Merge patch series "RISC-V: Dynamic ftrace support for RV32I"

Jamie Iles <jamie@jamieiles.com> says:

This series enables dynamic ftrace support for RV32I bringing it to
parity with RV64I.  Most of the work is already there, this is largely
just assembly fixes to handle register sizes, correct handling of the
psABI calling convention and Kconfig change.

Validated with all ftrace boot time self test with qemu for RV32I and
RV64I in addition to real tracing on an RV32I FPGA design.

* b4-shazam-merge:
  RISC-V: enable dynamic ftrace for RV32I
  RISC-V: preserve a1 in mcount
  RISC-V: reduce mcount save space on RV32
  RISC-V: use REG_S/REG_L for mcount

Link: https://lore.kernel.org/r/20221115200832.706370-1-jamie@jamieiles.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

2 files changed, 28 insertions, 26 deletions

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 3b41165a8b10..8d47562be90c 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -131,6 +131,11 @@ config RISCV
 	select TRACE_IRQFLAGS_SUPPORT
 	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_REGS if HAVE_DYNAMIC_FTRACE
+	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
+	select HAVE_FUNCTION_GRAPH_TRACER
+	select HAVE_FUNCTION_TRACER if !XIP_KERNEL
 
 config ARCH_MMAP_RND_BITS_MIN
 	default 18 if 64BIT
@@ -276,11 +281,6 @@ config ARCH_RV64I
 	bool "RV64I"
 	select 64BIT
 	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_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
-	select HAVE_FUNCTION_GRAPH_TRACER
-	select HAVE_FUNCTION_TRACER if !XIP_KERNEL
 	select SWIOTLB if MMU
 
 endchoice
diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S
index 6d462681c9c0..30102aadc4d7 100644
--- a/arch/riscv/kernel/mcount.S
+++ b/arch/riscv/kernel/mcount.S
@@ -15,8 +15,8 @@
 
 	.macro SAVE_ABI_STATE
 	addi	sp, sp, -16
-	sd	s0, 0(sp)
-	sd	ra, 8(sp)
+	REG_S	s0, 0*SZREG(sp)
+	REG_S	ra, 1*SZREG(sp)
 	addi	s0, sp, 16
 	.endm
 
@@ -25,24 +25,26 @@
 	 * register if a0 was not saved.
 	 */
 	.macro SAVE_RET_ABI_STATE
-	addi	sp, sp, -32
-	sd	s0, 16(sp)
-	sd	ra, 24(sp)
-	sd	a0, 8(sp)
-	addi	s0, sp, 32
+	addi	sp, sp, -4*SZREG
+	REG_S	s0, 2*SZREG(sp)
+	REG_S	ra, 3*SZREG(sp)
+	REG_S	a0, 1*SZREG(sp)
+	REG_S	a1, 0*SZREG(sp)
+	addi	s0, sp, 4*SZREG
 	.endm
 
 	.macro RESTORE_ABI_STATE
-	ld	ra, 8(sp)
-	ld	s0, 0(sp)
+	REG_L	ra, 1*SZREG(sp)
+	REG_L	s0, 0*SZREG(sp)
 	addi	sp, sp, 16
 	.endm
 
 	.macro RESTORE_RET_ABI_STATE
-	ld	ra, 24(sp)
-	ld	s0, 16(sp)
-	ld	a0, 8(sp)
-	addi	sp, sp, 32
+	REG_L	ra, 3*SZREG(sp)
+	REG_L	s0, 2*SZREG(sp)
+	REG_L	a0, 1*SZREG(sp)
+	REG_L	a1, 0*SZREG(sp)
+	addi	sp, sp, 4*SZREG
 	.endm
 
 ENTRY(ftrace_stub)
@@ -71,9 +73,9 @@ ENTRY(return_to_handler)
 	mv	a0, t6
 #endif
 	call	ftrace_return_to_handler
-	mv	a1, a0
+	mv	a2, a0
 	RESTORE_RET_ABI_STATE
-	jalr	a1
+	jalr	a2
 ENDPROC(return_to_handler)
 #endif
 
@@ -82,16 +84,16 @@ ENTRY(MCOUNT_NAME)
 	la	t4, ftrace_stub
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	la	t0, ftrace_graph_return
-	ld	t1, 0(t0)
+	REG_L	t1, 0(t0)
 	bne	t1, t4, do_ftrace_graph_caller
 
 	la	t3, ftrace_graph_entry
-	ld	t2, 0(t3)
+	REG_L	t2, 0(t3)
 	la	t6, ftrace_graph_entry_stub
 	bne	t2, t6, do_ftrace_graph_caller
 #endif
 	la	t3, ftrace_trace_function
-	ld	t5, 0(t3)
+	REG_L	t5, 0(t3)
 	bne	t5, t4, do_trace
 	ret
 
@@ -101,10 +103,10 @@ ENTRY(MCOUNT_NAME)
  * prepare_to_return(&ra_to_caller_of_caller, ra_to_caller)
  */
 do_ftrace_graph_caller:
-	addi	a0, s0, -8
+	addi	a0, s0, -SZREG
 	mv	a1, ra
 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
-	ld	a2, -16(s0)
+	REG_L	a2, -2*SZREG(s0)
 #endif
 	SAVE_ABI_STATE
 	call	prepare_ftrace_return
@@ -117,7 +119,7 @@ do_ftrace_graph_caller:
  * (*ftrace_trace_function)(ra_to_caller, ra_to_caller_of_caller)
  */
 do_trace:
-	ld	a1, -8(s0)
+	REG_L	a1, -SZREG(s0)
 	mv	a0, ra
 
 	SAVE_ABI_STATE