PR target/96260 - KASAN should work even back-end not porting anything.

 - Most KASAN function don't need any porting anything in back-end
   except asan stack protection.

 - However kernel will given shadow offset when enable asan stack
   protection, so eveything in KASAN can work if shadow offset is given.

 - Verified with x86 and risc-v.

 - Verified with RISC-V linux kernel.

gcc/ChangeLog:

	PR target/96260
	* asan.c (asan_shadow_offset_set_p): New.
	* asan.h (asan_shadow_offset_set_p): Ditto.
	* toplev.c (process_options): Allow -fsanitize=kernel-address
	even TARGET_ASAN_SHADOW_OFFSET not implemented, only check when
	asan stack protection is enabled.

gcc/testsuite/ChangeLog:

	PR target/96260
	* gcc.target/riscv/pr91441.c: Update warning message.
	* gcc.target/riscv/pr96260.c: New.

1 files changed, 2 insertions, 0 deletions

diff --git a/gcc/asan.h b/gcc/asan.h
index 9efd33f..114b457 100644
--- a/gcc/asan.h
+++ b/gcc/asan.h
@@ -129,6 +129,8 @@ asan_var_and_redzone_size (unsigned HOST_WIDE_INT size)
 
 extern bool set_asan_shadow_offset (const char *);
 
+extern bool asan_shadow_offset_set_p ();
+
 extern void set_sanitized_sections (const char *);
 
 extern bool asan_sanitize_stack_p (void);