#103 ret2kern restores flags correctly

Signed-off-by: Daniele Ahmed <ahmeddan amazon ,com>
KernelTestFramework · Oct 3, 2020 · d0f08ee · d0f08ee
1 parent 689c2ac
commit d0f08ee
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Showing 3 changed files with 25 additions and 6 deletions.
diff --git a/arch/x86/entry.S b/arch/x86/entry.S
@@ -84,18 +84,17 @@ END_FUNC(handle_exception)
 ENTRY(usermode_call_asm)
     /* FIXME: Add 32-bit support */
 
+    /* will be restored on entering back in kernel mode */
+    PUSHF
+
     mov %_ASM_SP, %gs:(%rdx)
 
     /* SS + SP */
     push $__USER_DS
     push %gs:(%rcx)
 
     /* EFLAGS */
-#if defined(__x86_64__)
-    pushfq
-#else
-    pushf
-#endif
+    PUSHF
 
     orl $X86_EFLAGS_IOPL, (%_ASM_SP)
 

diff --git a/common/kernel.c b/common/kernel.c
@@ -36,7 +36,11 @@ extern int usermode_call_asm(user_func_t fn, void *fn_arg, unsigned long ret2ker
                              unsigned long user_stack);
 
 void ret2kern_handler(void) {
-    asm volatile("mov %%gs:(%0), %%" STR(_ASM_SP)::"r"(offsetof(percpu_t, ret2kern_sp)));
+    /* clang-format off */
+    asm volatile("mov %%gs:(%0), %%" STR(_ASM_SP) "\n"
+                 "POPF \n"
+                 ::"r"(offsetof(percpu_t, ret2kern_sp)));
+    /* clang-format on */
 }
 
 int usermode_call(user_func_t fn, void *fn_arg) {

diff --git a/include/arch/x86/asm-macros.h b/include/arch/x86/asm-macros.h
@@ -94,6 +94,22 @@
     pop %_ASM_AX
 .endm
 
+.macro PUSHF
+#if defined(__x86_64__)
+    pushfq
+#else
+    pushf
+#endif
+.endm
+
+.macro POPF
+#if defined(__x86_64__)
+    popfq
+#else
+    popf
+#endif
+.endm
+
 #define GLOBAL(name) \
     .global name;    \
 name: