MIPS: add handling for generic and EJTAG exceptions

Add exception handlers for generic and EJTAG exceptions. Most of
the assembly code is imported from Linux kernel and adapted to U-Boot.
The exception vector table will be reserved above the stack before
U-Boot is relocated. The exception handlers will be installed and
activated after relocation in the initr_traps hook function.

Generic exceptions are handled by showing a CPU register dump similar
to Linux kernel. For example:

malta # md 1
00000001:
Ooops:
$ 0   : 00000000 00000000 00000009 00000004
$ 4   : 8ff7e108 00000000 0000003a 00000000
$ 8   : 00000008 00000001 8ff7cd18 00000004
$12   : 00000002 00000000 00000005 0000003a
$16   : 00000004 00000040 00000001 00000001
$20   : 00000000 8fff53c0 00000008 00000004
$24   : ffffffff 8ffdea44
$28   : 90001650 8ff7cd00 00000004 8ffe6818
Hi    : 00000000
Lo    : 00000004
epc   : 8ffe6848 (text bfc28848)
ra    : 8ffe6818 (text bfc28818)
Status: 00000006
Cause : 00000410 (ExcCode 04)
BadVA : 8ff9e928
PrId  : 00019300
 ### ERROR ### Please RESET the board ###

EJTAG exceptions are checked for SDBBP and delegated to the SDBBP handler
if necessary. Otherwise the debug mode will simply be exited. The SDBBP
handler currently prints the contents of registers c0_depc and c0_debug.
This could be extended in the future to handle semi-hosting according to
the MIPS UHI specification.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Reviewed-by: Paul Burton <paul.burton@imgtec.com>
Tested-by: Paul Burton <paul.burton@imgtec.com>

diff --git a/arch/mips/include/asm/system.h b/arch/mips/include/asm/system.h
index e6435cc..c9c5961 100644 (file)
--- a/arch/mips/include/asm/system.h
+++ b/arch/mips/include/asm/system.h
@@ -262,4 +262,12 @@ extern void __die_if_kernel(const char *, struct pt_regs *, const char *where,
 #define die_if_kernel(msg, regs)                                       \
        __die_if_kernel(msg, regs, __FILE__ ":"__FUNCTION__, __LINE__)
 
+static inline void execution_hazard_barrier(void)
+{
+       __asm__ __volatile__(
+               ".set noreorder\n"
+               "ehb\n"
+               ".set reorder");
+}
+
 #endif /* _ASM_SYSTEM_H */

diff --git a/arch/mips/include/asm/u-boot-mips.h b/arch/mips/include/asm/u-boot-mips.h
index 1f527bb..71ff41d 100644 (file)
--- a/arch/mips/include/asm/u-boot-mips.h
+++ b/arch/mips/include/asm/u-boot-mips.h
@@ -5,4 +5,8 @@
 #ifndef _U_BOOT_MIPS_H_
 #define _U_BOOT_MIPS_H_
 
+void exc_handler(void);
+void except_vec3_generic(void);
+void except_vec_ejtag_debug(void);
+
 #endif /* _U_BOOT_MIPS_H_ */

diff --git a/arch/mips/lib/Makefile b/arch/mips/lib/Makefile
index 02607f7..659c6ad 100644 (file)
--- a/arch/mips/lib/Makefile
+++ b/arch/mips/lib/Makefile
@@ -7,7 +7,9 @@
 
 obj-y  += cache.o
 obj-y  += cache_init.o
+obj-y  += genex.o
 obj-y  += stack.o
+obj-y  += traps.o
 
