Gianluca Borello a60dd35d2e bpf: change bpf_perf_event_output arg5 type to ARG_CONST_SIZE_OR_ZERO ... Commit 9fd29c08e5 ("bpf: improve verifier ARG_CONST_SIZE_OR_ZERO semantics") relaxed the treatment of ARG_CONST_SIZE_OR_ZERO due to the way the compiler generates optimized BPF code when checking boundaries of an argument from C code. A typical example of this optimized code can be generated using the bpf_perf_event_output helper when operating on variable memory: /* len is a generic scalar */ if (len > 0 && len <= 0x7fff) bpf_perf_event_output(ctx, &perf_map, 0, buf, len); 110: (79) r5 = *(u64 *)(r10 -40) 111: (bf) r1 = r5 112: (07) r1 += -1 113: (25) if r1 > 0x7ffe goto pc+6 114: (bf) r1 = r6 115: (18) r2 = 0xffff94e5f166c200 117: (b7) r3 = 0 118: (bf) r4 = r7 119: (85) call bpf_perf_event_output#25 R5 min value is negative, either use unsigned or 'var &= const' With this code, the verifier loses track of the variable. Replacing arg5 with ARG_CONST_SIZE_OR_ZERO is thus desirable since it avoids this quite common case which leads to usability issues, and the compiler generates code that the verifier can more easily test: if (len <= 0x7fff) bpf_perf_event_output(ctx, &perf_map, 0, buf, len); or bpf_perf_event_output(ctx, &perf_map, 0, buf, len & 0x7fff); No changes to the bpf_perf_event_output helper are necessary since it can handle a case where size is 0, and an empty frame is pushed. Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: Gianluca Borello <g.borello@gmail.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>		2017-11-22 21:40:54 +01:00
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blktrace.c
bpf_trace.c
ftrace.c
Kconfig
Makefile
power-traces.c
ring_buffer_benchmark.c
ring_buffer.c
rpm-traces.c
trace_benchmark.c
trace_benchmark.h
trace_branch.c
trace_clock.c
trace_entries.h
trace_event_perf.c
trace_events_filter_test.h
trace_events_filter.c
trace_events_hist.c
trace_events_trigger.c
trace_events.c
trace_export.c
trace_functions_graph.c
trace_functions.c
trace_hwlat.c
trace_irqsoff.c
trace_kdb.c
trace_kprobe.c
trace_mmiotrace.c
trace_nop.c
trace_output.c
trace_output.h
trace_printk.c
trace_probe.c
trace_probe.h
trace_sched_switch.c
trace_sched_wakeup.c
trace_selftest_dynamic.c
trace_selftest.c
trace_seq.c
trace_stack.c
trace_stat.c
trace_stat.h
trace_syscalls.c
trace_uprobe.c
trace.c
trace.h
tracing_map.c
tracing_map.h