diff --git a/arch/um/include/kern_util.h b/arch/um/include/kern_util.h
index 50a49691e0e62fd3666851de8b70c2b521d1074f..8d7f7c1cb9c64e40dd96cd17f8e65fe3b9a323da 100644
--- a/arch/um/include/kern_util.h
+++ b/arch/um/include/kern_util.h
@@ -117,4 +117,7 @@ extern void sigio_handler(int sig, union uml_pt_regs *regs);
extern void copy_sc(union uml_pt_regs *regs, void *from);
+unsigned long to_irq_stack(int sig, unsigned long *mask_out);
+unsigned long from_irq_stack(int nested);
+
#endif
diff --git a/arch/um/kernel/dyn.lds.S b/arch/um/kernel/dyn.lds.S
index e36f92b463ce04dc64ec0f076954e48cf0cb276a..87a4e4427d8db2e3e7a83fd8ee0667d287516029 100644
--- a/arch/um/kernel/dyn.lds.S
+++ b/arch/um/kernel/dyn.lds.S
@@ -97,6 +97,8 @@ SECTIONS
.data : {
. = ALIGN(KERNEL_STACK_SIZE); /* init_task */
*(.data.init_task)
+ . = ALIGN(KERNEL_STACK_SIZE);
+ *(.data.init_irqstack)
*(.data .data.* .gnu.linkonce.d.*)
SORT(CONSTRUCTORS)
}
diff --git a/arch/um/kernel/init_task.c b/arch/um/kernel/init_task.c
index f5385a3799bb70ac868c676d15b62ceb84553331..d4f1d1ab252ba0757e47499db066bdb09cbf62bc 100644
--- a/arch/um/kernel/init_task.c
+++ b/arch/um/kernel/init_task.c
@@ -1,5 +1,5 @@
-/*
- * Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
+/*
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,intel.linux}.com)
* Licensed under the GPL
*/
@@ -33,14 +33,18 @@ EXPORT_SYMBOL(init_task);
/*
* Initial thread structure.
*
- * We need to make sure that this is 16384-byte aligned due to the
+ * We need to make sure that this is aligned due to the
* way process stacks are handled. This is done by having a special
* "init_task" linker map entry..
*/
-union thread_union init_thread_union
-__attribute__((__section__(".data.init_task"))) =
-{ INIT_THREAD_INFO(init_task) };
+union thread_union init_thread_union
+ __attribute__((__section__(".data.init_task"))) =
+ { INIT_THREAD_INFO(init_task) };
+
+union thread_union cpu0_irqstack
+ __attribute__((__section__(".data.init_irqstack"))) =
+ { INIT_THREAD_INFO(init_task) };
void unprotect_stack(unsigned long stack)
{
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index a9651a175eb54bad75b15a4721e9d94f0ae6e221..dba04d88b4320bde93b7ce4bee3f728193fd257f 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -32,6 +32,7 @@
#include "sigio.h"
#include "um_malloc.h"
#include "misc_constants.h"
+#include "as-layout.h"
/*
* Generic, controller-independent functions:
@@ -468,3 +469,113 @@ int init_aio_irq(int irq, char *name, irq_handler_t handler)
out:
return err;
}
+
+/*
+ * IRQ stack entry and exit:
+ *
+ * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
+ * and switch over to the IRQ stack after some preparation. We use
+ * sigaltstack to receive signals on a separate stack from the start.
+ * These two functions make sure the rest of the kernel won't be too
+ * upset by being on a different stack. The IRQ stack has a
+ * thread_info structure at the bottom so that current et al continue
+ * to work.
+ *
+ * to_irq_stack copies the current task's thread_info to the IRQ stack
+ * thread_info and sets the tasks's stack to point to the IRQ stack.
+ *
+ * from_irq_stack copies the thread_info struct back (flags may have
+ * been modified) and resets the task's stack pointer.
+ *
+ * Tricky bits -
+ *
+ * What happens when two signals race each other? UML doesn't block
+ * signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal
+ * could arrive while a previous one is still setting up the
+ * thread_info.
+ *
+ * There are three cases -
+ * The first interrupt on the stack - sets up the thread_info and
+ * handles the interrupt
+ * A nested interrupt interrupting the copying of the thread_info -
+ * can't handle the interrupt, as the stack is in an unknown state
+ * A nested interrupt not interrupting the copying of the
+ * thread_info - doesn't do any setup, just handles the interrupt
+ *
+ * The first job is to figure out whether we interrupted stack setup.
