restore XCR0 on xsave capable CPUs:
*/
if (boot_cpu_has(X86_FEATURE_XSAVE))
- xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
+ xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_user);
}

/*
@@ -853,7 +851,7 @@ void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
* have not enabled. Remember that pcntxt_mask is
* what we write to the XCR0 register.
*/
- WARN_ONCE(!(xfeatures_mask & xstate_feature),
+ WARN_ONCE(!(xfeatures_mask_user & xstate_feature),
"get of unsupported state");
/*
* This assumes the last 'xsave*' instruction to
--
2.17.1