ftrace, ia64: IA64 dynamic ftrace support
commita14a07b8018b714e03a39ff2180c66e307ef4238
authorShaohua Li <shaohua.li@intel.com>
Fri, 9 Jan 2009 03:29:49 +0000 (9 11:29 +0800)
committerIngo Molnar <mingo@elte.hu>
Wed, 14 Jan 2009 11:11:31 +0000 (14 12:11 +0100)
tree7c4b9249f862969b80b74e5e11e56480b0e3d15c
parentd3e75ff14bc1453c4762428395aac9953a023efc
ftrace, ia64: IA64 dynamic ftrace support

IA64 dynamic ftrace support.
The original _mcount stub for each function is like:
alloc r40=ar.pfs,12,8,0
mov r43=r0;;
mov r42=b0
mov r41=r1
nop.i 0x0
br.call.sptk.many b0 = _mcount;;

The patch convert it to below for nop:
[MII] nop.m 0x0
mov r3=ip
nop.i 0x0
[MLX] nop.m 0x0
nop.x 0x0;;
This isn't completely nop, as there is one instuction 'mov r3=ip', but
it should be light and harmless for code follow it.

And below is for call
[MII] nop.m 0x0
mov r3=ip
nop.i 0x0
[MLX] nop.m 0x0
brl.many .;;
In this way, only one instruction is changed to convert code between nop
and call. This should meet dyn-ftrace's requirement.
But this requires CPU support brl instruction, so dyn-ftrace isn't
supported for old Itanium system. Assume there are quite few such old
system running.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
arch/ia64/Kconfig
arch/ia64/include/asm/ftrace.h
arch/ia64/kernel/Makefile
arch/ia64/kernel/entry.S
arch/ia64/kernel/ftrace.c [new file with mode: 0644]