[PATCH 1/3] x86: Register state saving

[Pekka Enberg]

This patch introduces a save_registers() function that can be used to
take a snapshot of general purpose registers. This is needed in the
gc_alloc() function to save registers in case we need to enter a
safepoint and need to scan them for references.

We also need a save_signal_registers() function for converting gregset_t
to struct register_state so we can pass register contents to the
gc_safepoint() function.

Cc: Tomek Grabiec <tgrab...@gmail.com>
Cc: Vegard Nossum <vegard.nos...@gmail.com>
Signed-off-by: Pekka Enberg <penb...@cs.helsinki.fi>
---
 arch/x86/include/arch/registers_32.h |   52 +++++++++++++++++++++++++++++----
 1 files changed, 45 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/arch/registers_32.h 
b/arch/x86/include/arch/registers_32.h
index 30fa29d..9b4c858 100644
--- a/arch/x86/include/arch/registers_32.h
+++ b/arch/x86/include/arch/registers_32.h
@@ -1,11 +1,11 @@
-#ifndef __X86_REGISTERS_32_H
-#define __X86_REGISTERS_32_H
+#ifndef X86_REGISTERS_32_H
+#define X86_REGISTERS_32_H
 
-#include <limits.h>
+#include "vm/types.h"
+
+#include <ucontext.h>  /* for gregset_t */
 #include <stdbool.h>
-#include <stdint.h>
-#include <assert.h>
-#include <vm/types.h>
+#include <limits.h>
 
 enum machine_reg {
        MACH_REG_EAX,
@@ -55,4 +55,42 @@ const char *reg_name(enum machine_reg reg);
 
 bool reg_supports_type(enum machine_reg reg, enum vm_type type);
 
-#endif /* __X86_REGISTERS_32_H */
+struct register_state {
+       union {
+               unsigned long           regs[6];
+               struct {
+                       unsigned long   eax;
+                       unsigned long   ebx;
+                       unsigned long   ecx;
+                       unsigned long   edi;
+                       unsigned long   edx;
+                       unsigned long   esi;
+               };
+       };
+};
+
+#define SAVE_REG(reg, dst)  \
+       __asm__ volatile ("movl %%" reg ", %0\n\t" : "=m"(dst))
+
+static inline void save_registers(struct register_state *regs)
+{
+       SAVE_REG("eax", regs->eax);
+       SAVE_REG("ebx", regs->ebx);
+       SAVE_REG("ecx", regs->ecx);
+       SAVE_REG("edx", regs->edx);
+       SAVE_REG("edi", regs->edi);
+       SAVE_REG("esi", regs->esi);
+}
+
+static inline void
+save_signal_registers(struct register_state *regs, gregset_t gregs)
+{
+        regs->eax = gregs[REG_EAX];
+        regs->ebx = gregs[REG_EBX];
+        regs->ecx = gregs[REG_ECX];
+        regs->edx = gregs[REG_EDX];
+        regs->esi = gregs[REG_ESI];
+        regs->edi = gregs[REG_EDI];
+}
+
+#endif /* X86_REGISTERS_32_H */
-- 
1.5.6.3


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