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Fix vfork(). Now that arguments are kept on the stack, the way that arguments are passed from parent to child in vfork() must change. This bug has always been present, but was not visible with the old strdup() way of passing arguments

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This commit is contained in:
Gregory Nutt
2014-09-29 10:45:44 -06:00
parent d35492e703
commit 1dc9768c1a
3 changed files with 115 additions and 34 deletions
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sched/task/task_vfork.c
+104 -23
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@@ -63,6 +63,98 @@
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: vfork_namesetup
*
* Description:
* Copy the task name.
*
* Input Parameters:
* tcb - Address of the new task's TCB
* name - Name of the new task
*
* Return Value:
* None
*
****************************************************************************/
#if CONFIG_TASK_NAME_SIZE > 0
static inline void vfork_namesetup(FAR struct task_tcb_s *parent,
FAR struct task_tcb_s *child)
{
/* Copy the name from the parent into the child TCB */
strncpy(child->cmn.name, parent->cmn.name, CONFIG_TASK_NAME_SIZE);
}
#else
# define vfork_namesetup(p,c)
#endif /* CONFIG_TASK_NAME_SIZE */
/****************************************************************************
* Name: vfork_stackargsetup
*
* Description:
* Clone the task arguments in the same relative positions on the child's
* stack.
*
* Input Parameters:
* parent - Address of the parent task's TCB
* child - Address of the child task's TCB
*
* Return Value:
* Zero (OK) on success; a negated errno on failure.
*
****************************************************************************/
static inline void vfork_stackargsetup(FAR struct task_tcb_s *parent,
FAR struct task_tcb_s *child)
{
uintptr_t offset;
int i;
/* Get the address correction */
offset = child->cmn.xcp.regs[REG_SP] - parent->cmn.xcp.regs[REG_SP];
/* Copy the adjusted address for each argument */
for (i = 0; i < CONFIG_MAX_TASK_ARGS && parent->argv[i]; i++)
{
uintptr_t newaddr = (uintptr_t)parent->argv[i] + offset;
child->argv[i] = (FAR char *)newaddr;
}
/* Put a terminator entry at the end of the child argv[] array. */
child->argv[i] = NULL;
}
/****************************************************************************
* Name: vfork_argsetup
*
* Description:
* Clone the argument list from the parent to the child.
*
* Input Parameters:
* parent - Address of the parent task's TCB
* child - Address of the child task's TCB
*
* Return Value:
* OK
*
****************************************************************************/
static inline void vfork_argsetup(FAR struct task_tcb_s *parent,
FAR struct task_tcb_s *child)
{
/* Clone the task name */
vfork_namesetup(parent, child);
/* Adjust and copy the argv[] array. */
vfork_stackargsetup(parent, child);
}
/****************************************************************************
* Public Functions
****************************************************************************/
@@ -78,7 +170,7 @@
* called, or calls any other function before successfully calling _exit()
* or one of the exec family of functions.
*
* This functin provides one step in the overall vfork() sequence: It
* This function provides one step in the overall vfork() sequence: It
* Allocates and initializes the child task's TCB. The overall sequence is:
*
* 1) User code calls vfork(). vfork() is provided in architecture-specific
@@ -89,7 +181,7 @@
* - Allocation of the child task's TCB.
* - Initialization of file descriptors and streams
* - Configuration of environment variables
* - Setup the intput parameters for the task.
* - Setup the input parameters for the task.
* - Initialization of the TCB (including call to up_initial_state()
* 4) up_vfork() provides any additional operating context. up_vfork must:
* - Allocate and initialize the stack
@@ -98,13 +190,13 @@
* 5) up_vfork() then calls task_vforkstart()
* 6) task_vforkstart() then executes the child thread.
*
* Input Paremeters:
* retaddr - The return address from vfork() where the child task
* will be started.
* Input Parameters:
* parent - Address of the parent task's TCB
* child - Address of the child task's TCB
*
* Returned Value:
* Upon successful completion, task_vforksetup() returns a pointer to
* newly allocated and initalized child task's TCB. NULL is returned
* newly allocated and initialized child task's TCB. NULL is returned
* on any failure and the errno is set appropriately.
*
****************************************************************************/
@@ -201,7 +293,7 @@ errout_with_tcb:
* called, or calls any other function before successfully calling _exit()
* or one of the exec family of functions.
*
* This functin provides one step in the overall vfork() sequence: It
* This function provides one step in the overall vfork() sequence: It
* starts execution of the previously initialized TCB. The overall
* sequence is:
*
@@ -212,7 +304,7 @@ errout_with_tcb:
* - Allocation of the child task's TCB.
* - Initialization of file descriptors and streams
* - Configuration of environment variables
* - Setup the intput parameters for the task.
* - Setup the input parameters for the task.
* - Initialization of the TCB (including call to up_initial_state()
* 4) vfork() provides any additional operating context. vfork must:
* - Allocate and initialize the stack
@@ -221,7 +313,7 @@ errout_with_tcb:
* 5) vfork() then calls task_vforkstart()
* 6) task_vforkstart() then executes the child thread.
*
* Input Paremeters:
* Input Parameters:
* retaddr - The return address from vfork() where the child task
* will be started.
*
@@ -235,10 +327,7 @@ errout_with_tcb:
pid_t task_vforkstart(FAR struct task_tcb_s *child)
{
#if CONFIG_TASK_NAME_SIZE > 0
struct tcb_s *parent = (FAR struct tcb_s *)g_readytorun.head;
#endif
FAR const char *name;
pid_t pid;
int rc;
int ret;
@@ -246,15 +335,7 @@ pid_t task_vforkstart(FAR struct task_tcb_s *child)
svdbg("Starting Child TCB=%p, parent=%p\n", child, g_readytorun.head);
DEBUGASSERT(child);
/* Setup to pass parameters to the new task */
#if CONFIG_TASK_NAME_SIZE > 0
name = parent->name;
#else
name = NULL;
#endif
(void)task_argsetup(child, name, (FAR char * const *)NULL);
vfork_argsetup(parent, child);
/* Now we have enough in place that we can join the group */
@@ -282,7 +363,7 @@ pid_t task_vforkstart(FAR struct task_tcb_s *child)
/* Since the child task has the same priority as the parent task, it is
* now ready to run, but has not yet ran. It is a requirement that
* the parent enivornment be stable while vfork runs; the child thread
* the parent environment be stable while vfork runs; the child thread
* is still dependent on things in the parent thread... like the pointers
* into parent thread's stack which will still appear in the child's
* registers and environment.
@@ -293,7 +374,7 @@ pid_t task_vforkstart(FAR struct task_tcb_s *child)
* execv/l(), that should be all that is needed.
*
* Hmmm.. this is probably not sufficient. What if we are running
* SCHED_RR? What if the child thread is suspeneded and rescheduled
* SCHED_RR? What if the child thread is suspended and rescheduled
* after the parent thread again?
*/