In RISC-V architecture, when we enable the ftrace_graph tracer on some
functions, the function tracings on other functions will suffer extra
graph tracing work. In essence, graph_ops isn't limited by its func_hash
due to the global ftrace_graph_[regs]_call label. That should be corrected.
What inspires me is the commit 0c0593b45c9b ("x86/ftrace: Make function
graph use ftrace directly") that uses graph_ops::func function to install
return_hooker and makes the function called against its func_hash.
This series of patches makes function graph use ftrace directly for riscv.
If FTRACE_WITH_REGS isn't defined, ftrace_caller keeps ftrace_graph_call
so that it can be replaced with the calling of prepare_ftrace_return by
the enable/disable helper.
As for defining FTRACE_WITH_REGS, ftrace_caller is adjusted to save the
necessary regs against the pt_regs layout, so it can reasonably call the
graph_ops::func function - ftrace_graph_func. And ftrace_graph_[regs]_call
and its enable/disable helper aren't needed.
The tests generated by CONFIG_FTRACE_STARTUP_TEST have passed in the local
qemu-system-riscv64 virt machine. The following is the log during startup.
```
Nov 15 03:07:13 stage4 kernel: Testing tracer function: PASSED
Nov 15 03:07:13 stage4 kernel: Testing dynamic ftrace: PASSED
Nov 15 03:07:13 stage4 kernel: Testing dynamic ftrace ops #1:
Nov 15 03:07:13 stage4 kernel: (1 0 1 0 0)
Nov 15 03:07:13 stage4 kernel: (1 1 2 0 0)
Nov 15 03:07:13 stage4 kernel: (2 1 3 0 365)
Nov 15 03:07:13 stage4 kernel: (2 2 4 0 399)
Nov 15 03:07:13 stage4 kernel: (3 2 4 0 146071)
Nov 15 03:07:13 stage4 kernel: (3 3 5 0 146105) PASSED
Nov 15 03:07:13 stage4 kernel: Testing dynamic ftrace ops #2:
Nov 15 03:07:13 stage4 kernel: (1 0 1 589 0)
Nov 15 03:07:13 stage4 kernel: (1 1 2 635 0)
Nov 15 03:07:13 stage4 kernel: (2 1 3 1 2)
Nov 15 03:07:13 stage4 kernel: (2 2 4 125 126)
Nov 15 03:07:13 stage4 kernel: (3 2 4 146001 146078)
Nov 15 03:07:13 stage4 kernel: (3 3 5 146035 146112) PASSED
Nov 15 03:07:13 stage4 kernel: Testing ftrace recursion: PASSED
Nov 15 03:07:13 stage4 kernel: Testing ftrace recursion safe: PASSED
Nov 15 03:07:13 stage4 kernel: Testing ftrace regs: PASSED
Nov 15 03:07:13 stage4 kernel: Testing tracer nop: PASSED
Nov 15 03:07:13 stage4 kernel: Testing tracer irqsoff: PASSED
Nov 15 03:07:13 stage4 kernel: Testing tracer wakeup:
Nov 15 03:07:13 stage4 kernel: sched: DL replenish lagged too much
Nov 15 03:07:13 stage4 kernel: PASSED
Nov 15 03:07:13 stage4 kernel: Testing tracer wakeup_rt: PASSED
Nov 15 03:07:13 stage4 kernel: Testing tracer wakeup_dl: PASSED
Nov 15 03:07:13 stage4 kernel: Testing tracer function_graph: PASSED
```
Note that the changes of mcount-dyn.S conflicts with this unmerged
commit (riscv: entry: consolidate general regs saving/restoring).
https://lore.kernel.org/linux-riscv/[email protected]/
Song Shuai (3):
riscv/ftrace: add ftrace_graph_func
riscv/ftrace: SAVE_ALL supports lightweight save
riscv/ftrace: cleanup ftrace_caller and ftrace_regs_caller
arch/riscv/include/asm/ftrace.h | 13 ++-
arch/riscv/kernel/ftrace.c | 35 ++++----
arch/riscv/kernel/mcount-dyn.S | 145 +++++++++++++++++++++++---------
3 files changed, 136 insertions(+), 57 deletions(-)
--
2.20.1
In order to make the function graph use ftrace directly, ftrace_caller
should be adjusted to save the necessary regs against the pt_regs layout
so it can call ftrace_graph_func reasonably.
