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Message-ID: <20250428152225.66044-6-mchauras@linux.ibm.com>
Date: Mon, 28 Apr 2025 20:52:24 +0530
From: Mukesh Kumar Chaurasiya <mchauras@...ux.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: maddy@...ux.ibm.com, mpe@...erman.id.au, npiggin@...il.com,
christophe.leroy@...roup.eu, naveen@...nel.org,
neeraj.upadhyay@...nel.org, vschneid@...hat.com, tglx@...utronix.de,
frederic@...nel.org, ankur.a.arora@...cle.com, sshegde@...ux.ibm.com,
bigeasy@...utronix.de, kees@...nel.org, oleg@...hat.com,
peterz@...radead.org, tzimmermann@...e.de, namcao@...utronix.de,
kan.liang@...ux.intel.com, mcgrof@...nel.org, rppt@...nel.org,
atrajeev@...ux.vnet.ibm.com, anjalik@...ux.ibm.com,
coltonlewis@...gle.com, linuxppc-dev@...ts.ozlabs.org,
Mukesh Kumar Chaurasiya <mchauras@...ux.ibm.com>
Subject: [RFC V1 3/6] powerpc: introduce arch_enter_from_user_mode
Introduce arch_enter_from_user_mode required by syscall entry.
Signed-off-by: Mukesh Kumar Chaurasiya <mchauras@...ux.ibm.com>
---
arch/powerpc/include/asm/entry-common.h | 96 +++++++++++++++++++++++++
arch/powerpc/include/asm/interrupt.h | 23 ++++++
arch/powerpc/kernel/interrupt.c | 22 ------
3 files changed, 119 insertions(+), 22 deletions(-)
diff --git a/arch/powerpc/include/asm/entry-common.h b/arch/powerpc/include/asm/entry-common.h
index e9e4220a1d225..804f6d019ec95 100644
--- a/arch/powerpc/include/asm/entry-common.h
+++ b/arch/powerpc/include/asm/entry-common.h
@@ -5,7 +5,103 @@
#ifdef CONFIG_GENERIC_ENTRY
+#include <asm/cputime.h>
+#include <asm/interrupt.h>
#include <asm/stacktrace.h>
+#include <asm/tm.h>
+
+static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs)
+{
+ if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
+ BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED);
+
+ BUG_ON(regs_is_unrecoverable(regs));
+ BUG_ON(!user_mode(regs));
+ BUG_ON(regs_irqs_disabled(regs));
+
+#ifdef CONFIG_PPC_PKEY
+ if (mmu_has_feature(MMU_FTR_PKEY)) {
+ unsigned long amr, iamr;
+ bool flush_needed = false;
+ /*
+ * When entering from userspace we mostly have the AMR/IAMR
+ * different from kernel default values. Hence don't compare.
+ */
+ amr = mfspr(SPRN_AMR);
+ iamr = mfspr(SPRN_IAMR);
+ regs->amr = amr;
+ regs->iamr = iamr;
+ if (mmu_has_feature(MMU_FTR_KUAP)) {
+ mtspr(SPRN_AMR, AMR_KUAP_BLOCKED);
+ flush_needed = true;
+ }
+ if (mmu_has_feature(MMU_FTR_BOOK3S_KUEP)) {
+ mtspr(SPRN_IAMR, AMR_KUEP_BLOCKED);
+ flush_needed = true;
+ }
+ if (flush_needed)
+ isync();
+ } else
+#endif
+ kuap_assert_locked();
+
+ booke_restore_dbcr0();
+
+ account_cpu_user_entry();
+
+ account_stolen_time();
+
+ /*
+ * This is not required for the syscall exit path, but makes the
+ * stack frame look nicer. If this was initialised in the first stack
+ * frame, or if the unwinder was taught the first stack frame always
+ * returns to user with IRQS_ENABLED, this store could be avoided!
