From: Nick Terrell <terrelln@fb.com>
Date: Fri, 25 Sep 2020 01:04:44 +0000 (-0700)
Subject: [superblock] Reduce stack usage by correctly sizing header buffers
X-Git-Tag: v1.4.7~69^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f1cbeec039aa59dadda10f89d49a544311106fbf;p=thirdparty%2Fzstd.git

[superblock] Reduce stack usage by correctly sizing header buffers
---

diff --git a/lib/common/zstd_internal.h b/lib/common/zstd_internal.h
index 79887c9ed..f57f8f83f 100644
--- a/lib/common/zstd_internal.h
+++ b/lib/common/zstd_internal.h
@@ -186,6 +186,10 @@ typedef enum { set_basic, set_rle, set_compressed, set_repeat } symbolEncodingTy
 #define OffFSELog   8
 #define MaxFSELog  MAX(MAX(MLFSELog, LLFSELog), OffFSELog)
 
+#define ZSTD_MAX_HUF_HEADER_SIZE 128 /* header + <= 127 byte tree description */
+/* Each table cannot take more than #symbols * FSELog bits */
+#define ZSTD_MAX_FSE_HEADERS_SIZE (((MaxML + 1) * MLFSELog + (MaxLL + 1) * LLFSELog + (MaxOff + 1) * OffFSELog + 7) / 8)
+
 static UNUSED_ATTR const U32 LL_bits[MaxLL+1] = {
      0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0,
diff --git a/lib/compress/zstd_compress_superblock.c b/lib/compress/zstd_compress_superblock.c
index 144c120d2..e23e619ee 100644
--- a/lib/compress/zstd_compress_superblock.c
+++ b/lib/compress/zstd_compress_superblock.c
@@ -29,7 +29,7 @@
  *  This metadata is populated in ZSTD_buildSuperBlockEntropy_literal() */
 typedef struct {
     symbolEncodingType_e hType;
-    BYTE hufDesBuffer[500]; /* TODO give name to this value */
+    BYTE hufDesBuffer[ZSTD_MAX_HUF_HEADER_SIZE];
     size_t hufDesSize;
 } ZSTD_hufCTablesMetadata_t;
 
@@ -42,7 +42,7 @@ typedef struct {
     symbolEncodingType_e llType;
     symbolEncodingType_e ofType;
     symbolEncodingType_e mlType;
-    BYTE fseTablesBuffer[500]; /* TODO give name to this value */
+    BYTE fseTablesBuffer[ZSTD_MAX_FSE_HEADERS_SIZE];
     size_t fseTablesSize;
     size_t lastCountSize; /* This is to account for bug in 1.3.4. More detail in ZSTD_compressSubBlock_sequences() */
 } ZSTD_fseCTablesMetadata_t;