From 6085d6f69562472c389679052dcfe66cf3068a76 Mon Sep 17 00:00:00 2001 From: Yao Qi Date: Tue, 4 Aug 2015 14:34:14 +0100 Subject: [PATCH] Disable Z0 packet on aarch64 on multi-arch debugging In multi-arch debugging, if GDB sends Z0 packet, GDBserver should be able to do several things below: - choose the right breakpoint instruction to insert according to the information available, such as 'kind' in Z0 packet and address, - choose the right breakpoint instruction to check memory writes and validate inserted memory breakpoint - be aware of different breakpoint instructions in $ARCH_breakpoint_at. unfortunately GDBserver can't do them now. Although x86 GDBserver supports multi-arch, it doesn't need to support them above because breakpoint instruction on i686 and x86_64 is the same. However, breakpoint instructions on aarch64 and arm (arm mode, thumb1, and thumb2) are different. I tried to teach aarch64 GDBserver backend to be really multi-arch-capable in the following ways, - linux_low_target return the right breakpoint instruction according to the 'kind' in Z0 packet, and insert_memory_breakpoint can do the right thing. - once breakpoint is inserted, the breakpoint data and length is recorded in each breakpoint object, so that validate_breakpoint and check_mem_write can get the right breakpoint instruction from each breakpoint object, rather than from global variable breakpoint_data. - linux_low_target needs another hook function for pc increment after hitting a breakpoint. - let set_breakpoint_at, which is widely used for tracepoint, use the 'default' breakpoint instruction. We can always use aarch64 breakpoint instruction since arm doesn't support tracepoint yet. looks it is not a small piece of work, so I decide to disable Z0 packet on multi-arch, which means aarch64 GDBserver only supports Z0 packet if it is started to debug only one process (extended protocol is not used) and process target description is 64-bit. gdb/gdbserver: 2015-08-04 Yao Qi * linux-aarch64-low.c (aarch64_supports_z_point_type): Return 0 for Z_PACKET_SW_BP if it may be used in multi-arch debugging. * server.c (extended_protocol): Remove "static". * server.h (extended_protocol): Declare it. --- gdb/gdbserver/ChangeLog | 7 +++++++ gdb/gdbserver/linux-aarch64-low.c | 16 ++++++++++++++++ gdb/gdbserver/server.c | 2 +- gdb/gdbserver/server.h | 1 + 4 files changed, 25 insertions(+), 1 deletion(-) diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog index be13f9b..1227686 100644 --- a/gdb/gdbserver/ChangeLog +++ b/gdb/gdbserver/ChangeLog @@ -1,5 +1,12 @@ 2015-08-04 Yao Qi + * linux-aarch64-low.c (aarch64_supports_z_point_type): Return + 0 for Z_PACKET_SW_BP if it may be used in multi-arch debugging. + * server.c (extended_protocol): Remove "static". + * server.h (extended_protocol): Declare it. + +2015-08-04 Yao Qi + * linux-aarch64-low.c (aarch64_get_pc): Get PC register on both aarch64 and aarch32. (aarch64_set_pc): Likewise. diff --git a/gdb/gdbserver/linux-aarch64-low.c b/gdb/gdbserver/linux-aarch64-low.c index 3512ce9..90d2b43 100644 --- a/gdb/gdbserver/linux-aarch64-low.c +++ b/gdb/gdbserver/linux-aarch64-low.c @@ -364,6 +364,22 @@ aarch64_supports_z_point_type (char z_type) switch (z_type) { case Z_PACKET_SW_BP: + { + if (!extended_protocol && is_64bit_tdesc ()) + { + /* Only enable Z0 packet in non-multi-arch debugging. If + extended protocol is used, don't enable Z0 packet because + GDBserver may attach to 32-bit process. */ + return 1; + } + else + { + /* Disable Z0 packet so that GDBserver doesn't have to handle + different breakpoint instructions (aarch64, arm, thumb etc) + in multi-arch debugging. */ + return 0; + } + } case Z_PACKET_HW_BP: case Z_PACKET_WRITE_WP: case Z_PACKET_READ_WP: diff --git a/gdb/gdbserver/server.c b/gdb/gdbserver/server.c index 2918770..f15b7be 100644 --- a/gdb/gdbserver/server.c +++ b/gdb/gdbserver/server.c @@ -49,7 +49,7 @@ ptid_t general_thread; int server_waiting; -static int extended_protocol; +int extended_protocol; static int response_needed; static int exit_requested; diff --git a/gdb/gdbserver/server.h b/gdb/gdbserver/server.h index 09a5624..9080151 100644 --- a/gdb/gdbserver/server.h +++ b/gdb/gdbserver/server.h @@ -87,6 +87,7 @@ extern int multi_process; extern int report_fork_events; extern int report_vfork_events; extern int non_stop; +extern int extended_protocol; /* True if the "swbreak+" feature is active. In that case, GDB wants us to report whether a trap is explained by a software breakpoint -- 2.7.4