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From:   Max Filippov <jcmvbkbc@gmail.com>
To:     linux-xtensa@linux-xtensa.org
Cc:     Chris Zankel <chris@zankel.net>, linux-kernel@vger.kernel.org,
        Max Filippov <jcmvbkbc@gmail.com>
Subject: [PATCH 08/10] xtensa: only build windowed register support code when needed
Date:   Mon, 18 Oct 2021 22:17:14 -0700
Message-Id: <20211019051716.4173-9-jcmvbkbc@gmail.com>
In-Reply-To: <20211019051716.4173-1-jcmvbkbc@gmail.com>
References: <20211019051716.4173-1-jcmvbkbc@gmail.com>
MIME-Version: 1.0
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There's no need in window overflow/underflow/alloca exception handlers
or window spill code when neither kernel nor userspace support windowed
registers. Don't build or link it.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
 arch/xtensa/include/asm/traps.h  |  2 ++
 arch/xtensa/kernel/entry.S       |  5 ++++-
 arch/xtensa/kernel/setup.c       |  2 ++
 arch/xtensa/kernel/signal.c      | 12 ++++++++++--
 arch/xtensa/kernel/traps.c       |  2 ++
 arch/xtensa/kernel/vectors.S     | 15 +++++++++++++++
 arch/xtensa/kernel/vmlinux.lds.S | 12 ++++++++++--
 7 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/arch/xtensa/include/asm/traps.h b/arch/xtensa/include/asm/traps.h
index f720a57d0a5b..6fa47cd8e02d 100644
--- a/arch/xtensa/include/asm/traps.h
+++ b/arch/xtensa/include/asm/traps.h
@@ -56,6 +56,7 @@ void secondary_trap_init(void);
 
 static inline void spill_registers(void)
 {
+#if defined(__XTENSA_WINDOWED_ABI__)
 #if XCHAL_NUM_AREGS > 16
 	__asm__ __volatile__ (
 		"	call8	1f\n"
@@ -96,6 +97,7 @@ static inline void spill_registers(void)
 		"	mov	a12, a12\n"
 		: : : "memory");
 #endif
+#endif
 }
 
 struct debug_table {
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index 8029ce24af92..99ab3c1a3387 100644
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -969,6 +969,7 @@ ENDPROC(unrecoverable_exception)
 	__XTENSA_HANDLER
 	.literal_position
 
+#ifdef SUPPORT_WINDOWED
 /*
  * Fast-handler for alloca exceptions
  *
@@ -1032,6 +1033,7 @@ ENTRY(fast_alloca)
 8:	j	_WindowUnderflow8
 4:	j	_WindowUnderflow4
 ENDPROC(fast_alloca)
+#endif
 
 #ifdef CONFIG_USER_ABI_CALL0_PROBE
 /*
@@ -1228,7 +1230,8 @@ ENDPROC(fast_syscall_xtensa)
  * Note: We assume the stack pointer is EXC_TABLE_KSTK in the fixup handler.
  */
 
-#ifdef CONFIG_FAST_SYSCALL_SPILL_REGISTERS
+#if defined(CONFIG_FAST_SYSCALL_SPILL_REGISTERS) && \
+		defined(USER_SUPPORT_WINDOWED)
 
 ENTRY(fast_syscall_spill_registers)
 
diff --git a/arch/xtensa/kernel/setup.c b/arch/xtensa/kernel/setup.c
index ed184106e4cf..3638fb98a1ab 100644
--- a/arch/xtensa/kernel/setup.c
+++ b/arch/xtensa/kernel/setup.c
@@ -349,8 +349,10 @@ void __init setup_arch(char **cmdline_p)
 #endif
 
 #ifdef CONFIG_VECTORS_ADDR
+#ifdef SUPPORT_WINDOWED
 	mem_reserve(__pa(&_WindowVectors_text_start),
 		    __pa(&_WindowVectors_text_end));
+#endif
 
 	mem_reserve(__pa(&_DebugInterruptVector_text_start),
 		    __pa(&_DebugInterruptVector_text_end));
diff --git a/arch/xtensa/kernel/signal.c b/arch/xtensa/kernel/signal.c
index c4d77dbfb61a..f6c949895b3e 100644
--- a/arch/xtensa/kernel/signal.c
+++ b/arch/xtensa/kernel/signal.c
@@ -45,12 +45,13 @@ struct rt_sigframe
 	unsigned int window[4];
 };
 
-/* 
+#if defined(USER_SUPPORT_WINDOWED)
+/*
  * Flush register windows stored in pt_regs to stack.
  * Returns 1 for errors.
  */
 
-int
+static int
 flush_window_regs_user(struct pt_regs *regs)
 {
 	const unsigned long ws = regs->windowstart;
@@ -121,6 +122,13 @@ flush_window_regs_user(struct pt_regs *regs)
 errout:
 	return err;
 }
+#else
+static int
+flush_window_regs_user(struct pt_regs *regs)
+{
+	return 0;
+}
+#endif
 
