Re: [uml-devel] [UML] Problems building and running 2.6.17-rc4 on x86-64

[Jeff Dike]

On Mon, May 15, 2006 at 12:29:58PM -0300, Alberto Bertogli wrote:
> Sure, here it is:
> (gdb) disas stub_segv_handler

Sorry, I misread the error message and asked for the wrong thing.
Your UML is seeing a process segfault during a system call, before the
SIGTRAP expected at the end of the system call.  I don't know what's
happening there.

Can you apply the following patch, which will just give you a register
dump of the process, and send me the output?

Index: linux-2.6.16/arch/um/os-Linux/skas/process.c
===================================================================
--- linux-2.6.16.orig/arch/um/os-Linux/skas/process.c
+++ linux-2.6.16/arch/um/os-Linux/skas/process.c
@@ -45,6 +45,22 @@ int is_skas_winch(int pid, int fd, void 
 	return(1);
 }
 
+static int ptrace_dump_regs(int pid)
+{
+        unsigned long regs[HOST_FRAME_SIZE];
+        int i;
+
+        if(ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
+                return -errno;
+        else {
+                printk("Stub registers -\n");
+                for(i = 0; i < HOST_FRAME_SIZE; i++)
+                        printk("\t%d - %lx\n", i, regs[i]);
+        }
+
+        return 0;
+}
+
 void wait_stub_done(int pid, int sig, char * fname)
 {
 	int n, status, err;
@@ -68,18 +84,10 @@ void wait_stub_done(int pid, int sig, ch
 
 	if((n < 0) || !WIFSTOPPED(status) ||
 	   (WSTOPSIG(status) != SIGUSR1 && WSTOPSIG(status) != SIGTRAP)){
-		unsigned long regs[HOST_FRAME_SIZE];
-
-		if(ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
-			printk("Failed to get registers from stub, "
-			       "errno = %d\n", errno);
-		else {
-			int i;
-
-			printk("Stub registers -\n");
-			for(i = 0; i < HOST_FRAME_SIZE; i++)
-				printk("\t%d - %lx\n", i, regs[i]);
-		}
+                err = ptrace_dump_regs(pid);
+                if(err)
+                        printk("Failed to get registers from stub, "
+                               "errno = %d\n", -err);
 		panic("%s : failed to wait for SIGUSR1/SIGTRAP, "
 		      "pid = %d, n = %d, errno = %d, status = 0x%x\n",
 		      fname, pid, n, errno, status);
@@ -146,9 +154,14 @@ static void handle_trap(int pid, union u
 
 		CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED));
 		if((err < 0) || !WIFSTOPPED(status) ||
-		   (WSTOPSIG(status) != SIGTRAP + 0x80))
+		   (WSTOPSIG(status) != SIGTRAP + 0x80)){
+                        err = ptrace_dump_regs(pid);
+                        if(err)
+                                printk("Failed to get registers from process, "
+                                       "errno = %d\n", -err);
 			panic("handle_trap - failed to wait at end of syscall, "
 			      "errno = %d, status = %d\n", errno, status);
+                }
 	}
 
 	handle_syscall(regs);
-
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