What restriction is perf_event_paranoid == 1 actually putting on x86 perf?

In this case CPU event refers to monitoring events per CPU rather than per task. For perf tools this restricts the usage of -C, –cpu= Count only on the list of CPUs provided. Multiple CPUs can be provided as a comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0-2. In … Read more

What’s the purpose of the UD2 opcode in the Linux kernel?

It’s the BUG() macro from include/asm-i386/bug.h. /* * Tell the user there is some problem. * The offending file and line are encoded after the “officially * undefined” opcode for parsing in the trap handler. */ #ifdef CONFIG_DEBUG_BUGVERBOSE #define BUG() \ __asm__ __volatile__( “ud2\n” \ “\t.word %c0\n” \ “\t.long %c1\n” \ : : “i” (__LINE__), … Read more

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