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SubjectRe: [PATCH v2 0/6] bpf: correct broken uapi for BPF_PROG_TYPE_PERF_EVENT program type
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On 12/05/2017 04:53 PM, Daniel Borkmann wrote:
> On 12/04/2017 10:56 AM, Hendrik Brueckner wrote:
>> Perf tool bpf selftests revealed a broken uapi for s390 and arm64.
>> With the BPF_PROG_TYPE_PERF_EVENT program type the bpf_perf_event
>> structure exports the pt_regs structure for all architectures.
>>
>> This fails for s390 and arm64 because pt_regs are not part of the
>> user api and kept in-kernel only. To mitigate the broken uapi,
>> introduce a wrapper that exports pt_regs in an asm-generic way.
>> For arm64, export the exising user_pt_regs structure. For s390,
>> introduce a user_pt_regs structure that exports the beginning of
>> pt_regs.
>>
>> Note that user_pt_regs must export from the beginning of pt_regs
>> as BPF_PROG_TYPE_PERF_EVENT program type is not the only type for
>> running BPF programs.
>>
>> Some more background:
>> For the bpf_perf_event, there is a uapi definition that is
>> passed to the BPF program. For other "probe" points like
>> trace points, kprobes, and uprobes, there is no uapi and the
>> BPF program is always passed pt_regs (which is OK as the BPF
>> program runs in the kernel context). The perf tool can attach
>> BPF programs to all of these "probe" points and, optionally,
>> can create a BPF prologue to access particular arguments
>> (passed as registers). For this, it uses DWARF/CFI
>> information to obtain the register and calls a perf-arch
>> backend function, regs_query_register_offset(). This function
>> returns the index into (user_)pt_regs for a particular
>> register. Then, perf creates a BPF prologue that accesses
>> this register based on the passed stucture from the "probe"
>> point.
>>
>> Part of this series, are also updates to the testing and bpf selftest
>> to deal with asm-specifics. To complete the bpf support in perf, the
>> the regs_query_register_offset function is added for s390 to support
>> BPF prologue creation.
>>
>> Changelog v1 -> v2:
>> - Correct kbuild test bot issues by including
>> asm-generic/bpf_perf_event.h for archictectures that do not have
>> their own asm version.
>> - Added patch to clean-up whitespace and coding style issues in s390
>> asm/ptrace.h (#4/6) as suggested by Alexei.
>>
>>
>> Hendrik Brueckner (6):
>> bpf: correct broken uapi for BPF_PROG_TYPE_PERF_EVENT program type
>> s390/bpf: correct broken uapi for BPF_PROG_TYPE_PERF_EVENT program
>> type
>> arm64/bpf: correct broken uapi for BPF_PROG_TYPE_PERF_EVENT program
>> type
>> s390/uapi: correct whitespace & coding style in asm/ptrace.h
>> selftests/bpf: sync kernel headers and introduce arch support in
>> Makefile
>> perf s390: add regs_query_register_offset()
>
> Series looks good to me, thanks for working on this Hendrik! If nobody
> hollers, I would take the fixes via bpf tree later tonight.

Done, applied to bpf, thanks Hendrik!

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