Port of JEP 386: Alpine Linux Port to jdk8u

[Andrew Haley]

On 4/28/22 18:16, Stephanie Crater wrote:
> Would the community be open to a port of JEP 386: Alpine Linux Port [1]/JDK-8247589 [2] to OpenJDK jdk8u? A backport of JDK-8247589 to 11u has recently been integrated by BellSoft, and many OpenJDK vendors (BellSoft Liberica, Azul Zulu, Amazon Corretto) provide a jdk8 for Alpine Linux. We believe there is sufficient user demand for Alpine/musl support on jdk8u, but would be interested in the opinions of other vendors on this as well.

In principle, yes. I don't much like the actual patch, which sprinkles
changes like

#ifndef MUSL_LIBC
#include <sys/poll.h>
#else
#include <poll.h>
#endif

and (Yuck! Could they really not have factored this in a better way?)

+#ifndef MUSL_LIBC
    st->print("pc =" INTPTR_FORMAT "  ", uc->uc_mcontext.regs->nip);
    st->print("lr =" INTPTR_FORMAT "  ", uc->uc_mcontext.regs->link);
    st->print("ctr=" INTPTR_FORMAT "  ", uc->uc_mcontext.regs->ctr);
@@ -576,6 +604,16 @@ void os::print_context(outputStream *st, void *context) {
      st->print("r%-2d=" INTPTR_FORMAT "  ", i, uc->uc_mcontext.regs->gpr[i]);
      if (i % 3 == 2) st->cr();
    }
+#else // Musl
+  st->print("pc =" INTPTR_FORMAT "  ", uc->uc_mcontext.gp_regs[PT_NIP]);
+  st->print("lr =" INTPTR_FORMAT "  ", uc->uc_mcontext.gp_regs[PT_LNK]);
+  st->print("ctr=" INTPTR_FORMAT "  ", uc->uc_mcontext.gp_regs[PT_CTR]);
+  st->cr();
+  for (int i = 0; i < 32; i++) {
+    st->print("r%-2d=" INTPTR_FORMAT "  ", i, uc->uc_mcontext.gp_regs[i]);
+    if (i % 3 == 2) st->cr();
+  }

in many places, but I have to admit that none of it looks very risky.
My concern is more to do with maintainability, with #ifndef MUSL_LIBC
occurring 25 times in the patch. But we're supposed to change patches
as little as possible when backporting.

-- 
Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
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