SAVE_ALL now saves all the regs according to the pt_regs struct. Here
introduces a lightweight option for SAVE_ALL to save only the necessary
regs for ftrace_caller.
For convenience, the original argument setup for the tracing function in
ftrace_[regs]_caller is killed and appended to the tail of SAVE_ALL.
Signed-off-by: Song Shuai <[email protected]>
---
arch/riscv/kernel/mcount-dyn.S | 110 +++++++++++++++++++++++++++------
1 file changed, 92 insertions(+), 18 deletions(-)
diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
index d171eca623b6..2f0a280bd7a0 100644
--- a/arch/riscv/kernel/mcount-dyn.S
+++ b/arch/riscv/kernel/mcount-dyn.S
@@ -56,7 +56,51 @@
.endm
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
- .macro SAVE_ALL
+
+/**
+* SAVE_ALL - save regs against the pt_regs struct
+*
+* @all: tell if saving all the regs
+*
+* If all is set, all the regs will be saved, otherwise only ABI
+* related regs (a0-a7,epc,ra and optional s0) will be saved.
+*
+* For convenience the argument setup for tracing function is appended here.
+* Especially $sp is passed as the 4th argument of the tracing function.
+*
+* After the stack is established,
+*
+* 0(sp) stores the PC of the traced function which can be accessed
+* by &(fregs)->regs->epc in tracing function. Note that the real
+* function entry address should be computed with -FENTRY_RA_OFFSET.
+*
+* 8(sp) stores the function return address (i.e. parent IP) that
+* can be accessed by &(fregs)->regs->ra in tracing function.
+*
+* The other regs are saved at the respective localtion and accessed
+* by the respective pt_regs member.
+*
+* Here is the layout of stack for your reference.
+*
+*
+* =========
+* | pip |
+* PT_SIZE_ON_STACK -> =========
+* + ..... +
+* + t3-t6 +
+* + s2-s11+
+* + a0-a7 + --++++-> ftrace_caller saved
+* + s1 + +
+* + s0 + --+
+* + t0-t2 + +
+* + tp + +
+* + gp + +
+* + sp + +
+* + ra + --+ // parent IP
+* sp -> + epc + --+ // PC of the traced function
+* +++++++++
+**/
+ .macro SAVE_ALL, all=0
addi sp, sp, -SZREG
addi sp, sp, -PT_SIZE_ON_STACK
@@ -67,14 +111,8 @@
REG_S x1, PT_RA(sp)
REG_L x1, PT_EPC(sp)
- REG_S x2, PT_SP(sp)
- REG_S x3, PT_GP(sp)
- REG_S x4, PT_TP(sp)
- REG_S x5, PT_T0(sp)
- REG_S x6, PT_T1(sp)
- REG_S x7, PT_T2(sp)
- REG_S x8, PT_S0(sp)
- REG_S x9, PT_S1(sp)
