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| author | David S. Miller | 2014-10-23 21:58:13 +0200 |
|---|---|---|
| committer | David S. Miller | 2014-10-24 18:52:49 +0200 |
| commit | ef3e035c3a9b81da8a778bc333d10637acf6c199 (patch) | |
| tree | 4659112780d9a0630c5ffd7167405e2c916d9707 /arch/sparc/prom/cif.S | |
| parent | Merge tag 'ntb-3.18' of git://github.com/jonmason/ntb (diff) | |
| download | kernel-qcow2-linux-ef3e035c3a9b81da8a778bc333d10637acf6c199.tar.gz kernel-qcow2-linux-ef3e035c3a9b81da8a778bc333d10637acf6c199.tar.xz kernel-qcow2-linux-ef3e035c3a9b81da8a778bc333d10637acf6c199.zip | |
sparc64: Fix register corruption in top-most kernel stack frame during boot.
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>
Diffstat (limited to 'arch/sparc/prom/cif.S')
| -rw-r--r-- | arch/sparc/prom/cif.S | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/arch/sparc/prom/cif.S b/arch/sparc/prom/cif.S index 9c86b4b7d429..8050f381f518 100644 --- a/arch/sparc/prom/cif.S +++ b/arch/sparc/prom/cif.S @@ -11,11 +11,10 @@ .text .globl prom_cif_direct prom_cif_direct: + save %sp, -192, %sp sethi %hi(p1275buf), %o1 or %o1, %lo(p1275buf), %o1 - ldx [%o1 + 0x0010], %o2 ! prom_cif_stack - save %o2, -192, %sp - ldx [%i1 + 0x0008], %l2 ! prom_cif_handler + ldx [%o1 + 0x0008], %l2 ! prom_cif_handler mov %g4, %l0 mov %g5, %l1 mov %g6, %l3 |