Re: [PATCH] mips: vdso: conditionalize 32-bit time functions on COMPAT_32BIT_TIME

From: Jason A. Donenfeld
Date: Mon Dec 30 2019 - 10:58:34 EST


Makes sense w.r.t. time32 situation.

I still think that in spite of that there's still something weird
happening with the mips VDSO.

Here's a register dump before the call:

$ 0 : 0000000000000000 0000000000000001 0000000010000000 fffffffffffffffc
$ 4 : 0000000000000002 000000007fff2e40 0000000000000000 0000000000000001
$ 8 : 0000000000000000 0000000000000000 0000000000000000 0000000000000000
$12 : 0000000000000000 000000000000000a ffffffff80000000 000000007fffffda
$16 : 0000000010001ba8 0000005800000015 0000000010000000 0000000010000000
$20 : 0000000010000000 0000000010000000 0000000000000000 0000000077ff2ae8
$24 : 0000000000000005 0000000077fa1d18
$28 : 0000000010019cf0 000000007fff2e40 0000000000000000 0000000010000c30
Hi : 0000000000000000
Lo : 0000000000000000
epc : 0000000077fa1d18 0x77fa1d18
ra : 0000000010000c30 0x10000c30

And here it is immediately after:

$ 0 : 0000000000000000 0000000000000001 ffffffffffffffa7 000000007fff5000
$ 4 : 0000000000000002 000000007fff2e40 0000000077ff2000 0000000000000001
$ 8 : 0000000000000006 0000000000000020 0000000000000002 0000000000000000
$12 : 0000000000000000 0000000000001852 ffffffff80156160 000000007fffffda
$16 : 0000000010001ba8 0000005800000015 0000000010000000 0000000010000000
$20 : 0000000010000000 0000000010000000 0000000000000000 0000000077ff2b00
$24 : 0000000000000005 0000000000000000
$28 : 000000007fff5000 000000007fff2e30 0000000000000000 0000000077fa1e00
Hi : 0000000000000000
Lo : 0000000000000000
epc : 0000000077fa1e00 0x77fa1e00
ra : 0000000077fa1e00 0x77fa1e00

I wonder if a toolchain option or compiler bug or something is causing
the vdso to not restore certain registers (gp? ra?).