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| author | Kevin O'Connor <kevin@koconnor.net> | 2014-11-05 09:05:36 -0500 |
|---|---|---|
| committer | Kevin O'Connor <kevin@koconnor.net> | 2014-11-12 12:17:57 -0500 |
| commit | aa66d6539cb11720477f2219a5821a9de1916384 (patch) | |
| tree | 5e0cd3c967b3096142c39bf105a3b34aa1a0dc04 /src/entryfuncs.S | |
| parent | b4eb6fc5cc051e18d07f9483c093c9c32cece2f7 (diff) | |
| download | seabios-aa66d6539cb11720477f2219a5821a9de1916384.tar.gz | |
Use an aligned stack offset when entering on the extra stack
The size of 'struct bregs' is not evenly divisible by four and where
the assembler placed a 'struct bregs' on the extra stack as part of
entering into the C functions it caused the C functions to run with a
non-aligned stack. It's technically not correct to use an unaligned
stack and it is certainly less efficient.
This patch avoids using BREGS_size (the sizeof struct bregs) and
instead introduces PUSHBREGS_size (the size of the general purpose
registers in struct bregs) in the assembler. Where the code actually
did use the %cs:%ip and flags, an extra 8 (instead of 6) bytes are
added to maintain a sane alignment.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
Diffstat (limited to 'src/entryfuncs.S')
| -rw-r--r-- | src/entryfuncs.S | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/src/entryfuncs.S b/src/entryfuncs.S index cc1f4332..7368bb6d 100644 --- a/src/entryfuncs.S +++ b/src/entryfuncs.S @@ -9,6 +9,8 @@ * Macros for save and restore of 'struct bregs' registers ****************************************************************/ +#define PUSHBREGS_size 32 + // Save registers (matches struct bregs) to stack .macro PUSHBREGS pushl %eax |