Messages in this thread | | | Subject | Re: [RFC V3] mm: Generalize and rename notify_page_fault() as kprobe_page_fault() | From | Anshuman Khandual <> | Date | Mon, 10 Jun 2019 08:09:11 +0530 |
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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@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/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.
> >> + ret = 1; > > can do 'return true;' directly here > >> + } >> + return ret; > > And 'return false' here.
Makes sense, will drop ret.
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