* [Bug kprobes/2064] Support pagepoint probes
2005-12-17 6:03 [Bug kprobes/2064] New: Support pagepoint probes jkenisto at us dot ibm dot com
@ 2005-12-17 23:22 ` marcelo dot tosatti at cyclades dot com
2005-12-18 1:36 ` [Bug kprobes/2064] New: " Marcelo Tosatti
` (5 subsequent siblings)
6 siblings, 0 replies; 9+ messages in thread
From: marcelo dot tosatti at cyclades dot com @ 2005-12-17 23:22 UTC (permalink / raw)
To: systemtap
------- Additional Comments From marcelo dot tosatti at cyclades dot com 2005-12-17 23:22 -------
Subject: Re: New: Support pagepoint probes
Hi jkenisto,
On Fri, Dec 16, 2005 at 09:10:45PM -0000, jkenisto at us dot ibm dot com wrote:
> It has been requested that we support "pagepoint" probes. Such a probe is
> analogous to a watchpoint probe; but with a pagepoint probe, neither the number
> of concurrent probes nor the size of the probed area is limited by the CPU's
> debug-register architecture.
And I suppose these probes need to work on physical and also on virtual
page addresses for particular processes?
> Pagepoint probes would presumably be implemented by fussing the permission bits
> on the probed page(s) and hooking the page-fault handler (or exploiting the
> existing kprobes hook).
I encountered a similar requirement for a project to track page accesses
(on a per-virtual-mapping basis, not physical addresses), and it was
solved by:
- disabling the PRESENT bit of the pagetable in question
- setting "PAGE_DISABLED" bit (using a free bit in the pte flags)
- hook in the pagefault handler to identify disabled pte's, reinstantiate them
immediately, and call my private accounting function.
Plan is to convert the hook to SystemTap if possible.
diff --git a/include/asm-i386/pgtable.h b/include/asm-i386/pgtable.h
index 088a945..db8c3f7 100644
--- a/include/asm-i386/pgtable.h
+++ b/include/asm-i386/pgtable.h
@@ -116,7 +116,7 @@ void paging_init(void);
#define _PAGE_DIRTY 0x040
#define _PAGE_PSE 0x080 /* 4 MB (or 2MB) page, Pentium+, if present.. */
#define _PAGE_GLOBAL 0x100 /* Global TLB entry PPro+ */
-#define _PAGE_UNUSED1 0x200 /* available for programmer */
+#define _PAGE_DISABLED 0x200 /* for pagetrace */
#define _PAGE_UNUSED2 0x400
#define _PAGE_UNUSED3 0x800
@@ -225,6 +225,7 @@ static inline int pte_read(pte_t pte) {
static inline int pte_dirty(pte_t pte) { return (pte).pte_low & _PAGE_DIRTY; }
static inline int pte_young(pte_t pte) { return (pte).pte_low & _PAGE_ACCESSED; }
static inline int pte_write(pte_t pte) { return (pte).pte_low & _PAGE_RW; }
+static inline int pte_disabled(pte_t pte) { return (pte).pte_low & _PAGE_DISABLED; }
static inline int pte_huge(pte_t pte) { return ((pte).pte_low & __LARGE_PTE) == __LARGE_PTE; }
/*
@@ -237,11 +238,15 @@ static inline pte_t pte_exprotect(pte_t
static inline pte_t pte_mkclean(pte_t pte) { (pte).pte_low &= ~_PAGE_DIRTY; return pte; }
static inline pte_t pte_mkold(pte_t pte) { (pte).pte_low &= ~_PAGE_ACCESSED; return pte; }
static inline pte_t pte_wrprotect(pte_t pte) { (pte).pte_low &= ~_PAGE_RW; return pte; }
+static inline pte_t pte_presprotect(pte_t pte) { (pte).pte_low &= ~_PAGE_PRESENT; return pte; }
+static inline pte_t pte_enable(pte_t pte) { (pte).pte_low &= ~_PAGE_DISABLED; return pte; }
static inline pte_t pte_mkread(pte_t pte) { (pte).pte_low |= _PAGE_USER; return pte; }
static inline pte_t pte_mkexec(pte_t pte) { (pte).pte_low |= _PAGE_USER; return pte; }
