Le 10/06/2019 à 04:39, Anshuman Khandual a écrit :
On 06/07/2019 09:01 PM, Christophe Leroy wrote:
Le 07/06/2019 à 12:34, Anshuman Khandual a écrit :
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@xxxxxxxxxxxxxxxxxxx
Cc: linux-ia64@xxxxxxxxxxxxxxx
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Cc: linux-s390@xxxxxxxxxxxxxxx
Cc: linux-sh@xxxxxxxxxxxxxxx
Cc: sparclinux@xxxxxxxxxxxxxxx
Cc: x86@xxxxxxxxxx
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
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/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;
ret is pointless.
+
+ /*
+ * 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))
don't need an 'if A if B', can do 'if A && B'
Which will make it a very lengthy condition check.
Yes. But is that a problem at all ?
For me the following would be easier to read.
if (kprobes_built_in() && !preemptible() && !user_mode(regs) &&
kprobe_running() && kprobe_fault_handler(regs, trap))
ret = 1;
Christophe
+ ret = 1;
can do 'return true;' directly here
+ }
+ return ret;
And 'return false' here.
Makes sense, will drop ret.
