| Message ID | 1391579584-412-1-git-send-email-nathan_lynch@mentor.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Feb 05, 2014 at 05:53:04AM +0000, Nathan Lynch wrote: > When __kernel_clock_gettime is called with a CLOCK_MONOTONIC_COARSE or > CLOCK_REALTIME_COARSE clock id, it returns incorrectly to whatever the > caller has placed in x2 ("ret x2" to return from the fast path). Fix > this by saving x30/LR to x2 only in code that will call > __do_get_tspec, restoring x30 afterward, and using a plain "ret" to > return from the routine. > > Also: while the resulting tv_nsec value for CLOCK_REALTIME and > CLOCK_MONOTONIC must be computed using intermediate values that are > left-shifted by cs_shift (x12, set by __do_get_tspec), the results for > coarse clocks should be calculated using unshifted values > (xtime_coarse_nsec is in units of actual nanoseconds). The current > code shifts intermediate values by x12 unconditionally, but x12 is > uninitialized when servicing a coarse clock. Fix this by setting x12 > to 0 once we know we are dealing with a coarse clock id. > > Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> > --- Thanks for the quick update Nathan! Acked-by: Will Deacon <will.deacon@arm.com> Catalin: both of these are candidates for stable. Will
On Wed, Feb 05, 2014 at 10:09:45AM +0000, Will Deacon wrote: > On Wed, Feb 05, 2014 at 05:53:04AM +0000, Nathan Lynch wrote: > > When __kernel_clock_gettime is called with a CLOCK_MONOTONIC_COARSE or > > CLOCK_REALTIME_COARSE clock id, it returns incorrectly to whatever the > > caller has placed in x2 ("ret x2" to return from the fast path). Fix > > this by saving x30/LR to x2 only in code that will call > > __do_get_tspec, restoring x30 afterward, and using a plain "ret" to > > return from the routine. > > > > Also: while the resulting tv_nsec value for CLOCK_REALTIME and > > CLOCK_MONOTONIC must be computed using intermediate values that are > > left-shifted by cs_shift (x12, set by __do_get_tspec), the results for > > coarse clocks should be calculated using unshifted values > > (xtime_coarse_nsec is in units of actual nanoseconds). The current > > code shifts intermediate values by x12 unconditionally, but x12 is > > uninitialized when servicing a coarse clock. Fix this by setting x12 > > to 0 once we know we are dealing with a coarse clock id. > > > > Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> > > --- > > Thanks for the quick update Nathan! > > Acked-by: Will Deacon <will.deacon@arm.com> > > Catalin: both of these are candidates for stable. And by this you mean Cc: stable... Applied, thanks.
diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S index f0a6d10b5211..fe652ffd34c2 100644 --- a/arch/arm64/kernel/vdso/gettimeofday.S +++ b/arch/arm64/kernel/vdso/gettimeofday.S @@ -103,6 +103,8 @@ ENTRY(__kernel_clock_gettime) bl __do_get_tspec seqcnt_check w9, 1b + mov x30, x2 + cmp w0, #CLOCK_MONOTONIC b.ne 6f @@ -118,6 +120,9 @@ ENTRY(__kernel_clock_gettime) ccmp w0, #CLOCK_MONOTONIC_COARSE, #0x4, ne b.ne 8f + /* xtime_coarse_nsec is already right-shifted */ + mov x12, #0 + /* Get coarse timespec. */ adr vdso_data, _vdso_data 3: seqcnt_acquire @@ -156,7 +161,7 @@ ENTRY(__kernel_clock_gettime) lsr x11, x11, x12 stp x10, x11, [x1, #TSPEC_TV_SEC] mov x0, xzr - ret x2 + ret 7: mov x30, x2 8: /* Syscall fallback. */
When __kernel_clock_gettime is called with a CLOCK_MONOTONIC_COARSE or CLOCK_REALTIME_COARSE clock id, it returns incorrectly to whatever the caller has placed in x2 ("ret x2" to return from the fast path). Fix this by saving x30/LR to x2 only in code that will call __do_get_tspec, restoring x30 afterward, and using a plain "ret" to return from the routine. Also: while the resulting tv_nsec value for CLOCK_REALTIME and CLOCK_MONOTONIC must be computed using intermediate values that are left-shifted by cs_shift (x12, set by __do_get_tspec), the results for coarse clocks should be calculated using unshifted values (xtime_coarse_nsec is in units of actual nanoseconds). The current code shifts intermediate values by x12 unconditionally, but x12 is uninitialized when servicing a coarse clock. Fix this by setting x12 to 0 once we know we are dealing with a coarse clock id. Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> --- Changes from v1: - Save x30/lr only when branching to __do_get_tspec, and restore it afterward. Use plain "ret" to return instead of "ret x2". - Better explanation for setting x12 (shift) to zero. arch/arm64/kernel/vdso/gettimeofday.S | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)