v3: Changed patch 1/2 to incorporate feedback from Steven Rostedt and Masami Hiramatsu: rename helper function check_ftrace_location() to arch_check_ftrace_location() and convert it to a weak function, so architectures can override it without the need for new config option.
v2: Changed patch 1/2 to incorporate feedback from Masami Hiramatsu, and introduce a new helper function check_ftrace_location(). The requested ftracetest has been sent as an own patch set, since it has no dependency to these patches. v1: We would like to implement an architecture specific variant of "kprobes on ftrace" without using the current HAVE_KPROBES_ON_FTRACE infrastructure which is currently only used by x86. The rationale for these two patches is: - we want to patch the first instruction of the mcount code block to reduce the overhead of the function tracer - we'd like to keep the ftrace_caller function as simple as possible and not require it to generate a 100% valid pt_regs structure as required by the combination of DYNAMIC_FTRACE_WITH_REGS and HAVE_KPROBES_ON_FTRACE. This allows us to not generate the psw mask field in the pt_regs structure on each function tracer enabled function, which otherwise would be very expensive. Besides that program check generated pt_regs contents are "more" accurate than program generated ones and don't require any maintenance. And also we can keep the ftrace and kprobes backends quite separated. In order to make this work a small common code change is necessary which removes a check if kprobe is being placed on an ftrace location (see first patch). If possible, I'd like to have an ACK from at least one of the kprobes maintainers for the first patch and bring it upstream via the s390 tree. Thanks, Heiko Heiko Carstens (2): kprobes: introduce weak arch_check_ftrace_location() helper function s390/ftrace,kprobes: allow to patch first instruction arch/s390/include/asm/ftrace.h | 52 ++++++++++++++-- arch/s390/include/asm/kprobes.h | 1 + arch/s390/include/asm/lowcore.h | 4 +- arch/s390/include/asm/pgtable.h | 12 ++++ arch/s390/kernel/asm-offsets.c | 1 - arch/s390/kernel/early.c | 4 -- arch/s390/kernel/ftrace.c | 132 +++++++++++++++++++++++++--------------- arch/s390/kernel/kprobes.c | 92 ++++++++++++++++++++-------- arch/s390/kernel/mcount.S | 1 + arch/s390/kernel/setup.c | 2 - arch/s390/kernel/smp.c | 1 - include/linux/kprobes.h | 1 + kernel/kprobes.c | 18 +++--- scripts/recordmcount.c | 2 +- scripts/recordmcount.pl | 2 +- 15 files changed, 226 insertions(+), 99 deletions(-) -- 1.8.5.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
