I’m happy with this from AArch64 side. Alan. > On 15 Jan 2020, at 11:51, Luis Machado wrote: > > New in v3: > > - Code cleanups based on reviews. > > New in v2: > > - Fixed misc problems based on reviews. > - Switched to using gdbarch_program_breakpoint_here_p as opposed to > gdbarch_insn_is_breakpoint. > - Fixed matching of brk instructions. Previously the mask was incorrect, which > was showing up as a few failures in the testsuite. Now it is clean. > - New testcase (separate patch). > - Moved program_breakpoint_here () to arch-utils.c and made it the default > implementation of gdbarch_program_breakpoint_here_p. > > -- > > It was reported to me that program breakpoints (permanent ones inserted into > the code itself) other than the one GDB uses for AArch64 (0xd4200000) do not > generate visible stops when continuing, and GDB will continue spinning > infinitely. > > This happens because GDB, upon hitting one of those program breakpoints, thinks > the SIGTRAP came from a delayed breakpoint hit... > > (gdb) x/i $pc > => 0x4005c0 : brk #0x90f > (gdb) c > Continuing. > infrun: clear_proceed_status_thread (process 14198) > infrun: proceed (addr=0xffffffffffffffff, signal=GDB_SIGNAL_DEFAULT) > infrun: proceed: resuming process 14198 > infrun: resume (step=0, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 14198] at 0x4005c0 > infrun: infrun_async(1) > infrun: prepare_to_wait > infrun: target_wait (-1.0.0, status) = > infrun: 14198.14198.0 [process 14198], > infrun: status->kind = stopped, signal = GDB_SIGNAL_TRAP > infrun: handle_inferior_event status->kind = stopped, signal = GDB_SIGNAL_TRAP > infrun: stop_pc = 0x4005c0 > infrun: delayed software breakpoint trap, ignoring > infrun: no stepping, continue > infrun: resume (step=0, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 14198] at 0x4005c0 > infrun: prepare_to_wait > infrun: target_wait (-1.0.0, status) = > infrun: 14198.14198.0 [process 14198], > infrun: status->kind = stopped, signal = GDB_SIGNAL_TRAP > infrun: handle_inferior_event status->kind = stopped, signal = GDB_SIGNAL_TRAP > infrun: stop_pc = 0x4005c0 > infrun: delayed software breakpoint trap, ignoring > infrun: no stepping, continue > infrun: resume (step=0, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 14198] at 0x4005c0 > infrun: prepare_to_wait > infrun: target_wait (-1.0.0, status) = > infrun: 14198.14198.0 [process 14198], > infrun: status->kind = stopped, signal = GDB_SIGNAL_TRAP > infrun: handle_inferior_event status->kind = stopped, signal = GDB_SIGNAL_TRAP > infrun: stop_pc = 0x4005c0 > infrun: delayed software breakpoint trap, ignoring > infrun: no stepping, continue > infrun: resume (step=0, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 14198] at 0x4005c0 > infrun: prepare_to_wait > infrun: target_wait (-1.0.0, status) = > infrun: 14198.14198.0 [process 14198], > infrun: status->kind = stopped, signal = GDB_SIGNAL_TRAP > infrun: handle_inferior_event status->kind = stopped, signal = GDB_SIGNAL_TRAP > infrun: stop_pc = 0x4005c0 > infrun: delayed software breakpoint trap, ignoring > infrun: no stepping, continue > infrun: resume (step=0, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 14198] at 0x4005c0 > infrun: prepare_to_wait > infrun: target_wait (-1.0.0, status) = > infrun: 14198.14198.0 [process 14198], > infrun: status->kind = stopped, signal = GDB_SIGNAL_TRAP > ... > > ... which is not the case. > > If the program breakpoint is one GDB recognizes, then it will stop when it > hits it. > > (gdb) x/i $pc > => 0x4005c0 : brk #0x0 > (gdb) c > Continuing. > infrun: clear_proceed_status_thread (process 14193) > infrun: proceed (addr=0xffffffffffffffff, signal=GDB_SIGNAL_DEFAULT) > infrun: proceed: resuming process 14193 > infrun: resume (step=0, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 14193] at 0x4005c0 > infrun: infrun_async(1) > infrun: prepare_to_wait > infrun: target_wait (-1.0.0, status) = > infrun: 14193.14193.0 [process 14193], > infrun: status->kind = stopped, signal = GDB_SIGNAL_TRAP > infrun: handle_inferior_event status->kind = stopped, signal = GDB_SIGNAL_TRAP > infrun: stop_pc = 0x4005c0 > infrun: random signal (GDB_SIGNAL_TRAP) > infrun: stop_waiting > infrun: stop_all_threads > infrun: stop_all_threads, pass=0, iterations=0 > infrun: process 14193 not executing > infrun: stop_all_threads, pass=1, iterations=1 > infrun: process 14193 not executing > infrun: stop_all_threads done > > Program received signal SIGTRAP, Trace/breakpoint trap. > problem_function () at brk_0.c:7 > 7 asm("brk %0\n\t" ::"n"(0x0)); > infrun: infrun_async(0) > > Otherwise GDB will keep trying to resume the inferior and will keep > seeing the SIGTRAP's, without stopping. > > To the user it appears GDB has gone into an infinite loop, interruptible only > by Ctrl-C. > > Also, windbg seems to use a different variation of AArch64 breakpoint compared > to GDB. This causes problems when debugging Windows on ARM binaries, when > program breakpoints are being used. > > The proposed patch creates a new gdbarch method (gdbarch_program_breakpoint_here_p) > that tells GDB whether the underlying instruction is a breakpoint instruction > or not. > > This is more general than only checking for the instruction GDB uses as > breakpoint. > > The existing logic is still preserved for targets that do not implement this > new gdbarch method. > > The end result is like so: > > (gdb) x/i $pc > => 0x4005c0 : brk #0x90f > (gdb) c > Continuing. > infrun: clear_proceed_status_thread (process 16417) > infrun: proceed (addr=0xffffffffffffffff, signal=GDB_SIGNAL_DEFAULT) > infrun: proceed: resuming process 16417 > infrun: resume (step=0, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 16417] at 0x4005c0 > infrun: infrun_async(1) > infrun: prepare_to_wait > infrun: target_wait (-1.0.0, status) = > infrun: 16417.16417.0 [process 16417], > infrun: status->kind = stopped, signal = GDB_SIGNAL_TRAP > infrun: handle_inferior_event status->kind = stopped, signal = GDB_SIGNAL_TRAP > infrun: stop_pc = 0x4005c0 > infrun: random signal (GDB_SIGNAL_TRAP) > infrun: stop_waiting > infrun: stop_all_threads > infrun: stop_all_threads, pass=0, iterations=0 > infrun: process 16417 not executing > infrun: stop_all_threads, pass=1, iterations=1 > infrun: process 16417 not executing > infrun: stop_all_threads done > > Program received signal SIGTRAP, Trace/breakpoint trap. > problem_function () at brk.c:7 > 7 asm("brk %0\n\t" ::"n"(0x900 + 0xf)); > infrun: infrun_async(0) > > gdb/ChangeLog: > > 2020-01-15 Luis Machado > > * aarch64-tdep.c (BRK_INSN_MASK): Define to 0xffe0001f. > (BRK_INSN_MASK): Define to 0xd4200000. > (aarch64_program_breakpoint_here_p): New