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Bug 695985: Provide CFI for the code address GDB checks when a return address points at JaegerThrowpoline's or JaegerInterpoline's entry point. r=sfink
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This commit is contained in:
Jim Blandy
parent
89192a393d
commit
4b1daeff70
@ -191,6 +191,69 @@ JS_STATIC_ASSERT(offsetof(FrameRegs, sp) == 0);
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# define HIDE_SYMBOL(name)
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#endif
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/*
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* Notes about DWARF Call Frame Information (CFI) annotations:
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*
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* A .cfi directive placed in assembly code describes how to recover the
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* caller's registers when control is at or after that directive. That is,
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* they describe the states that hold between one instruction and the next,
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* not the instructions themselves. Later directives override earlier
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* directives.
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*
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* In DWARF CFI, each stack frame has a Canonical Frame Address (CFA) that
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* remains constant throughout the frame's lifetime. Exactly where it is is
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* a matter of convention; on the x86 and x86_64, for example, the CFA
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* points just after the end of the current stack frame: the address of the
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* next word after the return address. The CFI annotations describe 1) how
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* to compute the CFA at each point in the function, and 2) given the CFA,
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* where the caller's value of each register has been saved. (CFI specifies
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* saved registers' locations relative to the CFA, instead of the stack
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* pointer, so that when we push or pop the stack, we need only adjust our
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* rule for computing the CFA, not the rule for each saved register.)
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*
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* Quick reference:
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*
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* .cfi_startproc, .cfi_endproc
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* Put these at the beginning and end of the block of code you're
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* annotating.
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*
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* (The following directives apply starting at the point they appear until
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* they are overridden or until the .cfi_endproc.)
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*
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* .cfi_def_cfa REGISTER, OFFSET
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* The CFA is the value of REGISTER plus OFFSET.
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*
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* .cfi_def_cfa_offset OFFSET
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* The CFA is the value of the same register as before, but now adding OFFSET.
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*
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* .cfi_def_cfa_register REGISTER
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* The CFA is now the value of REGISTER, adding the same offset as before.
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*
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* .cfi_offset REGISTER, OFFSET
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* The caller's value of REGISTER is saved at OFFSET from the current CFA.
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* (This is the directive that actually says something interesting.)
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*
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* There are other directives that compute the CFA, a saved register's address,
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* or a saved register's value, in more complex ways, but the above are the ones
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* we use here.
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*
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* Special rules for JaegerThrowpoline and friends:
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*
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* In ordinary code, return addresses always point directly after a call
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* instruction. When GDB looks up the CFI for a return address it got from the
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* stack (as opposed to the current PC), it uses the CFI just before the return
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* address --- the CFI associated with the call instruction --- to do the
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* unwinding. However, JaegerMonkey uses hacks that edit return addresses to
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* point directly at the first instruction of JaegerThrowpoline,
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* JaegerInterpoline, and their ilk, so GDB ends up trying to use the CFI
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* associated with whatever instruction lies immediately *before* the given
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* entry point.
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*
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* We make sure our CFI covers the code address GDB will actually use, by
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* placing a 'nop' *before* the entry point --- it is never executed --- and
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* having our CFI apply starting at that nop.
