Messages in this thread | | | Date | Wed, 19 Jun 2019 13:26:37 +0530 | From | "Naveen N. Rao" <> | Subject | Re: [PATCH 5/7] powerpc/ftrace: Update ftrace_location() for powerpc -mprofile-kernel |
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Steven Rostedt wrote: > On Tue, 18 Jun 2019 23:53:11 +0530 > "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote: > >> Naveen N. Rao wrote: >> > Steven Rostedt wrote: >> >> On Tue, 18 Jun 2019 20:17:04 +0530 >> >> "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote: >> >> >> >>> @@ -1551,7 +1551,7 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end) >> >>> key.flags = end; /* overload flags, as it is unsigned long */ >> >>> >> >>> for (pg = ftrace_pages_start; pg; pg = pg->next) { >> >>> - if (end < pg->records[0].ip || >> >>> + if (end <= pg->records[0].ip || >> >> >> >> This breaks the algorithm. "end" is inclusive. That is, if you look for >> >> a single byte, where "start" and "end" are the same, and it happens to >> >> be the first ip on the pg page, it will be skipped, and not found. >> > >> > Thanks. It looks like I should be over-riding ftrace_location() instead. >> > I will update this patch. >> >> I think I will have ftrace own the two instruction range, regardless of >> whether the preceding instruction is a 'mflr r0' or not. This simplifies >> things and I don't see an issue with it as of now. I will do more >> testing to confirm. >> >> - Naveen >> >> >> --- a/arch/powerpc/kernel/trace/ftrace.c >> +++ b/arch/powerpc/kernel/trace/ftrace.c >> @@ -951,6 +951,16 @@ void arch_ftrace_update_code(int command) >> } >> >> #ifdef CONFIG_MPROFILE_KERNEL >> +/* >> + * We consider two instructions -- 'mflr r0', 'bl _mcount' -- to be part >> + * of ftrace. When checking for the first instruction, we want to include >> + * the next instruction in the range check. >> + */ >> +unsigned long ftrace_location(unsigned long ip) >> +{ >> + return ftrace_location_range(ip, ip + MCOUNT_INSN_SIZE); >> +} >> + >> /* Returns 1 if we patched in the mflr */ >> static int __ftrace_make_call_prep(struct dyn_ftrace *rec) >> { >> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c >> index 21d8e201ee80..122e2bb4a739 100644 >> --- a/kernel/trace/ftrace.c >> +++ b/kernel/trace/ftrace.c >> @@ -1573,7 +1573,7 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end) >> * the function tracer. It checks the ftrace internal tables to >> * determine if the address belongs or not. >> */ >> -unsigned long ftrace_location(unsigned long ip) >> +unsigned long __weak ftrace_location(unsigned long ip) >> { >> return ftrace_location_range(ip, ip); >> } > > Actually, instead of making this a weak function, let's do this: > > > In include/ftrace.h: > > #ifndef FTRACE_IP_EXTENSION > # define FTRACE_IP_EXTENSION 0 > #endif > > > In arch/powerpc/include/asm/ftrace.h > > #define FTRACE_IP_EXTENSION MCOUNT_INSN_SIZE > > > Then we can just have: > > unsigned long ftrace_location(unsigned long ip) > { > return ftrace_location_range(ip, ip + FTRACE_IP_EXTENSION); > }
Thanks, that's indeed nice. I hope you don't mind me adding your SOB for that.
- Naveen
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