 obj-$(CONFIG_CMD_BOOTM) += bootm.o
 

diff --git a/arch/mips/lib/genex.S b/arch/mips/lib/genex.S
new file mode 100644 (file)
index 0000000..2d6d7b0
--- /dev/null
+++ b/arch/mips/lib/genex.S
@@ -0,0 +1,224 @@
+/*
+ * Copyright (C) 1994 - 2000, 2001, 2003 Ralf Baechle
+ * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
+ * Copyright (C) 2002, 2007  Maciej W. Rozycki
+ * Copyright (C) 2001, 2012 MIPS Technologies, Inc.  All rights reserved.
+ *
+ * SPDX-License-Identifier:    GPL-2.0+
+ */
+
+#include <asm/asm.h>
+#include <asm/regdef.h>
+#include <asm/mipsregs.h>
+#include <asm/asm-offsets.h>
+
+#define STATMASK 0x1f
+
+       .set    noreorder
+
+       /*
+        * Macros copied and adapted from Linux MIPS
+        */
+       .macro  SAVE_AT
+       .set    push
+       .set    noat
+       LONG_S  $1, PT_R1(sp)
+       .set    pop
+       .endm
+
+       .macro  SAVE_TEMP
+#if __mips_isa_rev < 6
+       mfhi    v1
+#endif
+#ifdef CONFIG_32BIT
+       LONG_S  $8, PT_R8(sp)
+       LONG_S  $9, PT_R9(sp)
+#endif
+       LONG_S  $10, PT_R10(sp)
+       LONG_S  $11, PT_R11(sp)
+       LONG_S  $12, PT_R12(sp)
+#if __mips_isa_rev < 6
+       LONG_S  v1, PT_HI(sp)
+       mflo    v1
+#endif
+       LONG_S  $13, PT_R13(sp)
+       LONG_S  $14, PT_R14(sp)
+       LONG_S  $15, PT_R15(sp)
+       LONG_S  $24, PT_R24(sp)
+#if __mips_isa_rev < 6
+       LONG_S  v1, PT_LO(sp)
+#endif
+       .endm
+
+       .macro  SAVE_STATIC
+       LONG_S  $16, PT_R16(sp)
+       LONG_S  $17, PT_R17(sp)
+       LONG_S  $18, PT_R18(sp)
+       LONG_S  $19, PT_R19(sp)
+       LONG_S  $20, PT_R20(sp)
+       LONG_S  $21, PT_R21(sp)
+       LONG_S  $22, PT_R22(sp)
+       LONG_S  $23, PT_R23(sp)
+       LONG_S  $30, PT_R30(sp)
+       .endm
+
+       .macro  SAVE_SOME
+       .set    push
+       .set    noat
+       PTR_SUBU k1, sp, PT_SIZE
+       LONG_S  sp, PT_R29(k1)
+       move    sp, k1
+
+       LONG_S  $3, PT_R3(sp)
+       LONG_S  $0, PT_R0(sp)
+       mfc0    v1, CP0_STATUS
+       LONG_S  $2, PT_R2(sp)
+       LONG_S  v1, PT_STATUS(sp)
+       LONG_S  $4, PT_R4(sp)
+       mfc0    v1, CP0_CAUSE
+       LONG_S  $5, PT_R5(sp)
+       LONG_S  v1, PT_CAUSE(sp)
+       LONG_S  $6, PT_R6(sp)
+       MFC0    v1, CP0_EPC
+       LONG_S  $7, PT_R7(sp)
+#ifdef CONFIG_64BIT
+       LONG_S  $8, PT_R8(sp)
+       LONG_S  $9, PT_R9(sp)
+#endif
+       LONG_S  v1, PT_EPC(sp)
+       LONG_S  $25, PT_R25(sp)
+       LONG_S  $28, PT_R28(sp)
+       LONG_S  $31, PT_R31(sp)
+       .set    pop
+       .endm
+
+       .macro  RESTORE_AT
+       .set    push
+       .set    noat
+       LONG_L  $1,  PT_R1(sp)
+       .set    pop
+       .endm
+
+       .macro  RESTORE_TEMP
+#if __mips_isa_rev < 6
+       LONG_L  $24, PT_LO(sp)
+       mtlo    $24
+       LONG_L  $24, PT_HI(sp)
