Hi,
it seems the XScale vector table handling code in OpenOCD is only partially
implemented: the code to use user-provided vectors is there, but there is no
way to set these variables, and also no code that syncs the cached vectors
with the RAM contents.
The attached patch adds a "xscale vector_table" command that allows to set
the values that are written in the mini-IC (plus documentation updates that
describe why this is needed).
Using the correct values, I can now start and debug a Linux kernel on my
IXP425 board from openocd - this would before crash after "uncompressing
kernel", because the cached exception vectors were completely off.
This is only tested on big-endian IXP42x, but even if it does not work on
other CPUs, it should not break any existing functionality.
cu
Michael
Index: src/target/xscale.c
===================================================================
--- src/target/xscale.c (revision 2606)
+++ src/target/xscale.c (working copy)
@@ -5,6 +5,9 @@
* Copyright (C) 2007,2008 Ãyvind Harboe *
* oyvind.har...@zylin.com *
* *
+ * Copyright (C) 2009 Michael Schwingen *
+ * mich...@schwingen.org *
+ * *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
@@ -3384,6 +3387,65 @@
}
+int xscale_handle_vector_table_command(command_context_t *cmd_ctx, char *cmd, char **args, int argc)
+{
+ target_t *target = get_current_target(cmd_ctx);
+ armv4_5_common_t *armv4_5;
+ xscale_common_t *xscale;
+ int err = 0;
+
+ if (xscale_get_arch_pointers(target, &armv4_5, &xscale) != ERROR_OK)
+ {
+ return ERROR_OK;
+ }
+
+ if (argc == 0) /* print current settings */
+ {
+ int idx;
+
+ command_print(cmd_ctx, "active user-set static vectors:");
+ for (idx = 1; idx < 8; idx++)
+ if (xscale->static_low_vectors_set & (1 << idx))
+ command_print(cmd_ctx, "low %d: 0x%x", idx, xscale->static_low_vectors[idx]);
+ for (idx = 1; idx < 8; idx++)
+ if (xscale->static_high_vectors_set & (1 << idx))
+ command_print(cmd_ctx, "high %d: 0x%x", idx, xscale->static_high_vectors[idx]);
+ return ERROR_OK;
+ }
+
+ if (argc != 3)
+ err = 1;
+ else
+ {
+ int idx;
+ uint32_t vec;
+ idx = strtoul(args[1], NULL, 0);
+ vec = strtoul(args[2], NULL, 0);
+
+ if (idx < 1 || idx >= 8)
+ err = 1;
+
+ if (!err && strcmp(args[0], "low") == 0)
+ {
+ xscale->static_low_vectors_set |= (1<<idx);
+ xscale->static_low_vectors[idx] = vec;
+ }
+ else if (!err && (strcmp(args[0], "high") == 0))
+ {
+ xscale->static_high_vectors_set |= (1<<idx);
+ xscale->static_high_vectors[idx] = vec;
+ }
+ else
+ err = 1;
+ }
+
+ if (err)
+ command_print(cmd_ctx, "usage: xscale vector_table <high|low> <index> <code>");
+
+ return ERROR_OK;
+}
+
+
int xscale_handle_trace_buffer_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc)
{
target_t *target = get_current_target(cmd_ctx);
@@ -3692,6 +3754,7 @@
register_command(cmd_ctx, xscale_cmd, "dcache", xscale_handle_idcache_command, COMMAND_EXEC, "['enable'|'disable'] the DCache");
register_command(cmd_ctx, xscale_cmd, "vector_catch", xscale_handle_vector_catch_command, COMMAND_EXEC, "<mask> of vectors that should be catched");
+ register_command(cmd_ctx, xscale_cmd, "vector_table", xscale_handle_vector_table_command, COMMAND_EXEC, "<high|low> <index> <code> set static code for exception handler entry");
register_command(cmd_ctx, xscale_cmd, "trace_buffer", xscale_handle_trace_buffer_command, COMMAND_EXEC, "<enable | disable> ['fill' [n]|'wrap']");
Index: doc/openocd.texi
===================================================================
--- doc/openocd.texi (revision 2606)
+++ doc/openocd.texi (working copy)
@@ -4877,6 +4877,52 @@
@subsection XScale specific commands
@cindex XScale
+Some notes about the debug implementation on the XScale CPUs:
+
+The XScale CPU provides a special debug-only mini-instruction cache
+(mini-IC) in which exception vectors and target-resident debug handler
+code are placed by OpenOCD. In order to get access to the CPU, OpenOCD
+must point vector 0 (the reset vector) to the entry of the debug
+handler. However, this means that the complete first cacheline in the
+mini-IC is marked valid, which makes the CPU fetch all exception
+handlers from the mini-IC, ignoring the code in RAM.
+
+OpenOCD currently does not sync the mini-IC entries with the RAM
+contents (which would fail anyway while the target is running), so
+the user must provide appropriate values using the @code{xscale
+vector_table} command.
+
+It is recommended to place a pc-relative indirect branch in the vector
+table, and put the branch destination somewhere in memory. Doing so
+makes sure the code in the vector table stays constant regardless of
+code layout in memory:
+...@example
+_vectors:
+ ldr pc,[pc,#0x100-8]
+ ldr pc,[pc,#0x100-8]
+ ldr pc,[pc,#0x100-8]
+ ldr pc,[pc,#0x100-8]
+ ldr pc,[pc,#0x100-8]
+ ldr pc,[pc,#0x100-8]
+ ldr pc,[pc,#0x100-8]
+ ldr pc,[pc,#0x100-8]
+ .org 0x100
+ .long real_reset_vector
+ .long real_ui_handler
+ .long real_swi_handler
+ .long real_pf_abort
+ .long real_data_abort
+ .long 0 /* unused */
+ .long real_irq_handler
+ .long real_fiq_handler
+...@end example
+
+The debug handler must be placed somewhere in the address space using
+the @code{xscale debug_handler} command. The allowed locations for the
+debug handler are either (0x800 - 0x1fef800) or (0xfe000800 -
+0xfffff800). The default value is 0xfe000800.
+
+
These commands are available to XScale based CPUs,
which are implementations of the ARMv5TE architecture.
@@ -4938,6 +4984,33 @@
If the optional parameter is provided, first set the bitmask to that value.
@end deffn
+The mask bits correspond with bit 16..23 in the DCSR:
+...@example
+0x01 Trap Reset
+0x02 Trap Undefined Instructions
+0x04 Trap Software Interrupt
+0x08 Trap Prefetch Abort
+0x10 Trap Data Abort
+0x20 reserved
+0x40 Trap IRQ
+0x80 Trap FIQ
+...@end example
+
+
+...@anchor{xscale vector_table}
+...@deffn Command {xscale vector_table} [<low|high> <index> <value>]
+...@cindex vector_table
+
+Set an entry in the mini-IC vector table. There are two tables: one for
+low vectors (at 0x00000000), and one for high vectors (0xFFFF0000), each
+holding the 8 exception vectors. @var{index} can be 1-7, because vector 0
+points to the debug handler entry and can not be overwritten.
+...@var{value} holds the 32-bit opcode that is placed in the mini-IC.
+
+Without arguments, the current settings are displayed.
+
+...@end deffn
+
@section ARMv6 Architecture
@cindex ARMv6
_______________________________________________
Openocd-development mailing list
Openocd-development@lists.berlios.de
https://lists.berlios.de/mailman/listinfo/openocd-development
