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elfctl: add knowledge about the la57 bit

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Reviewed by:	markj
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D49913
This commit is contained in:
Konstantin Belousov 2025-04-19 13:47:45 +03:00
parent 7a8440bf08
commit b989c1dd1e
2 changed files with 18 additions and 1 deletions
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14
usr.bin/elfctl/elfctl.1
View file

@ -95,6 +95,20 @@ Features may also be specified as a single combined value:
.Bd -literal -offset indent
elfctl -e =0x5 file
.Ed
.Sh NOTES
On amd64, on a machine with LA57 (5-level paging) mode supported and
enabled, if both
.Va la57
and
.Va la48
feature flags are specified, the
.Va la57
feature has priority over
.Va la48 .
The
.Va vm.pmap.prefer_uva_la48
sysctl MIB defines the default user address space size for binaries
which do not set either of these flags.
.Sh SEE ALSO
.Xr mitigations 7
.Sh HISTORY

5
usr.bin/elfctl/elfctl.c
View file

@ -67,7 +67,10 @@ static struct ControlFeatures featurelist[] = {
"Disable implicit PROT_MAX" },
{ "nostackgap", NT_FREEBSD_FCTL_STKGAP_DISABLE, "Disable stack gap" },
{ "wxneeded", NT_FREEBSD_FCTL_WXNEEDED, "Requires W+X mappings" },
{ "la48", NT_FREEBSD_FCTL_LA48, "amd64: Limit user VA to 48bit" },
{ "la48", NT_FREEBSD_FCTL_LA48,
"amd64: Limit user virtual addresses to 48 bits" },
{ "la57", NT_FREEBSD_FCTL_LA57,
"amd64: Allow the use of 57-bit virtual addresses when available" },
};
static struct option long_opts[] = {