ARM: 7299/1: ftrace: clear zero bit in reported IPs for Thumb-2
Rabin Vincent [Tue, 24 Jan 2012 15:52:52 +0000 (16:52 +0100)]
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>

arch/arm/kernel/entry-common.S

index 520889c..9fd0ba9 100644 (file)
@@ -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