[PATCH 4/6] x86, xsave: Track the offset, size of state in the xsave layout

[leann.ogasawara at canonical.com]

BugLink: https://bugs.launchpad.net/bugs/485548

Subleaves of the cpuid vector 0xd provides the offset and size of different
feature state that are managed by the xsave/xrstor. Track this for the upcoming
usage during signal handling.

Signed-off-by: Suresh Siddha <suresh.b.siddha at intel.com>
LKML-Reference: <20100719230205.262987929 at sbs-t61.sc.intel.com>
Signed-off-by: H. Peter Anvin <hpa at linux.intel.com>
(cherry picked from commit a1488f8bf4d72ad724700f6e982469a1240e4264)

Signed-off-by: Leann Ogasawara <leann.ogasawara at canonical.com>
---
 arch/x86/kernel/xsave.c |   29 +++++++++++++++++++++++++++++
 1 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 37e68fc..45d44ec 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -21,6 +21,8 @@ struct _fpx_sw_bytes fx_sw_reserved;
 struct _fpx_sw_bytes fx_sw_reserved_ia32;
 #endif
 
+static unsigned int *xstate_offsets, *xstate_sizes, xstate_features;
+
 /*
  * Check for the presence of extended state information in the
  * user fpstate pointer in the sigcontext.
@@ -301,12 +303,39 @@ void __cpuinit xsave_init(void)
 }
 
 /*
+ * Record the offsets and sizes of different state managed by the xsave
+ * memory layout.
+ */
+static void setup_xstate_features(void)
+{
+	int eax, ebx, ecx, edx, leaf = 0x2;
+
+	xstate_features = fls64(pcntxt_mask);
+	xstate_offsets = alloc_bootmem(xstate_features * sizeof(int));
+	xstate_sizes = alloc_bootmem(xstate_features * sizeof(int));
+
+	do {
+		cpuid_count(0xd, leaf, &eax, &ebx, &ecx, &edx);
+
+		if (eax == 0)
+			break;
+
+		xstate_offsets[leaf] = ebx;
+		xstate_sizes[leaf] = eax;
+
+		leaf++;
+	} while (1);
+}
+
+/*
  * setup the xstate image representing the init state
  */
 static void __init setup_xstate_init(void)
 {
 	init_xstate_buf = alloc_bootmem(xstate_size);
 	init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
+
+	setup_xstate_features();
 }
 
 /*
-- 
1.7.0.4