linux/Documentation/powerpc/ptrace.txt
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   1GDB intends to support the following hardware debug features of BookE
   2processors:
   3
   44 hardware breakpoints (IAC)
   52 hardware watchpoints (read, write and read-write) (DAC)
   62 value conditions for the hardware watchpoints (DVC)
   7
   8For that, we need to extend ptrace so that GDB can query and set these
   9resources. Since we're extending, we're trying to create an interface
  10that's extendable and that covers both BookE and server processors, so
  11that GDB doesn't need to special-case each of them. We added the
  12following 3 new ptrace requests.
  13
  141. PTRACE_PPC_GETHWDEBUGINFO
  15
  16Query for GDB to discover the hardware debug features. The main info to
  17be returned here is the minimum alignment for the hardware watchpoints.
  18BookE processors don't have restrictions here, but server processors have
  19an 8-byte alignment restriction for hardware watchpoints. We'd like to avoid
  20adding special cases to GDB based on what it sees in AUXV.
  21
  22Since we're at it, we added other useful info that the kernel can return to
  23GDB: this query will return the number of hardware breakpoints, hardware
  24watchpoints and whether it supports a range of addresses and a condition.
  25The query will fill the following structure provided by the requesting process:
  26
  27struct ppc_debug_info {
  28       unit32_t version;
  29       unit32_t num_instruction_bps;
  30       unit32_t num_data_bps;
  31       unit32_t num_condition_regs;
  32       unit32_t data_bp_alignment;
  33       unit32_t sizeof_condition; /* size of the DVC register */
  34       uint64_t features; /* bitmask of the individual flags */
  35};
  36
  37features will have bits indicating whether there is support for:
  38
  39#define PPC_DEBUG_FEATURE_INSN_BP_RANGE         0x1
  40#define PPC_DEBUG_FEATURE_INSN_BP_MASK          0x2
  41#define PPC_DEBUG_FEATURE_DATA_BP_RANGE         0x4
  42#define PPC_DEBUG_FEATURE_DATA_BP_MASK          0x8
  43
  442. PTRACE_SETHWDEBUG
  45
  46Sets a hardware breakpoint or watchpoint, according to the provided structure:
  47
  48struct ppc_hw_breakpoint {
  49        uint32_t version;
  50#define PPC_BREAKPOINT_TRIGGER_EXECUTE  0x1
  51#define PPC_BREAKPOINT_TRIGGER_READ     0x2
  52#define PPC_BREAKPOINT_TRIGGER_WRITE    0x4
  53        uint32_t trigger_type;       /* only some combinations allowed */
  54#define PPC_BREAKPOINT_MODE_EXACT               0x0
  55#define PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE     0x1
  56#define PPC_BREAKPOINT_MODE_RANGE_EXCLUSIVE     0x2
  57#define PPC_BREAKPOINT_MODE_MASK                0x3
  58        uint32_t addr_mode;          /* address match mode */
  59
  60#define PPC_BREAKPOINT_CONDITION_MODE   0x3
  61#define PPC_BREAKPOINT_CONDITION_NONE   0x0
  62#define PPC_BREAKPOINT_CONDITION_AND    0x1
  63#define PPC_BREAKPOINT_CONDITION_EXACT  0x1     /* different name for the same thing as above */
  64#define PPC_BREAKPOINT_CONDITION_OR     0x2
  65#define PPC_BREAKPOINT_CONDITION_AND_OR 0x3
  66#define PPC_BREAKPOINT_CONDITION_BE_ALL 0x00ff0000      /* byte enable bits */
  67#define PPC_BREAKPOINT_CONDITION_BE(n)  (1<<((n)+16))
  68        uint32_t condition_mode;     /* break/watchpoint condition flags */
  69
  70        uint64_t addr;
  71        uint64_t addr2;
  72        uint64_t condition_value;
  73};
  74
  75A request specifies one event, not necessarily just one register to be set.
  76For instance, if the request is for a watchpoint with a condition, both the
  77DAC and DVC registers will be set in the same request.
  78
  79With this GDB can ask for all kinds of hardware breakpoints and watchpoints
  80that the BookE supports. COMEFROM breakpoints available in server processors
  81are not contemplated, but that is out of the scope of this work.
  82
  83ptrace will return an integer (handle) uniquely identifying the breakpoint or
  84watchpoint just created. This integer will be used in the PTRACE_DELHWDEBUG
  85request to ask for its removal. Return -ENOSPC if the requested breakpoint
  86can't be allocated on the registers.
  87
  88Some examples of using the structure to:
  89
  90- set a breakpoint in the first breakpoint register
  91
  92  p.version         = PPC_DEBUG_CURRENT_VERSION;
  93  p.trigger_type    = PPC_BREAKPOINT_TRIGGER_EXECUTE;
  94  p.addr_mode       = PPC_BREAKPOINT_MODE_EXACT;
  95  p.condition_mode  = PPC_BREAKPOINT_CONDITION_NONE;
  96  p.addr            = (uint64_t) address;
  97  p.addr2           = 0;
  98  p.condition_value = 0;
  99
 100- set a watchpoint which triggers on reads in the second watchpoint register
 101
 102  p.version         = PPC_DEBUG_CURRENT_VERSION;
 103  p.trigger_type    = PPC_BREAKPOINT_TRIGGER_READ;
 104  p.addr_mode       = PPC_BREAKPOINT_MODE_EXACT;
 105  p.condition_mode  = PPC_BREAKPOINT_CONDITION_NONE;
 106  p.addr            = (uint64_t) address;
 107  p.addr2           = 0;
 108  p.condition_value = 0;
 109
 110- set a watchpoint which triggers only with a specific value
 111
 112  p.version         = PPC_DEBUG_CURRENT_VERSION;
 113  p.trigger_type    = PPC_BREAKPOINT_TRIGGER_READ;
 114  p.addr_mode       = PPC_BREAKPOINT_MODE_EXACT;
 115  p.condition_mode  = PPC_BREAKPOINT_CONDITION_AND | PPC_BREAKPOINT_CONDITION_BE_ALL;
 116  p.addr            = (uint64_t) address;
 117  p.addr2           = 0;
 118  p.condition_value = (uint64_t) condition;
 119
 120- set a ranged hardware breakpoint
 121
 122  p.version         = PPC_DEBUG_CURRENT_VERSION;
 123  p.trigger_type    = PPC_BREAKPOINT_TRIGGER_EXECUTE;
 124  p.addr_mode       = PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE;
 125  p.condition_mode  = PPC_BREAKPOINT_CONDITION_NONE;
 126  p.addr            = (uint64_t) begin_range;
 127  p.addr2           = (uint64_t) end_range;
 128  p.condition_value = 0;
 129
 1303. PTRACE_DELHWDEBUG
 131
 132Takes an integer which identifies an existing breakpoint or watchpoint
 133(i.e., the value returned from PTRACE_SETHWDEBUG), and deletes the
 134corresponding breakpoint or watchpoint..
 135
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