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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>
57 lines
1.3 KiB
C
57 lines
1.3 KiB
C
/*
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* init.c: Initialize internal variables used by the PROM
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* library functions.
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*
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* Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
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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/init.h>
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#include <linux/string.h>
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#include <linux/ctype.h>
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#include <asm/openprom.h>
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#include <asm/oplib.h>
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/* OBP version string. */
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char prom_version[80];
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/* The root node of the prom device tree. */
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int prom_stdout;
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phandle prom_chosen_node;
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/* You must call prom_init() before you attempt to use any of the
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* routines in the prom library.
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* It gets passed the pointer to the PROM vector.
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*/
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extern void prom_cif_init(void *);
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void __init prom_init(void *cif_handler)
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{
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phandle node;
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prom_cif_init(cif_handler);
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prom_chosen_node = prom_finddevice(prom_chosen_path);
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if (!prom_chosen_node || (s32)prom_chosen_node == -1)
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prom_halt();
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prom_stdout = prom_getint(prom_chosen_node, "stdout");
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node = prom_finddevice("/openprom");
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if (!node || (s32)node == -1)
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prom_halt();
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prom_getstring(node, "version", prom_version, sizeof(prom_version));
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prom_printf("\n");
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}
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void __init prom_init_report(void)
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{
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printk("PROMLIB: Sun IEEE Boot Prom '%s'\n", prom_version);
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printk("PROMLIB: Root node compatible: %s\n", prom_root_compatible);
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}
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