+       mthi    $24
+#endif
+#ifdef CONFIG_32BIT
+       LONG_L  $8, PT_R8(sp)
+       LONG_L  $9, PT_R9(sp)
+#endif
+       LONG_L  $10, PT_R10(sp)
+       LONG_L  $11, PT_R11(sp)
+       LONG_L  $12, PT_R12(sp)
+       LONG_L  $13, PT_R13(sp)
+       LONG_L  $14, PT_R14(sp)
+       LONG_L  $15, PT_R15(sp)
+       LONG_L  $24, PT_R24(sp)
+       .endm
+
+       .macro  RESTORE_STATIC
+       LONG_L  $16, PT_R16(sp)
+       LONG_L  $17, PT_R17(sp)
+       LONG_L  $18, PT_R18(sp)
+       LONG_L  $19, PT_R19(sp)
+       LONG_L  $20, PT_R20(sp)
+       LONG_L  $21, PT_R21(sp)
+       LONG_L  $22, PT_R22(sp)
+       LONG_L  $23, PT_R23(sp)
+       LONG_L  $30, PT_R30(sp)
+       .endm
+
+       .macro  RESTORE_SOME
+       .set    push
+       .set    reorder
+       .set    noat
+       mfc0    a0, CP0_STATUS
+       ori     a0, STATMASK
+       xori    a0, STATMASK
+       mtc0    a0, CP0_STATUS
+       li      v1, ST0_CU1 | ST0_FR | ST0_IM
+       and     a0, v1
+       LONG_L  v0, PT_STATUS(sp)
+       nor     v1, $0, v1
+       and     v0, v1
+       or      v0, a0
+       mtc0    v0, CP0_STATUS
+       LONG_L  v1, PT_EPC(sp)
+       MTC0    v1, CP0_EPC
+       LONG_L  $31, PT_R31(sp)
+       LONG_L  $28, PT_R28(sp)
+       LONG_L  $25, PT_R25(sp)
+#ifdef CONFIG_64BIT
+       LONG_L  $8, PT_R8(sp)
+       LONG_L  $9, PT_R9(sp)
+#endif
+       LONG_L  $7,  PT_R7(sp)
+       LONG_L  $6,  PT_R6(sp)
+       LONG_L  $5,  PT_R5(sp)
+       LONG_L  $4,  PT_R4(sp)
+       LONG_L  $3,  PT_R3(sp)
+       LONG_L  $2,  PT_R2(sp)
+       .set    pop
+       .endm
+
+       .macro  RESTORE_SP
+       LONG_L  sp, PT_R29(sp)
+       .endm
+
+NESTED(except_vec3_generic, 0, sp)
+       PTR_LA  k1, handle_reserved
+       jr      k1
+        nop
+       END(except_vec3_generic)
+
+NESTED(except_vec_ejtag_debug, 0, sp)
+       PTR_LA  k1, handle_ejtag_debug
+       jr      k1
+        nop
+       END(except_vec_ejtag_debug)
+
+NESTED(handle_reserved, PT_SIZE, sp)
+       SAVE_SOME
+       SAVE_AT
+       SAVE_TEMP
+       SAVE_STATIC
+
+       PTR_LA  t9, do_reserved
+       jr      t9
+        move   a0, sp
+       END(handle_reserved)
+
+NESTED(handle_ejtag_debug, PT_SIZE, sp)
+       .set    push
+       .set    noat
+       MTC0    k1, CP0_DESAVE
+
+       /* Check for SDBBP */
+       MFC0    k1, CP0_DEBUG
+       sll     k1, k1, 30
+       bgez    k1, ejtag_return
+        nop
+
+       SAVE_SOME
+       SAVE_AT
+       SAVE_TEMP
+       SAVE_STATIC
+
+       PTR_LA  t9, do_ejtag_debug
+       jalr    t9
+        move   a0, sp
+
+       RESTORE_TEMP
+       RESTORE_STATIC
+       RESTORE_AT
+       RESTORE_SOME
+       RESTORE_SP
+
+ejtag_return:
+       MFC0    k1, CP0_DESAVE
+       deret
+       .set pop
+       END(handle_ejtag_debug)

