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https://git.FreeBSD.org/src.git
synced 2025-01-12 14:29:28 +00:00
gdb(4): Implement qXfer:threads:read
This streams out an XML document over several GDB packets describing all threads in the system; their ids, name, and any loosely defined "extra info" we feel like including. For now, I have included a string version of the run state, similar to some of the DDB logic to stringify thread state. The benefit of supporting this in addition to the qfThreadInfo/qsThreadInfo packing is that in this mode, the host gdb does not ask for every thread's "qThreadExtraInfo," saving per-thread round-trips on "info threads." To use this feature, (k)gdb needs to be built with the --with-expat option. I would encourage enabling this option by default in our GDB port, if it is not already. Finally, there is another optional attribute you can specify per-thread called a "handle." Handles are arbitrarily long sequences of bytes, represented in the XML as hexadecimal. It is unclear to me how or if GDB actually uses handles for anything. So I have left them out.
This commit is contained in:
Conrad Meyer
parent
c4fbbfaa47
commit
5555afa14e
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=351368
@ -36,6 +36,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/pcpu.h>
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#include <sys/proc.h>
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#include <sys/reboot.h>
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#include <sys/sbuf.h>
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#include <machine/gdb_machdep.h>
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#include <machine/kdb.h>
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@ -252,11 +253,12 @@ gdb_do_qsupported(uint32_t *feat)
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*/
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gdb_tx_varhex(GDB_BUFSZ + strlen("$#nn") - 1);
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gdb_tx_str(";qXfer:threads:read+");
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/*
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* Future consideration:
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* - vCont
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* - multiprocess
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* - qXfer:threads:read
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*/
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gdb_tx_end();
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return;
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@ -266,6 +268,305 @@ gdb_do_qsupported(uint32_t *feat)
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gdb_tx_err(EINVAL);
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}
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/*
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* A qXfer_context provides a vaguely generic way to generate a multi-packet
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* response on the fly, making some assumptions about the size of sbuf writes
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* vs actual packet length constraints. A non-byzantine gdb host should allow
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* hundreds of bytes per packet or more.
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*
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* Upper layers are considered responsible for escaping the four forbidden
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* characters '# $ } *'.
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*/
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struct qXfer_context {
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struct sbuf sb;
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size_t last_offset;
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bool flushed;
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bool lastmessage;
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char xfer_buf[GDB_BUFSZ];
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};
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static int
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qXfer_drain(void *v, const char *buf, int len)
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{
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struct qXfer_context *qx;
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if (len < 0)
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return (-EINVAL);
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qx = v;
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if (qx->flushed) {
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/*
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* Overflow. We lost some message. Maybe the packet size is
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* ridiculously small.
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*/
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printf("%s: Overflow in qXfer detected.\n", __func__);
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return (-ENOBUFS);
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}
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qx->last_offset += len;
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qx->flushed = true;
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if (qx->lastmessage)
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gdb_tx_begin('l');
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else
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gdb_tx_begin('m');
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memcpy(gdb_txp, buf, len);
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gdb_txp += len;
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gdb_tx_end();
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return (len);
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}
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static int
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init_qXfer_ctx(struct qXfer_context *qx, uintmax_t len)
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{
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/* Protocol (max) length field includes framing overhead. */
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if (len < sizeof("$m#nn"))
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return (ENOSPC);
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len -= 4;
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len = ummin(len, GDB_BUFSZ - 1);
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qx->last_offset = 0;
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qx->flushed = false;
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qx->lastmessage = false;
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sbuf_new(&qx->sb, qx->xfer_buf, len, SBUF_FIXEDLEN);
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sbuf_set_drain(&qx->sb, qXfer_drain, qx);
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return (0);
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}
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/*
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* dst must be 2x strlen(max_src) + 1.
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*
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* Squashes invalid XML characters down to _. Sorry. Then escapes for GDB.
