[PATCH v5 01/12] riscv: ftrace: Fix to pass correct ftrace_regs to ftrace_func_t functions

Masami Hiramatsu (Google)
2023-09-24T13:36:06Z

Since ftrace_func_t requires to pass 'struct ftrace_regs *' as the 4th
argument even if FTRACE_OPS_FL_SAVE_REGS is not set, ftrace_caller must
pass 'struct ftrace_regs *', which is a partial pt_regs, on the stack
to the ftrace_func_t functions, so that the ftrace_func_t functions can
access some partial registers.

Fix to allocate 'struct ftrace_regs' (which has the same size of 'struct
pt_regs') on the stack and save partial (argument) registers on it
instead of reduced size custom data structure.

Fixes: afc76b8b8011 ("riscv: Using PATCHABLE_FUNCTION_ENTRY instead of MCOUNT")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
arch/riscv/kernel/mcount-dyn.S | 65 +++++++++++++++++-----------------------
1 file changed, 28 insertions(+), 37 deletions(-)

diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
index 669b8697aa38..84963680eff4 100644
--- a/arch/riscv/kernel/mcount-dyn.S
+++ b/arch/riscv/kernel/mcount-dyn.S
@@ -14,46 +14,37 @@
.text

#define FENTRY_RA_OFFSET 8
-#define ABI_SIZE_ON_STACK 80
-#define ABI_A0 0
-#define ABI_A1 8
-#define ABI_A2 16
-#define ABI_A3 24
-#define ABI_A4 32
-#define ABI_A5 40
-#define ABI_A6 48
-#define ABI_A7 56
-#define ABI_T0 64
-#define ABI_RA 72

.macro SAVE_ABI
- addi sp, sp, -ABI_SIZE_ON_STACK
-
- REG_S a0, ABI_A0(sp)
- REG_S a1, ABI_A1(sp)
- REG_S a2, ABI_A2(sp)
- REG_S a3, ABI_A3(sp)
- REG_S a4, ABI_A4(sp)
- REG_S a5, ABI_A5(sp)
- REG_S a6, ABI_A6(sp)
- REG_S a7, ABI_A7(sp)
- REG_S t0, ABI_T0(sp)
- REG_S ra, ABI_RA(sp)
+ addi sp, sp, -PT_SIZE_ON_STACK
+
+ /* Save t0 as epc for ftrace_regs_get_instruction_pointer() */
+ REG_S t0, PT_EPC(sp)
+ REG_S a0, PT_A0(sp)
+ REG_S a1, PT_A1(sp)
+ REG_S a2, PT_A2(sp)
+ REG_S a3, PT_A3(sp)
+ REG_S a4, PT_A4(sp)
+ REG_S a5, PT_A5(sp)
+ REG_S a6, PT_A6(sp)
+ REG_S a7, PT_A7(sp)
+ REG_S t0, PT_T0(sp)
+ REG_S ra, PT_RA(sp)
.endm

.macro RESTORE_ABI
- REG_L a0, ABI_A0(sp)
- REG_L a1, ABI_A1(sp)
- REG_L a2, ABI_A2(sp)
- REG_L a3, ABI_A3(sp)
- REG_L a4, ABI_A4(sp)
- REG_L a5, ABI_A5(sp)
- REG_L a6, ABI_A6(sp)
- REG_L a7, ABI_A7(sp)
- REG_L t0, ABI_T0(sp)
- REG_L ra, ABI_RA(sp)
-
- addi sp, sp, ABI_SIZE_ON_STACK
+ REG_L a0, PT_A0(sp)
+ REG_L a1, PT_A1(sp)
+ REG_L a2, PT_A2(sp)
+ REG_L a3, PT_A3(sp)
+ REG_L a4, PT_A4(sp)
+ REG_L a5, PT_A5(sp)
+ REG_L a6, PT_A6(sp)
+ REG_L a7, PT_A7(sp)
+ REG_L t0, PT_T0(sp)
+ REG_L ra, PT_RA(sp)
+
+ addi sp, sp, PT_SIZE_ON_STACK
.endm

#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
@@ -96,8 +87,8 @@ ftrace_call:
call ftrace_stub

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
- addi a0, sp, ABI_RA
- REG_L a1, ABI_T0(sp)
+ addi a0, sp, PT_RA
+ REG_L a1, PT_T0(sp)
addi a1, a1, -FENTRY_RA_OFFSET
#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
mv a2, s0