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Subject[PATCH v2 26/37] arm64: mte: Convert gcr_user into an exclude mask
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From: Vincenzo Frascino <vincenzo.frascino@arm.com>

The gcr_user mask is a per thread mask that represents the tags that are
excluded from random generation when the Memory Tagging Extension is
present and an 'irg' instruction is invoked.

gcr_user affects the behavior on EL0 only.

Currently that mask is an include mask and it is controlled by the user
via prctl() while GCR_EL1 accepts an exclude mask.

Convert the include mask into an exclude one to make it easier the
register setting.

Note: This change will affect gcr_kernel (for EL1) introduced with a
future patch.

Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
Change-Id: Id15c0b47582fb51594bb26fb8353d78c7d0953c1
---
arch/arm64/include/asm/processor.h | 2 +-
arch/arm64/kernel/mte.c | 29 +++++++++++++++--------------
2 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index fec204d28fce..ed9efa5be8eb 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -153,7 +153,7 @@ struct thread_struct {
#endif
#ifdef CONFIG_ARM64_MTE
u64 sctlr_tcf0;
- u64 gcr_user_incl;
+ u64 gcr_user_excl;
#endif
};

diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index e238ffde2679..858e75cfcaa0 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -140,23 +140,22 @@ static void set_sctlr_el1_tcf0(u64 tcf0)
preempt_enable();
}

-static void update_gcr_el1_excl(u64 incl)
+static void update_gcr_el1_excl(u64 excl)
{
- u64 excl = ~incl & SYS_GCR_EL1_EXCL_MASK;

/*
- * Note that 'incl' is an include mask (controlled by the user via
- * prctl()) while GCR_EL1 accepts an exclude mask.
+ * Note that the mask controlled by the user via prctl() is an
+ * include while GCR_EL1 accepts an exclude mask.
* No need for ISB since this only affects EL0 currently, implicit
* with ERET.
*/
sysreg_clear_set_s(SYS_GCR_EL1, SYS_GCR_EL1_EXCL_MASK, excl);
}

-static void set_gcr_el1_excl(u64 incl)
+static void set_gcr_el1_excl(u64 excl)
{
- current->thread.gcr_user_incl = incl;
- update_gcr_el1_excl(incl);
+ current->thread.gcr_user_excl = excl;
+ update_gcr_el1_excl(excl);
}

void flush_mte_state(void)
@@ -171,7 +170,7 @@ void flush_mte_state(void)
/* disable tag checking */
set_sctlr_el1_tcf0(SCTLR_EL1_TCF0_NONE);
/* reset tag generation mask */
- set_gcr_el1_excl(0);
+ set_gcr_el1_excl(SYS_GCR_EL1_EXCL_MASK);
}

void mte_thread_switch(struct task_struct *next)
@@ -182,7 +181,7 @@ void mte_thread_switch(struct task_struct *next)
/* avoid expensive SCTLR_EL1 accesses if no change */
if (current->thread.sctlr_tcf0 != next->thread.sctlr_tcf0)
update_sctlr_el1_tcf0(next->thread.sctlr_tcf0);
- update_gcr_el1_excl(next->thread.gcr_user_incl);
+ update_gcr_el1_excl(next->thread.gcr_user_excl);
}

void mte_suspend_exit(void)
@@ -190,13 +189,14 @@ void mte_suspend_exit(void)
if (!system_supports_mte())
return;

- update_gcr_el1_excl(current->thread.gcr_user_incl);
+ update_gcr_el1_excl(current->thread.gcr_user_excl);
}

long set_mte_ctrl(struct task_struct *task, unsigned long arg)
{
u64 tcf0;
- u64 gcr_incl = (arg & PR_MTE_TAG_MASK) >> PR_MTE_TAG_SHIFT;
+ u64 gcr_excl = ~((arg & PR_MTE_TAG_MASK) >> PR_MTE_TAG_SHIFT) &
+ SYS_GCR_EL1_EXCL_MASK;

if (!system_supports_mte())
return 0;
@@ -217,10 +217,10 @@ long set_mte_ctrl(struct task_struct *task, unsigned long arg)

if (task != current) {
task->thread.sctlr_tcf0 = tcf0;
- task->thread.gcr_user_incl = gcr_incl;
+ task->thread.gcr_user_excl = gcr_excl;
} else {
set_sctlr_el1_tcf0(tcf0);
- set_gcr_el1_excl(gcr_incl);
+ set_gcr_el1_excl(gcr_excl);
}

return 0;
@@ -229,11 +229,12 @@ long set_mte_ctrl(struct task_struct *task, unsigned long arg)
long get_mte_ctrl(struct task_struct *task)
{
unsigned long ret;
+ u64 incl = ~task->thread.gcr_user_excl & SYS_GCR_EL1_EXCL_MASK;

if (!system_supports_mte())
return 0;

- ret = task->thread.gcr_user_incl << PR_MTE_TAG_SHIFT;
+ ret = incl << PR_MTE_TAG_SHIFT;

switch (task->thread.sctlr_tcf0) {
case SCTLR_EL1_TCF0_NONE:
--
2.28.0.618.gf4bc123cb7-goog
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