diff options
| author | David S. Miller <davem@davemloft.net> | 2014-10-23 12:58:13 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-10-30 09:40:21 -0700 |
| commit | e81ef812f68862ab4818d34bfab4fdb2edcb242e (patch) | |
| tree | 9c72e8197eb1f1e5dec5007ff55ca96d6f46575a /arch/sparc/kernel/hvtramp.S | |
| parent | 5955d6d11085444fa7a705656b113774f57d910f (diff) | |
sparc64: Fix register corruption in top-most kernel stack frame during boot.
[ Upstream commit ef3e035c3a9b81da8a778bc333d10637acf6c199 ]
Meelis Roos reported that kernels built with gcc-4.9 do not boot, we
eventually narrowed this down to only impacting machines using
UltraSPARC-III and derivitive cpus.
The crash happens right when the first user process is spawned:
[ 54.451346] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004
[ 54.451346]
[ 54.571516] CPU: 1 PID: 1 Comm: init Not tainted 3.16.0-rc2-00211-gd7933ab #96
[ 54.666431] Call Trace:
[ 54.698453] [0000000000762f8c] panic+0xb0/0x224
[ 54.759071] [000000000045cf68] do_exit+0x948/0x960
[ 54.823123] [000000000042cbc0] fault_in_user_windows+0xe0/0x100
[ 54.902036] [0000000000404ad0] __handle_user_windows+0x0/0x10
[ 54.978662] Press Stop-A (L1-A) to return to the boot prom
[ 55.050713] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004
Further investigation showed that compiling only per_cpu_patch() with
an older compiler fixes the boot.
Detailed analysis showed that the function is not being miscompiled by
gcc-4.9, but it is using a different register allocation ordering.
With the gcc-4.9 compiled function, something during the code patching
causes some of the %i* input registers to get corrupted. Perhaps
we have a TLB miss path into the firmware that is deep enough to
cause a register window spill and subsequent restore when we get
back from the TLB miss trap.
Let's plug this up by doing two things:
1) Stop using the firmware stack for client interface calls into
the firmware. Just use the kernel's stack.
2) As soon as we can, call into a new function "start_early_boot()"
to put a one-register-window buffer between the firmware's
deepest stack frame and the top-most initial kernel one.
Reported-by: Meelis Roos <mroos@linux.ee>
Tested-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/sparc/kernel/hvtramp.S')
| -rw-r--r-- | arch/sparc/kernel/hvtramp.S | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/arch/sparc/kernel/hvtramp.S b/arch/sparc/kernel/hvtramp.S index b7ddcdd1dea..cdbfec299f2 100644 --- a/arch/sparc/kernel/hvtramp.S +++ b/arch/sparc/kernel/hvtramp.S @@ -109,7 +109,6 @@ hv_cpu_startup: sllx %g5, THREAD_SHIFT, %g5 sub %g5, (STACKFRAME_SZ + STACK_BIAS), %g5 add %g6, %g5, %sp - mov 0, %fp call init_irqwork_curcpu nop |