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Message-Id: <20221128101201.4144527-1-guoren@kernel.org> Date: Mon, 28 Nov 2022 05:12:00 -0500 From: guoren@...nel.org To: suagrfillet@...il.com, guoren@...nel.org Cc: aou@...s.berkeley.edu, bp@...e.de, jolsa@...hat.com, jpoimboe@...nel.org, linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org, mark.rutland@....com, mhiramat@...nel.org, palmer@...belt.com, paul.walmsley@...ive.com, peterz@...radead.org, rostedt@...dmis.org Subject: [PATCH 1/2] riscv: ftrace: Add DYNAMIC_FTRACE_WITH_DIRECT_CALLS support From: Song Shuai <suagrfillet@...il.com> This patch adds DYNAMIC_FTRACE_WITH_DIRECT_CALLS support for RISC-V. select the DYNAMIC_FTRACE_WITH_DIRECT_CALLS to provide the register_ftrace_direct[_multi] interfaces allowing users to register the customed trampoline (direct_caller) as the mcount for one or more target functions. And modify_ftrace_direct[_multi] are also provided for modifying direct_caller. To make the direct_caller and the other ftrace hooks (eg. function/fgraph tracer, k[ret]probes) co-exist, a temporary register is nominated to store the address of direct_caller in ftrace_regs_caller. After the setting of the address direct_caller by direct_ops->func and the RESTORE_REGS in ftrace_regs_caller, direct_caller will be jumped to by the `jr` inst. Signed-off-by: Song Shuai <suagrfillet@...il.com> Co-developed-by: Guo Ren <guoren@...nel.org> Signed-off-by: Guo Ren <guoren@...nel.org> --- Remove modification of mcount-dyn.S. (Guo Ren) --- arch/riscv/Kconfig | 1 + arch/riscv/include/asm/ftrace.h | 26 ++++++++++++++++++++++++++ 2 files changed, 27 insertions(+) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 1d0e5838b11b..2828537abfcd 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -278,6 +278,7 @@ config ARCH_RV64I select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 select HAVE_DYNAMIC_FTRACE if !XIP_KERNEL && MMU && $(cc-option,-fpatchable-function-entry=8) select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE + select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL select HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !PREEMPTION diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h index 84f856a3286e..d2c159cdfa5c 100644 --- a/arch/riscv/include/asm/ftrace.h +++ b/arch/riscv/include/asm/ftrace.h @@ -114,6 +114,32 @@ struct ftrace_regs; void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op, struct ftrace_regs *fregs); #define ftrace_graph_func ftrace_graph_func + +static inline void arch_ftrace_set_direct_caller(struct pt_regs *regs, unsigned long addr) +{ + /* + * Backup origin detour target (t0) in t1, and set t0 with addr. + * + * Here is the sample code for riscv direct_caller: + * + * addi sp,sp,-16 + * move t0,t1 + * ^^^^^^^^^^ + * sd t0,0(sp) + * sd ra,8(sp) + * call my_direct_func1 + * ld t0,0(sp) + * ld ra,8(sp) + * addi sp,sp,16 + * jr t0 + * + * (Set t0 with t1 for continuous detour, because t1 contains origin detour + * target) + */ + regs->t1 = regs->t0; + regs->t0 = addr; +} + #endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */ #endif /* __ASSEMBLY__ */ -- 2.36.1
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