Hi Guo,
On 1/3/23 04:35, guoren@xxxxxxxxxx wrote:
From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
Without noinstr the compiler is free to insert instrumentation (think
all the k*SAN, KCov, GCov, ftrace etc..) which can call code we're not
yet ready to run this early in the entry path, for instance it could
rely on RCU which isn't on yet, or expect lockdep state. (by peterz)
Link: https://lore.kernel.org/linux-riscv/YxcQ6NoPf3AH0EXe@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Reviewed-by: Björn Töpel <bjorn@xxxxxxxxxxxx>
Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Tested-by: Jisheng Zhang <jszhang@xxxxxxxxxx>
Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
---
arch/riscv/kernel/traps.c | 4 ++--
arch/riscv/mm/fault.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 549bde5c970a..96ec76c54ff2 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -95,9 +95,9 @@ static void do_trap_error(struct pt_regs *regs, int signo, int code,
}
#if defined(CONFIG_XIP_KERNEL) && defined(CONFIG_RISCV_ALTERNATIVE)
-#define __trap_section __section(".xip.traps")
+#define __trap_section __noinstr_section(".xip.traps")
#else
-#define __trap_section
+#define __trap_section noinstr
#endif
#define DO_ERROR_INFO(name, signo, code, str) \
asmlinkage __visible __trap_section void name(struct pt_regs *regs) \
diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index d86f7cebd4a7..b26f68eac61c 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -204,7 +204,7 @@ static inline bool access_error(unsigned long cause, struct vm_area_struct *vma)
* This routine handles page faults. It determines the address and the
* problem, and then passes it off to one of the appropriate routines.
*/
-asmlinkage void do_page_fault(struct pt_regs *regs)
+asmlinkage void noinstr do_page_fault(struct pt_regs *regs)
(I dug the archive but can't find the series before v4, so sorry if it
was already answered)
I think we should not disable the instrumentation of those trap handlers
as at least profiling them with ftrace would provide valuable
information (and gcov would be nice too): why do we need to do that? A
trap very early in the boot process is not recoverable anyway.
And I took a look at other architectures, none of them disables the
instrumentation on do_page_fault.
{
struct task_struct *tsk;
struct vm_area_struct *vma;