diff --git a/arch/mips/lib/traps.c b/arch/mips/lib/traps.c
new file mode 100644 (file)
index 0000000..18622c2
--- /dev/null
+++ b/arch/mips/lib/traps.c
@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) 1994 - 1999, 2000, 01, 06 Ralf Baechle
+ * Copyright (C) 1995, 1996 Paul M. Antoine
+ * Copyright (C) 1998 Ulf Carlsson
+ * Copyright (C) 1999 Silicon Graphics, Inc.
+ * Kevin D. Kissell, kevink@mips.com and Carsten Langgaard, carstenl@mips.com
+ * Copyright (C) 2002, 2003, 2004, 2005, 2007  Maciej W. Rozycki
+ * Copyright (C) 2000, 2001, 2012 MIPS Technologies, Inc.  All rights reserved.
+ * Copyright (C) 2014, Imagination Technologies Ltd.
+ *
+ * SPDX-License-Identifier:    GPL-2.0+
+ */
+
+#include <common.h>
+#include <asm/mipsregs.h>
+#include <asm/addrspace.h>
+#include <asm/system.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+static void show_regs(const struct pt_regs *regs)
+{
+       const int field = 2 * sizeof(unsigned long);
+       unsigned int cause = regs->cp0_cause;
+       unsigned int exccode;
+       int i;
+
+       /*
+        * Saved main processor registers
+        */
+       for (i = 0; i < 32; ) {
+               if ((i % 4) == 0)
+                       printf("$%2d   :", i);
+               if (i == 0)
+                       printf(" %0*lx", field, 0UL);
+               else if (i == 26 || i == 27)
+                       printf(" %*s", field, "");
+               else
+                       printf(" %0*lx", field, regs->regs[i]);
+
+               i++;
+               if ((i % 4) == 0)
+                       puts("\n");
+       }
+
+       printf("Hi    : %0*lx\n", field, regs->hi);
+       printf("Lo    : %0*lx\n", field, regs->lo);
+
+       /*
+        * Saved cp0 registers
+        */
+       printf("epc   : %0*lx (text %0*lx)\n", field, regs->cp0_epc,
+              field, regs->cp0_epc - gd->reloc_off);
+       printf("ra    : %0*lx (text %0*lx)\n", field, regs->regs[31],
+              field, regs->regs[31] - gd->reloc_off);
+
+       printf("Status: %08x\n", (uint32_t) regs->cp0_status);
+
+       exccode = (cause & CAUSEF_EXCCODE) >> CAUSEB_EXCCODE;
+       printf("Cause : %08x (ExcCode %02x)\n", cause, exccode);
+
+       if (1 <= exccode && exccode <= 5)
+               printf("BadVA : %0*lx\n", field, regs->cp0_badvaddr);
+
+       printf("PrId  : %08x\n", read_c0_prid());
+}
+
+void do_reserved(const struct pt_regs *regs)
+{
+       puts("\nOoops:\n");
+       show_regs(regs);
+       hang();
+}
+
+void do_ejtag_debug(const struct pt_regs *regs)
+{
+       const int field = 2 * sizeof(unsigned long);
+       unsigned long depc;
+       unsigned int debug;
+
+       depc = read_c0_depc();
+       debug = read_c0_debug();
+
+       printf("SDBBP EJTAG debug exception: c0_depc = %0*lx, DEBUG = %08x\n",
+              field, depc, debug);
+}
+
+static void set_handler(unsigned long offset, void *addr, unsigned long size)
+{
+       unsigned long ebase = gd->irq_sp;
+
+       memcpy((void *)(ebase + offset), addr, size);
+       flush_cache(ebase + offset, size);
+}
+
+void trap_init(ulong reloc_addr)
+{
+       unsigned long ebase = gd->irq_sp;
+
+       set_handler(0x180, &except_vec3_generic, 0x80);
+       set_handler(0x280, &except_vec_ejtag_debug, 0x80);
+
+       write_c0_ebase(ebase);
+       clear_c0_status(ST0_BEV);
+       execution_hazard_barrier();
+}