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ftrace, ia64: IA64 dynamic ftrace support

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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>
This commit is contained in:
Shaohua Li
2009-01-09 11:29:49 +08:00
committed by Ingo Molnar
parent d3e75ff14b
commit a14a07b801
5 changed files with 277 additions and 0 deletions
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13
arch/ia64/include/asm/ftrace.h
View File

@@ -8,6 +8,19 @@
extern void _mcount(unsigned long pfs, unsigned long r1, unsigned long b0, unsigned long r0);
#define mcount _mcount
#include <asm/kprobes.h>
/* In IA64, MCOUNT_ADDR is set in link time, so it's not a constant at compile time */
#define MCOUNT_ADDR (((struct fnptr *)mcount)->ip)
#define FTRACE_ADDR (((struct fnptr *)ftrace_caller)->ip)
static inline unsigned long ftrace_call_adjust(unsigned long addr)
{
/* second bundle, insn 2 */
return addr - 0x12;
}
struct dyn_arch_ftrace {
};
#endif
#endif /* CONFIG_FUNCTION_TRACER */