From 04f7fd70b9980f162aacf20706b4ea67b7d63db4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ole=20Andr=C3=A9=20Vadla=20Ravn=C3=A5s?= <oleavr@gmail.com>
Date: Wed, 15 Nov 2023 22:10:20 +0100
Subject: [PATCH] cpu-features: Improve the AVX2 detection

By also checking that the CPU supports XSAVE, and that the OS has
enabled it.

This means we can get rid of the Linux-specific `noxsave` detection,
and the "is actually enabled"-part is OS-agnostic.

Co-authored-by: Stefano Moioli <smxdev4@gmail.com>
---
 gum/gum.c | 46 ++++++++--------------------------------------
 1 file changed, 8 insertions(+), 38 deletions(-)

diff --git a/gum/gum.c b/gum/gum.c
index f6e6243f8..bd4c43199 100644
--- a/gum/gum.c
+++ b/gum/gum.c
@@ -1,5 +1,6 @@
 /*
  * Copyright (C) 2008-2022 Ole André Vadla Ravnås <oleavr@nowsecure.com>
+ * Copyright (C) 2023 Stefano Moioli <smxdev4@gmail.com>
  *
  * Licence: wxWindows Library Licence, Version 3.1
  */
@@ -719,7 +720,6 @@ gum_query_cpu_features (void)
 
 #if defined (HAVE_I386)
 
-static gboolean gum_query_noxsave (void);
 static gboolean gum_get_cpuid (guint level, guint * a, guint * b, guint * c,
     guint * d);
 
@@ -729,49 +729,19 @@ gum_do_query_cpu_features (void)
   GumCpuFeatures features = 0;
   guint a, b, c, d;
 
-  if (gum_query_noxsave ())
-    return features;
-
   if (gum_get_cpuid (7, &a, &b, &c, &d))
   {
-    if ((b & (1 << 5)) != 0)
-      features |= GUM_CPU_AVX2;
-  }
-
-  return features;
-}
-
-static gboolean
-gum_query_noxsave (void)
-{
-  gboolean noxsave = FALSE;
-
-#ifdef HAVE_LINUX
-  gchar * cmdline = NULL;
-  gchar ** params = NULL;
-  gint num_params, i;
+    gboolean cpu_has_avx2, cpu_has_xsave, os_enabled_xsave;
 
-  if (!g_file_get_contents ("/proc/cmdline", &cmdline, NULL, NULL))
-    goto beach;
+    cpu_has_avx2 = (b & (1 << 5)) != 0;
+    cpu_has_xsave = (c & (1 << 27)) != 0;
+    os_enabled_xsave = (c & (1 << 28)) != 0;
 
-  if (!g_shell_parse_argv (cmdline, &num_params, &params, NULL))
-    goto beach;
-
-  for (i = 0; i != num_params; i++)
-  {
-    if (strcmp (params[i], "noxsave") == 0)
-    {
-      noxsave = TRUE;
-      break;
-    }
+    if (cpu_has_avx2 && cpu_has_xsave && os_enabled_xsave)
+      features |= GUM_CPU_AVX2;
   }
 
-beach:
-  g_strfreev (params);
-  g_free (cmdline);
-#endif
-
-  return noxsave;
+  return features;
 }
 
 static gboolean