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[PATCH] MIPS: Calculate proper ebase value for 64-bit kernels

Subject: [PATCH] MIPS: Calculate proper ebase value for 64-bit kernels
From: David Daney <>
Date: Tue, 6 Apr 2010 13:29:50 -0700
Cc: David Daney <>
Original-recipient: rfc822;
The ebase is relative to CKSEG0 not CAC_BASE.  On a 32-bit kernel they
are the same thing, for a 64-bit kernel they are not.

It happens to kind of work on a 64-bit kernel as they both reference
the same physical memory.  However since the CPU uses the CKSEG0 base,
determining if a J instruction will reach always gives the wrong
result unless we use the same number the CPU uses.

Signed-off-by: David Daney <>
 arch/mips/kernel/traps.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 7ce84bb..b122f76 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -1706,7 +1706,7 @@ void __init trap_init(void)
                ebase = (unsigned long)
                        __alloc_bootmem(size, 1 << fls(size), 0);
        } else {
-               ebase = CAC_BASE;
+               ebase = CKSEG0;
                if (cpu_has_mips_r2)
                        ebase += (read_c0_ebase() & 0x3ffff000);

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