linux-kernel - [tip: x86/cleanups] x86/boot/64: Strip percpu address space when setting up GDT descriptors

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Message-ID: <172459512275.2215.9304580612288616565.tip-bot2@tip-bot2>
Date: Sun, 25 Aug 2024 14:12:02 -0000
From: "tip-bot2 for Uros Bizjak" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>, Thomas Gleixner <tglx@...utronix.de>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/cleanups] x86/boot/64: Strip percpu address space when
 setting up GDT descriptors

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@...il.com>
AuthorDate:    Mon, 19 Aug 2024 10:33:13 +02:00
Committer:     Thomas Gleixner <tglx@...utronix.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@...il.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.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,
 	};