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Subject[PATCH 1/2] riscv/ftrace: add DYNAMIC_FTRACE_WITH_DIRECT_CALLS support
Date
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@gmail.com>
---
arch/riscv/Kconfig | 1 +
arch/riscv/include/asm/ftrace.h | 6 ++++++
arch/riscv/kernel/mcount-dyn.S | 4 ++++
3 files changed, 11 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 39ec8d628cf6..d083ec08d0b6 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 01bebb28eabe..be4d57566139 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -114,6 +114,12 @@ 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)
+{
+ regs->t1 = addr;
+}
+
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */

#endif /* __ASSEMBLY__ */
diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
index 466c6ef217b1..b89c85a58569 100644
--- a/arch/riscv/kernel/mcount-dyn.S
+++ b/arch/riscv/kernel/mcount-dyn.S
@@ -233,6 +233,7 @@ ENDPROC(ftrace_caller)
#else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
ENTRY(ftrace_regs_caller)
SAVE_ABI_REGS 1
+ REG_S x0, PT_T1(sp)
PREPARE_ARGS

ftrace_regs_call:
@@ -241,7 +242,10 @@ ftrace_regs_call:


RESTORE_ABI_REGS 1
+ bnez t1,.Ldirect
jr t0
+.Ldirect:
+ jr t1
ENDPROC(ftrace_regs_caller)

ENTRY(ftrace_caller)
--
2.20.1
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