static inline pte_t pte_mkdirty(pte_t pte) { (pte).pte_low |= _PAGE_DIRTY; return pte; }
static inline pte_t pte_mkyoung(pte_t pte) { (pte).pte_low |= _PAGE_ACCESSED; return pte; }
static inline pte_t pte_mkwrite(pte_t pte) { (pte).pte_low |= _PAGE_RW; return pte; }
+static inline pte_t pte_mkpresent(pte_t pte) { (pte).pte_low |= _PAGE_PRESENT; return pte; }
+static inline pte_t pte_disable(pte_t pte) { (pte).pte_low |= _PAGE_DISABLED; return pte; }
static inline pte_t pte_mkhuge(pte_t pte) { (pte).pte_low |= __LARGE_PTE; return pte; }
#ifdef CONFIG_X86_PAE
diff --git a/mm/memory.c b/mm/memory.c
index 4b4fc3a..b57e808 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -418,7 +418,7 @@ copy_one_pte(struct mm_struct *dst_mm, s
struct page *page;
/* pte contains position in swap or file, so copy. */
- if (unlikely(!pte_present(pte))) {
+ if (unlikely(!pte_present(pte)) && !pte_disabled(pte)) {
if (!pte_file(pte)) {
swap_duplicate(pte_to_swp_entry(pte));
/* make sure dst_mm is on swapoff's mmlist. */
@@ -606,7 +606,7 @@ static unsigned long zap_pte_range(struc
(*zap_work)--;
continue;
}
- if (pte_present(ptent)) {
+ if (pte_present(ptent) || pte_disabled(ptent)) {
struct page *page;
(*zap_work) -= PAGE_SIZE;
@@ -908,7 +908,7 @@ struct page *follow_page(struct vm_area_
goto out;
pte = *ptep;
- if (!pte_present(pte))
+ if (!pte_present(pte) && !pte_disabled(pte))
goto unlock;
if ((flags & FOLL_WRITE) && !pte_write(pte))
goto unlock;
@@ -2199,6 +2199,18 @@ static inline int handle_pte_fault(struc
old_entry = entry = *pte;
if (!pte_present(entry)) {
+ if (pte_disabled(entry)) {
+ ptl = pte_lockptr(mm, pmd);
+ spin_lock(ptl);
+ if (unlikely(!pte_same(*pte, entry)))
+ goto unlock;
+ pgtrace(vma, 0, address);
+ set_pte_at(vma->vm_mm, address, pte, pte_enable(pte_mkpresent(entry)));
+ flush_tlb_page(vma, address);
+ update_mmu_cache(vma, address, entry);
+ pte_unmap(pte);
+ goto unlock;
+ }
if (pte_none(entry)) {
if (!vma->vm_ops || !vma->vm_ops->nopage)
return do_anonymous_page(mm, vma, address,
>
> --
> Summary: Support pagepoint probes
> Product: systemtap
> Version: unspecified
> Status: NEW
> Severity: enhancement
> Priority: P3
> Component: kprobes
> AssignedTo: systemtap at sources dot redhat dot com
> ReportedBy: jkenisto at us dot ibm dot com
>
>
> http://sourceware.org/bugzilla/show_bug.cgi?id=2064
>
> ------- You are receiving this mail because: -------
> You are the assignee for the bug, or are watching the assignee.
--
http://sourceware.org/bugzilla/show_bug.cgi?id=2064
------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [Bug kprobes/2064] New: Support pagepoint probes
2005-12-17 6:03 [Bug kprobes/2064] New: Support pagepoint probes jkenisto at us dot ibm dot com
2005-12-17 23:22 ` [Bug kprobes/2064] " marcelo dot tosatti at cyclades dot com
@ 2005-12-18 1:36 ` Marcelo Tosatti
2005-12-18 17:34 ` Andi Kleen
` (4 subsequent siblings)
6 siblings, 0 replies; 9+ messages in thread
From: Marcelo Tosatti @ 2005-12-18 1:36 UTC (permalink / raw)
To: jkenisto at us dot ibm dot com; +Cc: systemtap
Hi jkenisto,
On Fri, Dec 16, 2005 at 09:10:45PM -0000, jkenisto at us dot ibm dot com wrote:
> It has been requested that we support "pagepoint" probes. Such a probe is
> analogous to a watchpoint probe; but with a pagepoint probe, neither the number
> of concurrent probes nor the size of the probed area is limited by the CPU's
> debug-register architecture.
