On 17/06/2019 14:56, Catalin Marinas wrote: > On Wed, Jun 12, 2019 at 01:43:20PM +0200, Andrey Konovalov wrote: >> From: Catalin Marinas <catalin.marinas@xxxxxxx> >> >> It is not desirable to relax the ABI to allow tagged user addresses into >> the kernel indiscriminately. This patch introduces a prctl() interface >> for enabling or disabling the tagged ABI with a global sysctl control >> for preventing applications from enabling the relaxed ABI (meant for >> testing user-space prctl() return error checking without reconfiguring >> the kernel). The ABI properties are inherited by threads of the same >> application and fork()'ed children but cleared on execve(). >> >> The PR_SET_TAGGED_ADDR_CTRL will be expanded in the future to handle >> MTE-specific settings like imprecise vs precise exceptions. >> >> Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> > > A question for the user-space folk: if an application opts in to this > ABI, would you want the sigcontext.fault_address and/or siginfo.si_addr > to contain the tag? We currently clear it early in the arm64 entry.S but > we could find a way to pass it down if needed. to me it makes sense to keep the tag in si_addr / fault_address. but i don't know in detail how those fields are used currently. keeping the tag is certainly useful for MTE to debug wrong tag failures unless there is a separate mechanism for that.
