forked from Minki/linux
ef3e035c3a
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>
55 lines
1.1 KiB
C
55 lines
1.1 KiB
C
/*
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* p1275.c: Sun IEEE 1275 PROM low level interface routines
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*
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* Copyright (C) 1996,1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
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*/
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/smp.h>
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#include <linux/string.h>
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#include <linux/spinlock.h>
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#include <linux/irqflags.h>
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#include <asm/openprom.h>
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#include <asm/oplib.h>
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#include <asm/spitfire.h>
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#include <asm/pstate.h>
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#include <asm/ldc.h>
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struct {
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long prom_callback; /* 0x00 */
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void (*prom_cif_handler)(long *); /* 0x08 */
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} p1275buf;
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extern void prom_world(int);
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extern void prom_cif_direct(unsigned long *args);
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extern void prom_cif_callback(void);
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/*
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* This provides SMP safety on the p1275buf.
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*/
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DEFINE_RAW_SPINLOCK(prom_entry_lock);
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void p1275_cmd_direct(unsigned long *args)
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{
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unsigned long flags;
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local_save_flags(flags);
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local_irq_restore((unsigned long)PIL_NMI);
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raw_spin_lock(&prom_entry_lock);
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prom_world(1);
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prom_cif_direct(args);
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prom_world(0);
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raw_spin_unlock(&prom_entry_lock);
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local_irq_restore(flags);
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}
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void prom_cif_init(void *cif_handler, void *cif_stack)
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{
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p1275buf.prom_cif_handler = (void (*)(long *))cif_handler;
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}
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