GDB supports stopping on syscall entry and exit using the "catch syscall" command. It relies on 3 packets, which are currently not supported by QEMU:
* qSupported:QCatchSyscalls+ [1] * QCatchSyscalls: [2] * T05syscall_entry: and T05syscall_return: [3] Implement generation and handling of these packets. [1] https://sourceware.org/gdb/current/onlinedocs/gdb.html/General-Query-Packets.html#qSupported [2] https://sourceware.org/gdb/current/onlinedocs/gdb.html/General-Query-Packets.html#QCatchSyscalls [3] https://sourceware.org/gdb/current/onlinedocs/gdb.html/Stop-Reply-Packets.html Signed-off-by: Ilya Leoshkevich <i...@linux.ibm.com> --- gdbstub/gdbstub.c | 11 +++++++- gdbstub/internals.h | 16 +++++++++++ gdbstub/system.c | 1 + gdbstub/user-target.c | 39 +++++++++++++++++++++++++++ gdbstub/user.c | 51 +++++++++++++++++++++++++++++++++++- include/gdbstub/user.h | 29 ++++++++++++++++++-- include/user/syscall-trace.h | 7 +++-- 7 files changed, 148 insertions(+), 6 deletions(-) diff --git a/gdbstub/gdbstub.c b/gdbstub/gdbstub.c index 46d752bbc2c..7faf19508d1 100644 --- a/gdbstub/gdbstub.c +++ b/gdbstub/gdbstub.c @@ -1618,7 +1618,8 @@ static void handle_query_supported(GArray *params, void *user_ctx) g_string_append(gdbserver_state.str_buf, ";qXfer:auxv:read+"); } #endif - g_string_append(gdbserver_state.str_buf, ";qXfer:exec-file:read+"); + g_string_append(gdbserver_state.str_buf, ";qXfer:exec-file:read+" + ";QCatchSyscalls+"); #endif if (params->len && @@ -1810,6 +1811,14 @@ static const GdbCmdParseEntry gdb_gen_set_table[] = { .schema = "l0" }, #endif +#if defined(CONFIG_USER_ONLY) + { + .handler = gdb_handle_set_catch_syscalls, + .cmd = "CatchSyscalls:", + .cmd_startswith = 1, + .schema = "s0", + }, +#endif }; static void handle_gen_query(GArray *params, void *user_ctx) diff --git a/gdbstub/internals.h b/gdbstub/internals.h index 5c0c725e54c..6e0905ca328 100644 --- a/gdbstub/internals.h +++ b/gdbstub/internals.h @@ -10,6 +10,7 @@ #define GDBSTUB_INTERNALS_H #include "exec/cpu-common.h" +#include "qemu/bitops.h" #define MAX_PACKET_LENGTH 4096 @@ -46,6 +47,14 @@ enum RSState { RS_CHKSUM2, }; +enum GDBCatchSyscallsState { + GDB_CATCH_SYSCALLS_NONE, + GDB_CATCH_SYSCALLS_ALL, + GDB_CATCH_SYSCALLS_SELECTED, +}; +#define GDB_NR_SYSCALLS 1024 +typedef unsigned long GDBSyscallsMask[BITS_TO_LONGS(GDB_NR_SYSCALLS)]; + typedef struct GDBState { bool init; /* have we been initialised? */ CPUState *c_cpu; /* current CPU for step/continue ops */ @@ -70,6 +79,12 @@ typedef struct GDBState { * Must be set off after sending the stop reply itself. */ bool allow_stop_reply; + /* + * Store syscalls mask without memory allocation in order to avoid + * implementing synchronization. + */ + enum GDBCatchSyscallsState catch_syscalls_state; + GDBSyscallsMask catch_syscalls_mask; } GDBState; /* lives in main gdbstub.c */ @@ -194,6 +209,7 @@ void gdb_handle_v_file_close(GArray *params, void *user_ctx); /* user */ void gdb_handle_v_file_pread(GArray *params, void *user_ctx); /* user */ void gdb_handle_v_file_readlink(GArray *params, void *user_ctx); /* user */ void gdb_handle_query_xfer_exec_file(GArray *params, void *user_ctx); /* user */ +void gdb_handle_set_catch_syscalls(GArray *params, void *user_ctx); /* user */ void