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Re: [Qemu-devel] [PATCH v3 2/2] gdbstub: Fix vCont behaviour
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v3 2/2] gdbstub: Fix vCont behaviour |
Date: |
Wed, 25 Jan 2017 11:34:14 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 |
On 28/10/2016 19:15, Claudio Imbrenda wrote:
> When GDB issues a "vCont", QEMU was not handling it correctly when
> multiple VCPUs are active.
> For vCont, for each thread (VCPU), it can be specified whether to
> single step, continue or stop that thread. The default is to stop a
> thread.
> However, when (for example) "vCont;s:2" is issued, all VCPUs continue
> to run, although all but VCPU nr 2 are to be stopped.
>
> This patch completely rewrites the vCont parsing code.
>
> Please note that this improvement only works in system emulation mode,
> when in userspace emulation mode the old behaviour is preserved.
>
> Signed-off-by: Claudio Imbrenda <address@hidden>
> ---
> gdbstub.c | 189
> ++++++++++++++++++++++++++++++++++++++++++++++----------------
> 1 file changed, 142 insertions(+), 47 deletions(-)
>
> diff --git a/gdbstub.c b/gdbstub.c
> index b2e1b79..9bb548f 100644
> --- a/gdbstub.c
> +++ b/gdbstub.c
> @@ -386,6 +386,45 @@ static inline void gdb_continue(GDBState *s)
> #endif
> }
>
> +/*
> + * Resume execution, per CPU actions. For user-more emulation it's
> + * equivalent to gdb_continue .
> + */
> +static int gdb_continue_partial(GDBState *s, char *newstates)
> +{
> + int res = 0;
> +#ifdef CONFIG_USER_ONLY
> + s->running_state = 1;
> +#else
> + CPUState *cpu;
> +
> + if (!runstate_needs_reset()) {
> + if (vm_prepare_start()) {
> + return 0;
> + }
> +
> + CPU_FOREACH(cpu) {
> + switch (newstates[cpu_index(cpu) - 1]) {
> + case 0:
> + case 1:
> + break; /* nothing to do here */
> + case 's':
> + cpu_single_step(cpu, sstep_flags);
> + cpu_resume(cpu);
> + break;
> + case 'c':
> + cpu_resume(cpu);
> + break;
> + default:
> + res = -1;
> + break;
> + }
> + }
> + }
> +#endif
> + return res;
> +}
> +
> static void put_buffer(GDBState *s, const uint8_t *buf, int len)
> {
> #ifdef CONFIG_USER_ONLY
> @@ -784,6 +823,102 @@ static int is_query_packet(const char *p, const char
> *query, char separator)
> (p[query_len] == '\0' || p[query_len] == separator);
> }
>
> +/**
> + * gdb_handle_vcont - Parses and handles a vCont packet.
> + * returns -1 if a command is unsupported, -22 if there is a format error,
> + * 0 on success.
> + */
> +static int gdb_handle_vcont(GDBState *s, const char *p)
> +{
> + int res, idx, signal = 0;
> + char cur_action;
> + char *newstates;
> + unsigned long tmp;
> + CPUState *cpu;
> +
> + /* uninitialised CPUs stay 0 */
> + newstates = g_new0(char, max_cpus);
> +
> + /* mark valid CPUs with 1 */
> + CPU_FOREACH(cpu) {
> + newstates[cpu_index(cpu) - 1] = 1;
> + }
> +
> + /*
> + * res keeps track of what error we are returning, with -1 meaning
> + * that the command is unknown or unsupported, and thus returning
> + * an empty packet, while -22 returns an E22 packet due to
> + * invalid or incorrect parameters passed.
> + */
Please use ENOTSUP for unknown/unsupported and any other negative errno
value for invalid/incorrect parameters. This simplifies the code a bit
in this function, as we know that qemu_strtoul only returns -EINVAL or
-ERANGE.
> + res = 0;
> + while (*p) {
> + if (*p != ';') {
Use *p++ here.
> + res = -1;
> + break;
If you change all returns with error to a "goto out", you can avoid the
"if (!res)" at the end of the loop.
