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Commit b85e9680 authored by Jeff Dike's avatar Jeff Dike Committed by Linus Torvalds
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[PATCH] uml: fix TT mode by reverting "use fork instead of clone" 

With Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>

Revert the following patch, because of miscompilation problems in different
environments leading to UML not working *at all* in TT mode; it was merged
lately in 2.6 development cycle, a little after being written, and has
caused problems to lots of people; I know it's a bit too long, but it
shouldn't have been merged in first place, so I still apply for inclusion
in the -stable tree.  Anyone using this feature currently is either using
some older kernel (some reports even used 2.6.12-rc4-mm2) or using this
patch, as included in my -bs patchset.

For now there's not yet a fix for this patch, so for now the best thing is
to drop it (which was widely reported to give a working kernel, and as such
was even merged in -stable tree).

"Convert the boot-time host ptrace testing from clone to fork.  They were
essentially doing fork anyway.  This cleans up the code a bit, and makes
valgrind a bit happier about grinding it."

URL:
http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=98fdffccea6cc3fe9dba32c0fcc310bcb5d71529



Signed-off-by: default avatarJeff Dike <jdike@addtoit.com>
Signed-off-by: default avatarPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 2ca3310e

arch/um/kernel/process.c

+29 −19
Original line number Diff line number Diff line
@@ -131,7 +131,7 @@ int start_fork_tramp(void *thread_arg, unsigned long temp_stack, 
	return(arg.pid);

}



static int ptrace_child(void)

static int ptrace_child(void *arg)

{

	int ret;

	int pid = os_getpid(), ppid = getppid();
@@ -160,16 +160,20 @@ static int ptrace_child(void) 
	_exit(ret);

}



static int start_ptraced_child(void)

static int start_ptraced_child(void **stack_out)

{

	void *stack;

	unsigned long sp;

	int pid, n, status;

	

	pid = fork();

	if(pid == 0)

		ptrace_child();



	stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,

		     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

	if(stack == MAP_FAILED)

		panic("check_ptrace : mmap failed, errno = %d", errno);

	sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);

	pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);

	if(pid < 0)

		panic("check_ptrace : fork failed, errno = %d", errno);

		panic("check_ptrace : clone failed, errno = %d", errno);

	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));

	if(n < 0)

		panic("check_ptrace : wait failed, errno = %d", errno);
@@ -177,6 +181,7 @@ static int start_ptraced_child(void) 
		panic("check_ptrace : expected SIGSTOP, got status = %d",

		      status);



	*stack_out = stack;

	return(pid);

}
@@ -184,12 +189,12 @@ static int start_ptraced_child(void) 
 * just avoid using sysemu, not panic, but only if SYSEMU features are broken.

 * So only for SYSEMU features we test mustpanic, while normal host features

 * must work anyway!*/

static int stop_ptraced_child(int pid, int exitcode, int mustexit)

static int stop_ptraced_child(int pid, void *stack, int exitcode, int mustpanic)

{

	int status, n, ret = 0;



	if(ptrace(PTRACE_CONT, pid, 0, 0) < 0)

		panic("stop_ptraced_child : ptrace failed, errno = %d", errno);

		panic("check_ptrace : ptrace failed, errno = %d", errno);

	CATCH_EINTR(n = waitpid(pid, &status, 0));

	if(!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {

		int exit_with = WEXITSTATUS(status);
@@ -200,13 +205,15 @@ static int stop_ptraced_child(int pid, int exitcode, int mustexit) 
		printk("check_ptrace : child exited with exitcode %d, while "

		      "expecting %d; status 0x%x", exit_with,

		      exitcode, status);

		if (mustexit)

		if (mustpanic)

			panic("\n");

		else

			printk("\n");

		ret = -1;

	}



	if(munmap(stack, PAGE_SIZE) < 0)

		panic("check_ptrace : munmap failed, errno = %d", errno);

	return ret;

}
@@ -242,11 +249,12 @@ __uml_setup("nosysemu", nosysemu_cmd_param, 


static void __init check_sysemu(void)

{

	void *stack;

	int pid, syscall, n, status, count=0;



	printk("Checking syscall emulation patch for ptrace...");

	sysemu_supported = 0;

	pid = start_ptraced_child();

	pid = start_ptraced_child(&stack);



	if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)

		goto fail;
@@ -264,7 +272,7 @@ static void __init check_sysemu(void) 
		panic("check_sysemu : failed to modify system "

		      "call return, errno = %d", errno);



	if (stop_ptraced_child(pid, 0, 0) < 0)

	if (stop_ptraced_child(pid, stack, 0, 0) < 0)

		goto fail_stopped;



	sysemu_supported = 1;
@@ -272,7 +280,7 @@ static void __init check_sysemu(void) 
	set_using_sysemu(!force_sysemu_disabled);



	printk("Checking advanced syscall emulation patch for ptrace...");

	pid = start_ptraced_child();

	pid = start_ptraced_child(&stack);

	while(1){

		count++;

		if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
@@ -297,7 +305,7 @@ static void __init check_sysemu(void) 
			break;

		}

	}

	if (stop_ptraced_child(pid, 0, 0) < 0)

	if (stop_ptraced_child(pid, stack, 0, 0) < 0)

		goto fail_stopped;



	sysemu_supported = 2;
@@ -308,17 +316,18 @@ static void __init check_sysemu(void) 
	return;



fail:

	stop_ptraced_child(pid, 1, 0);

	stop_ptraced_child(pid, stack, 1, 0);

fail_stopped:

	printk("missing\n");

}



void __init check_ptrace(void)

{

	void *stack;

	int pid, syscall, n, status;



	printk("Checking that ptrace can change system call numbers...");

	pid = start_ptraced_child();

	pid = start_ptraced_child(&stack);



	if (ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)

		panic("check_ptrace: PTRACE_SETOPTIONS failed, errno = %d", errno);
@@ -345,7 +354,7 @@ void __init check_ptrace(void) 
			break;

		}

	}

	stop_ptraced_child(pid, 0, 1);

	stop_ptraced_child(pid, stack, 0, 1);

	printk("OK\n");

	check_sysemu();

}
@@ -380,10 +389,11 @@ extern void *__syscall_stub_start, __syscall_stub_end; 
static inline void check_skas3_ptrace_support(void)

{

	struct ptrace_faultinfo fi;

	void *stack;

	int pid, n;



	printf("Checking for the skas3 patch in the host...");

	pid = start_ptraced_child();

	pid = start_ptraced_child(&stack);



	n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);

	if (n < 0) {
@@ -402,7 +412,7 @@ static inline void check_skas3_ptrace_support(void) 
	}



	init_registers(pid);

	stop_ptraced_child(pid, 1, 1);

	stop_ptraced_child(pid, stack, 1, 1);

}



int can_do_skas(void)