[-next,V5,6/7] riscv: ftrace: Add DYNAMIC_FTRACE_WITH_DIRECT_CALLS support

Commit Message

Guo Ren Dec. 8, 2022, 9:12 a.m. UTC

From: Song Shuai <[e-mail]>

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 <[e-mail]>
Tested-by: Guo Ren <[e-mail]>
Signed-off-by: Guo Ren <[e-mail]>
---
 arch/riscv/Kconfig              | 1 +
 arch/riscv/include/asm/ftrace.h | 6 ++++++
 arch/riscv/kernel/mcount-dyn.S  | 4 ++++
 3 files changed, 11 insertions(+)

Patch

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index da59182cb5f1..27c2bc613ecd 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -133,6 +133,7 @@  config RISCV
 	select UACCESS_MEMCPY if !MMU
 	select ZONE_DMA32 if 64BIT
 	select HAVE_DYNAMIC_FTRACE if !XIP_KERNEL && MMU && $(cc-option,-fpatchable-function-entry=8)
+	select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE
 	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
 	select HAVE_FUNCTION_GRAPH_TRACER
diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index 84f856a3286e..4539f10fea56 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..fef7c460f991 100644
--- a/arch/riscv/kernel/mcount-dyn.S
+++ b/arch/riscv/kernel/mcount-dyn.S
@@ -232,6 +232,7 @@  ENDPROC(ftrace_caller)
 
 #else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
 ENTRY(ftrace_regs_caller)
+	move	t1, zero
 	SAVE_ABI_REGS 1
 	PREPARE_ARGS
 
@@ -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)