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[commit] Add software single stepping to moxie port
- From: Anthony Green <green at moxielogic dot com>
- To: gdb-patches at sourceware dot org
- Date: Thu, 05 Dec 2013 10:24:31 -0500
- Subject: [commit] Add software single stepping to moxie port
- Authentication-results: sourceware.org; auth=none
I'm committing the attached patch, which adds software single step
support to the moxie port. This was tested with a embedded gdb remote
protocol stub that fits into only 2k of on-chip ROM:
https://github.com/atgreen/moxie-cores/blob/master/firmware/tinystub.c
2013-12-05 Anthony Green <green@moxielogic.com>
* moxie-tdep.c (moxie_software_single_step): New function.
(INST2OFFSET): New helper macro.
(moxie_gdbarch_init): Call set_gdbarch_software_single_step.
(moxie_process_readu): Move this up in the file.
diff --git a/gdb/moxie-tdep.c b/gdb/moxie-tdep.c
index 201b50f..6e269a2 100644
--- a/gdb/moxie-tdep.c
+++ b/gdb/moxie-tdep.c
@@ -285,6 +285,187 @@ struct moxie_unwind_cache
struct trad_frame_saved_reg *saved_regs;
};
+/* Read an unsigned integer from the inferior, and adjust
+ endianess. */
+static ULONGEST
+moxie_process_readu (CORE_ADDR addr, gdb_byte *buf,
+ int length, enum bfd_endian byte_order)
+{
+ if (target_read_memory (addr, buf, length))
+ {
+ if (record_debug)
+ printf_unfiltered (_("Process record: error reading memory at "
+ "addr 0x%s len = %d.\n"),
+ paddress (target_gdbarch (), addr), length);
+ return -1;
+ }
+
+ return extract_unsigned_integer (buf, length, byte_order);
+}
+
+
+/* Helper macro to extract the signed 10-bit offset from a 16-bit
+ branch instruction. */
+#define INST2OFFSET(o) ((((signed short)((o & ((1<<10)-1))<<6))>>6)<<1)
+
+/* Insert a single step breakpoint. */
+
+static int
+moxie_software_single_step (struct frame_info *frame)
+{
+ struct gdbarch *gdbarch = get_frame_arch (frame);
+ struct address_space *aspace = get_frame_address_space (frame);
+ CORE_ADDR addr;
+ gdb_byte buf[4];
+ uint16_t inst;
+ uint32_t tmpu32;
+ ULONGEST fp;
+ enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+ struct regcache *regcache = get_current_regcache ();
+
+ addr = get_frame_pc (frame);
+
+ inst = (uint16_t) moxie_process_readu (addr, buf, 2, byte_order);
+
+ /* Decode instruction. */
+ if (inst & (1 << 15))
+ {
+ if (inst & (1 << 14))
+ {
+ /* This is a Form 3 instruction. */
+ int opcode = (inst >> 10 & 0xf);
+
+ switch (opcode)
+ {
+ case 0x00: /* beq */
+ case 0x01: /* bne */
+ case 0x02: /* blt */
+ case 0x03: /* bgt */
+ case 0x04: /* bltu */
+ case 0x05: /* bgtu */
+ case 0x06: /* bge */
+ case 0x07: /* ble */
+ case 0x08: /* bgeu */
+ case 0x09: /* bleu */
+ /* Insert breaks on both branches, because we can't currently tell
+ which way things will go. */
+ insert_single_step_breakpoint (gdbarch, aspace, addr + 2);
+ insert_single_step_breakpoint (gdbarch, aspace, addr + 2 + INST2OFFSET(inst));
+ break;
+ default:
+ {
+ /* Do nothing. */
+ break;
+ }
+ }
+ }
+ else
+ {
+ /* This is a Form 2 instruction. They are all 16 bits. */
+ insert_single_step_breakpoint (gdbarch, aspace, addr + 2);
+ }
+ }
+ else
+ {
+ /* This is a Form 1 instruction. */
+ int opcode = inst >> 8;
+
+ switch (opcode)
+ {
+ /* 16-bit instructions. */
+ case 0x00: /* nop */
+ case 0x02: /* mov (register-to-register) */
