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Subject[RFC V3] mm: Generalize and rename notify_page_fault() as kprobe_page_fault()
Date
Very similar definitions for notify_page_fault() are being used by multiple
architectures duplicating much of the same code. This attempts to unify all
of them into a generic implementation, rename it as kprobe_page_fault() and
then move it to a common header.

kprobes_built_in() can detect CONFIG_KPROBES, hence new kprobe_page_fault()
need not be wrapped again within CONFIG_KPROBES. Trap number argument can
now contain upto an 'unsigned int' accommodating all possible platforms.

kprobe_page_fault() goes the x86 way while dealing with preemption context.
As explained in these following commits the invoking context in itself must
be non-preemptible for kprobes processing context irrespective of whether
kprobe_running() or perhaps smp_processor_id() is safe or not. It does not
make much sense to continue when original context is preemptible. Instead
just bail out earlier.

commit a980c0ef9f6d
("x86/kprobes: Refactor kprobes_fault() like kprobe_exceptions_notify()")

commit b506a9d08bae ("x86: code clarification patch to Kprobes arch code")

Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-ia64@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: sparclinux@vger.kernel.org
Cc: x86@kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>

Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
Testing:

- Build and boot tested on arm64 and x86
- Build tested on some other archs (arm, sparc64, alpha, powerpc etc)

Changes in RFC V3:

- Updated the commit message with an explaination for new preemption behaviour
- Moved notify_page_fault() to kprobes.h with 'static nokprobe_inline' per Matthew
- Changed notify_page_fault() return type from int to bool per Michael Ellerman
- Renamed notify_page_fault() as kprobe_page_fault() per Peterz

Changes in RFC V2: (https://patchwork.kernel.org/patch/10974221/)

- Changed generic notify_page_fault() per Mathew Wilcox
- Changed x86 to use new generic notify_page_fault()
- s/must not/need not/ in commit message per Matthew Wilcox

Changes in RFC V1: (https://patchwork.kernel.org/patch/10968273/)

arch/arm/mm/fault.c | 24 +-----------------------
arch/arm64/mm/fault.c | 24 +-----------------------
arch/ia64/mm/fault.c | 24 +-----------------------
arch/powerpc/mm/fault.c | 23 ++---------------------
arch/s390/mm/fault.c | 16 +---------------
arch/sh/mm/fault.c | 18 ++----------------
arch/sparc/mm/fault_64.c | 16 +---------------
arch/x86/mm/fault.c | 21 ++-------------------
include/linux/kprobes.h | 16 ++++++++++++++++
9 files changed, 27 insertions(+), 155 deletions(-)

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 58f69fa..94a97a4 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -30,28 +30,6 @@

#ifdef CONFIG_MMU

-#ifdef CONFIG_KPROBES
-static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
-{
- int ret = 0;
-
- if (!user_mode(regs)) {
- /* kprobe_running() needs smp_processor_id() */
- preempt_disable();
- if (kprobe_running() && kprobe_fault_handler(regs, fsr))
- ret = 1;
- preempt_enable();
- }
-
- return ret;
-}
-#else
-static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
-{
- return 0;
-}
-#endif
-
/*
* This is useful to dump out the page tables associated with
* 'addr' in mm 'mm'.
@@ -266,7 +244,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
vm_fault_t fault;
unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;

- if (notify_page_fault(regs, fsr))
+ if (kprobe_page_fault(regs, fsr))
return 0;

tsk = current;
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index a30818e..8fe4bbc 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -70,28 +70,6 @@ static inline const struct fault_info *esr_to_debug_fault_info(unsigned int esr)
return debug_fault_info + DBG_ESR_EVT(esr);
}

-#ifdef CONFIG_KPROBES
-static inline int notify_page_fault(struct pt_regs *regs, unsigned int esr)
-{
- int ret = 0;
-
- /* kprobe_running() needs smp_processor_id() */
- if (!user_mode(regs)) {
- preempt_disable();
- if (kprobe_running() && kprobe_fault_handler(regs, esr))
- ret = 1;
- preempt_enable();
- }
-
- return ret;
-}
-#else
-static inline int notify_page_fault(struct pt_regs *regs, unsigned int esr)
-{
- return 0;
-}
-#endif
-
static void data_abort_decode(unsigned int esr)
{
pr_alert("Data abort info:\n");
@@ -446,7 +424,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
unsigned long vm_flags = VM_READ | VM_WRITE;
unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;

