diff options
Diffstat (limited to 'gdb/rs6000-tdep.c')
-rw-r--r-- | gdb/rs6000-tdep.c | 96 |
1 files changed, 95 insertions, 1 deletions
diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c index ba91686..96b28ec 100644 --- a/gdb/rs6000-tdep.c +++ b/gdb/rs6000-tdep.c @@ -707,7 +707,95 @@ rs6000_breakpoint_from_pc (CORE_ADDR *bp_addr, int *bp_size) } -/* AIX does not support PT_STEP. Simulate it. */ +/* Instruction masks used during single-stepping of atomic sequences. */ +#define LWARX_MASK 0xfc0007fe +#define LWARX_INSTRUCTION 0x7c000028 +#define LDARX_INSTRUCTION 0x7c0000A8 +#define STWCX_MASK 0xfc0007ff +#define STWCX_INSTRUCTION 0x7c00012d +#define STDCX_INSTRUCTION 0x7c0001ad +#define BC_MASK 0xfc000000 +#define BC_INSTRUCTION 0x40000000 + +/* Checks for an atomic sequence of instructions beginning with a LWARX/LDARX + instruction and ending with a STWCX/STDCX instruction. If such a sequence + is found, attempt to step through it. A breakpoint is placed at the end of + the sequence. */ + +static int +deal_with_atomic_sequence (struct regcache *regcache) +{ + CORE_ADDR pc = read_pc (); + CORE_ADDR breaks[2] = {-1, -1}; + CORE_ADDR loc = pc; + CORE_ADDR branch_bp; /* Breakpoint at branch instruction's destination. */ + int insn = read_memory_integer (loc, PPC_INSN_SIZE); + int insn_count; + int index; + int last_breakpoint = 0; /* Defaults to 0 (no breakpoints placed). */ + const int atomic_sequence_length = 16; /* Instruction sequence length. */ + const int opcode = BC_INSTRUCTION; /* Branch instruction's OPcode. */ + int bc_insn_count = 0; /* Conditional branch instruction count. */ + + /* Assume all atomic sequences start with a lwarx/ldarx instruction. */ + if ((insn & LWARX_MASK) != LWARX_INSTRUCTION + && (insn & LWARX_MASK) != LDARX_INSTRUCTION) + return 0; + + /* Assume that no atomic sequence is longer than "atomic_sequence_length" + instructions. */ + for (insn_count = 0; insn_count < atomic_sequence_length; ++insn_count) + { + loc += PPC_INSN_SIZE; + insn = read_memory_integer (loc, PPC_INSN_SIZE); + + /* Assume that there is at most one conditional branch in the atomic + sequence. If a conditional branch is found, put a breakpoint in + its destination address. */ + if ((insn & BC_MASK) == BC_INSTRUCTION) + { + if (bc_insn_count >= 1) + return 0; /* More than one conditional branch found, fallback + to the standard single-step code. */ + + branch_bp = branch_dest (opcode, insn, pc, breaks[0]); + + if (branch_bp != -1) + { + breaks[1] = branch_bp; + bc_insn_count++; + last_breakpoint++; + } + } + + if ((insn & STWCX_MASK) == STWCX_INSTRUCTION + || (insn & STWCX_MASK) == STDCX_INSTRUCTION) + break; + } + + /* Assume that the atomic sequence ends with a stwcx/stdcx instruction. */ + if ((insn & STWCX_MASK) != STWCX_INSTRUCTION + && (insn & STWCX_MASK) != STDCX_INSTRUCTION) + return 0; + + loc += PPC_INSN_SIZE; + insn = read_memory_integer (loc, PPC_INSN_SIZE); + + /* Insert a breakpoint right after the end of the atomic sequence. */ + breaks[0] = loc; + + /* Check for duplicated breakpoints. */ + if (last_breakpoint && (breaks[1] == breaks[0])) + last_breakpoint = 0; + + /* Effectively inserts the breakpoints. */ + for (index = 0; index <= last_breakpoint; index++) + insert_single_step_breakpoint (breaks[index]); + + return 1; +} + +/* AIX does not support PT_STEP. Simulate it. */ int rs6000_software_single_step (struct regcache *regcache) @@ -724,6 +812,9 @@ rs6000_software_single_step (struct regcache *regcache) insn = read_memory_integer (loc, 4); + if (deal_with_atomic_sequence (regcache)) + return 1; + breaks[0] = loc + breakp_sz; opcode = insn >> 26; breaks[1] = branch_dest (opcode, insn, loc, breaks[0]); @@ -3448,6 +3539,9 @@ rs6000_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches) set_gdbarch_inner_than (gdbarch, core_addr_lessthan); set_gdbarch_breakpoint_from_pc (gdbarch, rs6000_breakpoint_from_pc); + /* Handles single stepping of atomic sequences. */ + set_gdbarch_software_single_step (gdbarch, deal_with_atomic_sequence); + /* Handle the 64-bit SVR4 minimal-symbol convention of using "FN" for the descriptor and ".FN" for the entry-point -- a user specifying "break FN" will unexpectedly end up with a breakpoint |