Messages in this thread | | | From | Guo Ren <> | Date | Thu, 17 Nov 2022 09:55:41 +0800 | Subject | Re: [PATCH v2 2/3] riscv/ftrace: SAVE_ALL supports lightweight save |
| |
On Wed, Nov 16, 2022 at 4:45 PM Andrew Jones <ajones@ventanamicro.com> wrote: > > On Wed, Nov 16, 2022 at 11:13:04AM +0800, Song Shuai wrote: > > 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 > > I find it odd to have a macro name that includes 'ALL' in it > to require a parameter 'all' to be set in order to actually save > all. I suggest renaming the macro to something like SAVE_REGS. SAVE_ABI_REGS <arg> arg = 0 -> SAVE_ABI in pt_regs arg = 1 -> SAVE_REGS
SAVE_ABI_REGS keeps the pt_regs layout and needs more stack space than SAVE_ABI.
> > > +* > > +* 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 > > Please line up the comments. > > > .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 > > > > > > Thanks, > drew
-- Best Regards Guo Ren
| |