powerpc/mpc85xx: Don't relocate exception vectors

PATCH New Scott Wood 2 participants 4 messages Apr 8, 2015 – Apr 20, 2015 PowerPC

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Scott Wood

author

2015-04-08 01:20 UTC #0 lore raw

PATCH 1/2 powerpc/mpc85xx: Don't relocate exception vectors

Booke does not require exception vectors to be located at address zero. U-Boot was doing so anyway, simply because that's how it had been done on other PPC. The downside of this is that once the OS is loaded to address zero, the exception vectors have been overwritten -- which makes it difficult to diagnose a crash that happens after that point.

The IVOR setup and trap entry code is simplified somewhat as a result.

Also, there is no longer a need to align individual exceptions on 0x100 byte boundaries.

Signed-off-by Scott Wood <[email protected]>

---
 arch/powerpc/cpu/mpc85xx/start.S | 178 +++++++++++++--------------------------
 include/mpc85xx.h                |   4 -
 include/ppc_asm.tmpl             |  42 +++++++++
 3 files changed, 99 insertions(+), 125 deletions(-)

arch/powerpc/cpu/mpc85xx/start.S +57 ~~-121~~

index d8c9fb6..61883cb 100644
@@ -252,39 +252,36 @@ l2_disabled:
 	lis	r1,CONFIG_SYS_MONITOR_BASE at h
 	mtspr	IVPR,r1
 
-	lis	r3,(CONFIG_SYS_MONITOR_BASE & 0xffff)@h
-	ori	r3,r3,(CONFIG_SYS_MONITOR_BASE & 0xffff)@l
-
-	addi	r4,r3,CriticalInput - _start + _START_OFFSET
+	li	r4,CriticalInput at l
 	mtspr	IVOR0,r4	/* 0: Critical input */
-	addi	r4,r3,MachineCheck - _start + _START_OFFSET
+	li	r4,MachineCheck at l
 	mtspr	IVOR1,r4	/* 1: Machine check */
-	addi	r4,r3,DataStorage - _start + _START_OFFSET
+	li	r4,DataStorage at l
 	mtspr	IVOR2,r4	/* 2: Data storage */
-	addi	r4,r3,InstStorage - _start + _START_OFFSET
+	li	r4,InstStorage at l
 	mtspr	IVOR3,r4	/* 3: Instruction storage */
-	addi	r4,r3,ExtInterrupt - _start + _START_OFFSET
+	li	r4,ExtInterrupt at l
 	mtspr	IVOR4,r4	/* 4: External interrupt */
-	addi	r4,r3,Alignment - _start + _START_OFFSET
+	li	r4,Alignment at l
 	mtspr	IVOR5,r4	/* 5: Alignment */
-	addi	r4,r3,ProgramCheck - _start + _START_OFFSET
+	li	r4,ProgramCheck at l
 	mtspr	IVOR6,r4	/* 6: Program check */
-	addi	r4,r3,FPUnavailable - _start + _START_OFFSET
+	li	r4,FPUnavailable at l
 	mtspr	IVOR7,r4	/* 7: floating point unavailable */
-	addi	r4,r3,SystemCall - _start + _START_OFFSET
+	li	r4,SystemCall at l
 	mtspr	IVOR8,r4	/* 8: System call */
 	/* 9: Auxiliary processor unavailable(unsupported) */
-	addi	r4,r3,Decrementer - _start + _START_OFFSET
+	li	r4,Decrementer at l
 	mtspr	IVOR10,r4	/* 10: Decrementer */
-	addi	r4,r3,IntervalTimer - _start + _START_OFFSET
+	li	r4,IntervalTimer at l
 	mtspr	IVOR11,r4	/* 11: Interval timer */
-	addi	r4,r3,WatchdogTimer - _start + _START_OFFSET
+	li	r4,WatchdogTimer at l
 	mtspr	IVOR12,r4	/* 12: Watchdog timer */
-	addi	r4,r3,DataTLBError - _start + _START_OFFSET
+	li	r4,DataTLBError at l
 	mtspr	IVOR13,r4	/* 13: Data TLB error */
-	addi	r4,r3,InstructionTLBError - _start + _START_OFFSET
+	li	r4,InstructionTLBError at l
 	mtspr	IVOR14,r4	/* 14: Instruction TLB error */
-	addi	r4,r3,DebugBreakpoint - _start + _START_OFFSET
+	li	r4,DebugBreakpoint at l
 	mtspr	IVOR15,r4	/* 15: Debug */
 #endif

