| Message ID | 20201218192957.11035-3-rearnsha@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | Memory tagging support | expand |
On 12/19/20 12:59 AM, Richard Earnshaw via Libc-alpha wrote: > > Add a new glibc tunable: mem.tagging. This is a decimal constant in > the range 0-255 but used as a bit-field. > > Bit 0 enables use of tagged memory in the malloc family of functions. > Bit 1 enables precise faulting of tag failure on platforms where this > can be controlled. > Other bits are currently unused, but if set will cause memory tag > checking for the current process to be enabled in the kernel. > --- > elf/dl-tunables.list | 9 +++++++++ > manual/tunables.texi | 35 +++++++++++++++++++++++++++++++++++ > 2 files changed, 44 insertions(+) > > diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list > index e1d8225128..4c44ead715 100644 > --- a/elf/dl-tunables.list > +++ b/elf/dl-tunables.list > @@ -141,4 +141,13 @@ glibc { > default: 512 > } > } > + > + mem { > + tagging { > + type: INT_32 > + minval: 0 > + maxval: 255 > + security_level: SXID_IGNORE > + } > + } > } OK. > diff --git a/manual/tunables.texi b/manual/tunables.texi > index d72d7a5ec0..1bbdc88281 100644 > --- a/manual/tunables.texi > +++ b/manual/tunables.texi > @@ -36,6 +36,8 @@ their own namespace. > * POSIX Thread Tunables:: Tunables in the POSIX thread subsystem > * Hardware Capability Tunables:: Tunables that modify the hardware > capabilities seen by @theglibc{} > +* Memory Related Tunables:: Tunables that control the use of memory by > + @theglibc{}. > @end menu > > @node Tunable names > @@ -484,3 +486,36 @@ instead. > > This tunable is specific to i386 and x86-64. > @end deftp > + > +@node Memory Related Tunables > +@section Memory Related Tunables > +@cindex memory related tunables > + > +@deftp {Tunable namespace} glibc.mem > +This tunable namespace supports operations that affect the way @theglibc{} > +and the process manage memory. > +@end deftp > + That's a good description. > +@deftp Tunable glibc.mem.tagging > +If the hardware supports memory tagging, this tunable can be used to > +control the way @theglibc{} uses this feature. At present this is only > +supported on AArch64 systems with the MTE extention; it is ignored for > +all other systems. > + > +This tunable takes a value between 0 and 255 and acts as a bitmask > +that enables various capabilities. > + > +Bit 0 (the least significant bit) causes the malloc subsystem to allocate > +tagged memory, with each allocation being assigned a random tag. > + > +Bit 1 enables precise faulting mode for tag violations on systems that > +support deferred tag violation reporting. This may cause programs > +to run more slowly. > + > +Other bits are currently reserved. > + > +@Theglibc{} startup code will automatically enable memory tagging > +support in the kernel if this tunable has any non-zero value. > + > +The default value is @samp{0}, which disables all memory tagging. > +@end deftp Looks good to me. Siddhesh
diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list index e1d8225128..4c44ead715 100644 --- a/elf/dl-tunables.list +++ b/elf/dl-tunables.list @@ -141,4 +141,13 @@ glibc { default: 512 } } + + mem { + tagging { + type: INT_32 + minval: 0 + maxval: 255 + security_level: SXID_IGNORE + } + } } diff --git a/manual/tunables.texi b/manual/tunables.texi index d72d7a5ec0..1bbdc88281 100644 --- a/manual/tunables.texi +++ b/manual/tunables.texi @@ -36,6 +36,8 @@ their own namespace. * POSIX Thread Tunables:: Tunables in the POSIX thread subsystem * Hardware Capability Tunables:: Tunables that modify the hardware capabilities seen by @theglibc{} +* Memory Related Tunables:: Tunables that control the use of memory by + @theglibc{}. @end menu @node Tunable names @@ -484,3 +486,36 @@ instead. This tunable is specific to i386 and x86-64. @end deftp + +@node Memory Related Tunables +@section Memory Related Tunables +@cindex memory related tunables + +@deftp {Tunable namespace} glibc.mem +This tunable namespace supports operations that affect the way @theglibc{} +and the process manage memory. +@end deftp + +@deftp Tunable glibc.mem.tagging +If the hardware supports memory tagging, this tunable can be used to +control the way @theglibc{} uses this feature. At present this is only +supported on AArch64 systems with the MTE extention; it is ignored for +all other systems. + +This tunable takes a value between 0 and 255 and acts as a bitmask +that enables various capabilities. + +Bit 0 (the least significant bit) causes the malloc subsystem to allocate +tagged memory, with each allocation being assigned a random tag. + +Bit 1 enables precise faulting mode for tag violations on systems that +support deferred tag violation reporting. This may cause programs +to run more slowly. + +Other bits are currently reserved. + +@Theglibc{} startup code will automatically enable memory tagging +support in the kernel if this tunable has any non-zero value. + +The default value is @samp{0}, which disables all memory tagging. +@end deftp