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Clarify how entry frames link the to the next exit frame

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Entry frames use a dedicated (and nonstandard) slot to link to the
next exit frame's frame pointer. This slot is initialized using the
Isolate's `c_entry_fp_` field (1. we can't use rbp since it may
contain arbitrary values with -fomit-frame-pointer, and 2. V8 stack
walks skip over all C++ frames between exit- and entry frames).

This CL clarifies all this by:

- renaming EntryFrameConstants::kCallerFPOffset to
  kNextExitFrameFPOffset to avoid confusion with the
  StandardFrame::kCallerFPOffset constant.
- extending comments in JSEntry codegen.
- adding a static_assert as a link between the constant and related
  code.

Change-Id: I38ed6d2f6f8249e0befabff5d3f3a8f95426e04c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3936278
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Jakob Linke <jgruber@chromium.org>
Auto-Submit: Jakob Linke <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/main@{#84867}
This commit is contained in:
Jakob Linke 2022-12-15 12:16:00 +01:00 committed by V8 LUCI CQ
parent 20d32a7042
commit c505f9b37c
17 changed files with 58 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
src/builtins/arm/builtins-arm.cc
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@ -494,12 +494,13 @@ constexpr int kPushedStackSpace = kNumCalleeSaved * kPointerSize -
kPointerSize /* FP */ +
kNumDoubleCalleeSaved * kDoubleSize +
5 * kPointerSize /* r5, r6, r7, fp, lr */ +
EntryFrameConstants::kCallerFPOffset;
EntryFrameConstants::kNextExitFrameFPOffset;
// Assert that the EntryFrameConstants are in sync with the builtin.
static_assert(kPushedStackSpace == EntryFrameConstants::kDirectCallerSPOffset +
3 * kPointerSize /* r5, r6, r7*/ +
EntryFrameConstants::kCallerFPOffset,
static_assert(kPushedStackSpace ==
EntryFrameConstants::kDirectCallerSPOffset +
3 * kPointerSize /* r5, r6, r7*/ +
EntryFrameConstants::kNextExitFrameFPOffset,
"Pushed stack space and frame constants do not match. See "
"frame-constants-arm.h");
@ -529,7 +530,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
const RegList kCalleeSavedWithoutFp = kCalleeSaved - fp;
// Update |pushed_stack_space| when we manipulate the stack.
int pushed_stack_space = EntryFrameConstants::kCallerFPOffset;
int pushed_stack_space = EntryFrameConstants::kNextExitFrameFPOffset;
{
NoRootArrayScope no_root_array(masm);
@ -573,7 +574,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
Register scratch = r6;
// Set up frame pointer for the frame to be pushed.
__ add(fp, sp, Operand(-EntryFrameConstants::kCallerFPOffset));
__ add(fp, sp, Operand(-EntryFrameConstants::kNextExitFrameFPOffset));
// If this is the outermost JS call, set js_entry_sp value.
Label non_outermost_js;
@ -658,7 +659,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
// Reset the stack to the callee saved registers.
__ add(sp, sp,
Operand(-EntryFrameConstants::kCallerFPOffset -
Operand(-EntryFrameConstants::kNextExitFrameFPOffset -
kSystemPointerSize /* already popped one */));
__ ldm(ia_w, sp, {fp, lr});

4
src/builtins/loong64/builtins-loong64.cc
View File

@ -559,7 +559,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
__ St_d(zero_reg, MemOperand(s5, 0));
// Set up frame pointer for the frame to be pushed.
__ addi_d(fp, sp, -EntryFrameConstants::kCallerFPOffset);
__ addi_d(fp, sp, -EntryFrameConstants::kNextExitFrameFPOffset);
// Registers:
// either
@ -672,7 +672,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
__ St_d(a5, MemOperand(a4, 0));
// Reset the stack to the callee saved registers.
__ addi_d(sp, sp, -EntryFrameConstants::kCallerFPOffset);
__ addi_d(sp, sp, -EntryFrameConstants::kNextExitFrameFPOffset);
// Restore callee-saved fpu registers.
__ MultiPopFPU(kCalleeSavedFPU);

