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Message-Id: <49907feaae8275375ce09aa43e739c1aaa89d331.1687430631.git.christophe.leroy@csgroup.eu>
Date: Thu, 22 Jun 2023 12:54:24 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Michael Ellerman <mpe@...erman.id.au>,
Nicholas Piggin <npiggin@...il.com>,
Josh Poimboeuf <jpoimboe@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Sathvika Vasireddy <sv@...ux.ibm.com>,
Naveen N Rao <naveen@...nel.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2 02/14] powerpc/kuap: Avoid useless jump_label on empty function
Disassembly of interrupt_enter_prepare() shows a pointless nop
before the mftb
c000abf0 <interrupt_enter_prepare>:
c000abf0: 81 23 00 84 lwz r9,132(r3)
c000abf4: 71 29 40 00 andi. r9,r9,16384
c000abf8: 41 82 00 28 beq- c000ac20 <interrupt_enter_prepare+0x30>
c000abfc: ===> 60 00 00 00 nop <====
c000ac00: 7d 0c 42 e6 mftb r8
c000ac04: 80 e2 00 08 lwz r7,8(r2)
c000ac08: 81 22 00 28 lwz r9,40(r2)
c000ac0c: 91 02 00 24 stw r8,36(r2)
c000ac10: 7d 29 38 50 subf r9,r9,r7
c000ac14: 7d 29 42 14 add r9,r9,r8
c000ac18: 91 22 00 08 stw r9,8(r2)
c000ac1c: 4e 80 00 20 blr
c000ac20: 60 00 00 00 nop
c000ac24: 7d 5a c2 a6 mfmd_ap r10
c000ac28: 3d 20 de 00 lis r9,-8704
c000ac2c: 91 43 00 b0 stw r10,176(r3)
c000ac30: 7d 3a c3 a6 mtspr 794,r9
c000ac34: 4e 80 00 20 blr
That comes from the call to kuap_loc(), allthough __kuap_lock() is an
empty function on the 8xx.
To avoid that, only perform kuap_is_disabled() check when there is
something to do with __kuap_lock().
Do the same with __kuap_save_and_lock() and
__kuap_get_and_assert_locked().
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Reviewed-by: Nicholas Piggin <npiggin@...il.com>
---
v2: Add back comment about __kupa_lock() not needed on 64s
---
arch/powerpc/include/asm/book3s/32/kup.h | 6 ++---
arch/powerpc/include/asm/book3s/64/kup.h | 10 ++------
arch/powerpc/include/asm/kup.h | 25 ++++++++++----------
arch/powerpc/include/asm/nohash/32/kup-8xx.h | 11 ++++-----
arch/powerpc/include/asm/nohash/kup-booke.h | 8 +++++--
5 files changed, 27 insertions(+), 33 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h
index 678f9c9d89b6..466a19cfb4df 100644
--- a/arch/powerpc/include/asm/book3s/32/kup.h
+++ b/arch/powerpc/include/asm/book3s/32/kup.h
@@ -77,10 +77,6 @@ static inline void kuap_unlock(unsigned long addr, bool ool)
kuap_unlock_all_ool();
}
-static inline void __kuap_lock(void)
-{
-}
-
static inline void __kuap_save_and_lock(struct pt_regs *regs)
{
unsigned long kuap = current->thread.kuap;
@@ -92,6 +88,7 @@ static inline void __kuap_save_and_lock(struct pt_regs *regs)
current->thread.kuap = KUAP_NONE;
kuap_lock_addr(kuap, false);
}
+#define __kuap_save_and_lock __kuap_save_and_lock
static inline void kuap_user_restore(struct pt_regs *regs)
{
@@ -120,6 +117,7 @@ static inline unsigned long __kuap_get_and_assert_locked(void)
return kuap;
}
+#define __kuap_get_and_assert_locked __kuap_get_and_assert_locked
static __always_inline void __allow_user_access(void __user *to, const void __user *from,
u32 size, unsigned long dir)
diff --git a/arch/powerpc/include/asm/book3s/64/kup.h b/arch/powerpc/include/asm/book3s/64/kup.h
index 84c09e546115..2a7bd3ecc556 100644
--- a/arch/powerpc/include/asm/book3s/64/kup.h
+++ b/arch/powerpc/include/asm/book3s/64/kup.h
@@ -298,15 +298,9 @@ static inline unsigned long __kuap_get_and_assert_locked(void)
WARN_ON_ONCE(amr != AMR_KUAP_BLOCKED);
return amr;
}
+#define __kuap_get_and_assert_locked __kuap_get_and_assert_locked
-/* Do nothing, book3s/64 does that in ASM */
-static inline void __kuap_lock(void)
-{
-}
-
-static inline void __kuap_save_and_lock(struct pt_regs *regs)
-{
-}
+/* __kuap_lock() not required, book3s/64 does that in ASM */
/*
* We support individually allowing read or write, but we don't support nesting
diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h
index d751ddd08110..0a4e07175612 100644
--- a/arch/powerpc/include/asm/kup.h
+++ b/arch/powerpc/include/asm/kup.h
@@ -52,16 +52,9 @@ __bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
return false;
}
-static inline void __kuap_lock(void) { }
