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Improve unwind info for call_into_lisp

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Douglas Katzman 2017-12-06 23:03:13 -05:00
parent d43f330076
commit 5ec78a31f1
1 changed files with 5 additions and 9 deletions
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14
src/runtime/x86-64-assem.S
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@ -193,16 +193,12 @@ Lzero:
/* Alloc new frame. */
push %rbp # Dummy for return address
push %rbp # fp in save location S1
/* The call convention change from C to Lisp creates a minor backtrace
* glitch if interrupted right before the following mov. The address to
* which this function returns (saved %rip) won't be addressable by %rbp
* or %rsp. As an attempted fix, we could save the old rbp in rbx, and
* change the CFA register to rbx. That doesn't work, because the next
* frame (Lisp) doesn't specify how to restore rbx. Pushing the return
* address on the new stack could work. But the better thing is to use
* cfa_def_cfa_expression which is more complicated than I'm capable of */
mov %rsp,%rbp # The current sp marks start of new frame.
# Inform unwinder that the new frame has not been entered yet.
# The CFA is what it was (old RBP+16) before the preceding mov.
# This sequence encodes DW_CFA_def_cfa_expression
# DW_OP_breg7 (rsp): 0 / DW_OP_deref / DW_OP_lit16 / DW_OP_plus
.cfi_escape 0x0f, 5, 0x77, 0, 6, 0x40, 0x22
Lcall:
call *CLOSURE_FUN_OFFSET(%rax)