function. > (aarch64_gdbarch_init): Set gdbarch_program_breakpoint_here_p hook. > * arch-utils.c (default_program_breakpoint_here_p): Moved from > breakpoint.c. > * arch-utils.h (default_program_breakpoint_here_p): Moved from > breakpoint.h > * breakpoint.c (bp_loc_is_permanent): Changed return type to bool and > call gdbarch_program_breakpoint_here_p. > (program_breakpoint_here): Moved to arch-utils.c, renamed to > default_program_breakpoint_here_p, changed return type to bool and > simplified. > * breakpoint.h (program_breakpoint_here): Moved prototype to > arch-utils.h, renamed to default_program_breakpoint_here_p and changed > return type to bool. > * gdbarch.c: Regenerate. > * gdbarch.h: Regenerate. > * gdbarch.sh (program_breakpoint_here_p): New method. > * infrun.c (handle_signal_stop): Call > gdbarch_program_breakpoint_here_p. > --- > gdb/aarch64-tdep.c | 37 +++++++++++++++++++++++++++++++++++++ > gdb/arch-utils.c | 32 ++++++++++++++++++++++++++++++++ > gdb/arch-utils.h | 4 ++++ > gdb/breakpoint.c | 46 +++++++--------------------------------------- > gdb/breakpoint.h | 5 ----- > gdb/gdbarch.c | 23 +++++++++++++++++++++++ > gdb/gdbarch.h | 7 +++++++ > gdb/gdbarch.sh | 4 ++++ > gdb/infrun.c | 4 ++-- > 9 files changed, 116 insertions(+), 46 deletions(-) > > diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c > index 8451a916dc..7f32df3ec0 100644 > --- a/gdb/aarch64-tdep.c > +++ b/gdb/aarch64-tdep.c > @@ -1201,6 +1201,39 @@ aarch64_execute_dwarf_cfa_vendor_op (struct gdbarch *gdbarch, gdb_byte op, > return false; > } > > +/* Used for matching BRK instructions for AArch64. */ > +static constexpr uint32_t BRK_INSN_MASK = 0xffe0001f; > +static constexpr uint32_t BRK_INSN_BASE = 0xd4200000; > + > +/* Implementation of gdbarch_program_breakpoint_here_p for aarch64. */ > + > +static bool > +aarch64_program_breakpoint_here_p (gdbarch *gdbarch, CORE_ADDR address) > +{ > + const uint32_t insn_len = 4; > + gdb_byte target_mem[4]; > + > + /* Enable the automatic memory restoration from breakpoints while > + we read the memory. Otherwise we may find temporary breakpoints, ones > + inserted by GDB, and flag them as permanent breakpoints. */ > + scoped_restore restore_memory > + = make_scoped_restore_show_memory_breakpoints (0); > + > + if (target_read_memory (address, target_mem, insn_len) == 0) > + { > + uint32_t insn = > + (uint32_t) extract_unsigned_integer (target_mem, insn_len, > + gdbarch_byte_order_for_code (gdbarch)); > + > + /* Check if INSN is a BRK instruction pattern. There are multiple choices > + of such instructions with different immediate values. Different OS' > + may use a different variation, but they have the same outcome. */ > + return ((insn & BRK_INSN_MASK) == BRK_INSN_BASE); > + } > + > + return false; > +} > + > /* When arguments must be pushed onto the stack, they go on in reverse > order. The code below implements a FILO (stack) to do this. */ > > @@ -3357,6 +3390,10 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches) > set_gdbarch_execute_dwarf_cfa_vendor_op (gdbarch, > aarch64_execute_dwarf_cfa_vendor_op); > > + /* Permanent/Program breakpoint handling. */ > + set_gdbarch_program_breakpoint_here_p (gdbarch, > + aarch64_program_breakpoint_here_p); > + > /* Add some default predicates. */ > frame_unwind_append_unwinder (gdbarch, &aarch64_stub_unwind); > dwarf2_append_unwinders (gdbarch); > diff --git a/gdb/arch-utils.c b/gdb/arch-utils.c > index 92d7153ccb..04955ea847 100644 > --- a/gdb/arch-utils.c > +++ b/gdb/arch-utils.c > @@ -876,6 +876,38 @@ int default_insn_is_jump (struct gdbarch *gdbarch, CORE_ADDR addr) > return 0; > } > > +/* See arch-utils.h. */ > + > +bool > +default_program_breakpoint_here_p (struct gdbarch *gdbarch, > + CORE_ADDR address) > +{ > + int len; > + const gdb_byte *bpoint = gdbarch_breakpoint_from_pc (gdbarch, &address, &len); > + > + /* Software breakpoints unsupported? */ > + if (bpoint == nullptr) > + return false; > + > + gdb_byte *target_mem = (gdb_byte *) alloca (len); > + > + /* Enable the automatic memory restoration from breakpoints while > + we read the memory. Otherwise we may find temporary breakpoints, ones > + inserted by GDB, and flag them as permanent breakpoints. */ > + scoped_restore restore_memory > + = make_scoped_restore_show_memory_breakpoints (0); > + > + if (target_read_memory (address, target_mem, len) == 0) > + { > + /* Check if this is a breakpoint instruction for this architecture, > + including ones used by GDB. */ > + if (memcmp (target_mem, bpoint, len) == 0) > + return true; > + } > + > + return false; > +} > + > void > default_skip_permanent_breakpoint (struct regcache *regcache) > { > diff --git a/gdb/arch-utils.h b/gdb/arch-utils.h > index 3fb9ad317a..43d64b1f4f 100644 > --- a/gdb/arch-utils.h > +++ b/gdb/arch-utils.h > @@ -228,6 +228,10 @@ extern int default_insn_is_call (struct gdbarch *, CORE_ADDR); > extern int default_insn_is_ret (struct gdbarch *, CORE_ADDR); > extern int default_insn_is_jump (struct gdbarch *, CORE_ADDR); > > +/* Default implementation of gdbarch_program_breakpoint_here_p. */ > +extern bool default_program_breakpoint_here_p (struct gdbarch *gdbarch, > + CORE_ADDR addr); > + > /* Do-nothing version of vsyscall_range. Returns false. */ > > extern int default_vsyscall_range (struct gdbarch *gdbarch, struct mem_range *range); > diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c > index a7a378131a..5a9352c26f 100644 > --- a/gdb/breakpoint.c > +++ b/gdb/breakpoint.c > @@ -8515,7 +8515,7 @@ mention (struct breakpoint *b) > } > > > -static int bp_loc_is_permanent (struct bp_location *loc); > +static bool bp_loc_is_permanent (struct bp_location *loc); > > static struct bp_location * > add_location_to_breakpoint (struct breakpoint *b, > @@ -8581,42 +8581,10 @@ add_location_to_breakpoint (struct breakpoint *b, > } > > > -/* See breakpoint.h. */ > - > -int > -program_breakpoint_here_p (struct gdbarch *gdbarch, CORE_ADDR address) > -{ > - int len; > - CORE_ADDR addr; > - const gdb_byte *bpoint; > - gdb_byte *target_mem; > - > - addr = address; > - bpoint = gdbarch_breakpoint_from_pc (gdbarch, &addr, &len); > - > - /* Software breakpoints unsupported? */ > - if (bpoint == NULL) > - return 0; > - > - target_mem = (gdb_byte *) alloca (len); > - > - /* Enable the automatic memory restoration from breakpoints while > - we read the memory. Otherwise we could say about our temporary > - breakpoints they are permanent. */ > - scoped_restore restore_memory > - = make_scoped_restore_show_memory_breakpoints (0); > +/* Return true if LOC is pointing to a permanent breakpoint, > + return false otherwise. */ > > - if (target_read_memory (address, target_mem, len) == 0 > - && memcmp (target_mem, bpoint, len) == 0) > - return 1; > - > - return 0; > -} > - > -/* Return 1 if LOC is pointing to a permanent breakpoint, > - return 0 otherwise. */ > - > -static int > +static bool > bp_loc_is_permanent (struct bp_location *loc) > { > gdb_assert (loc != NULL); > @@ -8624,14 +8592,14 @@ bp_loc_is_permanent (struct bp_location *loc) > /* If we have a non-breakpoint-backed catchpoint or a software > watchpoint, just return 0. We should not attempt to read from > the addresses the locations of these breakpoint types point to. > - program_breakpoint_here_p, below, will attempt to read > + gdbarch_program_breakpoint_here_p, below, will attempt to read > memory. */ > if (!bl_address_is_meaningful (loc)) > - return 0; > + return false; > > scoped_restore_current_pspace_and_thread restore_pspace_thread; > switch_to_program_space_and_thread (loc->pspace); > - return program_breakpoint_here_p (loc->gdbarch, loc->address); > + return gdbarch_program_breakpoint_here_p (loc->gdbarch, loc->address); > } > > /* Build a command list for the dprintf corresponding to the current > diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h > index 13d8102c17..347aeb75f3 100644 > --- a/gdb/breakpoint.h > +++ b/gdb/breakpoint.h > @@ -1194,11 +1194,6 @@ enum breakpoint_here > > /* Prototypes for breakpoint-related functions. */ > > -/* Return 1 if there's a program/permanent breakpoint planted in > - memory at ADDRESS, return 0 otherwise. */ > - > -extern int program_breakpoint_here_p (struct gdbarch *gdbarch, CORE_ADDR address); > - > extern enum breakpoint_here breakpoint_here_p (const address_space *, > CORE_ADDR); > > diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c > index cc8569f5c9..d763fc85e6 100644 > --- a/gdb/gdbarch.c > +++ b/gdb/gdbarch.c > @@ -345,6 +345,7 @@ struct gdbarch > gdbarch_insn_is_call_ftype *insn_is_call; > gdbarch_insn_is_ret_ftype *insn_is_ret; > gdbarch_insn_is_jump_ftype *insn_is_jump; > + gdbarch_program_breakpoint_here_p_ftype *program_breakpoint_here_p; > gdbarch_auxv_parse_ftype *auxv_parse; > gdbarch_print_auxv_entry_ftype *print_auxv_entry; > gdbarch_vsyscall_range_ftype *vsyscall_range; > @@ -464,6 +465,7 @@ gdbarch_alloc (const struct gdbarch_info *info, > gdbarch->insn_is_call = default_insn_is_call; > gdbarch->insn_is_ret = default_insn_is_ret; > gdbarch->insn_is_jump = default_insn_is_jump; > + gdbarch->program_breakpoint_here_p = default_program_breakpoint_here_p; > gdbarch->print_auxv_entry = default_print_auxv_entry; > gdbarch->vsyscall_range = default_vsyscall_range; > gdbarch->infcall_mmap = default_infcall_mmap; > @@ -708,6 +710,7 @@ verify_gdbarch (struct gdbarch *gdbarch) > /* Skip verify of insn_is_call, invalid_p == 0 */ > /* Skip verify of insn_is_ret, invalid_p == 0 */ > /* Skip verify of insn_is_jump, invalid_p == 0 */ > + /* Skip verify of program_breakpoint_here_p, invalid_p == 0 */ > /* Skip verify of auxv_parse, has predicate. */ > /* Skip verify of print_auxv_entry, invalid_p == 0 */ > /* Skip verify of vsyscall_range, invalid_p == 0 */ > @@ -1248,6 +1251,9 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file) > fprintf_unfiltered (file, > "gdbarch_dump: process_record_signal = <%s>\n", > host_address_to_string (gdbarch->process_record_signal)); > + fprintf_unfiltered (file, > + "gdbarch_dump: program_breakpoint_here_p = <%s>\n", > + host_address_to_string (gdbarch->program_breakpoint_here_p)); > fprintf_unfiltered (file, > "gdbarch_dump: ps_regnum = %s\n", > plongest (gdbarch->ps_regnum)); > @@ -4928,6 +4934,23 @@ set_gdbarch_insn_is_jump (struct gdbarch *gdbarch, > gdbarch->insn_is_jump = insn_is_jump; > } > > +bool > +gdbarch_program_breakpoint_here_p (struct gdbarch *gdbarch, CORE_ADDR address) > +{ > + gdb_assert (gdbarch != NULL); > + gdb_assert (gdbarch->program_breakpoint_here_p != NULL); > + if (gdbarch_debug >= 2) > + fprintf_unfiltered (gdb_stdlog, "gdbarch_program_breakpoint_here_p called\n"); > + return gdbarch->program_breakpoint_here_p (gdbarch, address); > +} > + > +void > +set_gdbarch_program_breakpoint_here_p (struct gdbarch *gdbarch, > + gdbarch_program_breakpoint_here_p_ftype program_breakpoint_here_p) > +{ > + gdbarch->program_breakpoint_here_p = program_breakpoint_here_p; > +} > + > int > gdbarch_auxv_parse_p (struct gdbarch *gdbarch) > { > diff --git a/gdb/gdbarch.h b/gdb/gdbarch.h > index 9f32ac23ab..800a4e8b16 100644 > --- a/gdb/gdbarch.h > +++ b/gdb/gdbarch.h > @@ -1545,6 +1545,13 @@ typedef int (gdbarch_insn_is_jump_ftype) (struct gdbarch *gdbarch, CORE_ADDR add > extern int gdbarch_insn_is_jump (struct gdbarch *gdbarch, CORE_ADDR addr); > extern void set_gdbarch_insn_is_jump (struct gdbarch *gdbarch, gdbarch_insn_is_jump_ftype *insn_is_jump); > > +/* Return true if there's a program/permanent breakpoint planted in > + memory at ADDRESS, return false otherwise. */ > + > +typedef bool (gdbarch_program_breakpoint_here_p_ftype) (struct gdbarch *gdbarch, CORE_ADDR address); > +extern bool gdbarch_program_breakpoint_here_p (struct gdbarch *gdbarch, CORE_ADDR address); > +extern void set_gdbarch_program_breakpoint_here_p (struct gdbarch *gdbarch, gdbarch_program_breakpoint_here_p_ftype *program_breakpoint_here_p); > + > /* Read one auxv entry from *READPTR, not reading locations >= ENDPTR. > Return 0 if *READPTR is already at the end of the buffer. > Return -1 if there is insufficient buffer for a whole entry. > diff --git a/gdb/gdbarch.sh b/gdb/gdbarch.sh > index 0be3e88bb2..66b54dd700 100755 > --- a/gdb/gdbarch.sh > +++ b/gdb/gdbarch.sh > @@ -1152,6 +1152,10 @@ m;int;insn_is_ret;CORE_ADDR addr;addr;;default_insn_is_ret;;0 > # Return non-zero if the instruction at ADDR is a jump; zero otherwise. > m;int;insn_is_jump;CORE_ADDR addr;addr;;default_insn_is_jump;;0 > > +# Return true if there's a program/permanent breakpoint planted in > +# memory at ADDRESS, return false otherwise. > +m;bool;program_breakpoint_here_p;CORE_ADDR address;address;;default_program_breakpoint_here_p;;0 > + > # Read one auxv entry from *READPTR, not reading locations >= ENDPTR. > # Return 0 if *READPTR is already at the end of the buffer. > # Return -1 if there is insufficient buffer for a whole entry. > diff --git a/gdb/infrun.c b/gdb/infrun.c > index a8636284f1..494324d72b 100644 > --- a/gdb/infrun.c > +++ b/gdb/infrun.c > @@ -6157,8 +6157,8 @@ handle_signal_stop (struct execution_control_state *ecs) > been removed. */ > if (random_signal && target_stopped_by_sw_breakpoint ()) > { > - if (program_breakpoint_here_p (gdbarch, > - ecs->event_thread->suspend.stop_pc)) > + if (gdbarch_program_breakpoint_here_p (gdbarch, > + ecs->event_thread->suspend.stop_pc)) > { > struct regcache *regcache; > int decr_pc; > -- > 2.17.1 > &j!z޶׭שb֫rnr