And I suppose these probes need to work on physical and also on virtual
page addresses for particular processes?
> Pagepoint probes would presumably be implemented by fussing the permission bits
> on the probed page(s) and hooking the page-fault handler (or exploiting the
> existing kprobes hook).
I encountered a similar requirement for a project to track page accesses
(on a per-virtual-mapping basis, not physical addresses), and it was
solved by:
- disabling the PRESENT bit of the pagetable in question
- setting "PAGE_DISABLED" bit (using a free bit in the pte flags)
- hook in the pagefault handler to identify disabled pte's, reinstantiate them
immediately, and call my private accounting function.
Plan is to convert the hook to SystemTap if possible.
diff --git a/include/asm-i386/pgtable.h b/include/asm-i386/pgtable.h
index 088a945..db8c3f7 100644
--- a/include/asm-i386/pgtable.h
+++ b/include/asm-i386/pgtable.h
@@ -116,7 +116,7 @@ void paging_init(void);
#define _PAGE_DIRTY 0x040
#define _PAGE_PSE 0x080 /* 4 MB (or 2MB) page, Pentium+, if present.. */
#define _PAGE_GLOBAL 0x100 /* Global TLB entry PPro+ */
-#define _PAGE_UNUSED1 0x200 /* available for programmer */
+#define _PAGE_DISABLED 0x200 /* for pagetrace */
#define _PAGE_UNUSED2 0x400
#define _PAGE_UNUSED3 0x800
@@ -225,6 +225,7 @@ static inline int pte_read(pte_t pte) {
static inline int pte_dirty(pte_t pte) { return (pte).pte_low & _PAGE_DIRTY; }
static inline int pte_young(pte_t pte) { return (pte).pte_low & _PAGE_ACCESSED; }
static inline int pte_write(pte_t pte) { return (pte).pte_low & _PAGE_RW; }
+static inline int pte_disabled(pte_t pte) { return (pte).pte_low & _PAGE_DISABLED; }
static inline int pte_huge(pte_t pte) { return ((pte).pte_low & __LARGE_PTE) == __LARGE_PTE; }
/*
@@ -237,11 +238,15 @@ static inline pte_t pte_exprotect(pte_t
static inline pte_t pte_mkclean(pte_t pte) { (pte).pte_low &= ~_PAGE_DIRTY; return pte; }
static inline pte_t pte_mkold(pte_t pte) { (pte).pte_low &= ~_PAGE_ACCESSED; return pte; }
static inline pte_t pte_wrprotect(pte_t pte) { (pte).pte_low &= ~_PAGE_RW; return pte; }
+static inline pte_t pte_presprotect(pte_t pte) { (pte).pte_low &= ~_PAGE_PRESENT; return pte; }
+static inline pte_t pte_enable(pte_t pte) { (pte).pte_low &= ~_PAGE_DISABLED; return pte; }
static inline pte_t pte_mkread(pte_t pte) { (pte).pte_low |= _PAGE_USER; return pte; }
static inline pte_t pte_mkexec(pte_t pte) { (pte).pte_low |= _PAGE_USER; return pte; }
static inline pte_t pte_mkdirty(pte_t pte) { (pte).pte_low |= _PAGE_DIRTY; return pte; }
static inline pte_t pte_mkyoung(pte_t pte) { (pte).pte_low |= _PAGE_ACCESSED; return pte; }
static inline pte_t pte_mkwrite(pte_t pte) { (pte).pte_low |= _PAGE_RW; return pte; }
+static inline pte_t pte_mkpresent(pte_t pte) { (pte).pte_low |= _PAGE_PRESENT; return pte; }
+static inline pte_t pte_disable(pte_t pte) { (pte).pte_low |= _PAGE_DISABLED; return pte; }
static inline pte_t pte_mkhuge(pte_t pte) { (pte).pte_low |= __LARGE_PTE; return pte; }
#ifdef CONFIG_X86_PAE
diff --git a/mm/memory.c b/mm/memory.c
index 4b4fc3a..b57e808 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -418,7 +418,7 @@ copy_one_pte(struct mm_struct *dst_mm, s
struct page *page;
/* pte contains position in swap or file, so copy. */
- if (unlikely(!pte_present(pte))) {