4
src/builtins/mips64/builtins-mips64.cc
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@ -562,7 +562,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
__ Sd(zero_reg, MemOperand(s5));
// Set up frame pointer for the frame to be pushed.
__ daddiu(fp, sp, -EntryFrameConstants::kCallerFPOffset);
__ daddiu(fp, sp, -EntryFrameConstants::kNextExitFrameFPOffset);
// Registers:
// either
@ -674,7 +674,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
__ Sd(a5, MemOperand(a4));
// Reset the stack to the callee saved registers.
__ daddiu(sp, sp, -EntryFrameConstants::kCallerFPOffset);
__ daddiu(sp, sp, -EntryFrameConstants::kNextExitFrameFPOffset);
// Restore callee-saved fpu registers.
__ MultiPopFPU(kCalleeSavedFPU);

4
src/builtins/ppc/builtins-ppc.cc
View File

@ -868,7 +868,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
Register scratch = r9;
// Set up frame pointer for the frame to be pushed.
__ addi(fp, sp, Operand(-EntryFrameConstants::kCallerFPOffset));
__ addi(fp, sp, Operand(-EntryFrameConstants::kNextExitFrameFPOffset));
// If this is the outermost JS call, set js_entry_sp value.
Label non_outermost_js;
@ -956,7 +956,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
__ StoreU64(r6, MemOperand(scratch));
// Reset the stack to the callee saved registers.
__ addi(sp, sp, Operand(-EntryFrameConstants::kCallerFPOffset));
__ addi(sp, sp, Operand(-EntryFrameConstants::kNextExitFrameFPOffset));
// Restore callee-saved double registers.
__ MultiPopDoubles(kCalleeSavedDoubles);

4
src/builtins/riscv/builtins-riscv.cc
View File

@ -596,7 +596,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
// frames on top.
__ StoreWord(zero_reg, MemOperand(s5));
// Set up frame pointer for the frame to be pushed.
__ AddWord(fp, sp, -EntryFrameConstants::kCallerFPOffset);
__ AddWord(fp, sp, -EntryFrameConstants::kNextExitFrameFPOffset);
// Registers:
// either
// a1: entry address
@ -708,7 +708,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
__ StoreWord(a5, MemOperand(a4));
// Reset the stack to the callee saved registers.
__ AddWord(sp, sp, -EntryFrameConstants::kCallerFPOffset);
__ AddWord(sp, sp, -EntryFrameConstants::kNextExitFrameFPOffset);
// Restore callee-saved fpu registers.
__ MultiPopFPU(kCalleeSavedFPU);

8
src/builtins/s390/builtins-s390.cc
View File

@ -772,7 +772,7 @@ namespace {
constexpr int kPushedStackSpace =
(kNumCalleeSaved + 2) * kSystemPointerSize +
kNumCalleeSavedDoubles * kDoubleSize + 5 * kSystemPointerSize +
EntryFrameConstants::kCallerFPOffset - kSystemPointerSize;
EntryFrameConstants::kNextExitFrameFPOffset - kSystemPointerSize;
// Called with the native C calling convention. The corresponding function
// signature is either:
@ -871,10 +871,10 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
// Set up frame pointer for the frame to be pushed.
// Need to add kSystemPointerSize, because sp has one extra
// frame already for the frame type being pushed later.
__ lay(fp, MemOperand(sp, -EntryFrameConstants::kCallerFPOffset +
__ lay(fp, MemOperand(sp, -EntryFrameConstants::kNextExitFrameFPOffset +
kSystemPointerSize));
pushed_stack_space +=
EntryFrameConstants::kCallerFPOffset - kSystemPointerSize;
EntryFrameConstants::kNextExitFrameFPOffset - kSystemPointerSize;
// restore r6
__ mov(r6, r0);
@ -961,7 +961,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
__ StoreU64(r5, MemOperand(scrach));
// Reset the stack to the callee saved registers.
__ lay(sp, MemOperand(sp, -EntryFrameConstants::kCallerFPOffset));
__ lay(sp, MemOperand(sp, -EntryFrameConstants::kNextExitFrameFPOffset));
// Reload callee-saved preserved regs, return address reg (r14) and sp
__ LoadMultipleP(r6, sp, MemOperand(sp, 0));