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*/
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#if defined(__GNUC__) && !defined(_WIN64)
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/* If this assert fails, you need to realign VMFrame to 16 bytes. */
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@ -276,8 +339,7 @@ SYMBOL_STRING(JaegerTrampoline) ":" "\n"
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asm (
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".text\n"
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".globl " SYMBOL_STRING(JaegerTrampolineReturn) "\n"
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SYMBOL_STRING(JaegerTrampolineReturn) ":" "\n"
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/* See "Special rules for JaegerThrowpoline and friends", above. */
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CFI(".cfi_startproc" "\n")
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CFI(".cfi_def_cfa rbp, 16" "\n")
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CFI(".cfi_offset rbp, -16" "\n")
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@ -286,6 +348,9 @@ SYMBOL_STRING(JaegerTrampolineReturn) ":" "\n"
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CFI(".cfi_offset r14, -40" "\n")
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CFI(".cfi_offset r15, -48" "\n")
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CFI(".cfi_offset rbx, -56" "\n")
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CFI("nop" "\n")
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".globl " SYMBOL_STRING(JaegerTrampolineReturn) "\n"
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SYMBOL_STRING(JaegerTrampolineReturn) ":" "\n"
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"or %rdi, %rsi" "\n"
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"movq %rsi, 0x30(%rbx)" "\n"
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"movq %rsp, %rdi" "\n"
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@ -306,8 +371,7 @@ SYMBOL_STRING(JaegerTrampolineReturn) ":" "\n"
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asm (
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".text\n"
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".globl " SYMBOL_STRING(JaegerThrowpoline) "\n"
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SYMBOL_STRING(JaegerThrowpoline) ":" "\n"
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/* See "Special rules for JaegerThrowpoline and friends", above. */
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CFI(".cfi_startproc" "\n")
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CFI(".cfi_def_cfa rbp, 16" "\n")
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CFI(".cfi_offset rbp, -16" "\n")
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@ -316,6 +380,9 @@ SYMBOL_STRING(JaegerThrowpoline) ":" "\n"
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CFI(".cfi_offset r14, -40" "\n")
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CFI(".cfi_offset r15, -48" "\n")
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CFI(".cfi_offset rbx, -56" "\n")
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CFI("nop" "\n")
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".globl " SYMBOL_STRING(JaegerThrowpoline) "\n"
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SYMBOL_STRING(JaegerThrowpoline) ":" "\n"
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"movq %rsp, %rdi" "\n"
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"call " SYMBOL_STRING_RELOC(js_InternalThrow) "\n"
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"testq %rax, %rax" "\n"
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@ -339,8 +406,7 @@ SYMBOL_STRING(JaegerThrowpoline) ":" "\n"
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asm (
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".text\n"
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".globl " SYMBOL_STRING(JaegerInterpoline) "\n"
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SYMBOL_STRING(JaegerInterpoline) ":" "\n"
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/* See "Special rules for JaegerThrowpoline and friends", above. */
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CFI(".cfi_startproc" "\n")
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CFI(".cfi_def_cfa rbp, 16" "\n")
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CFI(".cfi_offset rbp, -16" "\n")
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@ -349,6 +415,9 @@ SYMBOL_STRING(JaegerInterpoline) ":" "\n"
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CFI(".cfi_offset r14, -40" "\n")
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CFI(".cfi_offset r15, -48" "\n")
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CFI(".cfi_offset rbx, -56" "\n")
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CFI("nop" "\n")
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".globl " SYMBOL_STRING(JaegerInterpoline) "\n"
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SYMBOL_STRING(JaegerInterpoline) ":" "\n"
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"movq %rsp, %rcx" "\n"
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"movq %rax, %rdx" "\n"
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"call " SYMBOL_STRING_RELOC(js_InternalInterpret) "\n"
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@ -379,8 +448,7 @@ SYMBOL_STRING(JaegerInterpoline) ":" "\n"
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asm (
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".text\n"
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".globl " SYMBOL_STRING(JaegerInterpolineScripted) "\n"
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SYMBOL_STRING(JaegerInterpolineScripted) ":" "\n"
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/* See "Special rules for JaegerThrowpoline and friends", above. */
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CFI(".cfi_startproc" "\n")
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CFI(".cfi_def_cfa rbp, 16" "\n")
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CFI(".cfi_offset rbp, -16" "\n")
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@ -389,6 +457,9 @@ SYMBOL_STRING(JaegerInterpolineScripted) ":" "\n"
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CFI(".cfi_offset r14, -40" "\n")
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CFI(".cfi_offset r15, -48" "\n")
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CFI(".cfi_offset rbx, -56" "\n")
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CFI("nop" "\n")
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".globl " SYMBOL_STRING(JaegerInterpolineScripted) "\n"
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SYMBOL_STRING(JaegerInterpolineScripted) ":" "\n"
