The following commit has been merged into the x86/percpu branch of tip:
Commit-ID: 0e3703630bd3fead041a6bfb3a3f2a9891af6c34
Gitweb: https://git.kernel.org/tip/0e3703630bd3fead041a6bfb3a3f2a9891af6c34
Author: Uros Bizjak <ubizjak@xxxxxxxxx>
AuthorDate: Mon, 04 Dec 2023 22:02:29 +01:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Mon, 11 Dec 2023 11:47:14 +01:00
x86/percpu: Fix "const_pcpu_hot" version generation failure
Version generation for "const_pcpu_hot" symbol failed because genksyms
doesn't know the __seg_gs keyword. Effectively revert commit 4604c052b84d
("x86/percpu: Declare const_pcpu_hot as extern const variable") and
use this_cpu_read_const() instead to avoid "sparse: dereference of
noderef expression" warning when reading const_pcpu_hot.
Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20231204210320.114429-1-ubizjak@xxxxxxxxx
---
arch/x86/include/asm/current.h | 5 +++--
arch/x86/include/asm/percpu.h | 7 +++++++
arch/x86/include/asm/processor.h | 2 +-
3 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/current.h b/arch/x86/include/asm/current.h
index 9fbd7cb..c8c5674 100644
--- a/arch/x86/include/asm/current.h
+++ b/arch/x86/include/asm/current.h
@@ -37,12 +37,13 @@ static_assert(sizeof(struct pcpu_hot) == 64);
DECLARE_PER_CPU_ALIGNED(struct pcpu_hot, pcpu_hot);
/* const-qualified alias to pcpu_hot, aliased by linker. */
-extern const struct pcpu_hot __percpu_seg_override const_pcpu_hot;
+DECLARE_PER_CPU_ALIGNED(const struct pcpu_hot __percpu_seg_override,
+ const_pcpu_hot);
static __always_inline struct task_struct *get_current(void)
{
if (IS_ENABLED(CONFIG_USE_X86_SEG_SUPPORT))
- return const_pcpu_hot.current_task;
+ return this_cpu_read_const(const_pcpu_hot.current_task);
return this_cpu_read_stable(pcpu_hot.current_task);
}
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 0f12b20..3859aba 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -28,6 +28,7 @@
#else /* ...!ASSEMBLY */
+#include <linux/build_bug.h>
#include <linux/kernel.h>
#include <linux/stringify.h>
@@ -462,6 +463,7 @@ do { \
#define this_cpu_write_8(pcp, val) __raw_cpu_write(volatile, pcp, val)
#endif
+#define this_cpu_read_const(pcp) __raw_cpu_read(, pcp)
#else /* CONFIG_USE_X86_SEG_SUPPORT */
#define raw_cpu_read_1(pcp) percpu_from_op(1, , "mov", pcp)
@@ -486,6 +488,11 @@ do { \
#define this_cpu_write_8(pcp, val) percpu_to_op(8, volatile, "mov", (pcp), val)
#endif
+/*
+ * The generic per-cpu infrastrucutre is not suitable for
+ * reading const-qualified variables.
+ */
+#define this_cpu_read_const(pcp) ({ BUILD_BUG(); (typeof(pcp))0; })
#endif /* CONFIG_USE_X86_SEG_SUPPORT */
#define raw_cpu_add_1(pcp, val) percpu_add_op(1, , (pcp), val)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index f20e876..a94a857 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -519,7 +519,7 @@ static __always_inline unsigned long current_top_of_stack(void)
* entry trampoline.
*/
if (IS_ENABLED(CONFIG_USE_X86_SEG_SUPPORT))
- return const_pcpu_hot.top_of_stack;
+ return this_cpu_read_const(const_pcpu_hot.top_of_stack);
return this_cpu_read_stable(pcpu_hot.top_of_stack);
}
|