@@ -1121,7 +1118,7 @@ switch_as:
 	/*--------------------------------------------------------------*/
 	lis	r3,CONFIG_SYS_MONITOR_BASE at h
 	ori	r3,r3,CONFIG_SYS_MONITOR_BASE at l
-	addi	r3,r3,_start_cont - _start + _START_OFFSET
+	addi	r3,r3,_start_cont - _start
 	mtlr	r3
 	blr
 #endif

@@ -1165,7 +1162,6 @@ _start_cont:
 	/* NOTREACHED - board_init_f() does not return */
 
 #ifndef MINIMAL_SPL
-	. = EXC_OFF_SYS_RESET
 	.globl	_start_of_vectors
 _start_of_vectors:

@@ -1185,7 +1181,6 @@ _start_of_vectors:
 	STD_EXCEPTION(0x0500, ExtInterrupt, ExtIntException)
 
 /* Alignment exception. */
-	. = 0x0600
 Alignment:
 	EXCEPTION_PROLOG(SRR0, SRR1)
 	mfspr	r4,DAR

@@ -1193,21 +1188,20 @@ Alignment:
 	mfspr	r5,DSISR
 	stw	r5,_DSISR(r21)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	EXC_XFER_TEMPLATE(Alignment, AlignmentException, MSR_KERNEL, COPY_EE)
+	EXC_XFER_TEMPLATE(0x600, Alignment, AlignmentException,
+		MSR_KERNEL, COPY_EE)
 
 /* Program check exception */
-	. = 0x0700
 ProgramCheck:
 	EXCEPTION_PROLOG(SRR0, SRR1)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	EXC_XFER_TEMPLATE(ProgramCheck, ProgramCheckException,
+	EXC_XFER_TEMPLATE(0x700, ProgramCheck, ProgramCheckException,
 		MSR_KERNEL, COPY_EE)
 
 	/* No FPU on MPC85xx.  This exception is not supposed to happen.
 	*/
 	STD_EXCEPTION(0x0800, FPUnavailable, UnknownException)
 
-	. = 0x0900
 /*
  * r0 - SYSCALL number
  * r3-... arguments

@@ -1293,32 +1287,22 @@ _end_of_vectors:
  * This code finishes saving the registers to the exception frame
  * and jumps to the appropriate handler for the exception.
  * Register r21 is pointer into trap frame, r1 has new stack pointer.
+ * r23 is the address of the handler.
  */
 	.globl	transfer_to_handler
 transfer_to_handler:
-	stw	r22,_NIP(r21)
-	lis	r22,MSR_POW at h
-	andc	r23,r23,r22
-	stw	r23,_MSR(r21)
 	SAVE_GPR(7, r21)
 	SAVE_4GPRS(8, r21)
 	SAVE_8GPRS(12, r21)
 	SAVE_8GPRS(24, r21)
 
-	mflr	r23
-	andi.	r24,r23,0x3f00		/* get vector offset */
-	stw	r24,TRAP(r21)
 	li	r22,0
 	stw	r22,RESULT(r21)
 	mtspr	SPRG2,r22		/* r1 is now kernel sp */
 
