diff options
Diffstat (limited to 'gdb/ia64-tdep.c')
| -rw-r--r-- | gdb/ia64-tdep.c | 56 |
1 files changed, 42 insertions, 14 deletions
diff --git a/gdb/ia64-tdep.c b/gdb/ia64-tdep.c index 7aef8ba..058930b 100644 --- a/gdb/ia64-tdep.c +++ b/gdb/ia64-tdep.c @@ -586,6 +586,23 @@ fetch_instruction (CORE_ADDR addr, instruction_type *it, long long *instr) SLOTNUM (`adress & 0x0f', value in the range <0..2>). We need to know SLOTNUM in ia64_memory_remove_breakpoint. + There is one special case where we need to be extra careful: + L-X instructions, which are instructions that occupy 2 slots + (The L part is always in slot 1, and the X part is always in + slot 2). We must refuse to insert breakpoints for an address + that points at slot 2 of a bundle where an L-X instruction is + present, since there is logically no instruction at that address. + However, to make things more interesting, the opcode of L-X + instructions is located in slot 2. This means that, to insert + a breakpoint at an address that points to slot 1, we actually + need to write the breakpoint in slot 2! Slot 1 is actually + the extended operand, so writing the breakpoint there would not + have the desired effect. Another side-effect of this issue + is that we need to make sure that the shadow contents buffer + does save byte 15 of our instruction bundle (this is the tail + end of slot 2, which wouldn't be saved if we were to insert + the breakpoint in slot 1). + ia64 16-byte bundle layout: | 5 bits | slot 0 with 41 bits | slot 1 with 41 bits | slot 2 with 41 bits | @@ -594,12 +611,11 @@ fetch_instruction (CORE_ADDR addr, instruction_type *it, long long *instr) == bp_tgt->shadow_len reqd \subset covered 0xABCDE0 0xABCDE0 0x10 <0x0...0x5> <0x0..0xF> 0xABCDE1 0xABCDE1 0xF <0x5...0xA> <0x1..0xF> - 0xABCDE1 L-X 0xABCDE1 L-X 0xF <0xA...0xF> <0x1..0xF> - L is always in slot 1 and X is always in slot 2, while the address is - using slot 1 the breakpoint instruction must be placed - to the slot 2 (requiring to shadow that last byte at 0xF). 0xABCDE2 0xABCDE2 0xE <0xA...0xF> <0x2..0xF> - + + L-X instructions are treated a little specially, as explained above: + 0xABCDE1 0xABCDE1 0xF <0xA...0xF> <0x1..0xF> + `objdump -d' and some other tools show a bit unjustified offsets: original PC byte where starts the instruction objdump offset 0xABCDE0 0xABCDE0 0xABCDE0 @@ -643,19 +659,25 @@ ia64_memory_insert_breakpoint (struct gdbarch *gdbarch, for addressing the SHADOW_CONTENTS placement. */ shadow_slotnum = slotnum; - /* Cover always the last byte of the bundle for the L-X slot case. */ + /* Always cover the last byte of the bundle in case we are inserting + a breakpoint on an L-X instruction. */ bp_tgt->shadow_len = BUNDLE_LEN - shadow_slotnum; - /* Check for L type instruction in slot 1, if present then bump up the slot - number to the slot 2. */ template = extract_bit_field (bundle, 0, 5); if (template_encoding_table[template][slotnum] == X) { + /* X unit types can only be used in slot 2, and are actually + part of a 2-slot L-X instruction. We cannot break at this + address, as this is the second half of an instruction that + lives in slot 1 of that bundle. */ gdb_assert (slotnum == 2); error (_("Can't insert breakpoint for non-existing slot X")); } if (template_encoding_table[template][slotnum] == L) { + /* L unit types can only be used in slot 1. But the associated + opcode for that instruction is in slot 2, so bump the slot number + accordingly. */ gdb_assert (slotnum == 1); slotnum = 2; } @@ -730,20 +752,26 @@ ia64_memory_remove_breakpoint (struct gdbarch *gdbarch, for addressing the SHADOW_CONTENTS placement. */ shadow_slotnum = slotnum; - /* Check for L type instruction in slot 1, if present then bump up the slot - number to the slot 2. */ template = extract_bit_field (bundle_mem, 0, 5); if (template_encoding_table[template][slotnum] == X) { + /* X unit types can only be used in slot 2, and are actually + part of a 2-slot L-X instruction. We refuse to insert + breakpoints at this address, so there should be no reason + for us attempting to remove one there, except if the program's + code somehow got modified in memory. */ gdb_assert (slotnum == 2); - warning (_("Cannot remove breakpoint at address %s " - "from non-existing slot X, memory has changed underneath"), + warning (_("Cannot remove breakpoint at address %s from non-existing " + "X-type slot, memory has changed underneath"), paddress (gdbarch, bp_tgt->placed_address)); do_cleanups (cleanup); return -1; } if (template_encoding_table[template][slotnum] == L) { + /* L unit types can only be used in slot 1. But the breakpoint + was actually saved using slot 2, so update the slot number + accordingly. */ gdb_assert (slotnum == 1); slotnum = 2; } @@ -768,8 +796,8 @@ ia64_memory_remove_breakpoint (struct gdbarch *gdbarch, bp_tgt->shadow_len); instr_saved = slotN_contents (bundle_saved, slotnum); - /* In BUNDLE_MEM be careful to modify only the bits belonging to SLOTNUM and - never any other possibly also stored in SHADOW_CONTENTS. */ + /* In BUNDLE_MEM, be careful to modify only the bits belonging to SLOTNUM + and not any of the other ones that are stored in SHADOW_CONTENTS. */ replace_slotN_contents (bundle_mem, instr_saved, slotnum); val = target_write_memory (addr, bundle_mem, BUNDLE_LEN); |