Hi Stable Team, On 10/19/20 7:19 PM, Vineet Gupta wrote: > This reverts commit 00fdec98d9881bf5173af09aebd353ab3b9ac729. > (but only from 5.2 and prior kernels) > > The original commit was a preventive fix based on code-review and was > auto-picked for stable back-port (for better or worse). > It was OK for v5.3+ kernels, but turned up needing an implicit change > 68e5c6f073bcf70 "(ARC: entry: EV_Trap expects r10 (vs. r9) to have > exception cause)" merged in v5.3 which itself was not backported. > So to summarize the stable backport of this patch for v5.2 and prior > kernels is busted and it won't boot. > > The obvious solution is backport 68e5c6f073bcf70 but that is a pain as > it doesn't revert cleanly and each of affected kernels (so far v4.19, > v4.14, v4.9, v4.4) needs a slightly different massaged varaint. > So the easier fix is to simply revert the backport from 5.2 and prior. > The issue was not a big deal as it would cause strace to sporadically > not work correctly. > > Waldemar Brodkorb first reported this when running ARC uClibc regressions > on latest stable kernels (with offending backport). Once he bisected it, > the analysis was trivial, so thx to him for this. > > Reported-by: Waldemar Brodkorb <wbx@xxxxxxxxxxxxx> > Bisected-by: Waldemar Brodkorb <wbx@xxxxxxxxxxxxx> > Cc: stable <stable@xxxxxxxxxxxxxxx> # 5.2 and prior > Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx> Can this revert be please applied to 4.19 and older kernels for the next cycle. Or is there is a procedural issue given this revert is not in mainline. I've described the issue in detail above so if there's a better/desirable way of reverting it from backports, please let me know. Thx, > --- > arch/arc/kernel/entry.S | 16 +++++++++++----- > 1 file changed, 11 insertions(+), 5 deletions(-) > > diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S > index ea00c8a17f07..60406ec62eb8 100644 > --- a/arch/arc/kernel/entry.S > +++ b/arch/arc/kernel/entry.S > @@ -165,6 +165,7 @@ END(EV_Extension) > tracesys: > ; save EFA in case tracer wants the PC of traced task > ; using ERET won't work since next-PC has already committed > + lr r12, [efa] > GET_CURR_TASK_FIELD_PTR TASK_THREAD, r11 > st r12, [r11, THREAD_FAULT_ADDR] ; thread.fault_address > > @@ -207,9 +208,15 @@ tracesys_exit: > ; Breakpoint TRAP > ; --------------------------------------------- > trap_with_param: > - mov r0, r12 ; EFA in case ptracer/gdb wants stop_pc > + > + ; stop_pc info by gdb needs this info > + lr r0, [efa] > mov r1, sp > > + ; Now that we have read EFA, it is safe to do "fake" rtie > + ; and get out of CPU exception mode > + FAKE_RET_FROM_EXCPN > + > ; Save callee regs in case gdb wants to have a look > ; SP will grow up by size of CALLEE Reg-File > ; NOTE: clobbers r12 > @@ -236,10 +243,6 @@ ENTRY(EV_Trap) > > EXCEPTION_PROLOGUE > > - lr r12, [efa] > - > - FAKE_RET_FROM_EXCPN > - > ;============ TRAP 1 :breakpoints > ; Check ECR for trap with arg (PROLOGUE ensures r10 has ECR) > bmsk.f 0, r10, 7 > @@ -247,6 +250,9 @@ ENTRY(EV_Trap) > > ;============ TRAP (no param): syscall top level > > + ; First return from Exception to pure K mode (Exception/IRQs renabled) > + FAKE_RET_FROM_EXCPN > + > ; If syscall tracing ongoing, invoke pre-post-hooks > GET_CURR_THR_INFO_FLAGS r10 > btst r10, TIF_SYSCALL_TRACE >