+ * This is done by xchging the signal mask with thread_info->pending.
+ * If the value that comes back is zero, then there is no setup in
+ * progress, and the interrupt can be handled. If the value is
+ * non-zero, then there is stack setup in progress. In order to have
+ * the interrupt handled, we leave our signal in the mask, and it will
+ * be handled by the upper handler after it has set up the stack.
+ *
+ * Next is to figure out whether we are the outer handler or a nested
+ * one. As part of setting up the stack, thread_info->real_thread is
+ * set to non-NULL (and is reset to NULL on exit). This is the
+ * nesting indicator. If it is non-NULL, then the stack is already
+ * set up and the handler can run.
+ */
+
+static unsigned long pending_mask;
+
+unsigned long to_irq_stack(int sig, unsigned long *mask_out)
+{
+ struct thread_info *ti;
+ unsigned long mask, old;
+ int nested;
+
+ mask = xchg(&pending_mask, 1 << sig);
+ if(mask != 0){
+ /* If any interrupts come in at this point, we want to
+ * make sure that their bits aren't lost by our
+ * putting our bit in. So, this loop accumulates bits
+ * until xchg returns the same value that we put in.
+ * When that happens, there were no new interrupts,
+ * and pending_mask contains a bit for each interrupt
+ * that came in.
+ */
+ old = 1 << sig;
+ do {
+ old |= mask;
+ mask = xchg(&pending_mask, old);
+ } while(mask != old);
+ return 1;
+ }
+
+ ti = current_thread_info();
+ nested = (ti->real_thread != NULL);
+ if(!nested){
+ struct task_struct *task;
+ struct thread_info *tti;
+
+ task = cpu_tasks[ti->cpu].task;
+ tti = task_thread_info(task);
+ *ti = *tti;
+ ti->real_thread = tti;
+ task->stack = ti;
+ }
+
+ mask = xchg(&pending_mask, 0);
+ *mask_out |= mask | nested;
+ return 0;
+}
+
+unsigned long from_irq_stack(int nested)
+{
+ struct thread_info *ti, *to;
+ unsigned long mask;
+
+ ti = current_thread_info();
+
+ pending_mask = 1;
+
+ to = ti->real_thread;
+ current->stack = to;
+ ti->real_thread = NULL;
+ *to = *ti;
+
+ mask = xchg(&pending_mask, 0);
+ return mask & ~1;
+}
+
diff --git a/arch/um/kernel/skas/process.c b/arch/um/kernel/skas/process.c
index a96ae1a0610e169a20ae953a1ab070a4fa8eac0c..2a69a7ce5792eedc43283e7f8adaefb7c7744314 100644
--- a/arch/um/kernel/skas/process.c
+++ b/arch/um/kernel/skas/process.c
@@ -163,8 +163,12 @@ static int start_kernel_proc(void *unused)
extern int userspace_pid[];
+extern char cpu0_irqstack[];
+
int start_uml_skas(void)
{
+ stack_protections((unsigned long) &cpu0_irqstack);
+ set_sigstack(cpu0_irqstack, THREAD_SIZE);
if(proc_mm)
userspace_pid[0] = start_userspace(0);
diff --git a/arch/um/kernel/uml.lds.S b/arch/um/kernel/uml.lds.S
index f6301274cf3cfea9fdb0eb3680cbe349da63fd57..bc59f97e34d00ab2886b75af77376e52d6edb432 100644
--- a/arch/um/kernel/uml.lds.S
+++ b/arch/um/kernel/uml.lds.S
@@ -59,6 +59,8 @@ SECTIONS
{
. = ALIGN(KERNEL_STACK_SIZE); /* init_task */
*(.data.init_task)
+ . = ALIGN(KERNEL_STACK_SIZE);
+ *(.data.init_irqstack)
*(.data)
*(.gnu.linkonce.d*)
CONSTRUCTORS
diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index 420ee86d0d1af37199440b851ac11e87d1cacb59..18e5c8b67eb8cebbe84db25bed7e64e623522dc9 100644
--- a/arch/um/os-Linux/signal.c
+++ b/arch/um/os-Linux/signal.c
@@ -117,6 +117,46 @@ void remove_sigstack(void)
void (*handlers[_NSIG])(int sig, struct sigcontext *sc);
+void handle_signal(int sig, struct sigcontext *sc)
+{
+ unsigned long pending = 0;
+
+ do {
+ int nested, bail;
+
+ /*
+ * pending comes back with one bit set for each
+ * interrupt that arrived while setting up the stack,
+ * plus a bit for this interrupt, plus the zero bit is
+ * set if this is a nested interrupt.
