[PATCH 11/14] uml: work around broken host PTRACE_SYSEMU

[Jeff Dike <jdike@addtoit.com>]

>From 81b956c3fec06a5091b9e8909724a8afc7fff1bc Mon Sep 17 00:00:00 2001

Fedora broke PTRACE_SYSEMU again, and UML crashes as a result when it
doesn't need to.  This patch makes the PTRACE_SYSEMU check fail gracefully
and makes UML fall back to PTRACE_SYSCALL.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 arch/um/os-Linux/start_up.c |   25 ++++++++++++++++---------
 1 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/arch/um/os-Linux/start_up.c b/arch/um/os-Linux/start_up.c
index b616e15..fd71bdb 100644
--- a/arch/um/os-Linux/start_up.c
+++ b/arch/um/os-Linux/start_up.c
@@ -122,8 +122,10 @@ static int stop_ptraced_child(int pid, int exitcode, int mustexit)
 {
 	int status, n, ret = 0;
 
-	if (ptrace(PTRACE_CONT, pid, 0, 0) < 0)
-		fatal_perror("stop_ptraced_child : ptrace failed");
+	if (ptrace(PTRACE_CONT, pid, 0, 0) < 0) {
+		perror("stop_ptraced_child : ptrace failed");
+		return -1;
+	}
 	CATCH_EINTR(n = waitpid(pid, &status, 0));
 	if (!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {
 		int exit_with = WEXITSTATUS(status);
@@ -203,7 +205,7 @@ static void __init check_sysemu(void)
 	if (n < 0)
 		fatal_perror("check_sysemu : wait failed");
 	if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
-		fatal("check_sysemu : expected SIGTRAP, got status = %d",
+		fatal("check_sysemu : expected SIGTRAP, got status = %d\n",
 		      status);
 
 	if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
@@ -245,9 +247,11 @@ static void __init check_sysemu(void)
 
 		if (WIFSTOPPED(status) &&
 		    (WSTOPSIG(status) == (SIGTRAP|0x80))) {
-			if (!count)
-				fatal("check_ptrace : SYSEMU_SINGLESTEP "
-				      "doesn't singlestep");
+			if (!count) {
+				non_fatal("check_ptrace : SYSEMU_SINGLESTEP "
+					  "doesn't singlestep");
+				goto fail;
+			}
 			n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
 				   os_getpid());
 			if (n < 0)
@@ -257,9 +261,12 @@ static void __init check_sysemu(void)
 		}
 		else if (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGTRAP))
 			count++;
-		else
-			fatal("check_ptrace : expected SIGTRAP or "
-			      "(SIGTRAP | 0x80), got status = %d", status);
+		else {
+			non_fatal("check_ptrace : expected SIGTRAP or "
+				  "(SIGTRAP | 0x80), got status = %d\n",
+				  status);
+			goto fail;
+		}
 	}
 	if (stop_ptraced_child(pid, 0, 0) < 0)
 		goto fail_stopped;
-- 
1.5.5.1