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Zero out unused bytes in snapshots (#1980)

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Compiled code blocks are sized in multiples of JMEM_ALIGNMENT,
but it's possible that some bytes at the end remain unused and get filled
with junk. This causes snapshot output to become nondeterministic.
To fix this, zero out the compiled code buffer before using it.

JerryScript-DCO-1.0-Signed-off-by: Martijn The martijn.the@intel.com
This commit is contained in:
Martijn Thé
2018-01-26 08:26:09 +01:00
committed by László Langó
parent 4b699e997a
commit 0d04c805ac
2 changed files with 34 additions and 0 deletions
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jerry-core/parser/js/js-parser.c
+14
View File
@@ -1379,6 +1379,9 @@ parser_post_processing (parser_context_t *context_p) /**< context */
size_t offset;
size_t length;
size_t total_size;
#ifdef JERRY_ENABLE_SNAPSHOT_SAVE
size_t total_size_used;
#endif
size_t initializers_length;
uint8_t real_offset;
uint8_t *byte_code_p;
@@ -1610,10 +1613,21 @@ parser_post_processing (parser_context_t *context_p) /**< context */
}
total_size += length + context_p->literal_count * sizeof (jmem_cpointer_t);
#ifdef JERRY_ENABLE_SNAPSHOT_SAVE
total_size_used = total_size;
#endif
total_size = JERRY_ALIGNUP (total_size, JMEM_ALIGNMENT);
compiled_code_p = (ecma_compiled_code_t *) parser_malloc (context_p, total_size);
#ifdef JERRY_ENABLE_SNAPSHOT_SAVE
// Avoid getting junk bytes at the end when bytes at the end remain unused:
if (total_size_used < total_size)
{
memset (((uint8_t *) compiled_code_p) + total_size_used, 0, total_size - total_size_used);
}
#endif
#ifdef JMEM_STATS
jmem_stats_allocate_byte_code_bytes (total_size);
#endif /* JMEM_STATS */
tests/unit-core/test-snapshot.c
+20
View File
@@ -123,6 +123,26 @@ main (void)
global_mode_snapshot_buffer,
SNAPSHOT_BUFFER_SIZE);
TEST_ASSERT (global_mode_snapshot_size != 0);
/* Check the snapshot data. Unused bytes should be filled with zeroes */
const uint8_t expected_data[] =
{
0x4A, 0x52, 0x52, 0x59, 0x08, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00,
0x01, 0x00, 0x00, 0x00, 0x18, 0x00, 0x00, 0x00,
0x03, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00,
0x00, 0x00, 0x00, 0x01, 0x03, 0x00, 0x28, 0x00,
0xB7, 0x46, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x02, 0x00, 0x01, 0x00, 0x21, 0x00, 0x00, 0x00,
0x00, 0x00, 0x01, 0x01, 0x01, 0x00, 0x47, 0x00,
0x1C, 0x00, 0x00, 0x00, 0x14, 0x00, 0x73, 0x74,
0x72, 0x69, 0x6E, 0x67, 0x20, 0x66, 0x72, 0x6F,
0x6D, 0x20, 0x73, 0x6E, 0x61, 0x70, 0x73, 0x68,
0x6F, 0x74, 0x00, 0x00,
};
TEST_ASSERT (sizeof (expected_data) == global_mode_snapshot_size);
TEST_ASSERT (0 == memcmp (expected_data, global_mode_snapshot_buffer, sizeof (expected_data)));
jerry_cleanup ();
jerry_init (JERRY_INIT_EMPTY);