+ case 0x05: /* add.l */
+ case 0x06: /* push */
+ case 0x07: /* pop */
+ case 0x0a: /* ld.l (register indirect) */
+ case 0x0b: /* st.l */
+ case 0x0e: /* cmp */
+ case 0x0f:
+ case 0x10:
+ case 0x11:
+ case 0x12:
+ case 0x13:
+ case 0x14:
+ case 0x15:
+ case 0x16:
+ case 0x17:
+ case 0x18:
+ case 0x1c: /* ld.b (register indirect) */
+ case 0x1e: /* st.b */
+ case 0x21: /* ld.s (register indirect) */
+ case 0x23: /* st.s */
+ case 0x26: /* and */
+ case 0x27: /* lshr */
+ case 0x28: /* ashl */
+ case 0x29: /* sub.l */
+ case 0x2a: /* neg */
+ case 0x2b: /* or */
+ case 0x2c: /* not */
+ case 0x2d: /* ashr */
+ case 0x2e: /* xor */
+ case 0x2f: /* mul.l */
+ case 0x31: /* div.l */
+ case 0x32: /* udiv.l */
+ case 0x33: /* mod.l */
+ case 0x34: /* umod.l */
+ insert_single_step_breakpoint (gdbarch, aspace, addr + 2);
+ break;
+
+ /* 48-bit instructions. */
+ case 0x01: /* ldi.l (immediate) */
+ case 0x08: /* lda.l */
+ case 0x09: /* sta.l */
+ case 0x0c: /* ldo.l */
+ case 0x0d: /* sto.l */
+ case 0x1b: /* ldi.b (immediate) */
+ case 0x1d: /* lda.b */
+ case 0x1f: /* sta.b */
+ case 0x20: /* ldi.s (immediate) */
+ case 0x22: /* lda.s */
+ case 0x24: /* sta.s */
+ case 0x36: /* ldo.b */
+ case 0x37: /* sto.b */
+ case 0x38: /* ldo.s */
+ case 0x39: /* sto.s */
+ insert_single_step_breakpoint (gdbarch, aspace, addr + 6);
+ break;
+
+ /* Control flow instructions. */
+ case 0x03: /* jsra */
+ case 0x1a: /* jmpa */
+ insert_single_step_breakpoint (gdbarch, aspace,
+ moxie_process_readu (addr + 2,
+ buf, 4,
+ byte_order));
+ break;
+
+ case 0x04: /* ret */
+ regcache_cooked_read_unsigned (regcache, MOXIE_FP_REGNUM, &fp);
+ insert_single_step_breakpoint (gdbarch, aspace,
+ moxie_process_readu (fp + 4,
+ buf, 4,
+ byte_order));
+ break;
+
+ case 0x19: /* jsr */
+ case 0x25: /* jmp */
+ regcache_raw_read (regcache,
+ (inst >> 4) & 0xf, (gdb_byte *) & tmpu32);
+ insert_single_step_breakpoint (gdbarch, aspace,
+ tmpu32);
+ break;
+
+ case 0x30: /* swi */
+ case 0x35: /* brk */
+ /* Unsupported, for now. */
+ break;
+ }
+ }
+
+ return 1;
+}
+
/* Implement the "read_pc" gdbarch method. */
static CORE_ADDR
@@ -495,24 +676,6 @@ moxie_dummy_id (struct gdbarch *gdbarch, struct frame_info *this_frame)
return frame_id_build (sp, get_frame_pc (this_frame));
}
-/* Read an unsigned integer from the inferior, and adjust
- endianess. */
-static ULONGEST
-moxie_process_readu (CORE_ADDR addr, gdb_byte *buf,
- int length, enum bfd_endian byte_order)
-{
- if (target_read_memory (addr, buf, length))
- {
- if (record_debug)
- printf_unfiltered (_("Process record: error reading memory at "
- "addr 0x%s len = %d.\n"),
- paddress (target_gdbarch (), addr), length);
- return -1;
- }
-
- return extract_unsigned_integer (buf, length, byte_order);
-}
-
/* Parse the current instruction and record the values of the registers and
memory that will be changed in current instruction to "record_arch_list".
Return -1 if something wrong. */
@@ -986,6 +1149,9 @@ moxie_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
/* Hook in the default unwinders. */
frame_unwind_append_unwinder (gdbarch, &moxie_frame_unwind);
+ /* Single stepping. */
+ set_gdbarch_software_single_step (gdbarch, moxie_software_single_step);
+
/* Support simple overlay manager. */
set_gdbarch_overlay_update (gdbarch, simple_overlay_update);