gdb_handle_query_attached(GArray *params, void *user_ctx); /* both */ diff --git a/gdbstub/system.c b/gdbstub/system.c index 83fd452800b..4c4bafd3bcc 100644 --- a/gdbstub/system.c +++ b/gdbstub/system.c @@ -44,6 +44,7 @@ static void reset_gdbserver_state(void) gdbserver_state.processes = NULL; gdbserver_state.process_num = 0; gdbserver_state.allow_stop_reply = false; + gdbserver_state.catch_syscalls_state = GDB_CATCH_SYSCALLS_NONE; } /* diff --git a/gdbstub/user-target.c b/gdbstub/user-target.c index c4bba4c72c7..442d15e9473 100644 --- a/gdbstub/user-target.c +++ b/gdbstub/user-target.c @@ -9,6 +9,7 @@ #include "qemu/osdep.h" #include "exec/gdbstub.h" +#include "gdbstub/user.h" #include "qemu.h" #include "internals.h" #ifdef CONFIG_LINUX @@ -418,3 +419,41 @@ void gdb_handle_query_xfer_exec_file(GArray *params, void *user_ctx) ts->bprm->filename + offset); gdb_put_strbuf(); } + +static bool should_catch_syscall(int num) +{ + switch (gdbserver_state.catch_syscalls_state) { + case GDB_CATCH_SYSCALLS_NONE: + return false; + case GDB_CATCH_SYSCALLS_ALL: + return true; + case GDB_CATCH_SYSCALLS_SELECTED: + if (num < 0 || num >= GDB_NR_SYSCALLS) { + return false; + } else { + return test_bit(num, gdbserver_state.catch_syscalls_mask); + } + default: + g_assert_not_reached(); + } +} + +void gdb_syscall_entry(CPUState *cs, int num) +{ + char reason[32]; + + if (should_catch_syscall(num)) { + snprintf(reason, sizeof(reason), "syscall_entry:%x;", num); + gdb_handlesig_reason(cs, TARGET_SIGTRAP, reason); + } +} + +void gdb_syscall_return(CPUState *cs, int num) +{ + char reason[32]; + + if (should_catch_syscall(num)) { + snprintf(reason, sizeof(reason), "syscall_return:%x;", num); + gdb_handlesig_reason(cs, TARGET_SIGTRAP, reason); + } +} diff --git a/gdbstub/user.c b/gdbstub/user.c index dbe1d9b8875..e02be56abf6 100644 --- a/gdbstub/user.c +++ b/gdbstub/user.c @@ -121,7 +121,7 @@ void gdb_qemu_exit(int code) exit(code); } -int gdb_handlesig(CPUState *cpu, int sig) +int gdb_handlesig_reason(CPUState *cpu, int sig, const char *reason) { char buf[256]; int n; @@ -141,6 +141,9 @@ int gdb_handlesig(CPUState *cpu, int sig) "T%02xthread:", gdb_target_signal_to_gdb(sig)); gdb_append_thread_id(cpu, gdbserver_state.str_buf); g_string_append_c(gdbserver_state.str_buf, ';'); + if (reason) { + g_string_append(gdbserver_state.str_buf, reason); + } gdb_put_strbuf(); gdbserver_state.allow_stop_reply = false; } @@ -499,3 +502,49 @@ void gdb_syscall_handling(const char *syscall_packet) gdb_put_packet(syscall_packet); gdb_handlesig(gdbserver_state.c_cpu, 0); } + +void gdb_handle_set_catch_syscalls(GArray *params, void *user_ctx) +{ + enum GDBCatchSyscallsState catch_syscalls_state; + const char *param = get_param(params, 0)->data; + GDBSyscallsMask catch_syscalls_mask; + bool catch_syscalls_none; + unsigned int num; + const char *p; + + catch_syscalls_none = strcmp(param, "0") == 0; + if (catch_syscalls_none || strcmp(param, "1") == 0) { + gdbserver_state.catch_syscalls_state = catch_syscalls_none ? + GDB_CATCH_SYSCALLS_NONE : + GDB_CATCH_SYSCALLS_ALL; + gdb_put_packet("OK"); + return; + } + + if (param[0] == '1' && param[1] == ';') { + catch_syscalls_state = GDB_CATCH_SYSCALLS_SELECTED; + memset(catch_syscalls_mask, 0, sizeof(catch_syscalls_mask)); + for (p = ¶m[2];; p++) { + if (qemu_strtoui(p, &p, 16, &num) || (*p && *p != ';')) { + goto err; + } + if (num >= GDB_NR_SYSCALLS) { + /* Fall back to reporting all syscalls. */ + catch_syscalls_state = GDB_CATCH_SYSCALLS_ALL; + } else { + set_bit(num, catch_syscalls_mask); + } + if (!