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Two Lucet-related fixes to stack overflow handling.

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Lucet uses stack probes rather than explicit stack limit checks as
Wasmtime does. In bytecodealliance/lucet#616, I have discovered that I
previously was not running some Lucet runtime tests with the new
backend, so was missing some test failures due to missing pieces in the
new backend.

This PR adds (i) calls to probestack, when enabled, in the prologue of
every function with a stack frame larger than one page (configurable via
flags); and (ii) trap metadata for every instruction on x86-64 that can
access the stack, hence be the first point at which a stack overflow is
detected when the stack pointer is decremented.
This commit is contained in:
Chris Fallin
2020-12-07 15:09:47 -08:00
parent efe7f37542
commit 3a01d14712
8 changed files with 169 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files

96
cranelift/codegen/src/isa/x64/inst/emit.rs
View File

@@ -182,6 +182,7 @@ impl LegacyPrefixes {
fn emit_std_enc_mem(
sink: &mut MachBuffer<Inst>,
state: &EmitState,
info: &EmitInfo,
prefixes: LegacyPrefixes,
opcodes: u32,
mut num_opcodes: usize,
@@ -194,7 +195,8 @@ fn emit_std_enc_mem(
// expression. But `enc_g` can be derived from a register of any class.
let srcloc = state.cur_srcloc();
if srcloc != SourceLoc::default() && mem_e.can_trap() {
let can_trap = mem_e.can_trap();
if srcloc != SourceLoc::default() && can_trap {
sink.add_trap(srcloc, TrapCode::HeapOutOfBounds);
}
@@ -202,6 +204,12 @@ fn emit_std_enc_mem(
match mem_e {
Amode::ImmReg { simm32, base, .. } => {
// If this is an access based off of RSP, it may trap with a stack overflow if it's the
// first touch of a new stack page.
if *base == regs::rsp() && !can_trap && info.flags().enable_probestack() {
sink.add_trap(srcloc, TrapCode::StackOverflow);
}
// First, the REX byte.
let enc_e = int_reg_enc(*base);
rex.emit_two_op(sink, enc_g, enc_e);
@@ -262,6 +270,12 @@ fn emit_std_enc_mem(
shift,
..
} => {
// If this is an access based off of RSP, it may trap with a stack overflow if it's the
// first touch of a new stack page.
if *reg_base == regs::rsp() && !can_trap && info.flags().enable_probestack() {
sink.add_trap(srcloc, TrapCode::StackOverflow);
}
let enc_base = int_reg_enc(*reg_base);
let enc_index = int_reg_enc(*reg_index);
@@ -350,6 +364,7 @@ fn emit_std_enc_enc(
fn emit_std_reg_mem(
sink: &mut MachBuffer<Inst>,
state: &EmitState,
info: &EmitInfo,
prefixes: LegacyPrefixes,
opcodes: u32,
num_opcodes: usize,
@@ -361,6 +376,7 @@ fn emit_std_reg_mem(
emit_std_enc_mem(
sink,
state,
info,
prefixes,
opcodes,
num_opcodes,
@@ -538,6 +554,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
LegacyPrefixes::None,
0x0FAF,
2,
@@ -597,6 +614,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
LegacyPrefixes::None,
opcode_m,
1,
@@ -654,6 +672,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
prefix,
opcode,
num_opcodes,
@@ -717,7 +736,9 @@ pub(crate) fn emit(
}
RegMem::Mem { addr: src } => {
let amode = src.finalize(state, sink);
emit_std_enc_mem(sink, state, prefix, opcode, 1, subopcode, &amode, rex_flags);
emit_std_enc_mem(
sink, state, info, prefix, opcode, 1, subopcode, &amode, rex_flags,
);
}
}
}
@@ -738,7 +759,9 @@ pub(crate) fn emit(
}
RegMem::Mem { addr: src } => {
let amode = src.finalize(state, sink);
emit_std_enc_mem(sink, state, prefix, 0xF7, 1, subopcode, &amode, rex_flags);
emit_std_enc_mem(
sink, state, info, prefix, 0xF7, 1, subopcode, &amode, rex_flags,
);
}
}
}
@@ -987,6 +1010,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
LegacyPrefixes::None,
opcodes,
num_opcodes,
@@ -1004,6 +1028,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
LegacyPrefixes::None,
0x8B,
1,
@@ -1019,6 +1044,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
