From 1047405bf7ec74170bed2a0da1002bc529b7e194 Mon Sep 17 00:00:00 2001
From: Tim Abbott <tabbott@mit.edu>
Date: Tue, 7 Oct 2008 21:04:31 -0400
Subject: [PATCH] Add support for run-pre matching CONFIG_DYNAMIC_FTRACE
 kernels.

Current gcc does not support compiling with both -ffunction-sections
and -pg.  Thus, this patch is only useful when using a compiler that
has been patched to allow compiling with both -ffunction-sections and
-pg enabled.

Signed-off-by: Tim Abbott <tabbott@mit.edu>
---
 kmodsrc/Makefile.in        |  3 ++-
 kmodsrc/x86/ksplice-arch.c | 31 +++++++++++++++++++++++++++++--
 objmanip.c                 |  4 ++++
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/kmodsrc/Makefile.in b/kmodsrc/Makefile.in
index 9d26f31..46bb5e7 100644
--- a/kmodsrc/Makefile.in
+++ b/kmodsrc/Makefile.in
@@ -110,7 +110,8 @@ RMSYMS = \
 	__start___kcrctab_gpl \
 	__start___kcrctab_gpl_future \
 	__start___kcrctab_unused \
-	__start___kcrctab_unused_gpl
+	__start___kcrctab_unused_gpl \
+	ftrace_trace_function
 
 quiet_cmd_ksplice-rmsyms = RMSYMS  $@
 cmd_ksplice-rmsyms = \
diff --git a/kmodsrc/x86/ksplice-arch.c b/kmodsrc/x86/ksplice-arch.c
index cd77d86..33c6a74 100644
--- a/kmodsrc/x86/ksplice-arch.c
+++ b/kmodsrc/x86/ksplice-arch.c
@@ -33,6 +33,12 @@ extern const char thread_return[];
 
 #ifndef CONFIG_FUNCTION_DATA_SECTIONS
 #include "udis86.h"
+#ifdef CONFIG_FTRACE
+#include <asm/ftrace.h>
+#include <linux/ftrace.h>
+
+extern ftrace_func_t ftrace_trace_function;
+#endif /* CONFIG_FTRACE */
 
 static abort_t compare_operands(struct ksplice_pack *pack,
 				const struct ksplice_section *sect,
@@ -49,6 +55,7 @@ static long ud_operand_lval(struct ud_operand *operand);
 static int next_run_byte(struct ud *ud);
 static bool is_nop(struct ud *ud);
 static bool is_unconditional_jump(struct ud *ud);
+static bool is_mcount_call(struct ud *ud, unsigned long addr);
 
 void initialize_ksplice_ud(struct ud *ud)
 {
@@ -108,7 +115,8 @@ static abort_t arch_run_pre_cmp(struct ksplice_pack *pack,
 						   safety_offset);
 			goto out;
 		}
-		if (is_nop(&pre_ud)) {
+		if (is_nop(&pre_ud) ||
+		    is_mcount_call(&pre_ud, (unsigned long)pre)) {
 			if (mode == RUN_PRE_DEBUG) {
 				ksdebug(pack, "| nop: ");
 				print_bytes(pack, run, 0, pre,
@@ -124,7 +132,8 @@ static abort_t arch_run_pre_cmp(struct ksplice_pack *pack,
 				ret = NO_MATCH;
 				goto out;
 			}
-			if (!is_nop(&run_ud))
+			if (!is_nop(&run_ud) &&
+			    !is_mcount_call(&run_ud, (unsigned long)run))
 				break;
 			if (mode == RUN_PRE_DEBUG) {
 				ksdebug(pack, "| nop: ");
@@ -386,6 +395,24 @@ static abort_t compare_operands(struct ksplice_pack *pack,
 	}
 }
 
+#ifdef CONFIG_FTRACE
+static bool is_mcount_call(struct ud *ud, unsigned long addr)
+{
+	unsigned long target = addr + ud_insn_len(ud) +
+	    ud_operand_lval(&ud->operand[0]);
+	if (ud->mnemonic == UD_Icall &&
+	    (target == (unsigned long)mcount ||
+	     target == (unsigned long)ftrace_trace_function))
+		return true;
+	return false;
+}
+#else /* !CONFIG_FTRACE */
+static bool is_mcount_call(struct ud *ud, unsigned long addr)
+{
+	return false;
+}
+#endif /* CONFIG_FTRACE */
+
 static bool is_nop(struct ud *ud)
 {
 	switch (ud->mnemonic) {
diff --git a/objmanip.c b/objmanip.c
index 28985d5..829c65c 100644
--- a/objmanip.c
+++ b/objmanip.c
@@ -1067,6 +1067,10 @@ void rm_some_relocs(struct supersect *ss)
 		if (mode("finalize") && bfd_is_und_section(sym_ptr->section))
 			rm_reloc = true;
 
+		if (strcmp(sym_ptr->name, "mcount") == 0 &&
+		    bfd_is_und_section(sym_ptr->section))
+			rm_reloc = false;
+
 		if (rm_reloc)
 			write_ksplice_reloc(ss, *relocp);
 		else
-- 
2.11.4.GIT