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Re: [RFC] Kernel livepatching support in GCC


From: Jiangjiji <jiangjiji@huawei.com>
Date: Sat, 10 Oct 2015 15:29:57 +0800
Subject: [PATCH] * gcc/config/aarch64/aarch64.opt: Add a new option.
 * gcc/config/aarch64/aarch64.c: Add some new functions and Macros.
 * gcc/config/aarch64/aarch64.h: Modify PROFILE_HOOK and FUNCTION_PROFILER.

Signed-off-by: Jiangjiji <jiangjiji@huawei.com>
Signed-off-by: Li Bin <huawei.libin@huawei.com>
---
 gcc/config/aarch64/aarch64.c   |   23 +++++++++++++++++++++++
 gcc/config/aarch64/aarch64.h   |   13 ++++++++-----
 gcc/config/aarch64/aarch64.opt |    4 ++++
 3 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 752df4e..c70b161 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -440,6 +440,17 @@ aarch64_is_long_call_p (rtx sym)
   return aarch64_decl_is_long_call_p (SYMBOL_REF_DECL (sym));
 }

+void
+aarch64_function_profiler (FILE *file, int labelno ATTRIBUTE_UNUSED)
+{
+	if (flag_fentry)
+	{
+		fprintf (file, "\tmov\tx9, x30\n");
+		fprintf (file, "\tbl\t__fentry__\n");
+		fprintf (file, "\tmov\tx30, x9\n");
+	}
+}
+
 /* Return true if the offsets to a zero/sign-extract operation
    represent an expression that matches an extend operation.  The
    operands represent the paramters from
@@ -7414,6 +7425,15 @@ aarch64_emit_unlikely_jump (rtx insn)
   add_int_reg_note (insn, REG_BR_PROB, very_unlikely);
 }

+/* Return true, if profiling code should be emitted before
+ * prologue. Otherwise it returns false.
+ * Note: For x86 with "hotfix" it is sorried.  */
+static bool
+aarch64_profile_before_prologue (void)
+{
+	return flag_fentry != 0;
+}
+
 /* Expand a compare and swap pattern.  */

 void
@@ -8454,6 +8474,9 @@ aarch64_cannot_change_mode_class (enum machine_mode from,
 #undef TARGET_ASM_ALIGNED_SI_OP
 #define TARGET_ASM_ALIGNED_SI_OP "\t.word\t"

+#undef TARGET_PROFILE_BEFORE_PROLOGUE
+#define TARGET_PROFILE_BEFORE_PROLOGUE aarch64_profile_before_prologue
+
 #undef TARGET_ASM_CAN_OUTPUT_MI_THUNK
 #define TARGET_ASM_CAN_OUTPUT_MI_THUNK \
   hook_bool_const_tree_hwi_hwi_const_tree_true
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index 77b2bb9..65e34fc 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -804,13 +804,16 @@ do {									     \
 #define PROFILE_HOOK(LABEL)						\
   {									\
     rtx fun, lr;							\
-    lr = get_hard_reg_initial_val (Pmode, LR_REGNUM);			\
-    fun = gen_rtx_SYMBOL_REF (Pmode, MCOUNT_NAME);			\
-    emit_library_call (fun, LCT_NORMAL, VOIDmode, 1, lr, Pmode);	\
+	if (!flag_fentry)
+	  {
+		lr = get_hard_reg_initial_val (Pmode, LR_REGNUM);			\
+		fun = gen_rtx_SYMBOL_REF (Pmode, MCOUNT_NAME);			\
+		emit_library_call (fun, LCT_NORMAL, VOIDmode, 1, lr, Pmode);	\
+	  }
   }

-/* All the work done in PROFILE_HOOK, but still required.  */
-#define FUNCTION_PROFILER(STREAM, LABELNO) do { } while (0)
+#define FUNCTION_PROFILER(STREAM, LABELNO)
+	aarch64_function_profiler(STREAM, LABELNO)

 /* For some reason, the Linux headers think they know how to define
    these macros.  They don't!!!  */
diff --git a/gcc/config/aarch64/aarch64.opt b/gcc/config/aarch64/aarch64.opt
index 266d873..9e4b408 100644
--- a/gcc/config/aarch64/aarch64.opt
+++ b/gcc/config/aarch64/aarch64.opt
@@ -124,3 +124,7 @@ Enum(aarch64_abi) String(ilp32) Value(AARCH64_ABI_ILP32)

 EnumValue
 Enum(aarch64_abi) String(lp64) Value(AARCH64_ABI_LP64)
+
+mfentry
+Target Report Var(flag_fentry) Init(0)
+Emit profiling counter call at function entry immediately after prologue.
-- 
1.7.1


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