-	lwz	r24,0(r23)		/* virtual address of handler */
-	lwz	r23,4(r23)		/* where to go when done */
-	mtspr	SRR0,r24
-	mtspr	SRR1,r20
-	mtlr	r23
-	SYNC
-	rfi				/* jump to handler, enable MMU */
+	mtctr	r23			/* virtual address of handler */
+	mtmsr	r20
+	bctrl
 
 int_return:
 	mfmsr	r28		/* Disable interrupts */

@@ -1728,7 +1712,7 @@ relocate_code:
  * initialization, now running from RAM.
  */
 
-	addi	r0,r10,in_ram - _start + _START_OFFSET
+	addi	r0,r10,in_ram - _start
 
 	/*
 	 * As IVPR is going to point RAM address,

@@ -1816,89 +1800,41 @@ clear_bss:
 	 */
 	.globl	trap_init
 trap_init:
-	mflr	r4			/* save link register		*/
-	GET_GOT
-	lwz	r7,GOT(_start_of_vectors)
-	lwz	r8,GOT(_end_of_vectors)
-
-	li	r9,0x100		/* reset vector always at 0x100 */
-
-	cmplw	0,r7,r8
-	bgelr				/* return if r7>=r8 - just in case */
-1:
-	lwz	r0,0(r7)
-	stw	r0,0(r9)
-	addi	r7,r7,4
-	addi	r9,r9,4
-	cmplw	0,r7,r8
-	bne	1b
+	/* Update IVORs as per relocation */
+	mtspr	IVPR,r3
 
-	/*
-	 * relocate `hdlr' and `int_return' entries
-	 */
-	li	r7,.L_CriticalInput - _start + _START_OFFSET
-	bl	trap_reloc
-	li	r7,.L_MachineCheck - _start + _START_OFFSET
-	bl	trap_reloc
-	li	r7,.L_DataStorage - _start + _START_OFFSET
-	bl	trap_reloc
-	li	r7,.L_InstStorage - _start + _START_OFFSET
-	bl	trap_reloc
-	li	r7,.L_ExtInterrupt - _start + _START_OFFSET
-	bl	trap_reloc
-	li	r7,.L_Alignment - _start + _START_OFFSET
-	bl	trap_reloc
-	li	r7,.L_ProgramCheck - _start + _START_OFFSET
-	bl	trap_reloc
-	li	r7,.L_FPUnavailable - _start + _START_OFFSET
-	bl	trap_reloc
-	li	r7,.L_Decrementer - _start + _START_OFFSET
-	bl	trap_reloc
-	li	r7,.L_IntervalTimer - _start + _START_OFFSET
-	li	r8,_end_of_vectors - _start + _START_OFFSET
-2:
-	bl	trap_reloc
-	addi	r7,r7,0x100		/* next exception vector	*/
-	cmplw	0,r7,r8
-	blt	2b
-
-	/* Update IVORs as per relocated vector table address */
-	li	r7,0x0100
-	mtspr	IVOR0,r7	/* 0: Critical input */
-	li	r7,0x0200
-	mtspr	IVOR1,r7	/* 1: Machine check */
-	li	r7,0x0300
-	mtspr	IVOR2,r7	/* 2: Data storage */
-	li	r7,0x0400
-	mtspr	IVOR3,r7	/* 3: Instruction storage */
-	li	r7,0x0500
-	mtspr	IVOR4,r7	/* 4: External interrupt */
-	li	r7,0x0600
-	mtspr	IVOR5,r7	/* 5: Alignment */
-	li	r7,0x0700
-	mtspr	IVOR6,r7	/* 6: Program check */
-	li	r7,0x0800
-	mtspr	IVOR7,r7	/* 7: floating point unavailable */
-	li	r7,0x0900
-	mtspr	IVOR8,r7	/* 8: System call */
+	li	r4,CriticalInput at l
+	mtspr	IVOR0,r4	/* 0: Critical input */
+	li	r4,MachineCheck at l
+	mtspr	IVOR1,r4	/* 1: Machine check */
+	li	r4,DataStorage at l
+	mtspr	IVOR2,r4	/* 2: Data storage */
+	li	r4,InstStorage at l
+	mtspr	IVOR3,r4	/* 3: Instruction storage */
+	li	r4,ExtInterrupt at l
+	mtspr	IVOR4,r4	/* 4: External interrupt */
+	li	r4,Alignment at l
+	mtspr	IVOR5,r4	/* 5: Alignment */
+	li	r4,ProgramCheck at l
+	mtspr	IVOR6,r4	/* 6: Program check */
+	li	r4,FPUnavailable at l
+	mtspr	IVOR7,r4	/* 7: floating point unavailable */
+	li	r4,SystemCall at l
+	mtspr	IVOR8,r4	/* 8: System call */
 	/* 9: Auxiliary processor unavailable(unsupported) */
-	li	r7,0x0a00
-	mtspr	IVOR10,r7	/* 10: Decrementer */
-	li	r7,0x0b00
-	mtspr	IVOR11,r7	/* 11: Interval timer */
-	li	r7,0x0c00
-	mtspr	IVOR12,r7	/* 12: Watchdog timer */
-	li	r7,0x0d00
-	mtspr	IVOR13,r7	/* 13: Data TLB error */
-	li	r7,0x0e00
-	mtspr	IVOR14,r7	/* 14: Instruction TLB error */
-	li	r7,0x0f00
-	mtspr	IVOR15,r7	/* 15: Debug */
-
-	lis	r7,0x0
-	mtspr	IVPR,r7
-
-	mtlr	r4			/* restore link register	*/
+	li	r4,Decrementer at l
+	mtspr	IVOR10,r4	/* 10: Decrementer */
+	li	r4,IntervalTimer at l
+	mtspr	IVOR11,r4	/* 11: Interval timer */
+	li	r4,WatchdogTimer at l
+	mtspr	IVOR12,r4	/* 12: Watchdog timer */
+	li	r4,DataTLBError at l
+	mtspr	IVOR13,r4	/* 13: Data TLB error */
+	li	r4,InstructionTLBError at l
+	mtspr	IVOR14,r4	/* 14: Instruction TLB error */
+	li	r4,DebugBreakpoint at l
+	mtspr	IVOR15,r4	/* 15: Debug */
+
 	blr
 
 .globl unlock_ram_in_cache

include/mpc85xx.h +0 -4

index 11d8985..3753e47 100644
@@ -6,10 +6,6 @@
 #ifndef	__MPC85xx_H__
 #define __MPC85xx_H__
 
-/* define for common ppc_asm.tmpl */
-#define EXC_OFF_SYS_RESET	0x100	/* System reset */
-#define _START_OFFSET		0
-
 #if defined(CONFIG_E500)
 #include <e500.h>
 #endif

include/ppc_asm.tmpl +42 -0

58 lines not on this page · raw message

Signature · 1 line

2.1.0

Scott Wood

author

2015-04-08 01:20 UTC #1 lore raw

PATCH 2/2 powerpc/mpc85xx: Remove some dead code

U-Boot does not have system calls (the services it exposes to standalone commands use a different mechanism), so the syscall handler is dead code. It's also broken code, as it assumes it is located at 0xc00 -- while even before the patch to stop relocating exception vectors to 0, U-Boot had the syscall at 0x900.

The critical and machine check return paths are never called -- the regular exception return path is used instead, which works because xSRR0/1 have already been saved and can be restored via the regular SRR0/1 (we don't care too much in U-Boot about taking a critical/mcheck inside another exception prolog/epilog).

Also remove a few other small unused functions.