 /*
  * Note: We don't copy double exception 'regs', we have to finish double exc. 
diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
index 874b6efc6fb3..4418438b13e6 100644
--- a/arch/xtensa/kernel/traps.c
+++ b/arch/xtensa/kernel/traps.c
@@ -97,7 +97,9 @@ static dispatch_init_table_t __initdata dispatch_init_table[] = {
 /* EXCCAUSE_INSTRUCTION_FETCH unhandled */
 /* EXCCAUSE_LOAD_STORE_ERROR unhandled*/
 { EXCCAUSE_LEVEL1_INTERRUPT,	0,	   do_interrupt },
+#ifdef SUPPORT_WINDOWED
 { EXCCAUSE_ALLOCA,		USER|KRNL, fast_alloca },
+#endif
 /* EXCCAUSE_INTEGER_DIVIDE_BY_ZERO unhandled */
 /* EXCCAUSE_PRIVILEGED unhandled */
 #if XCHAL_UNALIGNED_LOAD_EXCEPTION || XCHAL_UNALIGNED_STORE_EXCEPTION
diff --git a/arch/xtensa/kernel/vectors.S b/arch/xtensa/kernel/vectors.S
index 0eed5aa82914..407ece204e7c 100644
--- a/arch/xtensa/kernel/vectors.S
+++ b/arch/xtensa/kernel/vectors.S
@@ -226,6 +226,7 @@ ENTRY(_DoubleExceptionVector)
 
 	xsr	a0, depc		# get DEPC, save a0
 
+#ifdef SUPPORT_WINDOWED
 	movi	a2, WINDOW_VECTORS_VADDR
 	_bltu	a0, a2, .Lfixup
 	addi	a2, a2, WINDOW_VECTORS_SIZE
@@ -275,6 +276,10 @@ _DoubleExceptionVector_WindowUnderflow:
 	l32i	a0, a0, EXC_TABLE_FAST_USER
 	jx	a0
 
+#else
+	j	.Lfixup
+#endif
+
 	/*
 	 * We only allow the ITLB miss exception if we are in kernel space.
 	 * All other exceptions are unexpected and thus unrecoverable!
@@ -343,6 +348,7 @@ _DoubleExceptionVector_WindowUnderflow:
 	l32i	a0, a0, EXC_TABLE_FAST_USER
 	jx	a0
 
+#ifdef SUPPORT_WINDOWED
 	/*
 	 * Restart window OVERFLOW exception.
 	 * Currently:
@@ -475,9 +481,12 @@ _DoubleExceptionVector_handle_exception:
 	rsr	a0, depc
 	rotw	-3
 	j	1b
+#endif
 
 ENDPROC(_DoubleExceptionVector)
 
+#ifdef SUPPORT_WINDOWED
+
 /*
  * Fixup handler for TLB miss in double exception handler for window owerflow.
  * We get here with windowbase set to the window that was being spilled and
@@ -590,6 +599,8 @@ ENTRY(window_overflow_restore_a0_fixup)
 
 ENDPROC(window_overflow_restore_a0_fixup)
 
+#endif
+
 /*
  * Debug interrupt vector
  *
@@ -687,6 +698,8 @@ _SimulateUserKernelVectorException:
 	.section		.WindowVectors.text, "ax"
 
 
+#ifdef SUPPORT_WINDOWED
+
 /* 4-Register Window Overflow Vector (Handler) */
 
 ENTRY_ALIGN64(_WindowOverflow4)
@@ -787,4 +800,6 @@ ENTRY_ALIGN64(_WindowUnderflow12)
 
 ENDPROC(_WindowUnderflow12)
 
+#endif
+
 	.text
diff --git a/arch/xtensa/kernel/vmlinux.lds.S b/arch/xtensa/kernel/vmlinux.lds.S
index d23a6e38f062..eee270a039a4 100644
--- a/arch/xtensa/kernel/vmlinux.lds.S
+++ b/arch/xtensa/kernel/vmlinux.lds.S
@@ -94,7 +94,9 @@ SECTIONS
     . = ALIGN(PAGE_SIZE);
     _vecbase = .;
 
+#ifdef SUPPORT_WINDOWED
     SECTION_VECTOR2 (.WindowVectors.text, WINDOW_VECTORS_VADDR)
+#endif
 #if XCHAL_EXCM_LEVEL >= 2
     SECTION_VECTOR2 (.Level2InterruptVector.text, INTLEVEL2_VECTOR_VADDR)
 #endif
@@ -166,8 +168,10 @@ SECTIONS
     __boot_reloc_table_start = ABSOLUTE(.);
 
 #if !MERGED_VECTORS
+#ifdef SUPPORT_WINDOWED
     RELOCATE_ENTRY(_WindowVectors_text,
 		   .WindowVectors.text);
+#endif
 #if XCHAL_EXCM_LEVEL >= 2
     RELOCATE_ENTRY(_Level2InterruptVector_text,
 		   .Level2InterruptVector.text);
@@ -229,14 +233,18 @@ SECTIONS
 #if !MERGED_VECTORS
   /* The vectors are relocated to the real position at startup time */
 
+#ifdef SUPPORT_WINDOWED
   SECTION_VECTOR4 (_WindowVectors_text,
 		  .WindowVectors.text,
 		  WINDOW_VECTORS_VADDR,
-		  .dummy)
+		  LAST)
+#undef LAST
+#define LAST	.WindowVectors.text
+#endif
   SECTION_VECTOR4 (_DebugInterruptVector_text,
 		  .DebugInterruptVector.text,
 		  DEBUG_VECTOR_VADDR,
-		  .WindowVectors.text)
+		  LAST)
 #undef LAST
 #define LAST	.DebugInterruptVector.text
 #if XCHAL_EXCM_LEVEL >= 2
-- 
2.20.1