x86/boot/compressed: Pull global variable reference into startup32_load_idt()

In preparation for moving startup32_load_idt() out of head_64.S and
turning it into an ordinary function using the ordinary 32-bit calling
convention, pull the global variable reference to boot32_idt up into
startup32_load_idt() so that startup32_set_idt_entry() does not need to
discover its own runtime physical address, which will no longer be
correlated with startup_32 once this code is moved into .text.

While at it, give startup32_set_idt_entry() static linkage.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20221122161017.2426828-11-ardb@kernel.org

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index a2d1c031794480c73c3448fd72b5f41e42ed4c5e..f9926b3931c226b558f3fd1470154f5e3001a798 100644 (file)
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -728,16 +728,11 @@ SYM_DATA_END_LABEL(boot32_idt, SYM_L_GLOBAL, boot32_idt_end)
  *
  * %eax:       Handler address
  * %edx:       Vector number
- *
- * Physical offset is expected in %ebp
+ * %ecx:       IDT address
  */
-SYM_FUNC_START(startup32_set_idt_entry)
-       push    %ebx
-
-       /* IDT entry address to %ebx */
-       leal    rva(boot32_idt)(%ebp), %ebx
-       shl     $3, %edx
-       addl    %edx, %ebx
+SYM_FUNC_START_LOCAL(startup32_set_idt_entry)
+       /* IDT entry address to %ecx */
+       leal    (%ecx, %edx, 8), %ecx
 
        /* Build IDT entry, lower 4 bytes */
        movl    %eax, %edx
@@ -745,7 +740,7 @@ SYM_FUNC_START(startup32_set_idt_entry)
        orl     $(__KERNEL32_CS << 16), %edx    # Target code segment selector
 
        /* Store lower 4 bytes to IDT */
-       movl    %edx, (%ebx)
+       movl    %edx, (%ecx)
 
        /* Build IDT entry, upper 4 bytes */
        movl    %eax, %edx
@@ -753,15 +748,16 @@ SYM_FUNC_START(startup32_set_idt_entry)
        orl     $0x00008e00, %edx       # Present, Type 32-bit Interrupt Gate
 
        /* Store upper 4 bytes to IDT */
-       movl    %edx, 4(%ebx)
+       movl    %edx, 4(%ecx)
 
-       pop     %ebx
        RET
 SYM_FUNC_END(startup32_set_idt_entry)
 #endif
 
 SYM_FUNC_START(startup32_load_idt)
 #ifdef CONFIG_AMD_MEM_ENCRYPT
+       leal    rva(boot32_idt)(%ebp), %ecx
+
        /* #VC handler */
        leal    rva(startup32_vc_handler)(%ebp), %eax
        movl    $X86_TRAP_VC, %edx