Commit 66cb5917 authored by K.Prasad's avatar K.Prasad Committed by Frederic Weisbecker

hw-breakpoints: use the new wrapper routines to access debug registers in process/thread code

This patch enables the use of abstract debug registers in
process-handling routines, according to the new hardware breakpoint
Api.

[ Impact: adapt thread breakpoints handling code to the new breakpoint Api ]
Original-patch-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarK.Prasad <prasad@linux.vnet.ibm.com>
Reviewed-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
parent 1e350066
...@@ -15,6 +15,8 @@ ...@@ -15,6 +15,8 @@
#include <asm/uaccess.h> #include <asm/uaccess.h>
#include <asm/i387.h> #include <asm/i387.h>
#include <asm/ds.h> #include <asm/ds.h>
#include <asm/debugreg.h>
#include <asm/hw_breakpoint.h>
unsigned long idle_halt; unsigned long idle_halt;
EXPORT_SYMBOL(idle_halt); EXPORT_SYMBOL(idle_halt);
...@@ -46,6 +48,8 @@ void free_thread_xstate(struct task_struct *tsk) ...@@ -46,6 +48,8 @@ void free_thread_xstate(struct task_struct *tsk)
kmem_cache_free(task_xstate_cachep, tsk->thread.xstate); kmem_cache_free(task_xstate_cachep, tsk->thread.xstate);
tsk->thread.xstate = NULL; tsk->thread.xstate = NULL;
} }
if (unlikely(test_tsk_thread_flag(tsk, TIF_DEBUG)))
flush_thread_hw_breakpoint(tsk);
WARN(tsk->thread.ds_ctx, "leaking DS context\n"); WARN(tsk->thread.ds_ctx, "leaking DS context\n");
} }
...@@ -106,12 +110,8 @@ void flush_thread(void) ...@@ -106,12 +110,8 @@ void flush_thread(void)
clear_tsk_thread_flag(tsk, TIF_DEBUG); clear_tsk_thread_flag(tsk, TIF_DEBUG);
tsk->thread.debugreg[0] = 0; if (unlikely(test_tsk_thread_flag(tsk, TIF_DEBUG)))
tsk->thread.debugreg[1] = 0; flush_thread_hw_breakpoint(tsk);
tsk->thread.debugreg[2] = 0;
tsk->thread.debugreg[3] = 0;
tsk->thread.debugreg6 = 0;
tsk->thread.debugreg7 = 0;
memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array)); memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
/* /*
* Forget coprocessor state.. * Forget coprocessor state..
...@@ -193,16 +193,6 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p, ...@@ -193,16 +193,6 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
else if (next->debugctlmsr != prev->debugctlmsr) else if (next->debugctlmsr != prev->debugctlmsr)
update_debugctlmsr(next->debugctlmsr); update_debugctlmsr(next->debugctlmsr);
if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
set_debugreg(next->debugreg[0], 0);
set_debugreg(next->debugreg[1], 1);
set_debugreg(next->debugreg[2], 2);
set_debugreg(next->debugreg[3], 3);
/* no 4 and 5 */
set_debugreg(next->debugreg6, 6);
set_debugreg(next->debugreg7, 7);
}
if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^ if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^
test_tsk_thread_flag(next_p, TIF_NOTSC)) { test_tsk_thread_flag(next_p, TIF_NOTSC)) {
/* prev and next are different */ /* prev and next are different */
......
...@@ -61,6 +61,8 @@ ...@@ -61,6 +61,8 @@
#include <asm/idle.h> #include <asm/idle.h>
#include <asm/syscalls.h> #include <asm/syscalls.h>
#include <asm/ds.h> #include <asm/ds.h>
#include <asm/debugreg.h>
#include <asm/hw_breakpoint.h>
asmlinkage void ret_from_fork(void) __asm__("ret_from_fork"); asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
...@@ -265,7 +267,13 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, ...@@ -265,7 +267,13 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
task_user_gs(p) = get_user_gs(regs); task_user_gs(p) = get_user_gs(regs);
p->thread.io_bitmap_ptr = NULL;
tsk = current; tsk = current;
err = -ENOMEM;
if (unlikely(test_tsk_thread_flag(tsk, TIF_DEBUG)))
if (copy_thread_hw_breakpoint(tsk, p, clone_flags))
goto out;
if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) { if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr, p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
IO_BITMAP_BYTES, GFP_KERNEL); IO_BITMAP_BYTES, GFP_KERNEL);
...@@ -285,10 +293,13 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, ...@@ -285,10 +293,13 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
err = do_set_thread_area(p, -1, err = do_set_thread_area(p, -1,
(struct user_desc __user *)childregs->si, 0); (struct user_desc __user *)childregs->si, 0);
out:
if (err && p->thread.io_bitmap_ptr) { if (err && p->thread.io_bitmap_ptr) {
kfree(p->thread.io_bitmap_ptr); kfree(p->thread.io_bitmap_ptr);
p->thread.io_bitmap_max = 0; p->thread.io_bitmap_max = 0;
} }
if (err)
flush_thread_hw_breakpoint(p);
clear_tsk_thread_flag(p, TIF_DS_AREA_MSR); clear_tsk_thread_flag(p, TIF_DS_AREA_MSR);
