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uml: work around broken host PTRACE_SYSEMU

PATCH In review Jeff Dike 2 participants 2 messages Aug 5, 2008 – Aug 16, 2008 User-mode Linux (UML)

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PATCH 11/14 uml: work around broken host PTRACE_SYSEMU

From f1ef9167ca4494a8c6d71d0031c73e9c8841eadd

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 <[email protected]>
Signed-off-by Andrew Morton <[email protected]>
Signed-off-by Linus Torvalds <[email protected]>
---
 arch/um/os-Linux/start_up.c |   25 ++++++++++++++++---------
 1 files changed, 16 insertions(+), 9 deletions(-)
arch/um/os-Linux/start_up.c +16 -9
index b616e15..fd71bdb 100644
@@ -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;
Signature · 12 lines
1.5.5.1


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#1 lore raw

patch uml-work-around-broken-host-ptrace_sysemu.patch added to 2.6.25-stable tree

This is a note to let you know that we have just queued up the patch titled

Subject: uml: work around broken host PTRACE_SYSEMU

to the 2.6.25-stable tree. Its filename is

uml-work-around-broken-host-ptrace_sysemu.patch

A git repo of this tree can be found at
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

From [email protected] Tue Aug 5 13:14:58 2008
From: Jeff Dike <[email protected]>
Date: Tue, 5 Aug 2008 16:14:09 -0400
Subject: uml: work around broken host PTRACE_SYSEMU
To: [email protected]
Cc: LKML <[email protected]>, uml-devel <[email protected]>
Message-ID: <[email protected]>
Content-Disposition: inline

From: Jeff Dike <[email protected]>

commit f1ef9167ca4494a8c6d71d0031c73e9c8841eadd upstream

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 <[email protected]>
Signed-off-by Andrew Morton <[email protected]>
Signed-off-by Linus Torvalds <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 arch/um/os-Linux/start_up.c |   25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)
arch/um/os-Linux/start_up.c +16 -9
@@ -122,8 +122,10 @@ static int stop_ptraced_child(int pid, i
 {
 	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;

Patches currently in stable-queue which might be from [email protected] are

queue-2.6.25/uml-fix-build-when-slob-is-enabled.patch queue-2.6.25/uml-fix-bad-ntp-interaction-with-clock.patch queue-2.6.25/uml-physical-memory-shouldn-t-include-initial-stack.patch queue-2.6.25/uml-track-and-make-up-lost-ticks.patch queue-2.6.25/uml-missed-kmalloc-in-pcap_user.c.patch queue-2.6.25/uml-deal-with-host-time-going-backwards.patch queue-2.6.25/uml-deal-with-inaccessible-address-space-start.patch queue-2.6.25/uml-missing-export-of-csum_partial-on-uml-amd64.patch queue-2.6.25/uml-memcpy-export-needs-to-follow-host-declaration.patch queue-2.6.25/uml-stub-needs-to-tolerate-sigwinch.patch queue-2.6.25/uml-work-around-broken-host-ptrace_sysemu.patch queue-2.6.25/uml-fix-gcc-ices-and-unresolved-externs.patch queue-2.6.25/uml-fix-boot-crash.patch

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