From 3162d92dfb79a0b5fc03380b8819fa5f870ebf1e Mon Sep 17 00:00:00 2001 From: Dave Kleikamp Date: Mon, 8 Feb 2010 11:51:05 +0000 Subject: powerpc: Extended ptrace interface powerpc: Extended ptrace interface From: Dave Kleikamp Based on patches originally written by Torez Smith. Add a new extended ptrace interface so that user-space has a single interface for powerpc, without having to know the specific layout of the debug registers. Implement: PPC_PTRACE_GETHWDEBUGINFO PPC_PTRACE_SETHWDEBUG PPC_PTRACE_DELHWDEBUG Signed-off-by: Dave Kleikamp Acked-by: David Gibson Cc: Torez Smith Cc: Benjamin Herrenschmidt Cc: Josh Boyer Cc: Kumar Gala Cc: Sergio Durigan Junior Cc: Thiago Jung Bauermann Cc: linuxppc-dev list Signed-off-by: Benjamin Herrenschmidt --- Documentation/powerpc/ptrace.txt | 134 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 134 insertions(+) create mode 100644 Documentation/powerpc/ptrace.txt (limited to 'Documentation/powerpc') diff --git a/Documentation/powerpc/ptrace.txt b/Documentation/powerpc/ptrace.txt new file mode 100644 index 000000000000..f4a5499b7bc6 --- /dev/null +++ b/Documentation/powerpc/ptrace.txt @@ -0,0 +1,134 @@ +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 + +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; + +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.. -- cgit v1.2.3