From 83d1d1c053dbd0848c6e34d9098c23ce3738effd Mon Sep 17 00:00:00 2001
From: hsnovel <hsnovel@hsnovel>
Date: Tue, 6 Aug 2024 10:00:41 -0700
Subject: [PATCH] add failsafe for querying cache line size on linux

---
 src/cpuinfo/SDL_cpuinfo.c | 33 +++++++++++++++++++++++++++++----
 1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/src/cpuinfo/SDL_cpuinfo.c b/src/cpuinfo/SDL_cpuinfo.c
index 80790db9f..734960b23 100644
--- a/src/cpuinfo/SDL_cpuinfo.c
+++ b/src/cpuinfo/SDL_cpuinfo.c
@@ -69,6 +69,10 @@
 #endif
 #endif
 
+#if defined (SDL_PLATFORM_FREEBSD)
+#include <sys/param.h>
+#endif
+
 #if defined(SDL_PLATFORM_ANDROID) && defined(__arm__) && !defined(HAVE_GETAUXVAL)
 #include <cpu-features.h>
 #endif
@@ -841,6 +845,7 @@ static const char *SDL_GetCPUName(void)
 int SDL_GetCPUCacheLineSize(void)
 {
     const char *cpuType = SDL_GetCPUType();
+    int cacheline_size = SDL_CACHELINE_SIZE; /* initial guess */
     int a, b, c, d;
     (void)a;
     (void)b;
@@ -848,14 +853,34 @@ int SDL_GetCPUCacheLineSize(void)
     (void)d;
     if (SDL_strcmp(cpuType, "GenuineIntel") == 0 || SDL_strcmp(cpuType, "CentaurHauls") == 0 || SDL_strcmp(cpuType, "  Shanghai  ") == 0) {
         cpuid(0x00000001, a, b, c, d);
-        return ((b >> 8) & 0xff) * 8;
+        cacheline_size = ((b >> 8) & 0xff) * 8;
     } else if (SDL_strcmp(cpuType, "AuthenticAMD") == 0 || SDL_strcmp(cpuType, "HygonGenuine") == 0) {
         cpuid(0x80000005, a, b, c, d);
-        return c & 0xff;
+        cacheline_size = c & 0xff;
     } else {
-        /* Just make a guess here... */
-        return SDL_CACHELINE_SIZE;
+#if defined(HAVE_SYSCONF) && defined(_SC_LEVEL1_DCACHE_LINESIZE)
+        if ((cacheline_size = sysconf(_SC_LEVEL1_DCACHE_LINESIZE)) > 0) {
+            return cacheline_size;
+        } else {
+            cacheline_size = SDL_CACHELINE_SIZE;
+        }
+#endif
+#if defined(SDL_PLATFORM_LINUX)
+        {
+            FILE *f = fopen("/sys/devices/system/cpu/cpu0/cache/index0/coherency_line_size", "r");
+            if (f) {
+                int size;
+                if (fscanf(f, "%d", &size) == 1) {
+                    cacheline_size = size;
+                }
+                fclose(f);
+            }
+        }
+#elif defined(__FREEBSD__) && defined(CACHE_LINE_SIZE)
+        cacheline_size = CACHE_LINE_SIZE;
+#endif
     }
+    return cacheline_size;
 }
 
 #define SDL_CPUFEATURES_RESET_VALUE 0xFFFFFFFF