diff options
| author | Vadim Bendebury <vbendeb@chromium.org> | 2014-10-03 09:47:13 -0700 |
|---|---|---|
| committer | Stefan Reinauer <stefan.reinauer@coreboot.org> | 2015-04-02 21:43:16 +0200 |
| commit | b92e54333f75baa86bcda67b1beeb19669250f03 (patch) | |
| tree | ca46bc4a15fa17728bb9cae5638bf60d8b6d7a45 /src | |
| parent | 3e9ea16c54dfe9ac593f772e5ba2f020b2e27c99 (diff) | |
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')
| -rw-r--r-- | src/arch/mips/bootblock.S | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/src/arch/mips/bootblock.S b/src/arch/mips/bootblock.S index dbde803b14..f369e006fa 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. */ |