Messages in this thread Patch in this message | | | Date | Tue, 18 Jun 2019 23:53:11 +0530 | From | "Naveen N. Rao" <> | Subject | Re: [PATCH 5/7] powerpc/ftrace: Update ftrace_location() for powerpc -mprofile-kernel |
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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); }
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