[PATCH v8 RESEND 5/9] LoongArch/ftrace: Add HAVE_DYNAMIC_FTRACE_WITH_REGS support

From: Qing Zhang
Date: Wed Nov 16 2022 - 03:26:40 EST


This patch implements CONFIG_DYNAMIC_FTRACE_WITH_REGS on LoongArch, which allows
a traced function's arguments (and some other registers) to be captured
into a struct pt_regs, allowing these to be inspected and modified.

Co-developed-by: Jinyang He <hejinyang@xxxxxxxxxxx>
Signed-off-by: Jinyang He <hejinyang@xxxxxxxxxxx>
Signed-off-by: Qing Zhang <zhangqing@xxxxxxxxxxx>
---
arch/loongarch/Kconfig | 1 +
arch/loongarch/include/asm/ftrace.h | 1 +
arch/loongarch/kernel/ftrace_dyn.c | 17 ++++++++++++++
arch/loongarch/kernel/mcount_dyn.S | 36 +++++++++++++++++++++++++++--
4 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 615ce62422b8..12e3e91a68ae 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -90,6 +90,7 @@ config LOONGARCH
select HAVE_DEBUG_STACKOVERFLOW
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
+ select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_EBPF_JIT
select HAVE_EXIT_THREAD
select HAVE_FAST_GUP
diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
index 76ca58767f4d..e2803582e110 100644
--- a/arch/loongarch/include/asm/ftrace.h
+++ b/arch/loongarch/include/asm/ftrace.h
@@ -27,6 +27,7 @@ struct dyn_arch_ftrace {
struct dyn_ftrace;
int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
#define ftrace_init_nop ftrace_init_nop
+#define ARCH_SUPPORTS_FTRACE_OPS 1

#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* __ASSEMBLY__ */
diff --git a/arch/loongarch/kernel/ftrace_dyn.c b/arch/loongarch/kernel/ftrace_dyn.c
index 3fe791b6783e..ec3d951be50c 100644
--- a/arch/loongarch/kernel/ftrace_dyn.c
+++ b/arch/loongarch/kernel/ftrace_dyn.c
@@ -99,6 +99,23 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
return ftrace_modify_code(pc, old, new, true);
}

+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+ unsigned long addr)
+{
+ unsigned long pc;
+ long offset;
+ u32 old, new;
+
+ pc = rec->ip + LOONGARCH_INSN_SIZE;
+
+ old = larch_insn_gen_bl(pc, old_addr);
+ new = larch_insn_gen_bl(pc, addr);
+
+ return ftrace_modify_code(pc, old, new, true);
+}
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
+
void arch_ftrace_update_code(int command)
{
command |= FTRACE_MAY_SLEEP;
diff --git a/arch/loongarch/kernel/mcount_dyn.S b/arch/loongarch/kernel/mcount_dyn.S
index 0c12cc108e6f..02835186b463 100644
--- a/arch/loongarch/kernel/mcount_dyn.S
+++ b/arch/loongarch/kernel/mcount_dyn.S
@@ -27,7 +27,7 @@
* follows the LoongArch psABI well.
*/

- .macro ftrace_regs_entry
+ .macro ftrace_regs_entry allregs=0
PTR_ADDI sp, sp, -PT_SIZE
/* Save trace function ra at PT_ERA */
PTR_S ra, sp, PT_ERA
@@ -43,16 +43,48 @@
PTR_S a7, sp, PT_R11
PTR_S fp, sp, PT_R22

+ .if \allregs
+ PTR_S t0, sp, PT_R12
+ PTR_S t1, sp, PT_R13
+ PTR_S t2, sp, PT_R14
+ PTR_S t3, sp, PT_R15
+ PTR_S t4, sp, PT_R16
+ PTR_S t5, sp, PT_R17
+ PTR_S t6, sp, PT_R18
+ PTR_S t7, sp, PT_R19
+ PTR_S t8, sp, PT_R20
+ PTR_S s0, sp, PT_R23
+ PTR_S s1, sp, PT_R24
+ PTR_S s2, sp, PT_R25
+ PTR_S s3, sp, PT_R26
+ PTR_S s4, sp, PT_R27
+ PTR_S s5, sp, PT_R28
+ PTR_S s6, sp, PT_R29
+ PTR_S s7, sp, PT_R30
+ PTR_S s8, sp, PT_R31
+ PTR_S tp, sp, PT_R2
+ /* Clear it for later use as a flag sometimes. */
+ PTR_S zero, sp, PT_R0
+ PTR_S $r21, sp, PT_R21
+ .endif
+
PTR_ADDI t8, sp, PT_SIZE
PTR_S t8, sp, PT_R3

.endm

SYM_CODE_START(ftrace_caller)
- ftrace_regs_entry
+ ftrace_regs_entry allregs=0
b ftrace_common
SYM_CODE_END(ftrace_caller)

+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+SYM_CODE_START(ftrace_regs_caller)
+ ftrace_regs_entry allregs=1
+ b ftrace_common
+SYM_CODE_END(ftrace_regs_caller)
+#endif
+
SYM_CODE_START(ftrace_common)
PTR_ADDI a0, ra, -8 /* arg0: ip */
move a1, t0 /* arg1: parent_ip */
--
2.36.0