On Tue, Jan 30, 2024 at 05:04:55PM -0500, Stefan O'Rear wrote: > On Mon, Jan 29, 2024, at 9:13 PM, Charlie Jenkins wrote: > > On Mon, Jan 29, 2024 at 09:04:50PM -0500, Stefan O'Rear wrote: > >> On Mon, Jan 29, 2024, at 7:36 PM, Charlie Jenkins wrote: > >> > On riscv, mmap currently returns an address from the largest address > >> > space that can fit entirely inside of the hint address. This makes it > >> > such that the hint address is almost never returned. This patch raises > >> > the mappable area up to and including the hint address. This allows mmap > >> > to often return the hint address, which allows a performance improvement > >> > over searching for a valid address as well as making the behavior more > >> > similar to other architectures. > >> > >> This means that if an application or library opts in to Sv48 support by > >> passing a nonzero hint, it will lose the benefits of ASLR. > > > > sv48 is default. However your statement stands for opting into sv57. > > If they always pass the same hint address, only the first address will > > be deterministic though, correct? > > I think this is correct. > > >> > >> Allowing applications to opt in to a VA space smaller than the > >> architectural minimum seems like an independently useful feature. > >> Is there a reason to only add it for riscv64? > >> > > > > If there is interest, it can be added to other architectures as well. > > I meant as opposed to riscv32. That is a good point. I can include rv32 as well. - Charlie > > -s > > > - Charlie > > > >> -s > >> > >> > Signed-off-by: Charlie Jenkins <charlie@xxxxxxxxxxxx> > >> > --- > >> > Charlie Jenkins (3): > >> > riscv: mm: Use hint address in mmap if available > >> > selftests: riscv: Generalize mm selftests > >> > docs: riscv: Define behavior of mmap > >> > > >> > Documentation/arch/riscv/vm-layout.rst | 16 ++-- > >> > arch/riscv/include/asm/processor.h | 21 ++---- > >> > tools/testing/selftests/riscv/mm/mmap_bottomup.c | 20 +---- > >> > tools/testing/selftests/riscv/mm/mmap_default.c | 20 +---- > >> > tools/testing/selftests/riscv/mm/mmap_test.h | 93 +++++++++++++----------- > >> > 5 files changed, 66 insertions(+), 104 deletions(-) > >> > --- > >> > base-commit: 556e2d17cae620d549c5474b1ece053430cd50bc > >> > change-id: 20240119-use_mmap_hint_address-f9f4b1b6f5f1 > >> > -- > >> > - Charlie > >> > > >> > > >> > _______________________________________________ > >> > linux-riscv mailing list > >> > linux-riscv@xxxxxxxxxxxxxxxxxxx > >> > http://lists.infradead.org/mailman/listinfo/linux-riscv > > > > _______________________________________________ > > linux-riscv mailing list > > linux-riscv@xxxxxxxxxxxxxxxxxxx > > http://lists.infradead.org/mailman/listinfo/linux-riscv
