Make --gdb-attach=yes work properly; rather than trying to attach gdb
to itself, Valgrind forks a child, and uses ptrace to manipulate its
state into what the client state would be at that point, and attaches
gdb to that. In addition to giving gdb clean state to inspect, it
also stops mistakes in gdb (eg, continuing) from killing your target.
It also makes gdb strictly read-only; any state changes made from within
gdb will not be reflected in the running client. Patch from Tom Hughes.
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@2187 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/coregrind/vg_main.c b/coregrind/vg_main.c
index ee26d20..b1a74a4 100644
--- a/coregrind/vg_main.c
+++ b/coregrind/vg_main.c
@@ -31,6 +31,13 @@
#include "vg_include.h"
+#include <stdlib.h>
+#include <sys/ptrace.h>
+#include <sys/signal.h>
+#include <sys/user.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
/* ---------------------------------------------------------------------
Compute offsets into baseBlock. See comments in vg_include.h.
------------------------------------------------------------------ */
@@ -1745,27 +1752,86 @@
*output++ = '\0';
}
-/* RUNS ON THE CLIENT'S STACK, but on the real CPU. Start GDB and get
- it to attach to this process. Called if the user requests this
- service after an error has been shown, so she can poke around and
- look at parameters, memory, etc. You can't meaningfully get GDB to
- continue the program, though; to continue, quit GDB. */
-void VG_(start_GDB_whilst_on_client_stack) ( void )
+/* Start GDB and get it to attach to this process. Called if the user
+ requests this service after an error has been shown, so she can
+ poke around and look at parameters, memory, etc. You can't
+ meaningfully get GDB to continue the program, though; to continue,
+ quit GDB. */
+void VG_(start_GDB) ( Int tid )
{
- Int res;
- UChar buf[100];
+ Int pid;
- VG_(sprintf)(buf, "%s -nw /proc/%d/fd/%d %d",
- VG_(clo_GDB_path), VG_(getpid)(), VG_(clexecfd), VG_(getpid)());
- VG_(message)(Vg_UserMsg, "starting GDB with cmd: %s", buf);
- res = VG_(system)(buf);
- if (res == 0) {
- VG_(message)(Vg_UserMsg, "");
- VG_(message)(Vg_UserMsg,
- "GDB has detached. Valgrind regains control. We continue.");
- } else {
- VG_(message)(Vg_UserMsg, "Apparently failed!");
- VG_(message)(Vg_UserMsg, "");
+ if ((pid = fork()) == 0)
+ {
+ ptrace(PTRACE_TRACEME, 0, NULL, NULL);
+ VG_(kkill)(VG_(getpid)(), VKI_SIGSTOP);
+ }
+ else if (pid > 0)
+ {
+ struct user_regs_struct regs;
+ Int status;
+ Int res;
+
+ if (VG_(is_running_thread)( tid )) {
+ regs.xcs = VG_(baseBlock)[VGOFF_(m_cs)];
+ regs.xss = VG_(baseBlock)[VGOFF_(m_ss)];
+ regs.xds = VG_(baseBlock)[VGOFF_(m_ds)];
+ regs.xes = VG_(baseBlock)[VGOFF_(m_es)];
+ regs.xfs = VG_(baseBlock)[VGOFF_(m_fs)];
+ regs.xgs = VG_(baseBlock)[VGOFF_(m_gs)];
+ regs.eax = VG_(baseBlock)[VGOFF_(m_eax)];
+ regs.ebx = VG_(baseBlock)[VGOFF_(m_ebx)];
+ regs.ecx = VG_(baseBlock)[VGOFF_(m_ecx)];
+ regs.edx = VG_(baseBlock)[VGOFF_(m_edx)];
+ regs.esi = VG_(baseBlock)[VGOFF_(m_esi)];
+ regs.edi = VG_(baseBlock)[VGOFF_(m_edi)];
+ regs.ebp = VG_(baseBlock)[VGOFF_(m_ebp)];
+ regs.esp = VG_(baseBlock)[VGOFF_(m_esp)];
+ regs.eflags = VG_(baseBlock)[VGOFF_(m_eflags)];
+ regs.eip = VG_(baseBlock)[VGOFF_(m_eip)];
+ } else {
+ ThreadState* tst = & VG_(threads)[ tid ];
+
+ regs.xcs = tst->m_cs;
+ regs.xss = tst->m_ss;
+ regs.xds = tst->m_ds;
+ regs.xes = tst->m_es;
+ regs.xfs = tst->m_fs;
+ regs.xgs = tst->m_gs;
+ regs.eax = tst->m_eax;
+ regs.ebx = tst->m_ebx;
+ regs.ecx = tst->m_ecx;
+ regs.edx = tst->m_edx;
+ regs.esi = tst->m_esi;
+ regs.edi = tst->m_edi;
+ regs.ebp = tst->m_ebp;
+ regs.esp = tst->m_esp;
+ regs.eflags = tst->m_eflags;
+ regs.eip = tst->m_eip;
+ }
+
+ if ((res = VG_(waitpid)(pid, &status, 0)) == pid &&
+ WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP &&
+ ptrace(PTRACE_SETREGS, pid, NULL, ®s) == 0 &&
+ ptrace(PTRACE_DETACH, pid, NULL, SIGSTOP) == 0) {
+ UChar buf[VG_(strlen)(VG_(clo_GDB_path)) + 100];
+
+ VG_(sprintf)(buf, "%s -nw /proc/%d/fd/%d %d",
+ VG_(clo_GDB_path), VG_(main_pid), VG_(clexecfd), pid);
+ VG_(message)(Vg_UserMsg, "starting GDB with cmd: %s", buf);
+ res = VG_(system)(buf);
+ if (res == 0) {
+ VG_(message)(Vg_UserMsg, "");
+ VG_(message)(Vg_UserMsg,
+ "GDB has detached. Valgrind regains control. We continue.");
+ } else {
+ VG_(message)(Vg_UserMsg, "Apparently failed!");
+ VG_(message)(Vg_UserMsg, "");
+ }
+ }
+
+ VG_(kkill)(pid, VKI_SIGKILL);
+ VG_(waitpid)(pid, &status, 0);
}
}