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Changes continue_execution to not clobber stack that may be in use. #217

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Changes continue_execution to not clobber stack that may be in use. #217

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11 changes: 8 additions & 3 deletions sdk/trts/linux/trts_pic.S
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Original file line number Diff line number Diff line change
Expand Up @@ -553,7 +553,6 @@ DECLARE_LOCAL_FUNC continue_execution
mov SE_WORDSIZE*1(%xcx), %xax
push %xax # push xcx
mov SE_WORDSIZE*4(%xcx), %xax
sub $(SE_WORDSIZE), %xax # xax: xsp

# restore registers except xax, xcx, xsp
mov SE_WORDSIZE*2(%xcx), %xdx
Expand Down Expand Up @@ -585,8 +584,14 @@ DECLARE_LOCAL_FUNC continue_execution

# do not setup the new stack until info is not needed any more
# otherwise, info will be overwritten
mov %xcx, (%xax) # save xip to the new stack
# Offset the stack to avoid the red zone, which interrupts are allowed to
# write into. Using the __attribute__((interrupt)) on internal_handle_exception
# is hostile to older compilers.
mov %xcx, -128(%xax) # save xip to the new stack
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The patch doesn't really avoid the red zone, right? From this line, it saves the xip at the bottom of the red zone but it is still inside the red zone.

pop %xcx # restore xcx
pop %xsp # xsp: xax
xchg %xax, %xsp
ret

# The desired xip was stashed further up in the stack; retrieve it and jump
# there to resume execution.
jmp *-128(%xsp)