+ /* always save the ABI regs */
+
REG_S x10, PT_A0(sp)
REG_S x11, PT_A1(sp)
REG_S x12, PT_A2(sp)
@@ -83,6 +121,18 @@
REG_S x15, PT_A5(sp)
REG_S x16, PT_A6(sp)
REG_S x17, PT_A7(sp)
+
+ /* save leftover regs for ftrace_regs_caller*/
+
+ .if \all == 1
+ REG_S x2, PT_SP(sp)
+ REG_S x3, PT_GP(sp)
+ REG_S x4, PT_TP(sp)
+ REG_S x5, PT_T0(sp)
+ REG_S x6, PT_T1(sp)
+ REG_S x7, PT_T2(sp)
+ REG_S x8, PT_S0(sp)
+ REG_S x9, PT_S1(sp)
REG_S x18, PT_S2(sp)
REG_S x19, PT_S3(sp)
REG_S x20, PT_S4(sp)
@@ -97,22 +147,31 @@
REG_S x29, PT_T4(sp)
REG_S x30, PT_T5(sp)
REG_S x31, PT_T6(sp)
+ .else
+
+ /* save s0 for ftrace_caller if FP_TEST defined */
+
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+ REG_S x8, PT_S0(sp)
+#endif
+ .endif
+
+ /* setup 4 args for tracing functions */
+
+ addi a0, ra, -FENTRY_RA_OFFSET // ip
+ la a1, function_trace_op
+ REG_L a2, 0(a1) // op
+ REG_L a1, PT_SIZE_ON_STACK(sp) // parent_ip
+ mv a3, sp // fregs
.endm
- .macro RESTORE_ALL
+ .macro RESTORE_ALL, all=0
REG_L x1, PT_RA(sp)
addi sp, sp, PT_SIZE_ON_STACK
REG_S x1, (sp)
addi sp, sp, -PT_SIZE_ON_STACK
REG_L x1, PT_EPC(sp)
- REG_L x2, PT_SP(sp)
- REG_L x3, PT_GP(sp)
- REG_L x4, PT_TP(sp)
- REG_L x5, PT_T0(sp)
- REG_L x6, PT_T1(sp)
- REG_L x7, PT_T2(sp)
- REG_L x8, PT_S0(sp)
- REG_L x9, PT_S1(sp)
+
REG_L x10, PT_A0(sp)
REG_L x11, PT_A1(sp)
REG_L x12, PT_A2(sp)
@@ -121,6 +180,16 @@
REG_L x15, PT_A5(sp)
REG_L x16, PT_A6(sp)
REG_L x17, PT_A7(sp)
+
+ .if \all == 1
+ REG_L x2, PT_SP(sp)
+ REG_L x3, PT_GP(sp)
+ REG_L x4, PT_TP(sp)
+ REG_L x5, PT_T0(sp)
+ REG_L x6, PT_T1(sp)
+ REG_L x7, PT_T2(sp)
+ REG_L x8, PT_S0(sp)
+ REG_L x9, PT_S1(sp)
REG_L x18, PT_S2(sp)
REG_L x19, PT_S3(sp)
REG_L x20, PT_S4(sp)
@@ -136,6 +205,11 @@
REG_L x30, PT_T5(sp)
REG_L x31, PT_T6(sp)
+ .else
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+ REG_L x8, PT_S0(sp)
+#endif
+ .endif
addi sp, sp, PT_SIZE_ON_STACK
addi sp, sp, SZREG
.endm
--
2.20.1
Here implements ftrace_graph_func as the function graph tracing function
with FTRACE_WITH_REGS defined.
function_graph_func gets the point of the parent IP and the frame pointer
from fregs and call prepare_ftrace_return for function graph tracing.
If FTRACE_WITH_REGS isn't defined, the enable/disable helpers of
ftrace_graph_[regs]_call remain for serving the !FTRACE_WITH_REGS
version ftrace_caller.