- if (notify_page_fault(regs, esr))
+ if (kprobe_page_fault(regs, esr))
return 0;

tsk = current;
diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
index 5baeb02..22582f8 100644
--- a/arch/ia64/mm/fault.c
+++ b/arch/ia64/mm/fault.c
@@ -21,28 +21,6 @@

extern int die(char *, struct pt_regs *, long);

-#ifdef CONFIG_KPROBES
-static inline int notify_page_fault(struct pt_regs *regs, int trap)
-{
- int ret = 0;
-
- if (!user_mode(regs)) {
- /* kprobe_running() needs smp_processor_id() */
- preempt_disable();
- if (kprobe_running() && kprobe_fault_handler(regs, trap))
- ret = 1;
- preempt_enable();
- }
-
- return ret;
-}
-#else
-static inline int notify_page_fault(struct pt_regs *regs, int trap)
-{
- return 0;
-}
-#endif
-
/*
* Return TRUE if ADDRESS points at a page in the kernel's mapped segment
* (inside region 5, on ia64) and that page is present.
@@ -116,7 +94,7 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
/*
* This is to handle the kprobes on user space access instructions
*/
- if (notify_page_fault(regs, TRAP_BRKPT))
+ if (kprobe_page_fault(regs, TRAP_BRKPT))
return;

if (user_mode(regs))
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index ec6b7ad..f20ee668 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -42,26 +42,6 @@
#include <asm/debug.h>
#include <asm/kup.h>

-static inline bool notify_page_fault(struct pt_regs *regs)
-{
- bool ret = false;
-
-#ifdef CONFIG_KPROBES
- /* kprobe_running() needs smp_processor_id() */
- if (!user_mode(regs)) {
- preempt_disable();
- if (kprobe_running() && kprobe_fault_handler(regs, 11))
- ret = true;
- preempt_enable();
- }
-#endif /* CONFIG_KPROBES */
-
- if (unlikely(debugger_fault_handler(regs)))
- ret = true;
-
- return ret;
-}
-
/*
* Check whether the instruction inst is a store using
* an update addressing form which will update r1.
@@ -462,8 +442,9 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
int is_write = page_fault_is_write(error_code);
vm_fault_t fault, major = 0;
bool must_retry = false;
+ int kprobe_fault = kprobe_page_fault(regs, 11);

- if (notify_page_fault(regs))
+ if (unlikely(debugger_fault_handler(regs) || kprobe_fault))
return 0;

if (unlikely(page_fault_is_bad(error_code))) {
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 91ce03f..bb77a2c 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -67,20 +67,6 @@ static int __init fault_init(void)
}
early_initcall(fault_init);

-static inline int notify_page_fault(struct pt_regs *regs)
-{
- int ret = 0;
-
- /* kprobe_running() needs smp_processor_id() */
- if (kprobes_built_in() && !user_mode(regs)) {
- preempt_disable();
- if (kprobe_running() && kprobe_fault_handler(regs, 14))
- ret = 1;
- preempt_enable();
- }
- return ret;
-}
-
/*
* Find out which address space caused the exception.
* Access register mode is impossible, ignore space == 3.
@@ -411,7 +397,7 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access)
*/
clear_pt_regs_flag(regs, PIF_PER_TRAP);

- if (notify_page_fault(regs))
+ if (kprobe_page_fault(regs, 14))
return 0;

mm = tsk->mm;
diff --git a/arch/sh/mm/fault.c b/arch/sh/mm/fault.c
index 6defd2c6..74cd4ac 100644
--- a/arch/sh/mm/fault.c
+++ b/arch/sh/mm/fault.c
@@ -24,20 +24,6 @@
#include <asm/tlbflush.h>
#include <asm/traps.h>

