From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [RFC:PATCH 00/03] powerpc: Expose BookE debug registers through extended ptrace interface Mime-Version: 1.0 (Apple Message framework v1077) Content-Type: text/plain; charset=us-ascii From: Kumar Gala In-Reply-To: <20091210155709.6697.4635.sendpatchset@norville.austin.ibm.com> Date: Thu, 10 Dec 2009 20:23:35 -0600 Message-Id: References: <20091210155709.6697.4635.sendpatchset@norville.austin.ibm.com> To: Dave Kleikamp Cc: linuxppc-dev list , Sergio Durigan Junior , Torez Smith , Thiago Jung Bauermann , David Gibson List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Dec 10, 2009, at 9:57 AM, Dave Kleikamp wrote: > These patches implement an extention to the ptrace interface proposed = by > Thiago Bauermann and the the PowerPC gdb team. >=20 > GDB intends to support the following hardware debug features of BookE > processors: >=20 > 4 hardware breakpoints (IAC) > 2 hardware watchpoints (read, write and read-write) (DAC) > 2 value conditions for the hardware watchpoints (DVC) >=20 > 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 propose the > following 3 new ptrace requests described below. >=20 > There have been discussions of a generic hardware debug interface for = the > kernel which would hopefully contemplate all the functionality below = and > supersede it. But we need something that works now, and which enables = GDB > to be simpler and work with both Server and Embedded processors = without > special cases. >=20 > 1. PTRACE_PPC_GETHWDEBUGINFO >=20 > 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. >=20 > 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: >=20 > 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 */ > }; >=20 > features will have bits indicating whether there is support for: >=20 > #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 Is GDB smart enough to deal w/no condition_regs? On some Book-E devices = we have 2 IACs, 2 DACs, and 0 DVCs. Does it need to be in the features? - k=