Hi Andrew,
Thanks for taking a look.
Andrew Morton akpm@linux-foundation.org writes:
On Wed, 9 Nov 2022 22:11:03 +0000 Punit Agrawal punit.agrawal@bytedance.com wrote:
The proc-empty-vm test is implemented for x86_64 and fails to build for other architectures. Rather then emitting a compiler error it would be preferable to only build the test on supported architectures.
Why does it fail? What would be involved in making it available on other architectures?
The test is written to fail building on architectures other than x86_64.
#ifdef __amd64__ munmap(NULL, ((size_t)1 << 47) - 4096); #else #error "implement 'unmap everything'" #endif
I hit the build failure while semi-automating the running of tests on internal infrastructure.
I am not familiar with the issue being tested but after a bit of staring, it looks like there are two architecture dependent components to the tests -
1. TASK_SIZE / application memory layout - the test unmaps the entire the user virtual address space. For this, it needs to know the length to pass to munmap().
Although it's possible to add this per-architecture, I am not sure if there is a way to discover the length passed to munmap().
2. How the vsyscall page (if implemented) is mapped - this influences the known good values used for comparison in the test.
It doesn't look like vsyscall page is used on arm64 but I am not sure about the situation with other architectures.
(Alexey, please add if I've missed anything)
Thanks, Punit