[PATCH v2 13/14] gdbstub: Implement catching syscalls

From: Ilya Leoshkevich <iii(a)linux.ibm.com&gt; 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-Pack... [2] https://sourceware.org/gdb/current/onlinedocs/gdb.html/General-Query-Pack... [3] https://sourceware.org/gdb/current/onlinedocs/gdb.html/Stop-Reply-Packets... Signed-off-by: Ilya Leoshkevich <iii(a)linux.ibm.com&gt; Message-Id: <20240202152506.279476-5-iii(a)linux.ibm.com&gt; [AJB: GString -> g_strdup_printf] Signed-off-by: Alex Bennée <alex.bennee(a)linaro.org&gt; --- gdbstub/internals.h | 1 + gdbstub/gdbstub.c | 9 +++++ gdbstub/user.c | 91 +++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 101 insertions(+) diff --git a/gdbstub/internals.h b/gdbstub/internals.h index aeb0d9b5377..56b7c13b750 100644 --- a/gdbstub/internals.h +++ b/gdbstub/internals.h @@ -195,6 +195,7 @@ 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/gdbstub.c b/gdbstub/gdbstub.c index 46d752bbc2c..7e73e916bdc 100644 --- a/gdbstub/gdbstub.c +++ b/gdbstub/gdbstub.c @@ -1617,6 +1617,7 @@ static void handle_query_supported(GArray *params, void *user_ctx) if (gdbserver_state.c_cpu->opaque) { g_string_append(gdbserver_state.str_buf, ";qXfer:auxv:read+"); } + g_string_append(gdbserver_state.str_buf, ";QCatchSyscalls+"); #endif g_string_append(gdbserver_state.str_buf, ";qXfer:exec-file:read+"); #endif @@ -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/user.c b/gdbstub/user.c index 2ba01c17faf..14918d1a217 100644 --- a/gdbstub/user.c +++ b/gdbstub/user.c @@ -10,6 +10,7 @@ */ #include "qemu/osdep.h" +#include "qemu/bitops.h" #include "qemu/cutils.h" #include "qemu/sockets.h" #include "exec/hwaddr.h" @@ -21,11 +22,20 @@ #include "trace.h" #include "internals.h" +#define GDB_NR_SYSCALLS 1024 +typedef unsigned long GDBSyscallsMask[BITS_TO_LONGS(GDB_NR_SYSCALLS)]; + /* User-mode specific state */ typedef struct { int fd; char *socket_path; int running_state; + /* + * Store syscalls mask without memory allocation in order to avoid + * implementing synchronization. + */ + bool catch_all_syscalls; + GDBSyscallsMask catch_syscalls_mask; } GDBUserState; static GDBUserState gdbserver_user_state; @@ -503,10 +513,91 @@ void gdb_syscall_handling(const char *syscall_packet) gdb_handlesig(gdbserver_state.c_cpu, 0); } +static bool should_catch_syscall(int num) +{ + if (gdbserver_user_state.catch_all_syscalls) { + return true; + } + if (num < 0 || num >= GDB_NR_SYSCALLS) { + return false; + } + return test_bit(num, gdbserver_user_state.catch_syscalls_mask); +} + void gdb_syscall_entry(CPUState *cs, int num) { + if (should_catch_syscall(num)) { + g_autofree char *reason = g_strdup_printf("syscall_entry:%x;", num); + gdb_handlesig_reason(cs, gdb_target_sigtrap(), reason); + } } void gdb_syscall_return(CPUState *cs, int num) { + if (should_catch_syscall(num)) { + g_autofree char *reason = g_strdup_printf("syscall_return:%x;", num); + gdb_handlesig_reason(cs, gdb_target_sigtrap(), reason); + } +} + +void gdb_handle_set_catch_syscalls(GArray *params, void *user_ctx) +{ + const char *param = get_param(params, 0)->data; + GDBSyscallsMask catch_syscalls_mask; + bool catch_all_syscalls; + unsigned int num; + const char *p; + + /* "0" means not catching any syscalls. */ + if (strcmp(param, "0") == 0) { + gdbserver_user_state.catch_all_syscalls = false; + memset(gdbserver_user_state.catch_syscalls_mask, 0, + sizeof(gdbserver_user_state.catch_syscalls_mask)); + gdb_put_packet("OK"); + return; + } + + /* "1" means catching all syscalls. */ + if (strcmp(param, "1") == 0) { + gdbserver_user_state.catch_all_syscalls = true; + gdb_put_packet("OK"); + return; + } + + /* + * "1;..." means catching only the specified syscalls. + * The syscall list must not be empty. + */ + if (param[0] == '1' && param[1] == ';') { + catch_all_syscalls = false; + memset(catch_syscalls_mask, 0, sizeof(catch_syscalls_mask)); + for (p = &param[2];; p++) { + if (qemu_strtoui(p, &p, 16, &num) || (*p && *p != ';')) { + goto err; + } + if (num >= GDB_NR_SYSCALLS) { + /* + * Fall back to reporting all syscalls. Reporting extra + * syscalls is inefficient, but the spec explicitly allows it. + * Keep parsing in case there is a syntax error ahead. + */ + catch_all_syscalls = true; + } else { + set_bit(num, catch_syscalls_mask); + } + if (!*p) { + break; + } + } + gdbserver_user_state.catch_all_syscalls = catch_all_syscalls; + if (!catch_all_syscalls) { + memcpy(gdbserver_user_state.catch_syscalls_mask, + catch_syscalls_mask, sizeof(catch_syscalls_mask)); + } + gdb_put_packet("OK"); + return; + } + +err: + gdb_put_packet("E00"); } -- 2.39.2