+ * If bail is true, then we interrupted another
+ * handler setting up the stack. In this case, we
+ * have to return, and the upper handler will deal
+ * with this interrupt.
+ */
+ bail = to_irq_stack(sig, &pending);
+ if(bail)
+ return;
+
+ nested = pending & 1;
+ pending &= ~1;
+
+ while((sig = ffs(pending)) != 0){
+ sig--;
+ pending &= ~(1 << sig);
+ (*handlers[sig])(sig, sc);
+ }
+
+ /* Again, pending comes back with a mask of signals
+ * that arrived while tearing down the stack. If this
+ * is non-zero, we just go back, set up the stack
+ * again, and handle the new interrupts.
+ */
+ if(!nested)
+ pending = from_irq_stack(nested);
+ } while(pending);
+}
+
extern void hard_handler(int sig);
void set_handler(int sig, void (*handler)(int), int flags, ...)
diff --git a/arch/um/os-Linux/sys-i386/signal.c b/arch/um/os-Linux/sys-i386/signal.c
index 0d3eae5183526cc53aded9ce2e6ca66b6dc9574f..f311609f93daaf7079476a067e2e2ab24bc8a202 100644
--- a/arch/um/os-Linux/sys-i386/signal.c
+++ b/arch/um/os-Linux/sys-i386/signal.c
@@ -1,15 +1,13 @@
/*
- * Copyright (C) 2006 Jeff Dike (jdike@addtoit.com)
+ * Copyright (C) 2006 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Licensed under the GPL
*/
#include <signal.h>
-extern void (*handlers[])(int sig, struct sigcontext *sc);
+extern void handle_signal(int sig, struct sigcontext *sc);
void hard_handler(int sig)
{
- struct sigcontext *sc = (struct sigcontext *) (&sig + 1);
-
- (*handlers[sig])(sig, sc);
+ handle_signal(sig, (struct sigcontext *) (&sig + 1));
}
diff --git a/arch/um/os-Linux/sys-x86_64/signal.c b/arch/um/os-Linux/sys-x86_64/signal.c
index 3f369e5f976b724232e4cf4a4f9fe1e90782dbe0..82a388822cd35c55b006f9dbe0d3f1230b83b620 100644
--- a/arch/um/os-Linux/sys-x86_64/signal.c
+++ b/arch/um/os-Linux/sys-x86_64/signal.c
@@ -1,16 +1,16 @@
/*
- * Copyright (C) 2006 Jeff Dike (jdike@addtoit.com)
+ * Copyright (C) 2006 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Licensed under the GPL
*/
#include <signal.h>
-extern void (*handlers[])(int sig, struct sigcontext *sc);
+extern void handle_signal(int sig, struct sigcontext *sc);
void hard_handler(int sig)
{
struct ucontext *uc;
asm("movq %%rdx, %0" : "=r" (uc));
- (*handlers[sig])(sig, (struct sigcontext *) &uc->uc_mcontext);
+ handle_signal(sig, (struct sigcontext *) &uc->uc_mcontext);
}
diff --git a/include/asm-um/thread_info.h b/include/asm-um/thread_info.h
index 261e2f4528f6a62e1f5dd94c41ff06d5405beeed..18a13ba746053eb8da1dc912fda5957d0dc57577 100644
--- a/include/asm-um/thread_info.h
+++ b/include/asm-um/thread_info.h
@@ -22,6 +22,7 @@ struct thread_info {
0-0xBFFFFFFF for user
0-0xFFFFFFFF for kernel */
struct restart_block restart_block;
+ struct thread_info *real_thread; /* Points to non-IRQ stack */
};
#define INIT_THREAD_INFO(tsk) \
@@ -35,6 +36,7 @@ struct thread_info {
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
+ .real_thread = NULL, \
}
#define init_thread_info (init_thread_union.thread_info)