Author: Jason Molenda Date: 2020-01-07T16:13:23-08:00 New Revision: 5e2f4dc37b1bf72bd27e929a68fec18ae1f5cfa8
URL: https://github.com/llvm/llvm-project/commit/5e2f4dc37b1bf72bd27e929a68fec18ae1f5cfa8 DIFF: https://github.com/llvm/llvm-project/commit/5e2f4dc37b1bf72bd27e929a68fec18ae1f5cfa8.diff LOG: Rewrite comment about what watchpoints Aarch64 supports. Added: Modified: lldb/tools/debugserver/source/MacOSX/arm64/DNBArchImplARM64.cpp Removed: ################################################################################ diff --git a/lldb/tools/debugserver/source/MacOSX/arm64/DNBArchImplARM64.cpp b/lldb/tools/debugserver/source/MacOSX/arm64/DNBArchImplARM64.cpp index e8c40910567c..f99dbc48b128 100644 --- a/lldb/tools/debugserver/source/MacOSX/arm64/DNBArchImplARM64.cpp +++ b/lldb/tools/debugserver/source/MacOSX/arm64/DNBArchImplARM64.cpp @@ -689,27 +689,35 @@ uint32_t DNBArchMachARM64::EnableHardwareWatchpoint(nub_addr_t addr, if (size > 8) return INVALID_NUB_HW_INDEX; - // arm64 watchpoints really have an 8-byte alignment requirement. You can put - // a watchpoint on a 4-byte - // offset address but you can only watch 4 bytes with that watchpoint. - - // arm64 watchpoints on an 8-byte (double word) aligned addr can watch any - // bytes in that - // 8-byte long region of memory. They can watch the 1st byte, the 2nd byte, - // 3rd byte, etc, or any - // combination therein by setting the bits in the BAS [12:5] (Byte Address - // Select) field of - // the DBGWCRn_EL1 reg for the watchpoint. - - // If the MASK [28:24] bits in the DBGWCRn_EL1 allow a single watchpoint to - // monitor a larger region - // of memory (16 bytes, 32 bytes, or 2GB) but the Byte Address Select bitfield - // then selects a larger - // range of bytes, instead of individual bytes. See the ARMv8 Debug - // Architecture manual for details. - // This implementation does not currently use the MASK bits; the largest - // single region watched by a single - // watchpoint right now is 8-bytes. + // Aarch64 watchpoints are in one of two forms: (1) 1-8 bytes, aligned to + // an 8 byte address, or (2) a power-of-two size region of memory; minimum + // 8 bytes, maximum 2GB; the starting address must be aligned to that power + // of two. + // + // For (1), 1-8 byte watchpoints, using the Byte Address Selector field in + // DBGWCR<n>.BAS. Any of the bytes may be watched, but if multiple bytes + // are watched, the bytes selected must be contiguous. The start address + // watched must be doubleword (8-byte) aligned; if the start address is + // word (4-byte) aligned, only 4 bytes can be watched. + // + // For (2), the MASK field in DBGWCR<n>.MASK is used. + // + // See the ARM ARM, section "Watchpoint exceptions", and more specifically, + // "Watchpoint data address comparisons". + // + // debugserver today only supports (1) - the Byte Address Selector 1-8 byte + // watchpoints that are 8-byte aligned. To support larger watchpoints, + // debugserver would need to interpret the mach exception when the watched + // region was hit, see if the address accessed lies within the subset + // of the power-of-two region that lldb asked us to watch (v. ARM ARM, + // "Determining the memory location that caused a Watchpoint exception"), + // and silently resume the inferior (disable watchpoint, stepi, re-enable + // watchpoint) if the address lies outside the region that lldb asked us + // to watch. + // + // Alternatively, lldb would need to be prepared for a larger region + // being watched than it requested, and silently resume the inferior if + // the accessed address is outside the region lldb wants to watch. nub_addr_t aligned_wp_address = addr & ~0x7; uint32_t addr_dword_offset = addr & 0x7; _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