-static inline int notify_page_fault(struct pt_regs *regs, int trap)
-{
- int ret = 0;
-
- if (kprobes_built_in() && !user_mode(regs)) {
- preempt_disable();
- if (kprobe_running() && kprobe_fault_handler(regs, trap))
- ret = 1;
- preempt_enable();
- }
-
- return ret;
-}
-
static void
force_sig_info_fault(int si_signo, int si_code, unsigned long address,
struct task_struct *tsk)
@@ -415,14 +401,14 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
if (unlikely(fault_in_kernel_space(address))) {
if (vmalloc_fault(address) >= 0)
return;
- if (notify_page_fault(regs, vec))
+ if (kprobe_page_fault(regs, vec))
return;

bad_area_nosemaphore(regs, error_code, address);
return;
}

- if (unlikely(notify_page_fault(regs, vec)))
+ if (unlikely(kprobe_page_fault(regs, vec)))
return;

/* Only enable interrupts if they were on before the fault */
diff --git a/arch/sparc/mm/fault_64.c b/arch/sparc/mm/fault_64.c
index 8f8a604..6865f9c 100644
--- a/arch/sparc/mm/fault_64.c
+++ b/arch/sparc/mm/fault_64.c
@@ -38,20 +38,6 @@

int show_unhandled_signals = 1;

-static inline __kprobes int notify_page_fault(struct pt_regs *regs)
-{
- int ret = 0;
-
- /* kprobe_running() needs smp_processor_id() */
- if (kprobes_built_in() && !user_mode(regs)) {
- preempt_disable();
- if (kprobe_running() && kprobe_fault_handler(regs, 0))
- ret = 1;
- preempt_enable();
- }
- return ret;
-}
-
static void __kprobes unhandled_fault(unsigned long address,
struct task_struct *tsk,
struct pt_regs *regs)
@@ -285,7 +271,7 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)

fault_code = get_thread_fault_code();

- if (notify_page_fault(regs))
+ if (kprobe_page_fault(regs, 0))
goto exit_exception;

si_code = SEGV_MAPERR;
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 46df4c6..5400f4e 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -46,23 +46,6 @@ kmmio_fault(struct pt_regs *regs, unsigned long addr)
return 0;
}

-static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
-{
- if (!kprobes_built_in())
- return 0;
- if (user_mode(regs))
- return 0;
- /*
- * To be potentially processing a kprobe fault and to be allowed to call
- * kprobe_running(), we have to be non-preemptible.
- */
- if (preemptible())
- return 0;
- if (!kprobe_running())
- return 0;
- return kprobe_fault_handler(regs, X86_TRAP_PF);
-}
-
/*
* Prefetch quirks:
*
@@ -1280,7 +1263,7 @@ do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
return;

/* kprobes don't want to hook the spurious faults: */
- if (kprobes_fault(regs))
+ if (kprobe_page_fault(regs, X86_TRAP_PF))
return;

/*
@@ -1311,7 +1294,7 @@ void do_user_addr_fault(struct pt_regs *regs,
mm = tsk->mm;

/* kprobes don't want to hook the spurious faults: */
- if (unlikely(kprobes_fault(regs)))
+ if (unlikely(kprobe_page_fault(regs, X86_TRAP_PF)))
return;

/*
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 443d980..064dd15 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -458,4 +458,20 @@ static inline bool is_kprobe_optinsn_slot(unsigned long addr)
}
#endif

+static nokprobe_inline bool kprobe_page_fault(struct pt_regs *regs,
+ unsigned int trap)
+{
+ int ret = 0;
+
+ /*
+ * To be potentially processing a kprobe fault and to be allowed
+ * to call kprobe_running(), we have to be non-preemptible.
+ */
+ if (kprobes_built_in() && !preemptible() && !user_mode(regs)) {
+ if (kprobe_running() && kprobe_fault_handler(regs, trap))
+ ret = 1;
+ }
+ return ret;
+}
+
#endif /* _LINUX_KPROBES_H */
--
2.7.4
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