path: root/arch/sparc/kernel/head_64.S
diff options
authorDavid S. Miller <davem@davemloft.net>2014-10-23 12:58:13 -0700
committerDavid S. Miller <davem@davemloft.net>2014-10-24 09:52:49 -0700
commitef3e035c3a9b81da8a778bc333d10637acf6c199 (patch)
tree4659112780d9a0630c5ffd7167405e2c916d9707 /arch/sparc/kernel/head_64.S
parentMerge tag 'ntb-3.18' of git://github.com/jonmason/ntb (diff)
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/kernel/head_64.S')
1 files changed, 4 insertions, 36 deletions
diff --git a/arch/sparc/kernel/head_64.S b/arch/sparc/kernel/head_64.S
index 4fdeb8040d4d..3d61fcae7ee3 100644
--- a/arch/sparc/kernel/head_64.S
+++ b/arch/sparc/kernel/head_64.S
@@ -672,14 +672,12 @@ tlb_fixup_done:
sethi %hi(init_thread_union), %g6
or %g6, %lo(init_thread_union), %g6
ldx [%g6 + TI_TASK], %g4
- mov %sp, %l6
wr %g0, ASI_P, %asi
mov 1, %g1
sllx %g1, THREAD_SHIFT, %g1
sub %g1, (STACKFRAME_SZ + STACK_BIAS), %g1
add %g6, %g1, %sp
- mov 0, %fp
/* Set per-cpu pointer initially to zero, this makes
* the boot-cpu use the in-kernel-image per-cpu areas
@@ -706,44 +704,14 @@ tlb_fixup_done:
- mov %l6, %o1 ! OpenPROM stack
call prom_init
mov %l7, %o0 ! OpenPROM cif handler
- /* Initialize current_thread_info()->cpu as early as possible.
- * In order to do that accurately we have to patch up the get_cpuid()
- * assembler sequences. And that, in turn, requires that we know
- * if we are on a Starfire box or not. While we're here, patch up
- * the sun4v sequences as well.
+ /* To create a one-register-window buffer between the kernel's
+ * initial stack and the last stack frame we use from the firmware,
+ * do the rest of the boot from a C helper function.
- call check_if_starfire
- nop
- call per_cpu_patch
- nop
- call sun4v_patch
- nop
-#ifdef CONFIG_SMP
- call hard_smp_processor_id
- nop
- cmp %o0, NR_CPUS
- blu,pt %xcc, 1f
- nop
- call boot_cpu_id_too_large
- nop
- /* Not reached... */
- mov 0, %o0
- sth %o0, [%g6 + TI_CPU]
- call prom_init_report
- nop
- /* Off we go.... */
- call start_kernel
+ call start_early_boot
/* Not reached... */