RE: [PATCH v1] RISC-V: Fix out of range memory access when lto mode init

["Li, Pan2" <pan2.li@intel.com>]

Add Richard Biener for reviewing, sorry for inconvenient.

Pan

-----Original Message-----
From: Li, Pan2 <pan2.li@intel.com> 
Sent: Monday, June 19, 2023 4:07 PM
To: gcc-patches@gcc.gnu.org
Cc: juzhe.zhong@rivai.ai; rdapp.gcc@gmail.com; jeffreyalaw@gmail.com; Li, Pan2 <pan2.li@intel.com>; Wang, Yanzhang <yanzhang.wang@intel.com>; kito.cheng@gmail.com
Subject: [PATCH v1] RISC-V: Fix out of range memory access when lto mode init

From: Pan Li <pan2.li@intel.com>

We extend the machine mode from 8 to 16 bits already. But there still
one placing missing from the tree-streamer. It has one hard coded array
for the machine code like size 256.

In the lto pass, we memset the array by MAX_MACHINE_MODE count but the
value of the MAX_MACHINE_MODE will grow as more and more modes are added.
While the machine mode array in tree-streamer still leave 256 as is.

Then, when the MAX_MACHINE_MODE is greater than 256, the memset of
lto_output_init_mode_table will touch the memory out of range unexpected.

This patch would like to take the MAX_MACHINE_MODE as the size of the
array in tree-streamer, to make sure there is no potential unexpected
memory access in future.

Signed-off-by: Pan Li <pan2.li@intel.com>

gcc/ChangeLog:

	* tree-streamer.cc (streamer_mode_table): Use MAX_MACHINE_MODE
	as array size.
	* tree-streamer.h (streamer_mode_table): Ditto.
---
 gcc/tree-streamer.cc | 2 +-
 gcc/tree-streamer.h  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/gcc/tree-streamer.cc b/gcc/tree-streamer.cc
index ed65a7692e3..a28ef9c7920 100644
--- a/gcc/tree-streamer.cc
+++ b/gcc/tree-streamer.cc
@@ -35,7 +35,7 @@ along with GCC; see the file COPYING3.  If not see
    During streaming in, we translate the on the disk mode using this
    table.  For normal LTO it is set to identity, for ACCEL_COMPILER
    depending on the mode_table content.  */
-unsigned char streamer_mode_table[1 << 8];
+unsigned char streamer_mode_table[MAX_MACHINE_MODE];
 
 /* Check that all the TS_* structures handled by the streamer_write_* and
    streamer_read_* routines are exactly ALL the structures defined in
diff --git a/gcc/tree-streamer.h b/gcc/tree-streamer.h
index 170d61cf20b..51a292c8d80 100644
--- a/gcc/tree-streamer.h
+++ b/gcc/tree-streamer.h
@@ -75,7 +75,7 @@ void streamer_write_tree_body (struct output_block *, tree);
 void streamer_write_integer_cst (struct output_block *, tree);
 
 /* In tree-streamer.cc.  */
-extern unsigned char streamer_mode_table[1 << 8];
+extern unsigned char streamer_mode_table[MAX_MACHINE_MODE];
 void streamer_check_handled_ts_structures (void);
 bool streamer_tree_cache_insert (struct streamer_tree_cache_d *, tree,
 				 hashval_t, unsigned *);
-- 
2.34.1