init_per_cpu_var() returns pointer in the percpu address space while
rip_rel_ptr() expects pointer in the generic address space, resulting
in:

asm.h:124:63: error: passing argument 1 of ‘rip_rel_ptr’ from pointer to non-enclosed address space

when strict address space checks are enabled.

Add explicit casts to remove address space of the returned pointer.

Found by GCC's named address space checks.

There were no changes in the resulting object file.

Fixes: 11e36b0f7c21 ("x86/boot/64: Load the final kernel GDT during early boot directly, remove startup_gdt[]")
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
---
 arch/x86/kernel/head64.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index a817ed0724d1..2b7a4e28e72f 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -560,9 +560,11 @@ void early_setup_idt(void)
 void __head startup_64_setup_gdt_idt(void)
 {
 	void *handler = NULL;
+	struct desc_struct *gdt =
+		(void *)(__force unsigned long)init_per_cpu_var(gdt_page.gdt);
 
 	struct desc_ptr startup_gdt_descr = {
-		.address = (unsigned long)&RIP_REL_REF(init_per_cpu_var(gdt_page.gdt)),
+		.address = (unsigned long)&RIP_REL_REF(*gdt),
 		.size    = GDT_SIZE - 1,
 	};
 
-- 
2.46.0

On Mon, Aug 19 2024 at 10:33, Uros Bizjak wrote:
>
> Found by GCC's named address space checks.

Which GCC version?

Thanks

        tglx

The following commit has been merged into the x86/cleanups branch of tip:

Commit-ID:     b51207dc02ec3aeaa849e419f79055d7334845b6
Gitweb:        https://git.kernel.org/tip/b51207dc02ec3aeaa849e419f79055d7334845b6
Author:        Uros Bizjak <ubizjak@gmail.com>
AuthorDate:    Mon, 19 Aug 2024 10:33:13 +02:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Sun, 25 Aug 2024 16:07:51 +02:00

x86/boot/64: Strip percpu address space when setting up GDT descriptors

init_per_cpu_var() returns a pointer in the percpu address space while
rip_rel_ptr() expects a pointer in the generic address space.

When strict address space checks are enabled, GCC's named address space
checks fail:

  asm.h:124:63: error: passing argument 1 of 'rip_rel_ptr' from
                       pointer to non-enclosed address space

Add a explicit cast to remove address space of the returned pointer.

Fixes: 11e36b0f7c21 ("x86/boot/64: Load the final kernel GDT during early boot directly, remove startup_gdt[]")
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240819083334.148536-1-ubizjak@gmail.com

---
 arch/x86/kernel/head64.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index a817ed0..4b9d455 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -559,10 +559,11 @@ void early_setup_idt(void)
  */
 void __head startup_64_setup_gdt_idt(void)
 {
+	struct desc_struct *gdt = (void *)(__force unsigned long)init_per_cpu_var(gdt_page.gdt);
 	void *handler = NULL;
 
 	struct desc_ptr startup_gdt_descr = {
-		.address = (unsigned long)&RIP_REL_REF(init_per_cpu_var(gdt_page.gdt)),
+		.address = (unsigned long)&RIP_REL_REF(*gdt),
 		.size    = GDT_SIZE - 1,
 	};