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*/
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static void
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qXfer_escape_xmlattr_str(char *dst, size_t dstlen, const char *src)
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{
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static const char *forbidden = "#$}*";
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size_t i;
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char c;
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for (i = 0; i < dstlen - 1 && *src != 0; src++, i++) {
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c = *src;
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/* XML attr filter */
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if (c < 32)
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c = '_';
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/* We assume attributes will be "" quoted. */
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if (c == '<' || c == '&' || c == '"')
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c = '_';
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/* GDB escape. */
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if (strchr(forbidden, c) != NULL) {
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*dst++ = '}';
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c ^= 0x20;
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}
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*dst++ = c;
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}
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if (*src != 0)
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printf("XXX%s: overflow; API misuse\n", __func__);
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*dst = 0;
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}
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/*
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* Dynamically generate qXfer:threads document, one packet at a time.
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*
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* The format is loosely described[0], although it does not seem that the
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* <?xml?> mentioned on that page is required.
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*
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* [0]: https://sourceware.org/gdb/current/onlinedocs/gdb/Thread-List-Format.html
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*/
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static void
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do_qXfer_threads_read(void)
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{
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/* Kludgy context */
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static struct {
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struct qXfer_context qXfer;
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/* Kludgy state machine */
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struct thread *iter;
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enum {
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XML_START_THREAD, /* '<thread' */
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XML_THREAD_ID, /* ' id="xxx"' */
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XML_THREAD_CORE, /* ' core="yyy"' */
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XML_THREAD_NAME, /* ' name="zzz"' */
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XML_THREAD_EXTRA, /* '> ...' */
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XML_END_THREAD, /* '</thread>' */
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XML_SENT_END_THREADS, /* '</threads>' */
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} next_step;
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} ctx;
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static char td_name_escape[MAXCOMLEN * 2 + 1];
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const char *name_src;
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uintmax_t offset, len;
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int error;
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/* Annex part must be empty. */
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if (gdb_rx_char() != ':')
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goto misformed_request;
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if (gdb_rx_varhex(&offset) != 0 ||
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gdb_rx_char() != ',' ||
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gdb_rx_varhex(&len) != 0)
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goto misformed_request;
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/*
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* Validate resume xfers.
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*/
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if (offset != 0) {
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if (offset != ctx.qXfer.last_offset) {
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printf("%s: Resumed offset %ju != expected %ju\n",
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__func__, offset, ctx.qXfer.last_offset);
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error = ESPIPE;
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goto request_error;
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}
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ctx.qXfer.flushed = false;
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}
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if (offset == 0) {
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ctx.iter = kdb_thr_first();
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ctx.next_step = XML_START_THREAD;
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error = init_qXfer_ctx(&ctx.qXfer, len);
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if (error != 0)
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goto request_error;
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sbuf_cat(&ctx.qXfer.sb, "<threads>");
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}
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while (!ctx.qXfer.flushed && ctx.iter != NULL) {
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switch (ctx.next_step) {
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case XML_START_THREAD:
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ctx.next_step = XML_THREAD_ID;
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sbuf_cat(&ctx.qXfer.sb, "<thread");
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continue;
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case XML_THREAD_ID:
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ctx.next_step = XML_THREAD_CORE;
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sbuf_printf(&ctx.qXfer.sb, " id=\"%jx\"",
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(uintmax_t)ctx.iter->td_tid);
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continue;
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case XML_THREAD_CORE:
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ctx.next_step = XML_THREAD_NAME;
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if (ctx.iter->td_oncpu != NOCPU) {
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sbuf_printf(&ctx.qXfer.sb, " core=\"%d\"",
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ctx.iter->td_oncpu);
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}
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continue;
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case XML_THREAD_NAME:
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ctx.next_step = XML_THREAD_EXTRA;
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if (ctx.iter->td_name[0] != 0)
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name_src = ctx.iter->td_name;