Signed-off-by Scott Wood <[email protected]>

---
 arch/powerpc/cpu/mpc85xx/start.S | 138 +--------------------------------------
 include/common.h                 |   1 -
 2 files changed, 1 insertion(+), 138 deletions(-)

arch/powerpc/cpu/mpc85xx/start.S +1 ~~-137~~

index 61883cb..28f04ee 100644
@@ -1201,73 +1201,7 @@ ProgramCheck:
 	/* No FPU on MPC85xx.  This exception is not supposed to happen.
 	*/
 	STD_EXCEPTION(0x0800, FPUnavailable, UnknownException)
-
-/*
- * r0 - SYSCALL number
- * r3-... arguments
- */
-SystemCall:
-	addis	r11,r0,0	/* get functions table addr */
-	ori	r11,r11,0	/* Note: this code is patched in trap_init */
-	addis	r12,r0,0	/* get number of functions */
-	ori	r12,r12,0
-
-	cmplw	0,r0,r12
-	bge	1f
-
-	rlwinm	r0,r0,2,0,31	/* fn_addr = fn_tbl[r0] */
-	add	r11,r11,r0
-	lwz	r11,0(r11)
-
-	li	r20,0xd00-4	/* Get stack pointer */
-	lwz	r12,0(r20)
-	subi	r12,r12,12	/* Adjust stack pointer */
-	li	r0,0xc00+_end_back-SystemCall
-	cmplw	0,r0,r12	/* Check stack overflow */
-	bgt	1f
-	stw	r12,0(r20)
-
-	mflr	r0
-	stw	r0,0(r12)
-	mfspr	r0,SRR0
-	stw	r0,4(r12)
-	mfspr	r0,SRR1
-	stw	r0,8(r12)
-
-	li	r12,0xc00+_back-SystemCall
-	mtlr	r12
-	mtspr	SRR0,r11
-
-1:	SYNC
-	rfi
-_back:
-
-	mfmsr	r11			/* Disable interrupts */
-	li	r12,0
-	ori	r12,r12,MSR_EE
-	andc	r11,r11,r12
-	SYNC				/* Some chip revs need this... */
-	mtmsr	r11
-	SYNC
-
-	li	r12,0xd00-4		/* restore regs */
-	lwz	r12,0(r12)
-
-	lwz	r11,0(r12)
-	mtlr	r11
-	lwz	r11,4(r12)
-	mtspr	SRR0,r11
-	lwz	r11,8(r12)
-	mtspr	SRR1,r11
-
-	addi	r12,r12,12		/* Adjust stack pointer */
-	li	r20,0xd00-4
-	stw	r12,0(r20)
-
-	SYNC
-	rfi
-_end_back:
-
+	STD_EXCEPTION(0x0900, SystemCall, UnknownException)
 	STD_EXCEPTION(0x0a00, Decrementer, timer_interrupt)
 	STD_EXCEPTION(0x0b00, IntervalTimer, UnknownException)
 	STD_EXCEPTION(0x0c00, WatchdogTimer, UnknownException)

