On Sat, Feb 23, 2019 at 12:07 AM Dave Hansen dave.hansen@intel.com wrote:
On 2/22/19 4:53 AM, Andrey Konovalov wrote:
--- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -578,6 +578,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len, SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, unsigned long, prot) {
start = untagged_addr(start); return do_mprotect_pkey(start, len, prot, -1);}
@@ -586,6 +587,7 @@ SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len, unsigned long, prot, int, pkey) {
start = untagged_addr(start); return do_mprotect_pkey(start, len, prot, pkey);}
This seems to have taken the approach of going as close as possible to the syscall boundary and untagging the pointer there. I guess that's OK, but it does lead to more churn than necessary. For instance, why not just do the untagging in do_mprotect_pkey()?
I think that makes more sense, will do in the next version, thanks!
I think that's an overall design question. I kinda asked the same thing about patching call sites vs. VMA lookup functions.
Replied in the other thread.