RFR: 8367485: os::physical_memory is broken in 32-bit JVMs when running on 64-bit OSes [v9]

[Anton Artemov]

> Hi, please consider the following changes:
> 
> In this PR we address the overflow issue in `os::physical_memory()` on Linux, which can occur when running a 32-bit JVM on a 64-bit machine, introduced by https://bugs.openjdk.org/browse/JDK-8357086. The problem is that the product of _SC_PHYS_PAGES and _SC_PAGESIZE can overflow according to the documentation. 
> 
> The issue is addressed by changing the output type of all related functions to `uint64_t`.
> 
> Tested in tiers 1 - 5.

Anton Artemov has updated the pull request incrementally with one additional commit since the last revision:

  8367485: Alignment of vars in os_windows.cpp

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/27335/files
  - new: https://git.openjdk.org/jdk/pull/27335/files/23f62526..791faaeb

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27335&range=08
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27335&range=07-08

  Stats: 7 lines in 1 file changed: 0 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/27335.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27335/head:pull/27335

PR: https://git.openjdk.org/jdk/pull/27335