On Fri, Sep 06, 2024 at 04:59:40PM +1000, Michael Ellerman wrote:

Charlie Jenkins [off-list ref] writes:

quoted

Create a personality flag ADDR_LIMIT_47BIT to support applications
that wish to transition from running in environments that support at
most 47-bit VAs to environments that support larger VAs. This
personality can be set to cause all allocations to be below the 47-bit
boundary. Using MAP_FIXED with mmap() will bypass this restriction.

Signed-off-by: Charlie Jenkins <redacted>
---
 include/uapi/linux/personality.h | 1 +
 mm/mmap.c                        | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/include/uapi/linux/personality.h b/include/uapi/linux/personality.h
index 49796b7756af..cd3b8c154d9b 100644
--- a/include/uapi/linux/personality.h
+++ b/include/uapi/linux/personality.h

@@ -22,6 +22,7 @@ enum {
 	WHOLE_SECONDS =		0x2000000,
 	STICKY_TIMEOUTS	=	0x4000000,
 	ADDR_LIMIT_3GB = 	0x8000000,
+	ADDR_LIMIT_47BIT = 	0x10000000,
 };

I wonder if ADDR_LIMIT_128T would be clearer?

I don't follow, what does 128T represent?

Have you looked at writing an update for the personality(2) man page? :)

I will write an update to the man page if this patch is approved!

cheers

- Charlie