[patch V2 44/52] x86/fpu: Rename xfeatures_mask_user() to xfeatures_mask_uabi()

Thomas Gleixner
2021-06-14T16:40:30Z

Rename it so it's clear that this is about user ABI features which can
differ from the feature set which the kernel saves and restores because the
kernel handles e.g. PKRU differently. But the user ABI (ptrace, signal
frame) expects it to be there.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/include/asm/fpu/internal.h | 7 ++++++-
arch/x86/include/asm/fpu/xstate.h | 6 +++++-
arch/x86/kernel/fpu/core.c | 2 +-
arch/x86/kernel/fpu/signal.c | 10 +++++-----
arch/x86/kernel/fpu/xstate.c | 14 +++++++-------
5 files changed, 24 insertions(+), 15 deletions(-)

--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -319,7 +319,12 @@ static inline void xrstor_from_kernel(st
*/
static inline int xsave_to_user_sigframe(struct xregs_state __user *buf)
{
- u64 mask = xfeatures_mask_user();
+ /*
+ * Include the features which are not xsaved/rstored by the kernel
+ * internally, e.g. PKRU. That's user space ABI and also required
+ * to allow the signal handler to modify PKRU.
+ */
+ u64 mask = xfeatures_mask_uabi();
u32 lmask = mask;
u32 hmask = mask >> 32;
int err;
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -83,7 +83,11 @@ static inline u64 xfeatures_mask_supervi
return xfeatures_mask_all & XFEATURE_MASK_SUPERVISOR_SUPPORTED;
}

-static inline u64 xfeatures_mask_user(void)
+/*
+ * The xfeatures which are enabled in XCR0 and expected to be in ptrace
+ * buffers and signal frames.
+ */
+static inline u64 xfeatures_mask_uabi(void)
{
return xfeatures_mask_all & XFEATURE_MASK_USER_SUPPORTED;
}
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -470,7 +470,7 @@ void fpu__clear_user_states(struct fpu *
}

/* Reset user states in registers. */
- load_fpregs_from_init_fpstate(xfeatures_mask_user());
+ load_fpregs_from_init_fpstate(xfeatures_mask_uabi());

/*
* Now all FPU registers have their desired values. Inform the FPU
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -267,14 +267,14 @@ static int copy_user_to_fpregs_zeroing(v

if (use_xsave()) {
if (fx_only) {
- init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE;
+ init_bv = xfeatures_mask_uabi() & ~XFEATURE_MASK_FPSSE;

r = fxrstor_from_user_sigframe(buf);
if (!r)
xrstor_from_kernel(&init_fpstate.xsave, init_bv);
return r;
} else {
- init_bv = xfeatures_mask_user() & ~xbv;
+ init_bv = xfeatures_mask_uabi() & ~xbv;

r = xrstor_from_user_sigframe(buf, xbv);
if (!r && unlikely(init_bv))
@@ -429,7 +429,7 @@ static int __fpu__restore_sig(void __use
fpregs_unlock();

if (use_xsave() && !fx_only) {
- u64 init_bv = xfeatures_mask_user() & ~user_xfeatures;
+ u64 init_bv = xfeatures_mask_uabi() & ~user_xfeatures;

ret = copy_sigframe_from_user_to_xstate(&fpu->state.xsave, buf_fx);
if (ret)
@@ -463,7 +463,7 @@ static int __fpu__restore_sig(void __use
if (use_xsave()) {
u64 init_bv;

- init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE;
+ init_bv = xfeatures_mask_uabi() & ~XFEATURE_MASK_FPSSE;
xrstor_from_kernel(&init_fpstate.xsave, init_bv);
}

@@ -558,7 +558,7 @@ 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_user();
+ fx_sw_reserved.xfeatures = xfeatures_mask_uabi();
fx_sw_reserved.xstate_size = fpu_user_xstate_size;

if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -155,7 +155,7 @@ void fpu__init_cpu_xstate(void)
* managed by XSAVE{C, OPT, S} and XRSTOR{S}. Only XSAVE user
* states can be set here.
*/
- xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_user());
+ xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_uabi());

/*
* MSR_IA32_XSS sets supervisor states managed by XSAVES.
@@ -462,7 +462,7 @@ int xfeature_size(int xfeature_nr)
static int validate_user_xstate_header(const struct xstate_header *hdr)
{
/* No unknown or supervisor features may be set */
- if (hdr->xfeatures & ~xfeatures_mask_user())
+ if (hdr->xfeatures & ~xfeatures_mask_uabi())
return -EINVAL;

/* Userspace must use the uncompacted format */
@@ -764,7 +764,7 @@ void __init fpu__init_system_xstate(void
cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
xfeatures_mask_all |= ecx + ((u64)edx << 32);

- if ((xfeatures_mask_user() & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
+ if ((xfeatures_mask_uabi() & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
/*
* This indicates that something really unexpected happened
* with the enumeration. Disable XSAVE and try to continue
@@ -795,7 +795,7 @@ void __init fpu__init_system_xstate(void
* Update info used for ptrace frames; use standard-format size and no
* supervisor xstates:
*/
- update_regset_xstate_info(fpu_user_xstate_size, xfeatures_mask_user());
+ update_regset_xstate_info(fpu_user_xstate_size, xfeatures_mask_uabi());

fpu__init_prepare_fx_sw_frame();
setup_init_fpu_buf();
@@ -823,7 +823,7 @@ 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_user());
+ xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_uabi());

/*
* Restore IA32_XSS. The same CPUID bit enumerates support
@@ -1004,7 +1004,7 @@ void copy_uabi_xstate_to_membuf(struct m
break;

case XSTATE_COPY_XSAVE:
- header.xfeatures &= xfeatures_mask_user();
+ header.xfeatures &= xfeatures_mask_uabi();
break;
}

@@ -1049,7 +1049,7 @@ void copy_uabi_xstate_to_membuf(struct m
* compacted init_fpstate. The gap tracking will zero this
* later.
*/
- if (!(xfeatures_mask_user() & BIT_ULL(i)))
+ if (!(xfeatures_mask_uabi() & BIT_ULL(i)))
continue;

/*