On 8/6/25 6:35 AM, Sabyrzhan Tasbolatov wrote:

On Tue, Aug 5, 2025 at 10:19 PM Andrey Ryabinin [off-list ref] wrote:

quoted

On 8/5/25 4:26 PM, Sabyrzhan Tasbolatov wrote:

quoted

diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 9083bfdb773..8d14c8fc2cd 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig

@@ -5,6 +5,7 @@ menu "UML-specific options"
 config UML
      bool
      default y
+     select ARCH_DEFER_KASAN

select ARCH_DEFER_KASAN if STATIC_LINK

As pointed out in commit 5b301409e8bc("UML: add support for KASAN
under x86_64"),

: Also note that, while UML supports both KASAN in inline mode
(CONFIG_KASAN_INLINE)
: and static linking (CONFIG_STATIC_LINK), it does not support both at
the same time.

I've tested that for UML,
ARCH_DEFER_KASAN works if STATIC_LINK && KASAN_OUTLINE
ARCH_DEFER_KASAN works if KASAN_INLINE && !STATIC_LINK

ARCH_DEFER_KASAN if STATIC_LINK, and KASAN_INLINE=y by default from defconfig
crashes with SEGFAULT here (I didn't understand what it is, I think
the main() constructors
is not prepared in UML):

 ► 0       0x609d6f87 strlen+43
   1       0x60a20db0 _dl_new_object+48
   2       0x60a24627 _dl_non_dynamic_init+103
   3       0x60a25f9a __libc_init_first+42
   4       0x609eb6b2 __libc_start_main_impl+2434
   5       0x6004a025 _start+37

No surprise here, kasan_arch_is_ready() or ARCH_DEFER_KASAN doesn't work with KASAN_INLINE=y
This configuration combination (STATIC_LINK + KASAN_INLINE) wasn't possible before:

#ifndef kasan_arch_is_ready
static inline bool kasan_arch_is_ready(void)   { return true; }
#elif !defined(CONFIG_KASAN_GENERIC) || !defined(CONFIG_KASAN_OUTLINE)
#error kasan_arch_is_ready only works in KASAN generic outline mode!
#endif

Since this is the case only for UML, AFAIU, I don't think we want to change
conditions in lib/Kconfig.kasan. Shall I leave UML Kconfig as it is? e.g.

select ARCH_DEFER_KASAN

No, this should have if STATIC_LINK