p->thread.ds_ctx = NULL; p->thread.ds_ctx = NULL;
...@@ -427,6 +438,23 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) ...@@ -427,6 +438,23 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
lazy_load_gs(next->gs); lazy_load_gs(next->gs);
percpu_write(current_task, next_p); percpu_write(current_task, next_p);
/*
* There's a problem with moving the arch_install_thread_hw_breakpoint()
* call before current is updated. Suppose a kernel breakpoint is
* triggered in between the two, the hw-breakpoint handler will see that
* the 'current' task does not have TIF_DEBUG flag set and will think it
* is leftover from an old task (lazy switching) and will erase it. Then
* until the next context switch, no user-breakpoints will be installed.
*
* The real problem is that it's impossible to update both current and
* physical debug registers at the same instant, so there will always be
* a window in which they disagree and a breakpoint might get triggered.
* Since we use lazy switching, we are forced to assume that a
* disagreement means that current is correct and the exception is due
* to lazy debug register switching.
*/
if (unlikely(test_tsk_thread_flag(next_p, TIF_DEBUG)))
arch_install_thread_hw_breakpoint(next_p);
return prev_p; return prev_p;
} }
......
...@@ -55,6 +55,8 @@ ...@@ -55,6 +55,8 @@
#include <asm/idle.h> #include <asm/idle.h>
#include <asm/syscalls.h> #include <asm/syscalls.h>
#include <asm/ds.h> #include <asm/ds.h>
#include <asm/debugreg.h>
#include <asm/hw_breakpoint.h>
asmlinkage extern void ret_from_fork(void); asmlinkage extern void ret_from_fork(void);
...@@ -248,6 +250,8 @@ void release_thread(struct task_struct *dead_task) ...@@ -248,6 +250,8 @@ void release_thread(struct task_struct *dead_task)
BUG(); BUG();
} }
} }
if (unlikely(dead_task->thread.debugreg7))
flush_thread_hw_breakpoint(dead_task);
} }
static inline void set_32bit_tls(struct task_struct *t, int tls, u32 addr) static inline void set_32bit_tls(struct task_struct *t, int tls, u32 addr)
...@@ -303,12 +307,18 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, ...@@ -303,12 +307,18 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
p->thread.fs = me->thread.fs; p->thread.fs = me->thread.fs;
p->thread.gs = me->thread.gs; p->thread.gs = me->thread.gs;
p->thread.io_bitmap_ptr = NULL;
savesegment(gs, p->thread.gsindex); savesegment(gs, p->thread.gsindex);
savesegment(fs, p->thread.fsindex); savesegment(fs, p->thread.fsindex);
savesegment(es, p->thread.es); savesegment(es, p->thread.es);
savesegment(ds, p->thread.ds); savesegment(ds, p->thread.ds);
err = -ENOMEM;
if (unlikely(test_tsk_thread_flag(me, TIF_DEBUG)))
if (copy_thread_hw_breakpoint(me, p, clone_flags))
goto out;
if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) { if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
if (!p->thread.io_bitmap_ptr) { if (!p->thread.io_bitmap_ptr) {
...@@ -347,6 +357,9 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, ...@@ -347,6 +357,9 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
kfree(p->thread.io_bitmap_ptr); kfree(p->thread.io_bitmap_ptr);
p->thread.io_bitmap_max = 0; p->thread.io_bitmap_max = 0;
} }
if (err)
flush_thread_hw_breakpoint(p);
return err; return err;
} }
...@@ -492,6 +505,24 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) ...@@ -492,6 +505,24 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
*/ */
if (tsk_used_math(next_p) && next_p->fpu_counter > 5) if (tsk_used_math(next_p) && next_p->fpu_counter > 5)
math_state_restore(); math_state_restore();
/*
* There's a problem with moving the arch_install_thread_hw_breakpoint()
* call before current is updated. Suppose a kernel breakpoint is
* triggered in between the two, the hw-breakpoint handler will see that
* the 'current' task does not have TIF_DEBUG flag set and will think it
* is leftover from an old task (lazy switching) and will erase it. Then
* until the next context switch, no user-breakpoints will be installed.
*
* The real problem is that it's impossible to update both current and
* physical debug registers at the same instant, so there will always be
* a window in which they disagree and a breakpoint might get triggered.
* Since we use lazy switching, we are forced to assume that a
* disagreement means that current is correct and the exception is due
* to lazy debug register switching.
*/
if (unlikely(test_tsk_thread_flag(next_p, TIF_DEBUG)))
arch_install_thread_hw_breakpoint(next_p);
return prev_p; return prev_p;
} }
......
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