> + }
> + p++; /* skip the ; */
> +
> + /* unknown/invalid/unsupported command */
> + if (*p != 'C' && *p != 'S' && *p != 'c' && *p != 's') {
> + res = -1;
> + break;
> + }
> + cur_action = tolower(*p);
> + if (*p == 'C' || *p == 'S') {
> + if (qemu_strtoul(p + 1, &p, 16, &tmp)) {
> + res = -22;
> + break;
> + }
> + signal = gdb_signal_to_target(tmp);
> + } else {
> + p++;
> + }
Maybe:
cur_action = *p++;
if (cur_action == 'C' || cur_action == 'S') {
cur_action = tolower(cur_action);
res = qemu_strtoul(p, &p, 16, &tmp);
if (res < 0) {
goto out;
}
} else if (cur_action != 'c' && cur_action != 's') {
res = -ENOTSUP;
goto out;
}
What's the meaning of "signal" for system emulation?
> + /* thread specification. special values: (none), -1 = all; 0 = any */
> + if ((p[0] == ':' && p[1] == '-' && p[2] == '1') || (p[0] != ':')) {
> + for (idx = 0; idx < max_cpus; idx++) {
> + if (newstates[idx] == 1) {
> + newstates[idx] = cur_action;
> + }
> + }
> + if (*p == ':') {
> + p += 3;
> + }
Please place this "if" before the "for", to match what you do in the
"else if" case.
> + } else if (*p == ':') {
> + p++;
> + if (qemu_strtoul(p, &p, 16, &tmp)) {
> + res = -22;
> + break;
> + }
As suggested above, you can just assign the result of qemu_strtoul to res.
> + idx = tmp;
> + /* 0 means any thread, so we pick the first valid CPU */
> + if (!idx) {
> + CPU_FOREACH(cpu) {
> + idx = cpu_index(cpu);
> + break;
> + }
Can you use first_cpu here perhaps?
> + }
> +
> + /* invalid CPU specified */
> + if (!idx || idx > max_cpus || !newstates[idx - 1]) {
> + res = -22;
> + break;
> + }
> + /* only use if no previous match occourred */
> + if (newstates[idx - 1] == 1) {
> + newstates[idx - 1] = cur_action;
> + }
> + }
> + }
> + if (!res) {
> + s->signal = signal;
> + gdb_continue_partial(s, newstates);
> + }
> +
This would be the placement of the "out:" label.
Thanks,
Paolo
> + g_free(newstates);
> +
> + return res;
> +}
> +
> static int gdb_handle_packet(GDBState *s, const char *line_buf)
> {
> CPUState *cpu;
> @@ -829,60 +964,20 @@ static int gdb_handle_packet(GDBState *s, const char
> *line_buf)
> return RS_IDLE;
> case 'v':
> if (strncmp(p, "Cont", 4) == 0) {
> - int res_signal, res_thread;
> -
> p += 4;
> if (*p == '?') {
> put_packet(s, "vCont;c;C;s;S");
> break;
> }
> - res = 0;
> - res_signal = 0;
> - res_thread = 0;
> - while (*p) {
> - int action, signal;
> -
> - if (*p++ != ';') {
> - res = 0;
> - break;
> - }
> - action = *p++;
> - signal = 0;
> - if (action == 'C' || action == 'S') {
> - signal = gdb_signal_to_target(strtoul(p, (char **)&p,
> 16));
> - if (signal == -1) {
> - signal = 0;
> - }
> - } else if (action != 'c' && action != 's') {
> - res = 0;
> - break;
> - }
> - thread = 0;
> - if (*p == ':') {
> - thread = strtoull(p+1, (char **)&p, 16);
> - }
> - action = tolower(action);
> - if (res == 0 || (res == 'c' && action == 's')) {
> - res = action;
> - res_signal = signal;
> - res_thread = thread;
> - }
> - }
> +
> + res = gdb_handle_vcont(s, p);
> +
> if (res) {
> - if (res_thread != -1 && res_thread != 0) {
> - cpu = find_cpu(res_thread);
> - if (cpu == NULL) {
> - put_packet(s, "E22");
> - break;
> - }
> - s->c_cpu = cpu;
> - }
> - if (res == 's') {
> - cpu_single_step(s->c_cpu, sstep_flags);
> + if (res == -22) {
> + put_packet(s, "E22");
> + break;
> }
> - s->signal = res_signal;
> - gdb_continue(s);
> - return RS_IDLE;
> + goto unknown_command;
> }
> break;
> } else {
>
- Re: [Qemu-devel] [PATCH v3 2/2] gdbstub: Fix vCont behaviour,
Paolo Bonzini <=