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authorVadim Bendebury <vbendeb@chromium.org>2014-10-03 09:47:13 -0700
committerStefan Reinauer <stefan.reinauer@coreboot.org>2015-04-02 21:43:16 +0200
commitb92e54333f75baa86bcda67b1beeb19669250f03 (patch)
treeca46bc4a15fa17728bb9cae5638bf60d8b6d7a45 /src/arch/mips/bootblock.S
parent3e9ea16c54dfe9ac593f772e5ba2f020b2e27c99 (diff)
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mips: do not place branch instructions in branch delay slot
A branch instruction in a branch delay slot confuses the execution pipeline and causes an exception. bootblock.S was written 'by hand', has a branch instruction in branch delay slot and includes '.set noreorder' directive, which causes it to crash when trying to branch to main(). Adding a nop instruction fixes the problem. Also adding a nop after the last branch in the file just in case main() returns and the object linked next starts with a branch. BUG=chrome-os-partner:31438 TEST=Running on the simulator can reach main() now Change-Id: I0882b2eb5ce426f5a311018ffbb6f37a2ca64d98 Signed-off-by: Vadim Bendebury <vbendeb@chromium.org> Reviewed-on: https://chromium-review.googlesource.com/221421 Reviewed-by: Aaron Durbin <adurbin@chromium.org> Reviewed-on: http://review.coreboot.org/9183 Reviewed-by: Ronald G. Minnich <rminnich@gmail.com> Tested-by: build bot (Jenkins)
Diffstat (limited to 'src/arch/mips/bootblock.S')
-rw-r--r--src/arch/mips/bootblock.S8
1 files changed, 6 insertions, 2 deletions
diff --git a/src/arch/mips/bootblock.S b/src/arch/mips/bootblock.S
index dbde803b1..f369e006f 100644
--- a/src/arch/mips/bootblock.S
+++ b/src/arch/mips/bootblock.S
@@ -39,6 +39,10 @@ _start:
/* Run main */
b main
- /* Should never return from main. */
-2:
+ /*
+ * Should never return from main. Make sure there is no branch in the
+ * branch delay slot.
+ */
+2: nop
b 2b
+ nop /* Make sure there is no branch after this either. */