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Subject[PATCH 27/27] x86/pkeys: add PKRU value to init_fpstate
Date
The task's initiall PKRU value is set part for fpu__clear()/
copy_init_pkru_to_fpregs(). It is not part of init_fpstate.xsave and
instead it is set explictly.
If the user removes the PKRU state from XSAVE in the signal handler then
__fpu__restore_sig() will restore the missing bits from `init_fpstate'
and initialize the PKRU value to 0.

Add the `init_pkru_value' to `init_fpstate' so it is set to the init
value in such a case.

In theory we could drop copy_init_pkru_to_fpregs() because restoring the
PKRU at return-to-userland should be enough.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/x86/kernel/cpu/common.c | 5 +++++
arch/x86/mm/pkeys.c | 6 ++++++
2 files changed, 11 insertions(+)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index cb28e98a0659a..352fa19e63110 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -372,6 +372,8 @@ static bool pku_disabled;

static __always_inline void setup_pku(struct cpuinfo_x86 *c)
{
+ struct pkru_state *pk;
+
/* check the boot processor, plus compile options for PKU: */
if (!cpu_feature_enabled(X86_FEATURE_PKU))
return;
@@ -382,6 +384,9 @@ static __always_inline void setup_pku(struct cpuinfo_x86 *c)
return;

cr4_set_bits(X86_CR4_PKE);
+ pk = get_xsave_addr(&init_fpstate.xsave, XFEATURE_PKRU);
+ if (pk)
+ pk->pkru = init_pkru_value;
/*
* Seting X86_CR4_PKE will cause the X86_FEATURE_OSPKE
* cpuid bit to be set. We need to ensure that we
diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index 2ecbf4155f98f..1dcfc91c8f0c3 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -18,6 +18,7 @@

#include <asm/cpufeature.h> /* boot_cpu_has, ... */
#include <asm/mmu_context.h> /* vma_pkey() */
+#include <asm/fpu/internal.h> /* init_fpstate */

int __execute_only_pkey(struct mm_struct *mm)
{
@@ -161,6 +162,7 @@ static ssize_t init_pkru_read_file(struct file *file, char __user *user_buf,
static ssize_t init_pkru_write_file(struct file *file,
const char __user *user_buf, size_t count, loff_t *ppos)
{
+ struct pkru_state *pk;
char buf[32];
ssize_t len;
u32 new_init_pkru;
@@ -183,6 +185,10 @@ static ssize_t init_pkru_write_file(struct file *file,
return -EINVAL;

WRITE_ONCE(init_pkru_value, new_init_pkru);
+ pk = get_xsave_addr(&init_fpstate.xsave, XFEATURE_PKRU);
+ if (!pk)
+ return -EINVAL;
+ pk->pkru = new_init_pkru;
return count;
}

--
2.20.1
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