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commit 82349a5eb0e1122d5532a03367d91d5ee838722d
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Author: Serhei Makarov <smakarov@redhat.com>
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Date: Fri Mar 1 11:16:32 2019 -0500
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Don't print to /dev/kmsg if it's unavailable
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* stapbpf/stapbpf.cxx (kmsg): initialize to NULL.
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(prog_load): only print to kmsg if it's available.
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(main): warn if kmsg is unavailable.
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diff --git a/stapbpf/stapbpf.cxx b/stapbpf/stapbpf.cxx
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index 188724b..ae97d4b 100644
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--- a/stapbpf/stapbpf.cxx
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+++ b/stapbpf/stapbpf.cxx
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@@ -73,7 +73,7 @@ static int warnings = 1;
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static int exit_phase = 0;
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static int interrupt_message = 0;
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static FILE *output_f = stdout;
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-static FILE *kmsg;
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+static FILE *kmsg = NULL;
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static const char *module_name;
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static const char *module_basename;
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@@ -341,9 +341,12 @@ prog_load(Elf_Data *data, const char *name)
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if (data->d_size % sizeof(bpf_insn))
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fatal("program size not a multiple of %zu\n", sizeof(bpf_insn));
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- fprintf (kmsg, "%s (%s): stapbpf: %s, name: %s, d_size: %lu\n",
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- module_basename, script_name, VERSION, name, (unsigned long)data->d_size);
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- fflush (kmsg); // Otherwise, flush will only happen after the prog runs.
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+ if (kmsg != NULL)
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+ {
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+ fprintf (kmsg, "%s (%s): stapbpf: %s, name: %s, d_size: %lu\n",
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+ module_basename, script_name, VERSION, name, (unsigned long)data->d_size);
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+ fflush (kmsg); // Otherwise, flush will only happen after the prog runs.
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+ }
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int fd = bpf_prog_load(prog_type, static_cast<bpf_insn *>(data->d_buf),
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data->d_size, module_license, kernel_version);
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if (fd < 0)
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@@ -1575,5 +1578,7 @@ main(int argc, char **argv)
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- kmsg = fopen("/dev/kmsg", "a");
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+ kmsg = fopen("/dev/kmsg", "w");
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+ if (kmsg == NULL)
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+ fprintf(stderr, "WARNING: could not open /dev/kmsg for diagnostics: %s\n", strerror(errno));
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load_bpf_file(argv[optind]);
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init_internal_globals();
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