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[31.30.173.16]) by smtp.gmail.com with ESMTPSA id h23-20020a170906585700b007317f017e64sm6572448ejs.134.2022.11.16.00.45.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Nov 2022 00:45:41 -0800 (PST) Date: Wed, 16 Nov 2022 09:45:40 +0100 From: Andrew Jones To: Song Shuai Cc: guoren@kernel.org, rostedt@goodmis.org, mhiramat@kernel.org, mark.rutland@arm.com, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/3] riscv/ftrace: SAVE_ALL supports lightweight save Message-ID: <20221116084540.aslzynq4bmar6f46@kamzik> References: <20221116031305.286634-1-suagrfillet@gmail.com> <20221116031305.286634-3-suagrfillet@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221116031305.286634-3-suagrfillet@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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. > +* > +* 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