[PATCH v3 1/7] riscv: ftrace: support fastcc in Clang for WITH_ARGS

Andy Chiu
2024-11-27T17:30:02Z

From: Andy Chiu <andy.chiu@sifive.com>

Some caller-saved registers which are not defined as function arguments
in the ABI can still be passed as arguments when the kernel is compiled
with Clang. As a result, we must save and restore those registers to
prevent ftrace from clobbering them.

- [1]: https://reviews.llvm.org/D68559

Reported-by: Evgenii Shatokhin <e.shatokhin@yadro.com>
Closes: https://lore.kernel.org/linux-riscv/7e7c7914-445d-426d-89a0-59a9199c45b1@yadro.com/
Acked-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
---
arch/riscv/include/asm/ftrace.h | 7 +++++++
arch/riscv/kernel/asm-offsets.c | 7 +++++++
arch/riscv/kernel/mcount-dyn.S | 16 ++++++++++++++--
3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index 2cddd79ff21b..4ca7ce7f34d7 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -143,6 +143,13 @@ struct ftrace_regs {
unsigned long a5;
unsigned long a6;
unsigned long a7;
+#ifdef CONFIG_CC_IS_CLANG
+ unsigned long t2;
+ unsigned long t3;
+ unsigned long t4;
+ unsigned long t5;
+ unsigned long t6;
+#endif
};
};
};
diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c
index e94180ba432f..59789dfb2d5d 100644
--- a/arch/riscv/kernel/asm-offsets.c
+++ b/arch/riscv/kernel/asm-offsets.c
@@ -504,6 +504,13 @@ void asm_offsets(void)
DEFINE(FREGS_SP, offsetof(struct ftrace_regs, sp));
DEFINE(FREGS_S0, offsetof(struct ftrace_regs, s0));
DEFINE(FREGS_T1, offsetof(struct ftrace_regs, t1));
+#ifdef CONFIG_CC_IS_CLANG
+ DEFINE(FREGS_T2, offsetof(struct ftrace_regs, t2));
+ DEFINE(FREGS_T3, offsetof(struct ftrace_regs, t3));
+ DEFINE(FREGS_T4, offsetof(struct ftrace_regs, t4));
+ DEFINE(FREGS_T5, offsetof(struct ftrace_regs, t5));
+ DEFINE(FREGS_T6, offsetof(struct ftrace_regs, t6));
+#endif
DEFINE(FREGS_A0, offsetof(struct ftrace_regs, a0));
DEFINE(FREGS_A1, offsetof(struct ftrace_regs, a1));
DEFINE(FREGS_A2, offsetof(struct ftrace_regs, a2));
diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
index 745dd4c4a69c..e988bd26b28b 100644
--- a/arch/riscv/kernel/mcount-dyn.S
+++ b/arch/riscv/kernel/mcount-dyn.S
@@ -96,7 +96,13 @@
REG_S x8, FREGS_S0(sp)
#endif
REG_S x6, FREGS_T1(sp)
-
+#ifdef CONFIG_CC_IS_CLANG
+ REG_S x7, FREGS_T2(sp)
+ REG_S x28, FREGS_T3(sp)
+ REG_S x29, FREGS_T4(sp)
+ REG_S x30, FREGS_T5(sp)
+ REG_S x31, FREGS_T6(sp)
+#endif
// save the arguments
REG_S x10, FREGS_A0(sp)
REG_S x11, FREGS_A1(sp)
@@ -115,7 +121,13 @@
REG_L x8, FREGS_S0(sp)
#endif
REG_L x6, FREGS_T1(sp)
-
+#ifdef CONFIG_CC_IS_CLANG
+ REG_L x7, FREGS_T2(sp)
+ REG_L x28, FREGS_T3(sp)
+ REG_L x29, FREGS_T4(sp)
+ REG_L x30, FREGS_T5(sp)
+ REG_L x31, FREGS_T6(sp)
+#endif
// restore the arguments
REG_L x10, FREGS_A0(sp)
REG_L x11, FREGS_A1(sp)
--
2.39.3 (Apple Git-145)