From 15d03ed783d0bcd5e421e40c492afe4d406b51e0 Mon Sep 17 00:00:00 2001
From: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Date: Mon, 18 Jan 2021 08:58:09 -0500
Subject: [PATCH] pan/bi: Validate format 12 tuple count in disasm

We were throwing away this information. Let's just use a lookup table
and add an assertion. Would have caught a bug in this series resulting
in INSTR_INVALID_ENC faults.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8723>
---
 src/panfrost/bifrost/disassemble.c | 66 ++++++++++++------------------
 1 file changed, 27 insertions(+), 39 deletions(-)

diff --git a/src/panfrost/bifrost/disassemble.c b/src/panfrost/bifrost/disassemble.c
index f4c940c2da6..2c3c8931b50 100644
--- a/src/panfrost/bifrost/disassemble.c
+++ b/src/panfrost/bifrost/disassemble.c
@@ -567,45 +567,33 @@ static bool dump_clause(FILE *fp, uint32_t *words, unsigned *size, unsigned offs
                         case 0x7: {
                                 /* Format 12 */
                                 unsigned pos = tag & 0xf;
-                                // note that `pos' encodes both the total number of
-                                // instructions and the position in the constant stream,
-                                // presumably because decoded constants and instructions
-                                // share a buffer in the decoder, but we only care about
-                                // the position in the constant stream; the total number of
-                                // instructions is redundant.
-                                unsigned const_idx = 0;
-                                switch (pos) {
-                                case 0:
-                                case 1:
-                                case 2:
-                                case 6:
-                                        const_idx = 0;
-                                        break;
-                                case 3:
-                                case 4:
-                                case 7:
-                                case 9:
-                                        const_idx = 1;
-                                        break;
-                                case 5:
-                                case 0xa:
-                                        const_idx = 2;
-                                        break;
-                                case 8:
-                                case 0xb:
-                                case 0xc:
-                                        const_idx = 3;
-                                        break;
-                                case 0xd:
-                                        const_idx = 4;
-                                        break;
-                                case 0xe:
-                                        const_idx = 5;
-                                        break;
-                                default:
-                                        fprintf(fp, "# unknown pos 0x%x\n", pos);
-                                        break;
-                                }
+
+                                struct {
+                                        unsigned const_idx;
+                                        unsigned nr_tuples;
+                                } pos_table[0x10] = {
+                                        { 0, 1 },
+                                        { 0, 2 },
+                                        { 0, 4 },
+                                        { 1, 3 },
+                                        { 1, 5 },
+                                        { 2, 4 },
+                                        { 0, 7 },
+                                        { 1, 6 },
+                                        { 3, 5 },
+                                        { 1, 8 },
+                                        { 2, 7 },
+                                        { 3, 6 },
+                                        { 3, 8 },
+                                        { 4, 7 },
+                                        { 5, 6 },
+                                        { ~0, ~0 }
+                                };
+
+                                ASSERTED bool valid_count = pos_table[pos].nr_tuples == num_instrs;
+                                assert(valid_count && "INSTR_INVALID_ENC");
+
+                                unsigned const_idx = pos_table[pos].const_idx;
 
                                 if (num_consts < const_idx + 2)
                                         num_consts = const_idx + 2;