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On 4/8/19 3:20 PM, Tulio Magno Quites Machado Filho wrote:
That seems good to me.Carlos O'Donell <codonell@redhat.com> writes:On 4/5/19 5:16 AM, Florian Weimer wrote:* Carlos O'Donell:It is valuable that it be a trap, particularly for constant pools because it means that a jump into the constant pool will trap.Sorry, I don't understand why this matters in this context. Would you please elaborate?Sorry, I wasn't very clear. My point is only that any accidental jumps, either with off-by-one (like you fixed in gcc/glibc's signal unwinding most recently), result in a process fault rather than executing RSEQ_SIG as a valid instruction *and then* continuing onwards to the handler. A process fault is achieved either by a trap, or an invalid instruction, or a privileged insn (like suggested for MIPS in this thread).In that case, mtmsr (Move to Machine State Register) seems a good candidate. mtmsr is available both on 32 and 64 bits since their first implementations. It's a privileged instruction and should never appear in userspace code (causes SIGILL). Any comments?
Mathieu, What's required to move this forward for POWER? -- Cheers, Carlos.
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