Messages in this thread Patch in this message | | | From | Song Shuai <> | Subject | [PATCH v2 2/3] riscv/ftrace: SAVE_ALL supports lightweight save | Date | Wed, 16 Nov 2022 11:13:04 +0800 |
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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@gmail.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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