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Subject[RFC Patch 6/10] Use virtual debug registers in process/thread handling code
This patch enables the use of abstract/virtual debug registers in
process-handling routines.

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
---
arch/x86/kernel/process_32.c | 43 +++++++++++++++++++++++++------------------
arch/x86/kernel/process_64.c | 41 ++++++++++++++++++++++++-----------------
2 files changed, 49 insertions(+), 35 deletions(-)
Index: linux-hbkpt-lkml-29-rc2/arch/x86/kernel/process_32.c
===================================================================
--- linux-hbkpt-lkml-29-rc2.orig/arch/x86/kernel/process_32.c
+++ linux-hbkpt-lkml-29-rc2/arch/x86/kernel/process_32.c
@@ -60,6 +60,8 @@
#include <asm/idle.h>
#include <asm/syscalls.h>
#include <asm/ds.h>
+#include <asm/debugreg.h>
+#include <asm/hw_breakpoint.h>

asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");

@@ -231,6 +233,8 @@ EXPORT_SYMBOL(kernel_thread);
*/
void exit_thread(void)
{
+ struct task_struct *tsk = current;
+
/* The process may have allocated an io port bitmap... nuke it. */
if (unlikely(test_thread_flag(TIF_IO_BITMAP))) {
struct task_struct *tsk = current;
@@ -251,6 +255,8 @@ void exit_thread(void)
tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
put_cpu();
}
+ if (unlikely(tsk->thread.hw_breakpoint_info))
+ flush_thread_hw_breakpoint(tsk);

ds_exit_thread(current);
}
@@ -259,14 +265,9 @@ void flush_thread(void)
{
struct task_struct *tsk = current;

- tsk->thread.debugreg0 = 0;
- tsk->thread.debugreg1 = 0;
- tsk->thread.debugreg2 = 0;
- tsk->thread.debugreg3 = 0;
- tsk->thread.debugreg6 = 0;
- tsk->thread.debugreg7 = 0;
memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
- clear_tsk_thread_flag(tsk, TIF_DEBUG);
+ if (unlikely(tsk->thread.hw_breakpoint_info))
+ flush_thread_hw_breakpoint(tsk);
/*
* Forget coprocessor state..
*/
@@ -310,7 +311,15 @@ int copy_thread(int nr, unsigned long cl

savesegment(gs, p->thread.gs);

+ p->thread.hw_breakpoint_info = NULL;
+ p->thread.io_bitmap_ptr = NULL;
+
tsk = current;
+ err = -ENOMEM;
+ if (unlikely(tsk->thread.hw_breakpoint_info)) {
+ if (copy_thread_hw_breakpoint(tsk, p, clone_flags))
+ goto out;
+ }
if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
IO_BITMAP_BYTES, GFP_KERNEL);
@@ -329,11 +338,13 @@ int copy_thread(int nr, unsigned long cl
if (clone_flags & CLONE_SETTLS)
err = do_set_thread_area(p, -1,
(struct user_desc __user *)childregs->si, 0);
-
+ out:
if (err && p->thread.io_bitmap_ptr) {
kfree(p->thread.io_bitmap_ptr);
p->thread.io_bitmap_max = 0;
}
+ if (err)
+ flush_thread_hw_breakpoint(p);

ds_copy_thread(p, current);

@@ -435,16 +446,6 @@ __switch_to_xtra(struct task_struct *pre
else if (next->debugctlmsr != prev->debugctlmsr)
update_debugctlmsr(next->debugctlmsr);

