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>

1 files changed, 0 insertions, 1 deletions

diff --git a/src/asm-offsets.c b/src/asm-offsets.c
index 576bf343..b98f3b5a 100644
--- a/src/asm-offsets.c
+++ b/src/asm-offsets.c
@@ -20,5 +20,4 @@ void foo(void)
     OFFSET(BREGS_edi, bregs, edi);
     OFFSET(BREGS_flags, bregs, flags);
     OFFSET(BREGS_code, bregs, code);
-    DEFINE(BREGS_size, sizeof(struct bregs));
 }