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division safety, seperate leb functions to signed and unsigned

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This commit is contained in:
Richard Holland
2022-06-02 15:09:33 +00:00
parent 6571af7490
commit 0fe9fd2f81
1 changed files with 45 additions and 9 deletions
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54
src/ripple/app/hook/Guard.h
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@@ -27,8 +27,7 @@ inline uint64_t
parseLeb128(
std::vector<unsigned char> const& buf,
int start_offset,
int* end_offset,
bool is_signed = false)
int* end_offset)
{
uint64_t val = 0, shift = 0, i = start_offset;
while (i < buf.size())
@@ -50,7 +49,40 @@ parseLeb128(
continue;
}
*end_offset = i;
if (is_signed && shift < 64 && (b&0x40U))
return val;
}
return 0;
}
inline int64_t
parseSignedLeb128(
std::vector<unsigned char> const& buf,
int start_offset,
int* end_offset)
{
int64_t val = 0;
uint64_t shift = 0, i = start_offset;
while (i < buf.size())
{
uint64_t b = (uint64_t)(buf[i]);
int64_t last = val;
val += (b & 0x7FU) << shift;
if (val < last)
{
// overflow
throw std::overflow_error { "leb128 overflow" };
}
++i;
if (b & 0x80U)
{
shift += 7;
if (!(i < buf.size()))
throw std::length_error { "leb128 short or invalid" };
continue;
}
*end_offset = i;
if (shift < 64 && (b&0x40U))
val |= (~0 << shift);
return val;
@@ -91,10 +123,10 @@ parseLeb128(
}
#define LEB()\
parseLeb128(hook, i, &i, false)
parseLeb128(hook, i, &i)
#define SIGNED_LEB()\
parseLeb128(hook, i, &i, true)
parseSignedLeb128(hook, i, &i)
#define GUARD_ERROR(msg)\
{\
@@ -129,14 +161,15 @@ uint64_t compute_wce (const WasmBlkInf* blk)
worst_case_execution += compute_wce(&child);
}
if (blk->parent == 0)
if (blk->parent == 0 ||
blk->parent->iteration_bound == 0) // this condtion should never occur [defensively programmed]
return worst_case_execution;
// if the block has a parent then the quotient of its guard and its parent's guard
// gives us the loop iterations and thus the multiplier for the instruction count
double multiplier =
((double)(blk->iteration_bound)) /
((double)(blk->parent->iteration_bound));
((double)(blk->parent->iteration_bound));
if (multiplier < 1.0)
return worst_case_execution;
@@ -258,6 +291,9 @@ check_guard(
printf("iteration_bound: %d, call_func_idx: %ld, guard_func_idx: %d\n",
iteration_bound, call_func_idx, guard_func_idx);
if (iteration_bound == 0)
GUARD_ERROR("Guard call cannot specify 0 maxiter.");
if (call_func_idx != guard_func_idx)
GUARD_ERROR("Call after first and second i32.const at loop start was not _g");
}
@@ -463,7 +499,7 @@ check_guard(
{
ADVANCE(1);
}
else if (fc_type >= 0 && fc_type <= 7) // numeric instructions
else if (fc_type <= 7) // numeric instructions
{
// do nothing, these have no parameters
}
@@ -557,7 +593,7 @@ check_guard(
REQUIRE(1);
uint64_t v = LEB();
if (v >= 0 && v <= 11) // memargs only
if (v <= 11) // memargs only
{
REQUIRE(1); LEB();
REQUIRE(1); LEB();