LegacyPrefixes::None,
0x8D,
1,
@@ -1081,6 +1107,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
LegacyPrefixes::None,
opcodes,
num_opcodes,
@@ -1108,7 +1135,17 @@ pub(crate) fn emit(
};
// MOV r8, r/m8 is (REX.W==0) 88 /r
emit_std_reg_mem(sink, state, LegacyPrefixes::None, 0x88, 1, *src, dst, rex)
emit_std_reg_mem(
sink,
state,
info,
LegacyPrefixes::None,
0x88,
1,
*src,
dst,
rex,
)
}
2 => {
@@ -1116,6 +1153,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
LegacyPrefixes::_66,
0x89,
1,
@@ -1130,6 +1168,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
LegacyPrefixes::None,
0x89,
1,
@@ -1144,6 +1183,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
LegacyPrefixes::None,
0x89,
1,
@@ -1253,6 +1293,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
prefix,
opcode_bytes,
2,
@@ -1311,7 +1352,7 @@ pub(crate) fn emit(
let addr = &addr.finalize(state, sink);
// Whereas here we revert to the "normal" G-E ordering.
let opcode = if *size == 1 { 0x3A } else { 0x3B };
emit_std_reg_mem(sink, state, prefix, opcode, 1, *reg_g, addr, rex);
emit_std_reg_mem(sink, state, info, prefix, opcode, 1, *reg_g, addr, rex);
}
RegMemImm::Imm { simm32 } => {
@@ -1372,6 +1413,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
prefix,
opcode,
2,
@@ -1408,6 +1450,10 @@ pub(crate) fn emit(
}
Inst::Push64 { src } => {
if info.flags().enable_probestack() {
sink.add_trap(state.cur_srcloc(), TrapCode::StackOverflow);
}
match src {
RegMemImm::Reg { reg } => {
let enc_reg = int_reg_enc(*reg);
@@ -1423,6 +1469,7 @@ pub(crate) fn emit(
emit_std_enc_mem(
sink,
state,
info,
LegacyPrefixes::None,
0xFF,
1,
@@ -1454,6 +1501,9 @@ pub(crate) fn emit(
}
Inst::CallKnown { dest, opcode, .. } => {
if info.flags().enable_probestack() {
sink.add_trap(state.cur_srcloc(), TrapCode::StackOverflow);
}
if let Some(s) = state.take_stack_map() {
sink.add_stack_map(StackMapExtent::UpcomingBytes(5), s);
}
@@ -1469,6 +1519,9 @@ pub(crate) fn emit(
}
Inst::CallUnknown { dest, opcode, .. } => {
if info.flags().enable_probestack() {
sink.add_trap(state.cur_srcloc(), TrapCode::StackOverflow);
}
let start_offset = sink.cur_offset();
match dest {
RegMem::Reg { reg } => {
@@ -1489,6 +1542,7 @@ pub(crate) fn emit(
emit_std_enc_mem(
sink,
state,
info,
LegacyPrefixes::None,
0xFF,
1,
@@ -1587,6 +1641,7 @@ pub(crate) fn emit(
emit_std_enc_mem(
sink,
state,
info,
LegacyPrefixes::None,
0xFF,
1,
@@ -1733,6 +1788,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
prefix,
opcode,
num_opcodes,
@@ -1848,6 +1904,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
prefix,
opcode,
length,
@@ -1994,7 +2051,17 @@ pub(crate) fn emit(
!regs_swapped,
"No existing way to encode a mem argument in the ModRM r/m field."
);
emit_std_reg_mem(sink, state, prefix, opcode, len, dst.to_reg(), addr, rex);
emit_std_reg_mem(
sink,
state,
info,
prefix,
opcode,
len,
dst.to_reg(),
addr,
rex,
);
}
}
sink.put1(*imm);
@@ -2027,6 +2094,7 @@ pub(crate) fn emit(
emit_std_reg_mem(
sink,
state,
info,
prefix,
opcode,
2,
@@ -2091,7 +2159,17 @@ pub(crate) fn emit(
}
RegMem::Mem { addr } => {
let addr = &addr.finalize(state, sink);
emit_std_reg_mem(sink, state, prefix, opcode, 2, reg_g.to_reg(), addr, rex);
emit_std_reg_mem(
sink,
state,
info,
prefix,
opcode,
2,
reg_g.to_reg(),
addr,
rex,
);
}
}
}
@@ -2111,7 +2189,7 @@ pub(crate) fn emit(
}
RegMem::Mem { addr } => {
let addr = &addr.finalize(state, sink);
emit_std_reg_mem(sink, state, prefix, opcode, len, *dst, addr, rex);
emit_std_reg_mem(sink, state, info, prefix, opcode, len, *dst, addr, rex);
}
}
}
@@ -2625,7 +2703,7 @@ pub(crate) fn emit(
_ => unreachable!(),
};
let amode = dst.finalize(state, sink);
emit_std_reg_mem(sink, state, prefix, opcodes, 2, *src, &amode, rex);
emit_std_reg_mem(sink, state, info, prefix, opcodes, 2, *src, &amode, rex);
}
Inst::AtomicRmwSeq { ty, op } => {