Signed-off-by: Song Shuai <[email protected]>
---
arch/riscv/include/asm/ftrace.h | 13 +++++++++++--
arch/riscv/kernel/ftrace.c | 16 ++++++++++++++++
2 files changed, 27 insertions(+), 2 deletions(-)
diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index 04dad3380041..b33c98070972 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -81,8 +81,17 @@ do { \
struct dyn_ftrace;
int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
#define ftrace_init_nop ftrace_init_nop
-#endif
-#endif
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+struct ftrace_ops;
+struct ftrace_regs;
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *op, struct ftrace_regs *fregs);
+#define ftrace_graph_func ftrace_graph_func
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* _ASM_RISCV_FTRACE_H */
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index 2086f6585773..2d7ce77d4f33 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -196,6 +196,20 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
}
#ifdef CONFIG_DYNAMIC_FTRACE
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *op, struct ftrace_regs *fregs)
+{
+ struct pt_regs *regs = arch_ftrace_get_regs(fregs);
+ unsigned long *parent = (unsigned long *)&(regs->ra);
+
+ prepare_ftrace_return(parent, ip, frame_pointer(regs));
+}
+
+#else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
+
extern void ftrace_graph_call(void);
extern void ftrace_graph_regs_call(void);
int ftrace_enable_ftrace_graph_caller(void)
@@ -223,5 +237,7 @@ int ftrace_disable_ftrace_graph_caller(void)
return __ftrace_modify_call((unsigned long)&ftrace_graph_regs_call,
(unsigned long)&prepare_ftrace_return, false);
}
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
+
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
--
2.20.1
On Tue, Nov 15, 2022 at 02:15:23PM +0800, Song Shuai wrote:
> Here implements ftrace_graph_func as the function graph tracing function
> with FTRACE_WITH_REGS defined.
>
> function_graph_func gets the point of the parent IP and the frame pointer
> from fregs and call prepare_ftrace_return for function graph tracing.
>
> If FTRACE_WITH_REGS isn't defined, the enable/disable helpers of
> ftrace_graph_[regs]_call remain for serving the !FTRACE_WITH_REGS
> version ftrace_caller.
>
> Signed-off-by: Song Shuai <[email protected]>
Hey Song,
Last time I saw your email I'd swear it was "sugarfillet", just making
sure that it is not a typo.
Anyways, checkpatch is whinging about some parenthesis stuff:
https://patchwork.kernel.org/project/linux-riscv/patch/[email protected]/
Would be nice to fix that when you resping.
Thanks,
Conor.
> ---
> arch/riscv/include/asm/ftrace.h | 13 +++++++++++--
> arch/riscv/kernel/ftrace.c | 16 ++++++++++++++++
> 2 files changed, 27 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
> index 04dad3380041..b33c98070972 100644
> --- a/arch/riscv/include/asm/ftrace.h
> +++ b/arch/riscv/include/asm/ftrace.h
> @@ -81,8 +81,17 @@ do { \
> struct dyn_ftrace;
> int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
> #define ftrace_init_nop ftrace_init_nop
> -#endif
>
> -#endif
> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> +struct ftrace_ops;
> +struct ftrace_regs;
> +void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
> + struct ftrace_ops *op, struct ftrace_regs *fregs);
> +#define ftrace_graph_func ftrace_graph_func
> +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
> +
> +#endif /* __ASSEMBLY__ */
> +
> +#endif /* CONFIG_DYNAMIC_FTRACE */
>
> #endif /* _ASM_RISCV_FTRACE_H */
> diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
> index 2086f6585773..2d7ce77d4f33 100644
> --- a/arch/riscv/kernel/ftrace.c
> +++ b/arch/riscv/kernel/ftrace.c
> @@ -196,6 +196,20 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
> }
>
> #ifdef CONFIG_DYNAMIC_FTRACE
> +
> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> +
> +void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
> + struct ftrace_ops *op, struct ftrace_regs *fregs)
> +{
> + struct pt_regs *regs = arch_ftrace_get_regs(fregs);
> + unsigned long *parent = (unsigned long *)&(regs->ra);
> +
> + prepare_ftrace_return(parent, ip, frame_pointer(regs));
> +}
> +
> +#else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
> +
> extern void ftrace_graph_call(void);
> extern void ftrace_graph_regs_call(void);
> int ftrace_enable_ftrace_graph_caller(void)
> @@ -223,5 +237,7 @@ int ftrace_disable_ftrace_graph_caller(void)
> return __ftrace_modify_call((unsigned long)&ftrace_graph_regs_call,
> (unsigned long)&prepare_ftrace_return, false);
> }
> +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
> +
> #endif /* CONFIG_DYNAMIC_FTRACE */
> #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
> --
> 2.20.1
>