ARM: 7299/1: ftrace: clear zero bit in reported IPs for Thumb-2

The dynamic ftrace ops startup test currently fails on Thumb-2 kernels:

 Testing tracer function: PASSED
 Testing dynamic ftrace: PASSED
 Testing dynamic ftrace ops #1: (0 0 0 0 0) FAILED!

This is because while the addresses in the mcount records do not have
the zero bit set, the IP reported by the mcount call does have it set
(because it is copied from the LR).  This mismatch causes the ops
filtering in ftrace_ops_list_func() to not call the relevant tracers.

Fix this by clearing the zero bit before adjusting the LR for the mcount
instruction size.  Also, combine the mov+sub into a single sub
instruction.

Acked-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 9 insertions, 6 deletions

diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 520889cf1b5b..9fd0ba90c1d2 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -149,6 +149,11 @@ ENDPROC(ret_from_fork)
 #endif
 #endif
 
+.macro mcount_adjust_addr rd, rn
+        bic     \rd, \rn, #1            @ clear the Thumb bit if present
+        sub     \rd, \rd, #MCOUNT_INSN_SIZE
+.endm
+
 .macro __mcount suffix
         mcount_enter
         ldr     r0, =ftrace_trace_function
@@ -173,8 +178,7 @@ ENDPROC(ret_from_fork)
         mcount_exit
 
 1:      mcount_get_lr   r1                      @ lr of instrumented func
-        mov     r0, lr                          @ instrumented function
-        sub     r0, r0, #MCOUNT_INSN_SIZE
+        mcount_adjust_addr      r0, lr          @ instrumented function
         adr     lr, BSYM(2f)
         mov     pc, r2
 2:      mcount_exit
@@ -184,8 +188,7 @@ ENDPROC(ret_from_fork)
         mcount_enter
 
         mcount_get_lr   r1                      @ lr of instrumented func
-        mov     r0, lr                          @ instrumented function
-        sub     r0, r0, #MCOUNT_INSN_SIZE
+        mcount_adjust_addr      r0, lr          @ instrumented function
 
         .globl ftrace_call\suffix
 ftrace_call\suffix:
@@ -205,11 +208,11 @@ ftrace_graph_call\suffix:
 #ifdef CONFIG_DYNAMIC_FTRACE
         @ called from __ftrace_caller, saved in mcount_enter
         ldr     r1, [sp, #16]           @ instrumented routine (func)
+        mcount_adjust_addr      r1, r1
 #else
         @ called from __mcount, untouched in lr
-        mov     r1, lr                  @ instrumented routine (func)
+        mcount_adjust_addr      r1, lr  @ instrumented routine (func)
 #endif
-        sub     r1, r1, #MCOUNT_INSN_SIZE
         mov     r2, fp                  @ frame pointer
         bl      prepare_ftrace_return
         mcount_exit