[uClinux-dev] [PATCH 1/3] m68k: consistently call ret_from_exception in entry code

[gerg]

From: Greg Ungerer <gerg at uclinux.org>

The ret_from_excption code is referenced by its function name, or by a label
set at the start of its code. Modify all uses to consistently just use the
function name "ret_from_exception".

This will help when we come to merge the MMU and non-MMU entry code.

Signed-off-by: Greg Ungerer <gerg at uclinux.org>
---
arch/m68k/kernel/entry_mm.S | 13 ++++++-------
1 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/m68k/kernel/entry_mm.S b/arch/m68k/kernel/entry_mm.S
index 675a854..f2ecc64 100644
--- a/arch/m68k/kernel/entry_mm.S
+++ b/arch/m68k/kernel/entry_mm.S
@@ -57,7 +57,7 @@ ENTRY(buserr)
movel %sp,%sp at - | stack frame pointer argument
bsrl buserr_c
addql #4,%sp
- jra .Lret_from_exception
+ jra ret_from_exception

ENTRY(trap)
SAVE_ALL_INT
@@ -65,7 +65,7 @@ ENTRY(trap)
movel %sp,%sp at - | stack frame pointer argument
bsrl trap_c
addql #4,%sp
- jra .Lret_from_exception
+ jra ret_from_exception

| After a fork we jump here directly from resume,
| so that %d1 contains the previous task
@@ -74,7 +74,7 @@ ENTRY(ret_from_fork)
movel %d1,%sp at -
jsr schedule_tail
addql #4,%sp
- jra .Lret_from_exception
+ jra ret_from_exception

do_trace_entry:
movel #-ENOSYS,%sp@(PT_OFF_D0)| needed for strace
@@ -96,7 +96,7 @@ do_trace_exit:
jbsr syscall_trace
RESTORE_SWITCH_STACK
addql #4,%sp
- jra .Lret_from_exception
+ jra ret_from_exception

ENTRY(ret_from_signal)
movel %curptr@(TASK_STACK),%a1
@@ -115,7 +115,7 @@ ENTRY(ret_from_signal)
addql #4,%sp
1:
#endif
- jra .Lret_from_exception
+ jra ret_from_exception

ENTRY(system_call)
SAVE_ALL_SYS
@@ -154,7 +154,6 @@ syscall_exit_work:


ENTRY(ret_from_exception)
-.Lret_from_exception:
btst #5,%sp@(PT_OFF_SR) | check if returning to kernel
bnes 1f | if so, skip resched, signals
| only allow interrupts when we are really the last one on the
@@ -230,7 +229,7 @@ ret_from_last_interrupt:

/* check if we need to do software interrupts */
tstl irq_stat+CPUSTAT_SOFTIRQ_PENDING
- jeq .Lret_from_exception
+ jeq ret_from_exception
pea ret_from_exception
jra do_softirq

[gerg]

From: Greg Ungerer <gerg at uclinux.org>

There is a few places that the m68k entry code uses the bsrl instruction
to call other functions. That instruction is only supported on 68020 and
higher CPU types. If we use jbsr instead the code will be clean for all
68k and ColdFire CPU types.

Signed-off-by: Greg Ungerer <gerg at uclinux.org>
---
arch/m68k/kernel/entry_mm.S | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/m68k/kernel/entry_mm.S b/arch/m68k/kernel/entry_mm.S
index f2ecc64..fca00b4 100644
--- a/arch/m68k/kernel/entry_mm.S
+++ b/arch/m68k/kernel/entry_mm.S
@@ -55,7 +55,7 @@ ENTRY(buserr)
SAVE_ALL_INT
GET_CURRENT(%d0)
movel %sp,%sp at - | stack frame pointer argument
- bsrl buserr_c
+ jbsr buserr_c
addql #4,%sp
jra ret_from_exception

@@ -63,7 +63,7 @@ ENTRY(trap)
SAVE_ALL_INT
GET_CURRENT(%d0)
movel %sp,%sp at - | stack frame pointer argument
- bsrl trap_c
+ jbsr trap_c
addql #4,%sp
jra ret_from_exception

[gerg]

From: Greg Ungerer <gerg at uclinux.org>

Some of the entry.S code is common to both MMU and non-MMU builds.
So merge the entry_no.S and entry_mm.S files back into a single file.
With a little code movement we only need a single #ifdef.

Signed-off-by: Greg Ungerer <gerg at uclinux.org>
---
arch/m68k/kernel/{entry_mm.S => entry.S} | 105 ++++++++++++++++--------
arch/m68k/kernel/entry_no.S | 130 ------------------------------
2 files changed, 69 insertions(+), 166 deletions(-)
rename arch/m68k/kernel/{entry_mm.S => entry.S} (94%)
delete mode 100644 arch/m68k/kernel/entry_no.S

diff --git a/arch/m68k/kernel/entry_mm.S b/arch/m68k/kernel/entry.S
similarity index 94%
rename from arch/m68k/kernel/entry_mm.S
rename to arch/m68k/kernel/entry.S
index fca00b4..072626a 100644
--- a/arch/m68k/kernel/entry_mm.S
+++ b/arch/m68k/kernel/entry.S
@@ -51,6 +51,42 @@
.globl user_irqvec_fixup

.text
+ENTRY(sys_fork)
+ SAVE_SWITCH_STACK
+ pea %sp@(SWITCH_STACK_SIZE)
+ jbsr m68k_fork
+ addql #4,%sp
+ RESTORE_SWITCH_STACK
+ rts
+
+ENTRY(sys_clone)
+ SAVE_SWITCH_STACK
+ pea %sp@(SWITCH_STACK_SIZE)
+ jbsr m68k_clone
+ addql #4,%sp
+ RESTORE_SWITCH_STACK
+ rts
+
+ENTRY(sys_vfork)
+ SAVE_SWITCH_STACK
+ pea %sp@(SWITCH_STACK_SIZE)
+ jbsr m68k_vfork
+ addql #4,%sp
+ RESTORE_SWITCH_STACK
+ rts
+
+ENTRY(sys_sigreturn)
+ SAVE_SWITCH_STACK
+ jbsr do_sigreturn
+ RESTORE_SWITCH_STACK
+ rts
+
+ENTRY(sys_rt_sigreturn)
+ SAVE_SWITCH_STACK
+ jbsr do_rt_sigreturn
+ RESTORE_SWITCH_STACK
+ rts
+
ENTRY(buserr)
SAVE_ALL_INT
GET_CURRENT(%d0)
@@ -76,6 +112,38 @@ ENTRY(ret_from_fork)
addql #4,%sp
jra ret_from_exception

+#if defined(CONFIG_COLDFIRE) || !defined(CONFIG_MMU)
+
+#ifdef TRAP_DBG_INTERRUPT
+
+.globl dbginterrupt
+ENTRY(dbginterrupt)
+ SAVE_ALL_INT
+ GET_CURRENT(%d0)
+ movel %sp,%sp at - /* stack frame pointer argument */
+ jsr dbginterrupt_c
+ addql #4,%sp
+ jra ret_from_exception
+#endif
+
+ENTRY(reschedule)
+ /* save top of frame */
+ pea %sp@
+ jbsr set_esp0
+ addql #4,%sp
+ pea ret_from_exception
+ jmp schedule
+
+ENTRY(ret_from_user_signal)
+ moveq #__NR_sigreturn,%d0
+ trap #0
+
+ENTRY(ret_from_user_rt_signal)
+ movel #__NR_rt_sigreturn,%d0
+ trap #0
+
+#else
+
do_trace_entry:
movel #-ENOSYS,%sp@(PT_OFF_D0)| needed for strace
subql #4,%sp
@@ -273,42 +341,6 @@ ENTRY(bad_inthandler)
RESTORE_ALL


-ENTRY(sys_fork)
- SAVE_SWITCH_STACK
- pea %sp@(SWITCH_STACK_SIZE)
- jbsr m68k_fork
- addql #4,%sp
- RESTORE_SWITCH_STACK
- rts
-
-ENTRY(sys_clone)
- SAVE_SWITCH_STACK
- pea %sp@(SWITCH_STACK_SIZE)
- jbsr m68k_clone
- addql #4,%sp
- RESTORE_SWITCH_STACK
- rts
-
-ENTRY(sys_vfork)
- SAVE_SWITCH_STACK
- pea %sp@(SWITCH_STACK_SIZE)
- jbsr m68k_vfork
- addql #4,%sp
- RESTORE_SWITCH_STACK
- rts
-
-ENTRY(sys_sigreturn)
- SAVE_SWITCH_STACK
- jbsr do_sigreturn
- RESTORE_SWITCH_STACK
- rts
-
-ENTRY(sys_rt_sigreturn)
- SAVE_SWITCH_STACK
- jbsr do_rt_sigreturn
- RESTORE_SWITCH_STACK
- rts
-
resume:
/*
* Beware - when entering resume, prev (the current task) is
@@ -416,3 +448,4 @@ resume:

rts

+#endif /* CONFIG_MMU && !CONFIG_COLDFIRE */
diff --git a/arch/m68k/kernel/entry_no.S b/arch/m68k/kernel/entry_no.S
deleted file mode 100644
index d80cba4..0000000
--- a/arch/m68k/kernel/entry_no.S
+++ /dev/null
@@ -1,130 +0,0 @@
-/*
- * linux/arch/m68knommu/kernel/entry.S
- *
- * Copyright (C) 1999-2002, Greg Ungerer (gerg at snapgear.com)
- * Copyright (C) 1998 D. Jeff Dionne <jeff at lineo.ca>,
- * Kenneth Albanowski <kjahds at kjahds.com>,
- * Copyright (C) 2000 Lineo Inc. (www.lineo.com)
- *
- * Based on:
- *
- * linux/arch/m68k/kernel/entry.S
- *
- * Copyright (C) 1991, 1992 Linus Torvalds
- *
- * This file is subject to the terms and conditions of the GNU General Public
- * License. See the file README.legal in the main directory of this archive
- * for more details.
- *
- * Linux/m68k support by Hamish Macdonald
- *
- * 68060 fixes by Jesper Skov
- * ColdFire support by Greg Ungerer (gerg at snapgear.com)
- * 5307 fixes by David W. Miller
- * linux 2.4 support David McCullough <davidm at snapgear.com>
- */
-
-#include <linux/linkage.h>
-#include <asm/errno.h>
-#include <asm/setup.h>
-#include <asm/segment.h>
-#include <asm/asm-offsets.h>
-#include <asm/entry.h>
-#include <asm/unistd.h>
-
-.text
-
-.globl buserr
-.globl trap
-.globl ret_from_exception
-.globl ret_from_signal
-.globl sys_fork
-.globl sys_clone
-.globl sys_vfork
-
-ENTRY(buserr)
- SAVE_ALL_INT
- GET_CURRENT(%d0)
- movel %sp,%sp at - /* stack frame pointer argument */
- jsr buserr_c
- addql #4,%sp
- jra ret_from_exception
-
-ENTRY(trap)
- SAVE_ALL_INT
- GET_CURRENT(%d0)
- movel %sp,%sp at - /* stack frame pointer argument */
- jsr trap_c
- addql #4,%sp
- jra ret_from_exception
-
-#ifdef TRAP_DBG_INTERRUPT
-
-.globl dbginterrupt
-ENTRY(dbginterrupt)
- SAVE_ALL_INT
- GET_CURRENT(%d0)
- movel %sp,%sp at - /* stack frame pointer argument */
- jsr dbginterrupt_c
- addql #4,%sp
- jra ret_from_exception
-#endif
-
-ENTRY(reschedule)
- /* save top of frame */
- pea %sp@
- jbsr set_esp0
- addql #4,%sp
- pea ret_from_exception
- jmp schedule
-
-ENTRY(ret_from_fork)
- movel %d1,%sp at -
- jsr schedule_tail
- addql #4,%sp
- jra ret_from_exception
-
-ENTRY(sys_fork)
- SAVE_SWITCH_STACK
- pea %sp@(SWITCH_STACK_SIZE)
- jbsr m68k_fork
- addql #4,%sp
- RESTORE_SWITCH_STACK
- rts
-
-ENTRY(sys_vfork)
- SAVE_SWITCH_STACK
- pea %sp@(SWITCH_STACK_SIZE)
- jbsr m68k_vfork
- addql #4,%sp
- RESTORE_SWITCH_STACK
- rts
-
-ENTRY(sys_clone)
- SAVE_SWITCH_STACK
- pea %sp@(SWITCH_STACK_SIZE)
- jbsr m68k_clone
- addql #4,%sp
- RESTORE_SWITCH_STACK
- rts
-
-ENTRY(sys_sigreturn)
- SAVE_SWITCH_STACK
- jbsr do_sigreturn
- RESTORE_SWITCH_STACK
- rts
-
-ENTRY(sys_rt_sigreturn)
- SAVE_SWITCH_STACK
- jbsr do_rt_sigreturn
- RESTORE_SWITCH_STACK
- rts
-
-ENTRY(ret_from_user_signal)
- moveq #__NR_sigreturn,%d0
- trap #0
-
-ENTRY(ret_from_user_rt_signal)
- movel #__NR_rt_sigreturn,%d0
- trap #0
-

[Greg Ungerer]

Hi Andreas,

Post by gerg
The ret_from_excption code is referenced by its function name, or by a label
set at the start of its code. Modify all uses to consistently just use the
function name "ret_from_exception".

This will cause all branches to use the long variant, because
ret_from_exception is a global symbol (and thus overridable in the ELF
model). The point of the additional local label is to allow the
assembler to relax the branches.

Ah, ok. I was wondering why it was done this way.

The only problem cases for me in merging entry.S are the uses in:

buserr
trap
ret_from_fork

buserr and trap are not hot paths, so do you see any issue making
them the long variant?

I don't know that even the ret_from_fork case is too much to worry
about either. We have done an awfull lot of work up to this point,
a couple of bytes more and a long branch won't make any real difference
to performance here.

Regards
Greg


------------------------------------------------------------------------
Greg Ungerer -- Principal Engineer EMAIL: gerg at snapgear.com
SnapGear Group, McAfee PHONE: [phone]
8 Gardner Close FAX: [phone]
Milton, QLD, 4064, Australia WEB: http://www.SnapGear.com

[Andreas Schwab]

Post by gerg
The ret_from_excption code is referenced by its function name, or by a label
set at the start of its code. Modify all uses to consistently just use the
function name "ret_from_exception".

This will cause all branches to use the long variant, because
ret_from_exception is a global symbol (and thus overridable in the ELF
model). The point of the additional local label is to allow the
assembler to relax the branches.

Andreas.