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tracing/function-graph-tracer: support for x86-64 

Impact: extend and enable the function graph tracer to 64-bit x86

This patch implements the support for function graph tracer under x86-64.
Both static and dynamic tracing are supported.

This causes some small CPP conditional asm on arch/x86/kernel/ftrace.c I
wanted to use probe_kernel_read/write to make the return address
saving/patching code more generic but it causes tracing recursion.

That would be perhaps useful to implement a notrace version of these
function for other archs ports.

Note that arch/x86/process_64.c is not traced, as in X86-32. I first
thought __switch_to() was responsible of crashes during tracing because I
believed current task were changed inside but that's actually not the
case (actually yes, but not the "current" pointer).

So I will have to investigate to find the functions that harm here, to
enable tracing of the other functions inside (but there is no issue at
this time, while process_64.c stays out of -pg flags).

A little possible race condition is fixed inside this patch too. When the
tracer allocate a return stack dynamically, the current depth is not
initialized before but after. An interrupt could occur at this time and,
after seeing that the return stack is allocated, the tracer could try to
trace it with a random uninitialized depth. It's a prevention, even if I
hadn't problems with it.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tim Bird <tim.bird@am.sony.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Frederic Weisbecker 2008-12-02 00:20:39 +01:00 committed by Ingo Molnar
parent 222658e08f
commit 48d68b20d0
5 changed files with 89 additions and 3 deletions
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2
arch/x86/Kconfig
View File

@ -29,7 +29,7 @@ config X86
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_DYNAMIC_FTRACE
select HAVE_FUNCTION_TRACER
select HAVE_FUNCTION_GRAPH_TRACER if X86_32
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACE_MCOUNT_TEST
select HAVE_KVM if ((X86_32 && !X86_VOYAGER && !X86_VISWS && !X86_NUMAQ) || X86_64)
select HAVE_ARCH_KGDB if !X86_VOYAGER

1
arch/x86/kernel/Makefile
View File

@ -17,6 +17,7 @@ endif
ifdef CONFIG_FUNCTION_GRAPH_TRACER
# Don't trace __switch_to() but let it for function tracer
CFLAGS_REMOVE_process_32.o = -pg
CFLAGS_REMOVE_process_64.o = -pg
endif
#

74
arch/x86/kernel/entry_64.S
View File

@ -98,6 +98,12 @@ ftrace_call:
movq (%rsp), %rax
addq $0x38, %rsp
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
.globl ftrace_graph_call
ftrace_graph_call:
jmp ftrace_stub
#endif
.globl ftrace_stub
ftrace_stub:
retq
@ -110,6 +116,12 @@ ENTRY(mcount)
cmpq $ftrace_stub, ftrace_trace_function
jnz trace
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
cmpq $ftrace_stub, ftrace_graph_return
jnz ftrace_graph_caller
#endif
.globl ftrace_stub
ftrace_stub:
retq
@ -145,6 +157,68 @@ END(mcount)
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_TRACER */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ENTRY(ftrace_graph_caller)
cmpl $0, function_trace_stop
jne ftrace_stub
subq $0x38, %rsp
movq %rax, (%rsp)
movq %rcx, 8(%rsp)
movq %rdx, 16(%rsp)
movq %rsi, 24(%rsp)
movq %rdi, 32(%rsp)
movq %r8, 40(%rsp)
movq %r9, 48(%rsp)
leaq 8(%rbp), %rdi
movq 0x38(%rsp), %rsi
call prepare_ftrace_return
movq 48(%rsp), %r9
movq 40(%rsp), %r8
movq 32(%rsp), %rdi
movq 24(%rsp), %rsi
movq 16(%rsp), %rdx
movq 8(%rsp), %rcx
movq (%rsp), %rax
addq $0x38, %rsp
retq
END(ftrace_graph_caller)
.globl return_to_handler
return_to_handler:
subq $80, %rsp
movq %rax, (%rsp)
movq %rcx, 8(%rsp)
movq %rdx, 16(%rsp)
movq %rsi, 24(%rsp)
movq %rdi, 32(%rsp)
movq %r8, 40(%rsp)
movq %r9, 48(%rsp)
movq %r10, 56(%rsp)
movq %r11, 64(%rsp)
call ftrace_return_to_handler
movq %rax, 72(%rsp)
movq 64(%rsp), %r11
movq 56(%rsp), %r10
movq 48(%rsp), %r9
movq 40(%rsp), %r8
movq 32(%rsp), %rdi
movq 24(%rsp), %rsi
movq 16(%rsp), %rdx
movq 8(%rsp), %rcx
movq (%rsp), %rax
addq $72, %rsp
retq
#endif
#ifndef CONFIG_PREEMPT
#define retint_kernel retint_restore_args
#endif

11
arch/x86/kernel/ftrace.c
View File

@ -467,8 +467,13 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
* ignore such a protection.
*/
asm volatile(
#ifdef CONFIG_X86_64
"1: movq (%[parent_old]), %[old]\n"
"2: movq %[return_hooker], (%[parent_replaced])\n"
#else
"1: movl (%[parent_old]), %[old]\n"
"2: movl %[return_hooker], (%[parent_replaced])\n"
#endif
" movl $0, %[faulted]\n"
".section .fixup, \"ax\"\n"
@ -476,8 +481,13 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
".previous\n"
".section __ex_table, \"a\"\n"
#ifdef CONFIG_X86_64
" .quad 1b, 3b\n"
" .quad 2b, 3b\n"
#else
" .long 1b, 3b\n"
" .long 2b, 3b\n"
#endif
".previous\n"
: [parent_replaced] "=r" (parent), [old] "=r" (old),
@ -509,5 +519,4 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
ftrace_graph_entry(&trace);
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

4
kernel/trace/ftrace.c
View File

@ -1673,8 +1673,10 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list)
}
if (t->ret_stack == NULL) {
t->ret_stack = ret_stack_list[start++];
t->curr_ret_stack = -1;
/* Make sure IRQs see the -1 first: */
barrier();
t->ret_stack = ret_stack_list[start++];
atomic_set(&t->trace_overrun, 0);
}
} while_each_thread(g, t);