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riscv/ftrace: Add dynamic function graph tracer support 

Once the function_graph tracer is enabled, a filtered function has the
following call sequence:

* ftracer_caller         ==> on/off by ftrace_make_call/ftrace_make_nop
* ftrace_graph_caller
* ftrace_graph_call      ==> on/off by ftrace_en/disable_ftrace_graph_caller
* prepare_ftrace_return

Considering the following DYNAMIC_FTRACE_WITH_REGS feature, it would be
more extendable to have a ftrace_graph_caller function, instead of
calling prepare_ftrace_return directly in ftrace_caller.

Cc: Greentime Hu <greentime@andestech.com>
Signed-off-by: Alan Kao <alankao@andestech.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
This commit is contained in:
Alan Kao 2018-02-13 13:13:18 +08:00 committed by Palmer Dabbelt
parent c15ac4fd60
commit bc1a4c3a84
No known key found for this signature in database
GPG Key ID: EF4CA1502CCBAB41
2 changed files with 118 additions and 1 deletions
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55
arch/riscv/kernel/ftrace.c
View File

@ -139,4 +139,57 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
return;
*parent = return_hooker;
}
#endif
#ifdef CONFIG_DYNAMIC_FTRACE
extern void ftrace_graph_call(void);
int ftrace_enable_ftrace_graph_caller(void)
{
unsigned int call[2];
static int init_graph = 1;
int ret;
make_call(&ftrace_graph_call, &ftrace_stub, call);
/*
* When enabling graph tracer for the first time, ftrace_graph_call
* should contains a call to ftrace_stub. Once it has been disabled,
* the 8-bytes at the position becomes NOPs.
*/
if (init_graph) {
ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
call);
init_graph = 0;
} else {
ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
NULL);
}
if (ret)
return ret;
return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
(unsigned long)&prepare_ftrace_return, true);
}
int ftrace_disable_ftrace_graph_caller(void)
{
unsigned int call[2];
int ret;
make_call(&ftrace_graph_call, &prepare_ftrace_return, call);
/*
* This is to make sure that ftrace_enable_ftrace_graph_caller
* did the right thing.
*/
ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
call);
if (ret)
return ret;
return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
(unsigned long)&prepare_ftrace_return, false);
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

64
arch/riscv/kernel/mcount-dyn.S
View File

@ -14,18 +14,62 @@
.text
.macro SAVE_ABI_STATE
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
addi sp, sp, -48
sd s0, 32(sp)
sd ra, 40(sp)
addi s0, sp, 48
sd t0, 24(sp)
sd t1, 16(sp)
#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
sd t2, 8(sp)
#endif
#else
addi sp, sp, -16
sd s0, 0(sp)
sd ra, 8(sp)
addi s0, sp, 16
#endif
.endm
.macro RESTORE_ABI_STATE
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ld s0, 32(sp)
ld ra, 40(sp)
addi sp, sp, 48
#else
ld ra, 8(sp)
ld s0, 0(sp)
addi sp, sp, 16
#endif
.endm
.macro RESTORE_GRAPH_ARGS
ld a0, 24(sp)
ld a1, 16(sp)
#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
ld a2, 8(sp)
#endif
.endm
ENTRY(ftrace_graph_caller)
addi sp, sp, -16
sd s0, 0(sp)
sd ra, 8(sp)
addi s0, sp, 16
ftrace_graph_call:
.global ftrace_graph_call
/*
* Calling ftrace_enable/disable_ftrace_graph_caller would overwrite the
* call below. Check ftrace_modify_all_code for details.
*/
call ftrace_stub
ld ra, 8(sp)
ld s0, 0(sp)
addi sp, sp, 16
ret
ENDPROC(ftrace_graph_caller)
ENTRY(ftrace_caller)
/*
* a0: the address in the caller when calling ftrace_caller
@ -33,6 +77,20 @@ ENTRY(ftrace_caller)
*/
ld a1, -8(s0)
addi a0, ra, -MCOUNT_INSN_SIZE
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
* the graph tracer (specifically, prepare_ftrace_return) needs these
* arguments but for now the function tracer occupies the regs, so we
* save them in temporary regs to recover later.
*/
addi t0, s0, -8
mv t1, a0
#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
ld t2, -16(s0)
#endif
#endif
SAVE_ABI_STATE
ftrace_call:
.global ftrace_call
@ -45,6 +103,12 @@ ftrace_call:
* Check ftrace_modify_all_code for details.
*/
call ftrace_stub
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
RESTORE_GRAPH_ARGS
call ftrace_graph_caller
#endif
RESTORE_ABI_STATE
ret
ENDPROC(ftrace_caller)