-static inline void __kuap_save_and_lock(struct pt_regs *regs) { }
static inline void kuap_user_restore(struct pt_regs *regs) { }
static inline void __kuap_kernel_restore(struct pt_regs *regs, unsigned long amr) { }
-static inline unsigned long __kuap_get_and_assert_locked(void)
-{
- return 0;
-}
-
/*
* book3s/64/kup-radix.h defines these functions for the !KUAP case to flush
* the L1D cache after user accesses. Only include the empty stubs for other
@@ -87,27 +80,32 @@ bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
static __always_inline void kuap_assert_locked(void)
{
+#if defined(CONFIG_PPC_KUAP_DEBUG) && defined(__kuap_get_and_assert_locked)
if (kuap_is_disabled())
return;
- if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG))
- __kuap_get_and_assert_locked();
+ __kuap_get_and_assert_locked();
+#endif
}
static __always_inline void kuap_lock(void)
{
+#ifdef __kuap_lock
if (kuap_is_disabled())
return;
__kuap_lock();
+#endif
}
static __always_inline void kuap_save_and_lock(struct pt_regs *regs)
{
+#ifdef __kuap_save_and_lock
if (kuap_is_disabled())
return;
__kuap_save_and_lock(regs);
+#endif
}
static __always_inline void kuap_kernel_restore(struct pt_regs *regs, unsigned long amr)
@@ -120,10 +118,11 @@ static __always_inline void kuap_kernel_restore(struct pt_regs *regs, unsigned l
static __always_inline unsigned long kuap_get_and_assert_locked(void)
{
- if (kuap_is_disabled())
- return 0;
-
- return __kuap_get_and_assert_locked();
+#ifdef __kuap_get_and_assert_locked
+ if (!kuap_is_disabled())
+ return __kuap_get_and_assert_locked();
+#endif
+ return 0;
}
#ifndef CONFIG_PPC_BOOK3S_64
diff --git a/arch/powerpc/include/asm/nohash/32/kup-8xx.h b/arch/powerpc/include/asm/nohash/32/kup-8xx.h
index 8579210f2a6a..a372cd822887 100644
--- a/arch/powerpc/include/asm/nohash/32/kup-8xx.h
+++ b/arch/powerpc/include/asm/nohash/32/kup-8xx.h
@@ -20,15 +20,12 @@ static __always_inline bool kuap_is_disabled(void)
return static_branch_unlikely(&disable_kuap_key);
}
-static inline void __kuap_lock(void)
-{
-}
-
static inline void __kuap_save_and_lock(struct pt_regs *regs)
{
regs->kuap = mfspr(SPRN_MD_AP);
mtspr(SPRN_MD_AP, MD_APG_KUAP);
}
+#define __kuap_save_and_lock __kuap_save_and_lock
static inline void kuap_user_restore(struct pt_regs *regs)
{
@@ -39,13 +36,15 @@ static inline void __kuap_kernel_restore(struct pt_regs *regs, unsigned long kua
mtspr(SPRN_MD_AP, regs->kuap);
}
+#ifdef CONFIG_PPC_KUAP_DEBUG
static inline unsigned long __kuap_get_and_assert_locked(void)
{
- if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG))
- WARN_ON_ONCE(mfspr(SPRN_MD_AP) >> 16 != MD_APG_KUAP >> 16);
+ WARN_ON_ONCE(mfspr(SPRN_MD_AP) >> 16 != MD_APG_KUAP >> 16);
return 0;
}
+#define __kuap_get_and_assert_locked __kuap_get_and_assert_locked
+#endif
static inline void __allow_user_access(void __user *to, const void __user *from,
unsigned long size, unsigned long dir)
diff --git a/arch/powerpc/include/asm/nohash/kup-booke.h b/arch/powerpc/include/asm/nohash/kup-booke.h
index 823c5a3a96d8..71182cbe20c3 100644
--- a/arch/powerpc/include/asm/nohash/kup-booke.h
+++ b/arch/powerpc/include/asm/nohash/kup-booke.h
@@ -30,6 +30,7 @@ static inline void __kuap_lock(void)
mtspr(SPRN_PID, 0);
isync();
}
+#define __kuap_lock __kuap_lock
static inline void __kuap_save_and_lock(struct pt_regs *regs)
{
@@ -37,6 +38,7 @@ static inline void __kuap_save_and_lock(struct pt_regs *regs)
mtspr(SPRN_PID, 0);
isync();
}
+#define __kuap_save_and_lock __kuap_save_and_lock
static inline void kuap_user_restore(struct pt_regs *regs)
{
@@ -56,13 +58,15 @@ static inline void __kuap_kernel_restore(struct pt_regs *regs, unsigned long kua
/* Context synchronisation is performed by rfi */
}
+#ifdef CONFIG_PPC_KUAP_DEBUG
static inline unsigned long __kuap_get_and_assert_locked(void)
{
- if (IS_ENABLED(CONFIG_PPC_KUAP_DEBUG))
- WARN_ON_ONCE(mfspr(SPRN_PID));
+ WARN_ON_ONCE(mfspr(SPRN_PID));
return 0;
}
+#define __kuap_get_and_assert_locked __kuap_get_and_assert_locked
+#endif
static inline void __allow_user_access(void __user *to, const void __user *from,
unsigned long size, unsigned long dir)
--
2.40.1
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