[2/7] arm: ftrace: Add call modify mechanism

Commit Message

Abel Vesa Dec. 6, 2016, 5:06 p.m. UTC

Function ftrace_modify_call provides a way to replace ftrace_stub
with the ftrace function. This helps the klp_ftrace_handler to be
called via ftrace_ops_no_ops, which in turn will set the pc with
the patched function's starting address. This is used for
livepatching.

Signed-off-by: Abel Vesa <[e-mail]>
---
 arch/arm/kernel/ftrace.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

Comments

kernel test robot Dec. 7, 2016, 10:37 a.m. UTC | #1

Hi Abel,

[auto build test ERROR on linus/master]
[also build test ERROR on v4.9-rc8 next-20161206]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Abel-Vesa/arm-Add-livepatch-support/20161207-074210
config: arm-allmodconfig (attached as .config)
compiler: arm-linux-gnueabi-gcc (Debian 6.1.1-9) 6.1.1 20160705
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=arm 

Note: the linux-review/Abel-Vesa/arm-Add-livepatch-support/20161207-074210 HEAD 49113edc744f38a682a4afa9e904384bb00f2988 builds fine.
      It only hurts bisectibility.

All errors (new ones prefixed by >>):

>> arch/arm/kernel/ftrace.c:163:5: error: redefinition of 'ftrace_modify_call'
    int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
        ^~~~~~~~~~~~~~~~~~
   In file included from arch/arm/kernel/ftrace.c:15:0:
   include/linux/ftrace.h:595:19: note: previous definition of 'ftrace_modify_call' was here
    static inline int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
                      ^~~~~~~~~~~~~~~~~~

vim +/ftrace_modify_call +163 arch/arm/kernel/ftrace.c

   157		}
   158	#endif
   159	
   160		return ret;
   161	}
   162	
 > 163	int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
   164		       unsigned long addr)
   165	{
   166		unsigned long pc = rec->ip;

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Patch

diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index 3f17594..cb4543a 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -139,6 +139,15 @@  int ftrace_update_ftrace_func(ftrace_func_t func)
 
 	ret = ftrace_modify_code(pc, 0, new, false);
 
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+	if (!ret) {
+		pc = (unsigned long)&ftrace_regs_call;
+		new = ftrace_call_replace(pc, (unsigned long)func);
+
+		ret = ftrace_modify_code(pc, 0, new, false);
+	}
+#endif
+
 #ifdef CONFIG_OLD_MCOUNT
 	if (!ret) {
 		pc = (unsigned long)&ftrace_call_old;
@@ -151,6 +160,18 @@  int ftrace_update_ftrace_func(ftrace_func_t func)
 	return ret;
 }
 
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+	       unsigned long addr)
+{
+	unsigned long pc = rec->ip;
+	u32 old, new;
+
+	old = arm_gen_branch(pc, old_addr);
+	new = arm_gen_branch(pc, addr);
+
+	return ftrace_modify_code(pc, old, new, true);
+}
+
 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned long new, old;