+ if (unlikely(!pte_present(pte)) && !pte_disabled(pte)) {
if (!pte_file(pte)) {
swap_duplicate(pte_to_swp_entry(pte));
/* make sure dst_mm is on swapoff's mmlist. */
@@ -606,7 +606,7 @@ static unsigned long zap_pte_range(struc
(*zap_work)--;
continue;
}
- if (pte_present(ptent)) {
+ if (pte_present(ptent) || pte_disabled(ptent)) {
struct page *page;
(*zap_work) -= PAGE_SIZE;
@@ -908,7 +908,7 @@ struct page *follow_page(struct vm_area_
goto out;
pte = *ptep;
- if (!pte_present(pte))
+ if (!pte_present(pte) && !pte_disabled(pte))
goto unlock;
if ((flags & FOLL_WRITE) && !pte_write(pte))
goto unlock;
@@ -2199,6 +2199,18 @@ static inline int handle_pte_fault(struc
old_entry = entry = *pte;
if (!pte_present(entry)) {
+ if (pte_disabled(entry)) {
+ ptl = pte_lockptr(mm, pmd);
+ spin_lock(ptl);
+ if (unlikely(!pte_same(*pte, entry)))
+ goto unlock;
+ pgtrace(vma, 0, address);
+ set_pte_at(vma->vm_mm, address, pte, pte_enable(pte_mkpresent(entry)));
+ flush_tlb_page(vma, address);
+ update_mmu_cache(vma, address, entry);
+ pte_unmap(pte);
+ goto unlock;
+ }
if (pte_none(entry)) {
if (!vma->vm_ops || !vma->vm_ops->nopage)
return do_anonymous_page(mm, vma, address,
>
> --
> Summary: Support pagepoint probes
> Product: systemtap
> Version: unspecified
> Status: NEW
> Severity: enhancement
> Priority: P3
> Component: kprobes
> AssignedTo: systemtap at sources dot redhat dot com
> ReportedBy: jkenisto at us dot ibm dot com
>
>
> http://sourceware.org/bugzilla/show_bug.cgi?id=2064
>
> ------- You are receiving this mail because: -------
> You are the assignee for the bug, or are watching the assignee.
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [Bug kprobes/2064] New: Support pagepoint probes
2005-12-17 6:03 [Bug kprobes/2064] New: Support pagepoint probes jkenisto at us dot ibm dot com
2005-12-17 23:22 ` [Bug kprobes/2064] " marcelo dot tosatti at cyclades dot com
2005-12-18 1:36 ` [Bug kprobes/2064] New: " Marcelo Tosatti
@ 2005-12-18 17:34 ` Andi Kleen
2005-12-19 19:05 ` [Bug kprobes/2064] " jkenisto at us dot ibm dot com
` (3 subsequent siblings)
6 siblings, 0 replies; 9+ messages in thread
From: Andi Kleen @ 2005-12-18 17:34 UTC (permalink / raw)
To: systemtap, jkenisto
"jkenisto at us dot ibm dot com" <sourceware-bugzilla@sourceware.org> writes:
> It has been requested that we support "pagepoint" probes. Such a probe is
> analogous to a watchpoint probe; but with a pagepoint probe, neither the number
> of concurrent probes nor the size of the probed area is limited by the CPU's
> debug-register architecture.
>
> Pagepoint probes would presumably be implemented by fussing the permission bits
> on the probed page(s) and hooking the page-fault handler (or exploiting the
> existing kprobes hook).
Wouldn't that require either an x86 interpreter or SMP races when you
then replay the instruction? (when you temporarily unprotect the page)
Xen seems to have gone the first path for similar needs, but it always
looked quite bad to me (they seem to grow a new variant of x86
interpretation every month and even the original one seems to be quite
incomplete) Probably not a good idea to duplicate.
-Andi
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug kprobes/2064] Support pagepoint probes
2005-12-17 6:03 [Bug kprobes/2064] New: Support pagepoint probes jkenisto at us dot ibm dot com
` (2 preceding siblings ...)
2005-12-18 17:34 ` Andi Kleen
@ 2005-12-19 19:05 ` jkenisto at us dot ibm dot com
2009-04-14 17:18 ` fche at redhat dot com
` (2 subsequent siblings)
6 siblings, 0 replies; 9+ messages in thread
From: jkenisto at us dot ibm dot com @ 2005-12-19 19:05 UTC (permalink / raw)
To: systemtap
------- Additional Comments From jkenisto at us dot ibm dot com 2005-12-19 18:45 -------
Note from Andi Kleen <ak@suse.de>:
> Pagepoint probes would presumably be implemented by fussing the permission bits
> on the probed page(s) and hooking the page-fault handler (or exploiting the
> existing kprobes hook).
Wouldn't that require either an x86 interpreter or SMP races when you
then replay the instruction? (when you temporarily unprotect the page)
Xen seems to have gone the first path for similar needs, but it always
looked quite bad to me (they seem to grow a new variant of x86
interpretation every month and even the original one seems to be quite
incomplete) Probably not a good idea to duplicate.
-Andi
--
http://sourceware.org/bugzilla/show_bug.cgi?id=2064
------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug kprobes/2064] Support pagepoint probes
2005-12-17 6:03 [Bug kprobes/2064] New: Support pagepoint probes jkenisto at us dot ibm dot com
` (3 preceding siblings ...)
2005-12-19 19:05 ` [Bug kprobes/2064] " jkenisto at us dot ibm dot com
@ 2009-04-14 17:18 ` fche at redhat dot com
2009-04-14 18:54 ` mhiramat at redhat dot com
2009-04-14 18:58 ` jkenisto at us dot ibm dot com
6 siblings, 0 replies; 9+ messages in thread
From: fche at redhat dot com @ 2009-04-14 17:18 UTC (permalink / raw)
To: systemtap
------- Additional Comments From fche at redhat dot com 2009-04-14 17:17 -------
Is this duplicated by bug #6883 (kmmio hooks)?
--
http://sourceware.org/bugzilla/show_bug.cgi?id=2064
------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug kprobes/2064] Support pagepoint probes
2005-12-17 6:03 [Bug kprobes/2064] New: Support pagepoint probes jkenisto at us dot ibm dot com
` (4 preceding siblings ...)
2009-04-14 17:18 ` fche at redhat dot com
@ 2009-04-14 18:54 ` mhiramat at redhat dot com
2009-04-14 18:58 ` jkenisto at us dot ibm dot com
6 siblings, 0 replies; 9+ messages in thread
From: mhiramat at redhat dot com @ 2009-04-14 18:54 UTC (permalink / raw)
To: systemtap
------- Additional Comments From mhiramat at redhat dot com 2009-04-14 18:54 -------
(In reply to comment #3)
> Is this duplicated by bug #6883 (kmmio hooks)?
>
It seems that kmmio could be used for this purpose, logically.
--
http://sourceware.org/bugzilla/show_bug.cgi?id=2064
------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug kprobes/2064] Support pagepoint probes
2005-12-17 6:03 [Bug kprobes/2064] New: Support pagepoint probes jkenisto at us dot ibm dot com
` (5 preceding siblings ...)
2009-04-14 18:54 ` mhiramat at redhat dot com
@ 2009-04-14 18:58 ` jkenisto at us dot ibm dot com
6 siblings, 0 replies; 9+ messages in thread
From: jkenisto at us dot ibm dot com @ 2009-04-14 18:58 UTC (permalink / raw)
To: systemtap
------- Additional Comments From jkenisto at us dot ibm dot com 2009-04-14 18:58 -------
Subject: Re: Support pagepoint probes
On Tue, 2009-04-14 at 17:17 +0000, fche at redhat dot com wrote:
> ------- Additional Comments From fche at redhat dot com 2009-04-14 17:17 -------
> Is this duplicated by bug #6883 (kmmio hooks)?
>
>
kmmio hooks is #6983, not #6883. And I think that the two PRs address
substantially different things (memory-mapped I/O versus hardware
breakpoints) -- although the kmmio mechanism might be useful in
implementing #2064.
Jim
--
http://sourceware.org/bugzilla/show_bug.cgi?id=2064
------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.
^ permalink raw reply [flat|nested] 9+ messages in thread