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"movq 0x20(%rbx), %rbx" "\n" /* load prev */
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"movq %rbx, 0x38(%rsp)" "\n"
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"jmp " SYMBOL_STRING_RELOC(JaegerInterpoline) "\n"
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@ -454,14 +525,16 @@ SYMBOL_STRING(JaegerTrampoline) ":" "\n"
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asm (
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".text\n"
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".globl " SYMBOL_STRING(JaegerTrampolineReturn) "\n"
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SYMBOL_STRING(JaegerTrampolineReturn) ":" "\n"
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/* See "Special rules for JaegerThrowpoline and friends", above. */
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CFI(".cfi_startproc" "\n")
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CFI(".cfi_def_cfa ebp, 8" "\n")
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CFI(".cfi_offset ebp, -8" "\n")
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CFI(".cfi_offset esi, -12" "\n")
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CFI(".cfi_offset edi, -16" "\n")
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CFI(".cfi_offset ebx, -20" "\n")
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CFI("nop" "\n")
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".globl " SYMBOL_STRING(JaegerTrampolineReturn) "\n"
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SYMBOL_STRING(JaegerTrampolineReturn) ":" "\n"
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"movl %esi, 0x18(%ebp)" "\n"
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"movl %edi, 0x1C(%ebp)" "\n"
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"movl %esp, %ebp" "\n"
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@ -482,15 +555,17 @@ SYMBOL_STRING(JaegerTrampolineReturn) ":" "\n"
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asm (
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".text\n"
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".globl " SYMBOL_STRING(JaegerThrowpoline) "\n"
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SYMBOL_STRING(JaegerThrowpoline) ":" "\n"
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/* Align the stack to 16 bytes. */
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/* See "Special rules for JaegerThrowpoline and friends", above. */
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CFI(".cfi_startproc" "\n")
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CFI(".cfi_def_cfa ebp, 8" "\n")
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CFI(".cfi_offset ebp, -8" "\n")
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CFI(".cfi_offset esi, -12" "\n")
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CFI(".cfi_offset edi, -16" "\n")
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CFI(".cfi_offset ebx, -20" "\n")
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CFI("nop" "\n")
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".globl " SYMBOL_STRING(JaegerThrowpoline) "\n"
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SYMBOL_STRING(JaegerThrowpoline) ":" "\n"
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/* Align the stack to 16 bytes. */
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"pushl %esp" "\n"
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"pushl (%esp)" "\n"
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"pushl (%esp)" "\n"
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@ -519,14 +594,16 @@ SYMBOL_STRING(JaegerThrowpoline) ":" "\n"
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asm (
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".text\n"
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".globl " SYMBOL_STRING(JaegerInterpoline) "\n"
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SYMBOL_STRING(JaegerInterpoline) ":" "\n"
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/* See "Special rules for JaegerThrowpoline and friends", above. */
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CFI(".cfi_startproc" "\n")
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CFI(".cfi_def_cfa ebp, 8" "\n")
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CFI(".cfi_offset ebp, -8" "\n")
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CFI(".cfi_offset esi, -12" "\n")
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CFI(".cfi_offset edi, -16" "\n")
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CFI(".cfi_offset ebx, -20" "\n")
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CFI("nop" "\n")
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".globl " SYMBOL_STRING(JaegerInterpoline) "\n"
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SYMBOL_STRING(JaegerInterpoline) ":" "\n"
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/* Align the stack to 16 bytes. */
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"pushl %esp" "\n"
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"pushl %eax" "\n"
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@ -557,14 +634,16 @@ SYMBOL_STRING(JaegerInterpoline) ":" "\n"
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asm (
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".text\n"
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".globl " SYMBOL_STRING(JaegerInterpolineScripted) "\n"
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SYMBOL_STRING(JaegerInterpolineScripted) ":" "\n"
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/* See "Special rules for JaegerThrowpoline and friends", above. */
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CFI(".cfi_startproc" "\n")
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CFI(".cfi_def_cfa ebp, 8" "\n")
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CFI(".cfi_offset ebp, -8" "\n")
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CFI(".cfi_offset esi, -12" "\n")
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CFI(".cfi_offset edi, -16" "\n")
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CFI(".cfi_offset ebx, -20" "\n")
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CFI("nop" "\n")
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".globl " SYMBOL_STRING(JaegerInterpolineScripted) "\n"
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SYMBOL_STRING(JaegerInterpolineScripted) ":" "\n"
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"movl 0x10(%ebp), %ebp" "\n" /* load prev. :XXX: STATIC_ASSERT this */
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"movl %ebp, 0x1C(%esp)" "\n"
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"jmp " SYMBOL_STRING_RELOC(JaegerInterpoline) "\n"
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