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Message-Id: <20221115061525.112757-3-suagrfillet@gmail.com>
Date: Tue, 15 Nov 2022 14:15:24 +0800
From: Song Shuai <suagrfillet@...il.com>
To: guoren@...nel.org, rostedt@...dmis.org, mhiramat@...nel.org,
mark.rutland@....com, paul.walmsley@...ive.com, palmer@...belt.com,
aou@...s.berkeley.edu
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
Song Shuai <suagrfillet@...il.com>
Subject: [PATCH 2/3] riscv/ftrace: SAVE_ALL supports lightweight save
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 <suagrfillet@...il.com>
---
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
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