*p) { + break; + } + } + gdbserver_state.catch_syscalls_state = catch_syscalls_state; + memcpy(gdbserver_state.catch_syscalls_mask, catch_syscalls_mask, + sizeof(catch_syscalls_mask)); + gdb_put_packet("OK"); + return; + } + +err: + gdb_put_packet("E00"); +} diff --git a/include/gdbstub/user.h b/include/gdbstub/user.h index d392e510c59..68b6534130c 100644 --- a/include/gdbstub/user.h +++ b/include/gdbstub/user.h @@ -10,9 +10,10 @@ #define GDBSTUB_USER_H /** - * gdb_handlesig() - yield control to gdb + * gdb_handlesig_reason() - yield control to gdb * @cpu: CPU * @sig: if non-zero, the signal number which caused us to stop + * @reason: stop reason for stop reply packet or NULL * * This function yields control to gdb, when a user-mode-only target * needs to stop execution. If @sig is non-zero, then we will send a @@ -24,7 +25,18 @@ * or 0 if no signal should be delivered, ie the signal that caused * us to stop should be ignored. */ -int gdb_handlesig(CPUState *, int); +int gdb_handlesig_reason(CPUState *, int, const char *); + +/** + * gdb_handlesig() - yield control to gdb + * @cpu CPU + * @sig: if non-zero, the signal number which caused us to stop + * @see gdb_handlesig_reason() + */ +static inline int gdb_handlesig(CPUState *cpu, int sig) +{ + return gdb_handlesig_reason(cpu, sig, NULL); +} /** * gdb_signalled() - inform remote gdb of sig exit @@ -39,5 +51,18 @@ void gdb_signalled(CPUArchState *as, int sig); */ void gdbserver_fork(CPUState *cs); +/** + * gdb_syscall_entry() - inform gdb of syscall entry and yield control to it + * @cs: CPU + * @num: syscall number + */ +void gdb_syscall_entry(CPUState *cs, int num); + +/** + * gdb_syscall_entry() - inform gdb of syscall return and yield control to it + * @cs: CPU + * @num: syscall number + */ +void gdb_syscall_return(CPUState *cs, int num); #endif /* GDBSTUB_USER_H */ diff --git a/include/user/syscall-trace.h b/include/user/syscall-trace.h index 557f881a79b..b48b2b2d0ae 100644 --- a/include/user/syscall-trace.h +++ b/include/user/syscall-trace.h @@ -11,6 +11,7 @@ #define SYSCALL_TRACE_H #include "exec/user/abitypes.h" +#include "gdbstub/user.h" #include "qemu/plugin.h" #include "trace/trace-root.h" @@ -20,7 +21,7 @@ * could potentially unify the -strace code here as well. */ -static inline void record_syscall_start(void *cpu, int num, +static inline void record_syscall_start(CPUState *cpu, int num, abi_long arg1, abi_long arg2, abi_long arg3, abi_long arg4, abi_long arg5, abi_long arg6, @@ -29,11 +30,13 @@ static inline void record_syscall_start(void *cpu, int num, qemu_plugin_vcpu_syscall(cpu, num, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8); + gdb_syscall_entry(cpu, num); } -static inline void record_syscall_return(void *cpu, int num, abi_long ret) +static inline void record_syscall_return(CPUState *cpu, int num, abi_long ret) { qemu_plugin_vcpu_syscall_ret(cpu, num, ret); + gdb_syscall_return(cpu, num); } -- 2.43.0