+ */
+ irq_soft_mask_regs_set_state(regs, IRQS_ENABLED);
+
+ /*
+ * If system call is called with TM active, set _TIF_RESTOREALL to
+ * prevent RFSCV being used to return to userspace, because POWER9
+ * TM implementation has problems with this instruction returning to
+ * transactional state. Final register values are not relevant because
+ * the transaction will be aborted upon return anyway. Or in the case
+ * of unsupported_scv SIGILL fault, the return state does not much
+ * matter because it's an edge case.
+ */
+ if (IS_ENABLED(CONFIG_PPC_TRANSACTIONAL_MEM) &&
+ unlikely(MSR_TM_TRANSACTIONAL(regs->msr)))
+ set_bits(_TIF_RESTOREALL, ¤t_thread_info()->flags);
+
+ /*
+ * If the system call was made with a transaction active, doom it and
+ * return without performing the system call. Unless it was an
+ * unsupported scv vector, in which case it's treated like an illegal
+ * instruction.
+ */
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+ if (unlikely(MSR_TM_TRANSACTIONAL(regs->msr)) &&
+ !trap_is_unsupported_scv(regs)) {
+ /* Enable TM in the kernel, and disable EE (for scv) */
+ hard_irq_disable();
+ mtmsr(mfmsr() | MSR_TM);
+
+ /* tabort, this dooms the transaction, nothing else */
+ asm volatile(".long 0x7c00071d | ((%0) << 16)"
+ :: "r"(TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT));
+
+ /*
+ * Userspace will never see the return value. Execution will
+ * resume after the tbegin. of the aborted transaction with the
+ * checkpointed register state. A context switch could occur
+ * or signal delivered to the process before resuming the
+ * doomed transaction context, but that should all be handled
+ * as expected.
+ */
+ return;
+ }
+#endif // CONFIG_PPC_TRANSACTIONAL_MEM
+}
+#define arch_enter_from_user_mode arch_enter_from_user_mode
#endif /* CONFIG_GENERIC_ENTRY */
#endif /* _ASM_PPC_ENTRY_COMMON_H */
diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index 56bc8113b8cde..6edf064a0fea2 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -138,6 +138,29 @@ static inline void nap_adjust_return(struct pt_regs *regs)
#endif
}
+static inline void booke_load_dbcr0(void)
+{
+#ifdef CONFIG_PPC_ADV_DEBUG_REGS
+ unsigned long dbcr0 = current->thread.debug.dbcr0;
+
+ if (likely(!(dbcr0 & DBCR0_IDM)))
+ return;
+
+ /*
+ * Check to see if the dbcr0 register is set up to debug.
+ * Use the internal debug mode bit to do this.
+ */
+ mtmsr(mfmsr() & ~MSR_DE);
+ if (IS_ENABLED(CONFIG_PPC32)) {
+ isync();
+ global_dbcr0[smp_processor_id()] = mfspr(SPRN_DBCR0);
+ }
+ mtspr(SPRN_DBCR0, dbcr0);
+ mtspr(SPRN_DBSR, -1);
+#endif
+}
+
+
static inline void booke_restore_dbcr0(void)
{
#ifdef CONFIG_PPC_ADV_DEBUG_REGS
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index f656192f075fb..44afc65e0e0e0 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -74,28 +74,6 @@ static notrace __always_inline bool prep_irq_for_enabled_exit(bool restartable)
return true;
}
-static notrace void booke_load_dbcr0(void)
-{
-#ifdef CONFIG_PPC_ADV_DEBUG_REGS
- unsigned long dbcr0 = current->thread.debug.dbcr0;
-
- if (likely(!(dbcr0 & DBCR0_IDM)))
- return;
-
- /*
- * Check to see if the dbcr0 register is set up to debug.
- * Use the internal debug mode bit to do this.
- */
- mtmsr(mfmsr() & ~MSR_DE);
- if (IS_ENABLED(CONFIG_PPC32)) {
- isync();
- global_dbcr0[smp_processor_id()] = mfspr(SPRN_DBCR0);
- }
- mtspr(SPRN_DBCR0, dbcr0);
- mtspr(SPRN_DBSR, -1);
-#endif
-}
-
static notrace void check_return_regs_valid(struct pt_regs *regs)
{
#ifdef CONFIG_PPC_BOOK3S_64
--
2.49.0
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