RFR: 8284273: Early crashes in os::print_context on AArch64

[Andrew Haley]

On Mon, 16 May 2022 21:58:56 GMT, Gerard Ziemski <gziemski at openjdk.org> wrote:

> Here, we are concerned with two particular steps: "printing register info" and "printing registers, top of stack, instructions near pc". In those two steps we report 4 distinct chunks of info:
> 
>     1. registers' raw values (safe)
> 
>     2. registers' decoded content (risky)
> 
>     3. memory around the "sp" (risky)
> 
>     4. memory around the "pc" (risky)
> 
> 
> The issue here is that on some platforms (Linux aarch64) a single "step" contains 2, 3 and 4, all "risky" sections, so if we crash early in the step, we skip the rest of it and end up never reporting the later sections, ex:

I like this, but I'm curious about something. Couldn't we use `Safefetch` to handle the risky sections? Then we could carry on printing.

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PR: https://git.openjdk.java.net/jdk/pull/8736