@@ -1334,66 +1268,6 @@ int_return:
 	SYNC
 	rfi
 
-crit_return:
-	mfmsr	r28		/* Disable interrupts */
-	li	r4,0
-	ori	r4,r4,MSR_EE
-	andc	r28,r28,r4
-	SYNC			/* Some chip revs need this... */
-	mtmsr	r28
-	SYNC
-	lwz	r2,_CTR(r1)
-	lwz	r0,_LINK(r1)
-	mtctr	r2
-	mtlr	r0
-	lwz	r2,_XER(r1)
-	lwz	r0,_CCR(r1)
-	mtspr	XER,r2
-	mtcrf	0xFF,r0
-	REST_10GPRS(3, r1)
-	REST_10GPRS(13, r1)
-	REST_8GPRS(23, r1)
-	REST_GPR(31, r1)
-	lwz	r2,_NIP(r1)	/* Restore environment */
-	lwz	r0,_MSR(r1)
-	mtspr	SPRN_CSRR0,r2
-	mtspr	SPRN_CSRR1,r0
-	lwz	r0,GPR0(r1)
-	lwz	r2,GPR2(r1)
-	lwz	r1,GPR1(r1)
-	SYNC
-	rfci
-
-mck_return:
-	mfmsr	r28		/* Disable interrupts */
-	li	r4,0
-	ori	r4,r4,MSR_EE
-	andc	r28,r28,r4
-	SYNC			/* Some chip revs need this... */
-	mtmsr	r28
-	SYNC
-	lwz	r2,_CTR(r1)
-	lwz	r0,_LINK(r1)
-	mtctr	r2
-	mtlr	r0
-	lwz	r2,_XER(r1)
-	lwz	r0,_CCR(r1)
-	mtspr	XER,r2
-	mtcrf	0xFF,r0
-	REST_10GPRS(3, r1)
-	REST_10GPRS(13, r1)
-	REST_8GPRS(23, r1)
-	REST_GPR(31, r1)
-	lwz	r2,_NIP(r1)	/* Restore environment */
-	lwz	r0,_MSR(r1)
-	mtspr	SPRN_MCSRR0,r2
-	mtspr	SPRN_MCSRR1,r0
-	lwz	r0,GPR0(r1)
-	lwz	r2,GPR2(r1)
-	lwz	r1,GPR1(r1)
-	SYNC
-	rfmci
-
 /* Cache functions.
 */
 .globl flush_icache

@@ -1478,11 +1352,6 @@ dcache_status:
 	andi.	r3,r3,L1CSR0_DCE
 	blr
 
-	.globl get_pir
-get_pir:
-	mfspr	r3,PIR
-	blr
-
 	.globl get_pvr
 get_pvr:
 	mfspr	r3,PVR

@@ -1493,11 +1362,6 @@ get_svr:
 	mfspr	r3,SVR
 	blr
 
-	.globl wr_tcr
-wr_tcr:
-	mtspr	TCR,r3
-	blr
-
 /*------------------------------------------------------------------------------- */
 /* Function:	 in8 */
 /* Description:	 Input 8 bits */

include/common.h +0 -1

index 6df05b8..f2d0f64 100644
@@ -471,7 +471,6 @@ int testdram(void);
     defined(CONFIG_8xx)
 uint	get_immr      (uint);
 #endif
-uint	get_pir	      (void);
 #if defined(CONFIG_MPC5xxx)
 uint	get_svr       (void);
 #endif

Signature · 1 line

2.1.0

York Sun

Applied

2015-04-20 21:01 UTC #2 lore raw

PATCH 2/2 powerpc/mpc85xx: Remove some dead code

Quoted 12 lines · Scott Wood

U-Boot does not have system calls (the services it exposes to standalone commands use a different mechanism), so the syscall handler is dead code. It's also broken code, as it assumes it is located at 0xc00 -- while even before the patch to stop relocating exception vectors to 0, U-Boot had the syscall at 0x900.
The critical and machine check return paths are never called -- the regular exception return path is used instead, which works because xSRR0/1 have already been saved and can be restored via the regular SRR0/1 (we don't care too much in U-Boot about taking a critical/mcheck inside another exception prolog/epilog).

Quoted 4 lines

Also remove a few other small unused functions.
Signed-off-by Scott Wood <[email protected]>
---

Applied to mpc85xx master, awaiting upstream.

York

York Sun

Applied

2015-04-20 21:00 UTC #3 lore raw

PATCH 1/2 powerpc/mpc85xx: Don't relocate exception vectors

In reply to Scott Wood

Quoted 6 lines · Scott Wood

Booke does not require exception vectors to be located at address zero. U-Boot was doing so anyway, simply because that's how it had been done on other PPC. The downside of this is that once the OS is loaded to address zero, the exception vectors have been overwritten -- which makes it difficult to diagnose a crash that happens after that point.

Quoted 7 lines

The IVOR setup and trap entry code is simplified somewhat as a result.
Also, there is no longer a need to align individual exceptions on 0x100 byte boundaries.
Signed-off-by Scott Wood <[email protected]>
---

Applied to mpc85xx master, awaiting upstream.

York