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-GDB intends to support the following hardware debug features of BookE
-processors:
-
-4 hardware breakpoints (IAC)
-2 hardware watchpoints (read, write and read-write) (DAC)
-2 value conditions for the hardware watchpoints (DVC)
-
-For that, we need to extend ptrace so that GDB can query and set these
-resources. Since we're extending, we're trying to create an interface
-that's extendable and that covers both BookE and server processors, so
-that GDB doesn't need to special-case each of them. We added the
-following 3 new ptrace requests.
-
-1. PTRACE_PPC_GETHWDEBUGINFO
-
-Query for GDB to discover the hardware debug features. The main info to
-be returned here is the minimum alignment for the hardware watchpoints.
-BookE processors don't have restrictions here, but server processors have
-an 8-byte alignment restriction for hardware watchpoints. We'd like to avoid
-adding special cases to GDB based on what it sees in AUXV.
-
-Since we're at it, we added other useful info that the kernel can return to
-GDB: this query will return the number of hardware breakpoints, hardware
-watchpoints and whether it supports a range of addresses and a condition.
-The query will fill the following structure provided by the requesting process:
-
-struct ppc_debug_info {
- unit32_t version;
- unit32_t num_instruction_bps;
- unit32_t num_data_bps;
- unit32_t num_condition_regs;
- unit32_t data_bp_alignment;
- unit32_t sizeof_condition; /* size of the DVC register */
- uint64_t features; /* bitmask of the individual flags */
-};
-
-features will have bits indicating whether there is support for:
-
-#define PPC_DEBUG_FEATURE_INSN_BP_RANGE 0x1
-#define PPC_DEBUG_FEATURE_INSN_BP_MASK 0x2
-#define PPC_DEBUG_FEATURE_DATA_BP_RANGE 0x4
-#define PPC_DEBUG_FEATURE_DATA_BP_MASK 0x8
-#define PPC_DEBUG_FEATURE_DATA_BP_DAWR 0x10
-
-2. PTRACE_SETHWDEBUG
-
-Sets a hardware breakpoint or watchpoint, according to the provided structure:
-
-struct ppc_hw_breakpoint {
- uint32_t version;
-#define PPC_BREAKPOINT_TRIGGER_EXECUTE 0x1
-#define PPC_BREAKPOINT_TRIGGER_READ 0x2
-#define PPC_BREAKPOINT_TRIGGER_WRITE 0x4
- uint32_t trigger_type; /* only some combinations allowed */
-#define PPC_BREAKPOINT_MODE_EXACT 0x0
-#define PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE 0x1
-#define PPC_BREAKPOINT_MODE_RANGE_EXCLUSIVE 0x2
-#define PPC_BREAKPOINT_MODE_MASK 0x3
- uint32_t addr_mode; /* address match mode */
-
-#define PPC_BREAKPOINT_CONDITION_MODE 0x3
-#define PPC_BREAKPOINT_CONDITION_NONE 0x0
-#define PPC_BREAKPOINT_CONDITION_AND 0x1
-#define PPC_BREAKPOINT_CONDITION_EXACT 0x1 /* different name for the same thing as above */
-#define PPC_BREAKPOINT_CONDITION_OR 0x2
-#define PPC_BREAKPOINT_CONDITION_AND_OR 0x3
-#define PPC_BREAKPOINT_CONDITION_BE_ALL 0x00ff0000 /* byte enable bits */
-#define PPC_BREAKPOINT_CONDITION_BE(n) (1<<((n)+16))
- uint32_t condition_mode; /* break/watchpoint condition flags */
-
- uint64_t addr;
- uint64_t addr2;
- uint64_t condition_value;
-};
-
-A request specifies one event, not necessarily just one register to be set.
-For instance, if the request is for a watchpoint with a condition, both the
-DAC and DVC registers will be set in the same request.
-
-With this GDB can ask for all kinds of hardware breakpoints and watchpoints
-that the BookE supports. COMEFROM breakpoints available in server processors
-are not contemplated, but that is out of the scope of this work.
-
-ptrace will return an integer (handle) uniquely identifying the breakpoint or
-watchpoint just created. This integer will be used in the PTRACE_DELHWDEBUG
-request to ask for its removal. Return -ENOSPC if the requested breakpoint
-can't be allocated on the registers.
-
-Some examples of using the structure to:
-
-- set a breakpoint in the first breakpoint register
-
- p.version = PPC_DEBUG_CURRENT_VERSION;
- p.trigger_type = PPC_BREAKPOINT_TRIGGER_EXECUTE;
- p.addr_mode = PPC_BREAKPOINT_MODE_EXACT;
- p.condition_mode = PPC_BREAKPOINT_CONDITION_NONE;
- p.addr = (uint64_t) address;
- p.addr2 = 0;
- p.condition_value = 0;
-
-- set a watchpoint which triggers on reads in the second watchpoint register
-
- p.version = PPC_DEBUG_CURRENT_VERSION;
- p.trigger_type = PPC_BREAKPOINT_TRIGGER_READ;
- p.addr_mode = PPC_BREAKPOINT_MODE_EXACT;
- p.condition_mode = PPC_BREAKPOINT_CONDITION_NONE;
- p.addr = (uint64_t) address;
- p.addr2 = 0;
- p.condition_value = 0;
-
-- set a watchpoint which triggers only with a specific value
-
- p.version = PPC_DEBUG_CURRENT_VERSION;
- p.trigger_type = PPC_BREAKPOINT_TRIGGER_READ;
- p.addr_mode = PPC_BREAKPOINT_MODE_EXACT;
- p.condition_mode = PPC_BREAKPOINT_CONDITION_AND | PPC_BREAKPOINT_CONDITION_BE_ALL;
- p.addr = (uint64_t) address;
- p.addr2 = 0;
- p.condition_value = (uint64_t) condition;
-
-- set a ranged hardware breakpoint
-
- p.version = PPC_DEBUG_CURRENT_VERSION;
- p.trigger_type = PPC_BREAKPOINT_TRIGGER_EXECUTE;
- p.addr_mode = PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE;
- p.condition_mode = PPC_BREAKPOINT_CONDITION_NONE;
- p.addr = (uint64_t) begin_range;
- p.addr2 = (uint64_t) end_range;
- p.condition_value = 0;
-
-- set a watchpoint in server processors (BookS)
-
- p.version = 1;
- p.trigger_type = PPC_BREAKPOINT_TRIGGER_RW;
- p.addr_mode = PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE;
- or
- p.addr_mode = PPC_BREAKPOINT_MODE_EXACT;
-
- p.condition_mode = PPC_BREAKPOINT_CONDITION_NONE;
- p.addr = (uint64_t) begin_range;
- /* For PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE addr2 needs to be specified, where
- * addr2 - addr <= 8 Bytes.
- */
- p.addr2 = (uint64_t) end_range;
- p.condition_value = 0;
-
-3. PTRACE_DELHWDEBUG
-
-Takes an integer which identifies an existing breakpoint or watchpoint
-(i.e., the value returned from PTRACE_SETHWDEBUG), and deletes the
-corresponding breakpoint or watchpoint..