riscv: ftrace: support fastcc in Clang for WITH_ARGS

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/
Fixes: 7caa9765465f ("ftrace: riscv: move from REGS to ARGS")
Acked-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20250407180838.42877-1-andybnac@gmail.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>

diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index d627f63ee289c7964b1a5e481add02125376bcd3..d8b2138bd9c6642857153fe9f3b0f5a4c6618ff3 100644 (file)
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -146,6 +146,13 @@ struct __arch_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 16490755304e0c275a9600281d5975de74a585a1..7c43c8e26ae7f72a8445195bd785c5c5875f7cd5 100644 (file)
--- a/arch/riscv/kernel/asm-offsets.c
+++ b/arch/riscv/kernel/asm-offsets.c
@@ -501,6 +501,13 @@ void asm_offsets(void)
        DEFINE(FREGS_SP,            offsetof(struct __arch_ftrace_regs, sp));
        DEFINE(FREGS_S0,            offsetof(struct __arch_ftrace_regs, s0));
        DEFINE(FREGS_T1,            offsetof(struct __arch_ftrace_regs, t1));
+#ifdef CONFIG_CC_IS_CLANG
+       DEFINE(FREGS_T2,            offsetof(struct __arch_ftrace_regs, t2));
+       DEFINE(FREGS_T3,            offsetof(struct __arch_ftrace_regs, t3));
+       DEFINE(FREGS_T4,            offsetof(struct __arch_ftrace_regs, t4));
+       DEFINE(FREGS_T5,            offsetof(struct __arch_ftrace_regs, t5));
+       DEFINE(FREGS_T6,            offsetof(struct __arch_ftrace_regs, t6));
+#endif
        DEFINE(FREGS_A0,            offsetof(struct __arch_ftrace_regs, a0));
        DEFINE(FREGS_A1,            offsetof(struct __arch_ftrace_regs, a1));
        DEFINE(FREGS_A2,            offsetof(struct __arch_ftrace_regs, a2));

diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
index 745dd4c4a69c3571d539fa7a92107647a9dc3dba..e988bd26b28bd55ca2bc05fdd2625b499f6977f7 100644 (file)
--- 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)