19
src/builtins/x64/builtins-x64.cc
View File

@ -338,7 +338,14 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
{
NoRootArrayScope uninitialized_root_register(masm);
// Set up frame.
// Set up the frame.
//
// Note: at this point we are entering V8-generated code from C++ and thus
// rbp can be an arbitrary value (-fomit-frame-pointer). Since V8 still
// needs to know where the next interesting frame is for the purpose of
// stack walks, we instead push the stored EXIT frame fp
// (IsolateAddressId::kCEntryFPAddress) below to a dedicated slot.
__ pushq(rbp);
__ movq(rbp, rsp);
@ -392,6 +399,16 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
ExternalReference c_entry_fp = ExternalReference::Create(
IsolateAddressId::kCEntryFPAddress, masm->isolate());
{
// Keep this static_assert to preserve a link between the offset constant
// and the code location it refers to.
#ifdef V8_TARGET_OS_WIN
static_assert(EntryFrameConstants::kNextExitFrameFPOffset ==
-3 * kSystemPointerSize + -7 * kSystemPointerSize -
EntryFrameConstants::kXMMRegistersBlockSize);
#else
static_assert(EntryFrameConstants::kNextExitFrameFPOffset ==
-3 * kSystemPointerSize + -5 * kSystemPointerSize);
#endif // V8_TARGET_OS_WIN
Operand c_entry_fp_operand = masm->ExternalReferenceAsOperand(c_entry_fp);
__ Push(c_entry_fp_operand);

2
src/execution/arm/frame-constants-arm.h
View File

@ -33,7 +33,7 @@ class EntryFrameConstants : public AllStatic {
public:
// This is the offset to where JSEntry pushes the current value of
// Isolate::c_entry_fp onto the stack.
static constexpr int kCallerFPOffset = -3 * kSystemPointerSize;
static constexpr int kNextExitFrameFPOffset = -3 * kSystemPointerSize;
// Stack offsets for arguments passed to JSEntry.
static constexpr int kArgcOffset = +0 * kSystemPointerSize;

2
src/execution/arm64/frame-constants-arm64.h
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@ -49,7 +49,7 @@ class EntryFrameConstants : public AllStatic {
public:
// This is the offset to where JSEntry pushes the current value of
// Isolate::c_entry_fp onto the stack.
static constexpr int kCallerFPOffset = -3 * kSystemPointerSize;
static constexpr int kNextExitFrameFPOffset = -3 * kSystemPointerSize;
static constexpr int kFixedFrameSize = 4 * kSystemPointerSize;
// The following constants are defined so we can static-assert their values

12
src/execution/frames.cc
View File

@ -502,9 +502,9 @@ bool SafeStackFrameIterator::IsValidCaller(StackFrame* frame) {
// See EntryFrame::GetCallerState. It computes the caller FP address
// and calls ExitFrame::GetStateForFramePointer on it. We need to be
// sure that caller FP address is valid.
Address caller_fp =
Memory<Address>(frame->fp() + EntryFrameConstants::kCallerFPOffset);
if (!IsValidExitFrame(caller_fp)) return false;
Address next_exit_frame_fp = Memory<Address>(
frame->fp() + EntryFrameConstants::kNextExitFrameFPOffset);
if (!IsValidExitFrame(next_exit_frame_fp)) return false;
}
frame->ComputeCallerState(&state);
return IsValidStackAddress(state.sp) && IsValidStackAddress(state.fp) &&
@ -818,9 +818,9 @@ void EntryFrame::ComputeCallerState(State* state) const {
}
StackFrame::Type EntryFrame::GetCallerState(State* state) const {
const int offset = EntryFrameConstants::kCallerFPOffset;
Address fp = Memory<Address>(this->fp() + offset);
return ExitFrame::GetStateForFramePointer(fp, state);
Address next_exit_frame_fp =
Memory<Address>(fp() + EntryFrameConstants::kNextExitFrameFPOffset);
return ExitFrame::GetStateForFramePointer(next_exit_frame_fp, state);
}
#if V8_ENABLE_WEBASSEMBLY

2
src/execution/ia32/frame-constants-ia32.h
View File

@ -17,7 +17,7 @@ class EntryFrameConstants : public AllStatic {
public:
// This is the offset to where JSEntry pushes the current value of
// Isolate::c_entry_fp onto the stack.
static constexpr int kCallerFPOffset = -6 * kSystemPointerSize;
static constexpr int kNextExitFrameFPOffset = -6 * kSystemPointerSize;
// EntryFrame is used by JSEntry, JSConstructEntry and JSRunMicrotasksEntry.
// All of them take |root_register_value| as the first parameter.

