diff options
| author | Marco Elver <elver@google.com> | 2026-05-21 14:23:55 +0200 |
|---|---|---|
| committer | Dinh Nguyen <dinguyen@kernel.org> | 2026-05-21 18:50:46 -0500 |
| commit | e90ef85ada857819313000cc50c6edfcddec6850 (patch) | |
| tree | dac30ecccddc3779d08024193672c8ab409ec4b0 /arch/nios2 | |
| parent | 7734b168cad167a43e5bda19bc8ccc65669ec964 (diff) | |
nios2: Implement _THIS_IP_ using inline asm
Both GCC [1] and Clang [2] consider the generic version of _THIS_IP_ to
be broken:
#define _THIS_IP_ ({ __label__ __here; __here: (unsigned long)&&__here; })
In particular, the address of a label is only expected to be used with a
computed goto.
While the generic version more or less works today, it is known to be
brittle and may break with current and future optimizations. For
example, Clang -O2 always returns 1 when this function is inlined:
static inline unsigned long get_ip(void)
{ return ({ __label__ __here; __here: (unsigned long)&&__here; }); }
Fix it by overriding _THIS_IP_ in <asm/linkage.h> (which is included by
<linux/instruction_pointer.h>) using an architecture-specific inline asm
version. Additionally, avoiding taking the address of a label prevents
compilers from emitting spurious indirect branch targets (e.g. ENDBR or
BTI) under control-flow integrity schemes.
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120071 [1]
Link: https://github.com/llvm/llvm-project/issues/138272 [2]
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: David Laight <david.laight.linux@gmail.com>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
Diffstat (limited to 'arch/nios2')
| -rw-r--r-- | arch/nios2/include/asm/linkage.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/nios2/include/asm/linkage.h b/arch/nios2/include/asm/linkage.h index 211302301a8a..c4073235852b 100644 --- a/arch/nios2/include/asm/linkage.h +++ b/arch/nios2/include/asm/linkage.h @@ -12,4 +12,6 @@ #define __ALIGN .align 4 #define __ALIGN_STR ".align 4" +#define _THIS_IP_ ({ unsigned long __ip; asm volatile("nextpc %0" : "=r" (__ip)); __ip; }) + #endif |