marginally better thread debugging on Linux.

if you clone inside a traced pid, the child
is automatically attached and stopped,
apparently.

R=r
DELTA=63  (41 added, 12 deleted, 10 changed)
OCL=24096
CL=24106

diff --git a/src/libmach_amd64/linux.c b/src/libmach_amd64/linux.c
index 4fb5d49ba308516a9b2018af88261f3e2db47667..b25d9a3f86a0e2dfe72e9cfaec886cea1cace43d 100644 (file)
--- a/src/libmach_amd64/linux.c
+++ b/src/libmach_amd64/linux.c
@@ -28,6 +28,8 @@
 // THE SOFTWARE.
 
 #include <u.h>
+#include <sys/syscall.h>       /* for tkill */
+#include <unistd.h>
 #include <sys/ptrace.h>
 #include <sys/signal.h>
 #include <sys/wait.h>
@@ -53,8 +55,10 @@ struct user_regs_struct {
        unsigned long ds,es,fs,gs;
 };
 
+// return pid's state letter or -1 on error.
+// set *tpid to tracer pid
 static int
-isstopped(int pid)
+procstate(int pid, int *tpid)
 {
        char buf[1024];
        int fd, n;
@@ -62,21 +66,31 @@ isstopped(int pid)
 
        snprint(buf, sizeof buf, "/proc/%d/stat", pid);
        if((fd = open(buf, OREAD)) < 0)
-               return 0;
+               return -1;
        n = read(fd, buf, sizeof buf-1);
        close(fd);
        if(n <= 0)
-               return 0;
+               return -1;
        buf[n] = 0;
 
        /* command name is in parens, no parens afterward */
        p = strrchr(buf, ')');
        if(p == nil || *++p != ' ')
-               return 0;
+               return -1;
        ++p;
 
-       /* next is state - T is stopped for tracing */
-       return *p == 'T';
+       /* p is now state letter.  p+1 is tracer pid */
+       if(tpid)
+               *tpid = atoi(p+1);
+       return *p;
+}
+
+static int
+attached(int pid)
+{
+       int tpid;
+
+       return procstate(pid, &tpid) == 'T' && tpid == pid;
 }
 
 static int
@@ -84,13 +98,17 @@ waitstop(int pid)
 {
        int p, status;
 
-       if(isstopped(pid))
+       p = procstate(pid, nil);
+       if(p < 0)
+               return -1;
+       if(p == 'T')
                return 0;
+
        for(;;){
                p = waitpid(pid, &status, WUNTRACED|__WALL);
                if(p <= 0){
                        if(errno == ECHILD){
-                               if(isstopped(pid))
+                               if(procstate(pid, nil) == 'T')
                                        return 0;
                        }
                        return -1;
@@ -116,11 +134,11 @@ ptraceattach(int pid)
                return -1;
        }
 
-       if(ptrace(PTRACE_ATTACH, pid, 0, 0) < 0){
+       if(!attached(pid) && ptrace(PTRACE_ATTACH, pid, 0, 0) < 0){
                werrstr("ptrace attach %d: %r", pid);
                return -1;
        }
-       
+
        if(waitstop(pid) < 0){
                fprint(2, "waitstop %d: %r", pid);
                ptrace(PTRACE_DETACH, pid, 0, 0);
@@ -150,7 +168,7 @@ attachproc(int pid, Fhdr *fp)
        setmap(map, -1, fp->dataddr, mach->utop, fp->dataddr, "*data", ptracesegrw);
        return map;
 }
-       
+
 void
 detachproc(Map *m)
 {
@@ -296,7 +314,7 @@ ctlproc(int pid, char *msg)
                return waitstop(pid);
        }
        if(strcmp(msg, "stop") == 0){
-               if(kill(pid, SIGSTOP) < 0)
+               if(syscall(__NR_tkill, pid, SIGSTOP) < 0)
                        return -1;
                return waitstop(pid);
        }
@@ -332,7 +350,7 @@ procthreadpids(int pid, int **thread)
        int i, fd, nd, *t, nt;
        char buf[100];
        Dir *d;
-       
+
        snprint(buf, sizeof buf, "/proc/%d/task", pid);
        if((fd = open(buf, OREAD)) < 0)
                return -1;
@@ -463,7 +481,7 @@ ptraceregrw(Map *map, Seg *seg, uvlong addr, void *v, uint n, int isr)
 {
        int laddr;
        uvlong u;
-       
+
        if((laddr = go2linux(addr)) < 0){
                if(isr){
                        memset(v, 0, n);
@@ -472,7 +490,7 @@ ptraceregrw(Map *map, Seg *seg, uvlong addr, void *v, uint n, int isr)
                werrstr("register %llud not available", addr);
                return -1;
        }
-       
+
        if(isr){
                errno = 0;
                u = ptrace(PTRACE_PEEKUSER, map->pid, laddr, 0);
@@ -520,14 +538,25 @@ ptraceregrw(Map *map, Seg *seg, uvlong addr, void *v, uint n, int isr)
 
 ptraceerr:
        werrstr("ptrace %s register laddr=%d pid=%d: %r", isr ? "read" : "write", laddr, map->pid);
-       return -1;      
+       return -1;
 }
 
 char*
 procstatus(int pid)
 {
-       if(isstopped(pid))
-               return "Stopped";
+       int c;
 
+       c = procstate(pid, nil);
+       if(c < 0)
+               return "Dead";
+       switch(c) {
+       case 'T':
+               return "Stopped";
+       case 'Z':
+               return "Zombie";
+       case 'R':
+               return "Running";
+       // TODO: translate more characters here
+       }
        return "Running";
 }