2
src/execution/loong64/frame-constants-loong64.h
View File

@ -17,7 +17,7 @@ class EntryFrameConstants : public AllStatic {
public:
// This is the offset to where JSEntry pushes the current value of
// Isolate::c_entry_fp onto the stack.
static constexpr int kCallerFPOffset = -3 * kSystemPointerSize;
static constexpr int kNextExitFrameFPOffset = -3 * kSystemPointerSize;
};
class WasmLiftoffSetupFrameConstants : public TypedFrameConstants {

2
src/execution/mips64/frame-constants-mips64.h
View File

@ -17,7 +17,7 @@ class EntryFrameConstants : public AllStatic {
public:
// This is the offset to where JSEntry pushes the current value of
// Isolate::c_entry_fp onto the stack.
static constexpr int kCallerFPOffset = -3 * kSystemPointerSize;
static constexpr int kNextExitFrameFPOffset = -3 * kSystemPointerSize;
};
class WasmLiftoffSetupFrameConstants : public TypedFrameConstants {

6
src/execution/ppc/frame-constants-ppc.h
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@ -16,9 +16,9 @@ namespace internal {
class EntryFrameConstants : public AllStatic {
public:
// Need to take constant pool into account.
static constexpr int kCallerFPOffset = V8_EMBEDDED_CONSTANT_POOL_BOOL
? -4 * kSystemPointerSize
: -3 * kSystemPointerSize;
static constexpr int kNextExitFrameFPOffset = V8_EMBEDDED_CONSTANT_POOL_BOOL
? -4 * kSystemPointerSize
: -3 * kSystemPointerSize;
};
class WasmLiftoffSetupFrameConstants : public TypedFrameConstants {

2
src/execution/riscv/frame-constants-riscv.h
View File

@ -18,7 +18,7 @@ class EntryFrameConstants : public AllStatic {
public:
// This is the offset to where JSEntry pushes the current value of
// Isolate::c_entry_fp onto the stack.
static constexpr int kCallerFPOffset = -3 * kSystemPointerSize;
static constexpr int kNextExitFrameFPOffset = -3 * kSystemPointerSize;
};
class WasmLiftoffSetupFrameConstants : public TypedFrameConstants {

2
src/execution/s390/frame-constants-s390.h
View File

@ -15,7 +15,7 @@ namespace internal {
class EntryFrameConstants : public AllStatic {
public:
static constexpr int kCallerFPOffset = -3 * kSystemPointerSize;
static constexpr int kNextExitFrameFPOffset = -3 * kSystemPointerSize;
// Stack offsets for arguments passed to JSEntry.
static constexpr int kArgvOffset = 20 * kSystemPointerSize;

8
src/execution/x64/frame-constants-x64.h
View File

@ -26,9 +26,9 @@ class EntryFrameConstants : public AllStatic {
// On x64, there are 7 pushq() and 3 Push() calls between setting up rbp and
// pushing the c_entry_fp, plus we manually allocate kXMMRegistersBlockSize
// bytes on the stack.
static constexpr int kCallerFPOffset = -3 * kSystemPointerSize +
-7 * kSystemPointerSize -
kXMMRegistersBlockSize;
static constexpr int kNextExitFrameFPOffset = -3 * kSystemPointerSize +
-7 * kSystemPointerSize -
kXMMRegistersBlockSize;
// Stack offsets for arguments passed to JSEntry.
static constexpr int kArgcOffset = 6 * kSystemPointerSize;
@ -38,7 +38,7 @@ class EntryFrameConstants : public AllStatic {
// Isolate::c_entry_fp onto the stack.
// On x64, there are 5 pushq() and 3 Push() calls between setting up rbp and
// pushing the c_entry_fp.
static constexpr int kCallerFPOffset =
static constexpr int kNextExitFrameFPOffset =
-3 * kSystemPointerSize + -5 * kSystemPointerSize;
#endif
};