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]
Changes since v3:
- separate parameters preparation as PREPARE_ARGS [Guo Ren]
v3 link: https://lore.kernel.org/linux-riscv/[email protected]/
Changes since v2:
- line up the comments [Andrew]
- rename SAVE_ALL as SAVE_ABI_REGS [Guo Ren]
- consolidate the modifications of mcount-dyn.S into one patch [Guo Ren]
- adapt this series based on [riscv: ftrace: Fixup ftrace detour code][1] [Guo Ren]
[1]: https://lore.kernel.org/linux-riscv/[email protected]/
v2 Link: https://lore.kernel.org/linux-riscv/[email protected]/
Changes since v1:
- fix the checkpatch warnings in patch 1
v1 Link: https://lore.kernel.org/linux-riscv/[email protected]
Song Shuai (2):
riscv/ftrace: add ftrace_graph_func
riscv/ftrace: make ftrace_caller call ftrace_graph_func
arch/riscv/include/asm/ftrace.h | 13 ++-
arch/riscv/kernel/ftrace.c | 30 +++----
arch/riscv/kernel/mcount-dyn.S | 142 +++++++++++++++++++++++---------
3 files changed, 128 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
supersedes SAVE_ALL by SAVE_ABI_REGS which has an extra option to allow
saving only the necessary ABI-related regs for ftrace_caller.
ftrace_caller and ftrace_regs_caller save their regs with the respective
option of SAVE_ABI_REGS, then call the tracing function, especially
graph_ops's ftrace_graph_func. So the ftrace_graph_[regs]_call labels
aren't needed anymore if FTRACE_WITH_REGS is defined.
As the previous patch described, the ftrace_caller remains with its
ftrace_graph_call if FTRACE_WITH_REGS isn't defined,
For convenience, the original argument setup for the tracing function in
ftrace_[regs]_caller is separated as PREPARE_ARGS.
Signed-off-by: Song Shuai <[email protected]>
---
arch/riscv/kernel/mcount-dyn.S | 142 ++++++++++++++++++++++++---------
1 file changed, 104 insertions(+), 38 deletions(-)
diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
index 64bc79816f5e..466c6ef217b1 100644
--- a/arch/riscv/kernel/mcount-dyn.S
+++ b/arch/riscv/kernel/mcount-dyn.S
@@ -57,19 +57,52 @@
.endm
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
- .macro SAVE_ALL
+
+/**
+* SAVE_ABI_REGS - 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.
+*
+* 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.
+*
+* 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
+* +++++++++
+**/
+ .macro SAVE_ABI_REGS, all=0
addi sp, sp, -PT_SIZE_ON_STACK
REG_S t0, PT_EPC(sp)
REG_S x1, PT_RA(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)
@@ -78,6 +111,18 @@
REG_S x15, PT_A5(sp)
REG_S x16, PT_A6(sp)
REG_S x17, PT_A7(sp)
+
+ // save the leftover regs
+
+ .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)
@@ -92,19 +137,19 @@
REG_S x29, PT_T4(sp)
REG_S x30, PT_T5(sp)
REG_S x31, PT_T6(sp)
+
+ // save s0 if FP_TEST defined
+
+ .else
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+ REG_S x8, PT_S0(sp)
+#endif
+ .endif
.endm
- .macro RESTORE_ALL
+ .macro RESTORE_ABI_REGS, all=0
REG_L t0, PT_EPC(sp)
REG_L x1, PT_RA(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)
@@ -113,6 +158,16 @@
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)
@@ -128,10 +183,25 @@
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
.endm
+
+ .macro PREPARE_ARGS
+ addi a0, t0, -FENTRY_RA_OFFSET // ip
+ la a1, function_trace_op
+ REG_L a2, 0(a1) // op
+ REG_L a1, PT_RA(sp) // parent_ip
+ mv a3, sp // fregs
+ .endm
+
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
+#ifndef CONFIG_DYNAMIC_FTRACE_WITH_REGS
ENTRY(ftrace_caller)
SAVE_ABI
@@ -160,33 +230,29 @@ ftrace_graph_call:
jr t0
ENDPROC(ftrace_caller)
-#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+#else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
ENTRY(ftrace_regs_caller)
- SAVE_ALL
-
- addi a0, t0, -FENTRY_RA_OFFSET
- la a1, function_trace_op
- REG_L a2, 0(a1)
- REG_L a1, PT_RA(sp)
- mv a3, sp
+ SAVE_ABI_REGS 1
+ PREPARE_ARGS
ftrace_regs_call:
.global ftrace_regs_call
call ftrace_stub
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
- addi a0, sp, PT_RA
- REG_L a1, PT_T0(sp)
- addi a1, a1, -FENTRY_RA_OFFSET
-#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
- mv a2, s0
-#endif
-ftrace_graph_regs_call:
- .global ftrace_graph_regs_call
- call ftrace_stub
-#endif
- RESTORE_ALL
+ RESTORE_ABI_REGS 1
jr t0
ENDPROC(ftrace_regs_caller)
+
+ENTRY(ftrace_caller)
+ SAVE_ABI_REGS 0
+ PREPARE_ARGS
+
+ftrace_call:
+ .global ftrace_call
+ call ftrace_stub
+
+ RESTORE_ABI_REGS 0
+ jr t0
+ENDPROC(ftrace_caller)
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
--
2.20.1