- if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
- set_debugreg(next->debugreg0, 0);
- set_debugreg(next->debugreg1, 1);
- set_debugreg(next->debugreg2, 2);
- set_debugreg(next->debugreg3, 3);
- /* no 4 and 5 */
- set_debugreg(next->debugreg6, 6);
- set_debugreg(next->debugreg7, 7);
- }
-
if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^
test_tsk_thread_flag(next_p, TIF_NOTSC)) {
/* prev and next are different */
@@ -592,6 +593,12 @@ __switch_to(struct task_struct *prev_p,
loadsegment(gs, next->gs);

x86_write_percpu(current_task, next_p);
+ /*
+ * Handle debug registers. This must be done _after_ current
+ * is updated.
+ */
+ if (unlikely(test_tsk_thread_flag(next_p, TIF_DEBUG)))
+ switch_to_thread_hw_breakpoint(next_p);

return prev_p;
}
Index: linux-hbkpt-lkml-29-rc2/arch/x86/kernel/process_64.c
===================================================================
--- linux-hbkpt-lkml-29-rc2.orig/arch/x86/kernel/process_64.c
+++ linux-hbkpt-lkml-29-rc2/arch/x86/kernel/process_64.c
@@ -52,6 +52,8 @@
#include <asm/proto.h>
#include <asm/ia32.h>
#include <asm/idle.h>
+#include <asm/debugreg.h>
+#include <asm/hw_breakpoint.h>
#include <asm/syscalls.h>
#include <asm/ds.h>

@@ -256,13 +258,9 @@ void flush_thread(void)
}
clear_tsk_thread_flag(tsk, TIF_DEBUG);

- tsk->thread.debugreg0 = 0;
- tsk->thread.debugreg1 = 0;
- tsk->thread.debugreg2 = 0;
- tsk->thread.debugreg3 = 0;
- tsk->thread.debugreg6 = 0;
- tsk->thread.debugreg7 = 0;
memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
+ if (unlikely(tsk->thread.hw_breakpoint_info))
+ flush_thread_hw_breakpoint(tsk);
/*
* Forget coprocessor state..
*/
@@ -282,6 +280,8 @@ void release_thread(struct task_struct *
BUG();
}
}
+ if (unlikely(me->thread.hw_breakpoint_info))
+ flush_thread_hw_breakpoint(me);
}

static inline void set_32bit_tls(struct task_struct *t, int tls, u32 addr)
@@ -337,13 +337,21 @@ int copy_thread(int nr, unsigned long cl

p->thread.fs = me->thread.fs;
p->thread.gs = me->thread.gs;
+ p->thread.hw_breakpoint_info = NULL;
+ p->thread.io_bitmap_ptr = NULL;

savesegment(gs, p->thread.gsindex);
savesegment(fs, p->thread.fsindex);
savesegment(es, p->thread.es);
savesegment(ds, p->thread.ds);

- if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
+ err = -ENOMEM;
+ if (unlikely(me->thread.hw_breakpoint_info)) {
+ if (copy_thread_hw_breakpoint(me, p, clone_flags))
+ goto out;
+ }
+
+if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
if (!p->thread.io_bitmap_ptr) {
p->thread.io_bitmap_max = 0;
@@ -380,6 +388,9 @@ out:
kfree(p->thread.io_bitmap_ptr);
p->thread.io_bitmap_max = 0;
}
+ if (err)
+ flush_thread_hw_breakpoint(p);
+
return err;
}

@@ -482,16 +493,6 @@ static inline void __switch_to_xtra(stru
else if (next->debugctlmsr != prev->debugctlmsr)
update_debugctlmsr(next->debugctlmsr);

- if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
- loaddebug(next, 0);
- loaddebug(next, 1);
- loaddebug(next, 2);
- loaddebug(next, 3);
- /* no 4 and 5 */
- loaddebug(next, 6);
- loaddebug(next, 7);
- }
-
if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^
test_tsk_thread_flag(next_p, TIF_NOTSC)) {
/* prev and next are different */
@@ -514,6 +515,12 @@ static inline void __switch_to_xtra(stru
*/
memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
}
+ /*
+ * Handle debug registers. This must be done _after_ current
+ * is updated.
+ */
+ if (unlikely(test_tsk_thread_flag(next_p, TIF_DEBUG)))
+ switch_to_thread_hw_breakpoint(next_p);
}

/*

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