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else if (ctx.iter->td_proc != NULL &&
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ctx.iter->td_proc->p_comm[0] != 0)
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name_src = ctx.iter->td_proc->p_comm;
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else
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continue;
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qXfer_escape_xmlattr_str(td_name_escape,
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sizeof(td_name_escape), name_src);
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sbuf_printf(&ctx.qXfer.sb, " name=\"%s\"",
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td_name_escape);
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continue;
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case XML_THREAD_EXTRA:
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ctx.next_step = XML_END_THREAD;
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sbuf_putc(&ctx.qXfer.sb, '>');
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if (ctx.iter->td_state == TDS_RUNNING)
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sbuf_cat(&ctx.qXfer.sb, "Running");
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else if (ctx.iter->td_state == TDS_RUNQ)
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sbuf_cat(&ctx.qXfer.sb, "RunQ");
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else if (ctx.iter->td_state == TDS_CAN_RUN)
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sbuf_cat(&ctx.qXfer.sb, "CanRun");
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else if (TD_ON_LOCK(ctx.iter))
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sbuf_cat(&ctx.qXfer.sb, "Blocked");
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else if (TD_IS_SLEEPING(ctx.iter))
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sbuf_cat(&ctx.qXfer.sb, "Sleeping");
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else if (TD_IS_SWAPPED(ctx.iter))
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sbuf_cat(&ctx.qXfer.sb, "Swapped");
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else if (TD_AWAITING_INTR(ctx.iter))
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sbuf_cat(&ctx.qXfer.sb, "IthreadWait");
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else if (TD_IS_SUSPENDED(ctx.iter))
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sbuf_cat(&ctx.qXfer.sb, "Suspended");
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else
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sbuf_cat(&ctx.qXfer.sb, "???");
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continue;
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case XML_END_THREAD:
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ctx.next_step = XML_START_THREAD;
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sbuf_cat(&ctx.qXfer.sb, "</thread>");
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ctx.iter = kdb_thr_next(ctx.iter);
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continue;
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/*
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* This one isn't part of the looping state machine,
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* but GCC complains if you leave an enum value out of the
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* select.
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*/
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case XML_SENT_END_THREADS:
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/* NOTREACHED */
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break;
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}
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}
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if (ctx.qXfer.flushed)
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return;
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if (ctx.next_step != XML_SENT_END_THREADS) {
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ctx.next_step = XML_SENT_END_THREADS;
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sbuf_cat(&ctx.qXfer.sb, "</threads>");
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}
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if (ctx.qXfer.flushed)
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return;
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ctx.qXfer.lastmessage = true;
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sbuf_finish(&ctx.qXfer.sb);
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sbuf_delete(&ctx.qXfer.sb);
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ctx.qXfer.last_offset = 0;
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return;
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misformed_request:
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/*
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* GDB "General-Query-Packets.html" qXfer-read anchor specifically
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* documents an E00 code for malformed requests or invalid annex.
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* Non-zero codes indicate invalid offset or "error reading the data."
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*/
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error = 0;
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request_error:
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gdb_tx_err(error);
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return;
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}
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/*
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* A set of standardized transfers from "special data areas."
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*
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* We've already matched on "qXfer:" and advanced the rx packet buffer past
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* that bit. Parse out the rest of the packet and generate an appropriate
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* response.
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*/
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static void
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do_qXfer(void)
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{
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if (!gdb_rx_equal("threads:"))
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goto unrecognized;
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if (!gdb_rx_equal("read:"))
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goto unrecognized;
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do_qXfer_threads_read();
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return;
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unrecognized:
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gdb_tx_empty();
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return;
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}
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static int
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gdb_trap(int type, int code)
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{
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@ -425,6 +726,8 @@ gdb_trap(int type, int code)
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gdb_do_threadinfo(&thr_iter);
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} else if (gdb_rx_equal("sThreadInfo")) {
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gdb_do_threadinfo(&thr_iter);
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} else if (gdb_rx_equal("Xfer:")) {
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do_qXfer();
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} else if (gdb_rx_equal("Search:memory:")) {
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gdb_do_mem_search();
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} else if (!gdb_cpu_query())
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