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MIPS: Avoid potential hazard on Context register

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set_saved_sp reads Context register. Avoid reading stale value from
earlier incomplete write.

Issue found and fixed for head.S by Chris Dearman <chris@mips.com>.

Signed-off-by: Chris Dearman <chris@mips.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Ralf Baechle 2009-10-13 23:23:28 +02:00
parent cd847b7857
commit c2ea1d56ea
2 changed files with 4 additions and 0 deletions
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3
arch/mips/include/asm/mmu_context.h
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@ -16,6 +16,7 @@
#include <linux/smp.h>
#include <linux/slab.h>
#include <asm/cacheflush.h>
#include <asm/hazards.h>
#include <asm/tlbflush.h>
#ifdef CONFIG_MIPS_MT_SMTC
#include <asm/mipsmtregs.h>
@ -36,11 +37,13 @@ extern unsigned long pgd_current[];
#ifdef CONFIG_32BIT
#define TLBMISS_HANDLER_SETUP() \
write_c0_context((unsigned long) smp_processor_id() << 25); \
back_to_back_c0_hazard(); \
TLBMISS_HANDLER_SETUP_PGD(swapper_pg_dir)
#endif
#ifdef CONFIG_64BIT
#define TLBMISS_HANDLER_SETUP() \
write_c0_context((unsigned long) smp_processor_id() << 26); \
back_to_back_c0_hazard(); \
TLBMISS_HANDLER_SETUP_PGD(swapper_pg_dir)
#endif

1
arch/mips/kernel/head.S
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@ -191,6 +191,7 @@ NESTED(kernel_entry, 16, sp) # kernel entry point
/* Set the SP after an empty pt_regs. */
PTR_LI sp, _THREAD_SIZE - 32 - PT_SIZE
PTR_ADDU sp, $28
back_to_back_c0_hazard
set_saved_sp sp, t0, t1
PTR_SUBU sp, 4 * SZREG # init stack pointer