[kvm-unit-tests,v3,05/11] x86: Move load_gdt_tss() to desc.c

Commit Message

Varad Gautam April 26, 2022, 11:43 a.m. UTC

Split load_gdt_tss() functionality into:
1. Load gdt/tss
2. Setup segments in 64-bit mode and update %cs via far-return

and move load_gdt_tss() to desc.c to share this code between
EFI and non-EFI tests.

Move the segment setup code specific to EFI into
setup.c:setup_segments64().

Signed-off-by: Varad Gautam <[e-mail]>
---
 lib/x86/desc.c       |  6 ++++++
 lib/x86/desc.h       |  1 +
 lib/x86/setup.c      | 25 +++++++++++++++++++++++--
 x86/efi/efistart64.S | 27 ---------------------------
 4 files changed, 30 insertions(+), 29 deletions(-)

Patch

diff --git a/lib/x86/desc.c b/lib/x86/desc.c
index a3e7255..bb0b7b2 100644
--- a/lib/x86/desc.c
+++ b/lib/x86/desc.c
@@ -362,6 +362,12 @@  void set_gdt_entry(int sel, unsigned long base,  u32 limit, u8 type, u8 flags)
 #endif
 }
 
+void load_gdt_tss(size_t tss_offset)
+{
+	lgdt(&gdt_descr);
+	ltr(tss_offset);
+}
+
 #ifndef __x86_64__
 void set_gdt_task_gate(u16 sel, u16 tss_sel)
 {
diff --git a/lib/x86/desc.h b/lib/x86/desc.h
index d743504..7ac505a 100644
--- a/lib/x86/desc.h
+++ b/lib/x86/desc.h
@@ -222,6 +222,7 @@  void set_idt_entry(int vec, void *addr, int dpl);
 void set_idt_sel(int vec, u16 sel);
 void set_idt_dpl(int vec, u16 dpl);
 void set_gdt_entry(int sel, unsigned long base, u32 limit, u8 access, u8 gran);
+void load_gdt_tss(size_t tss_offset);
 void set_intr_alt_stack(int e, void *fn);
 void print_current_tss_info(void);
 handler handle_exception(u8 v, handler fn);
diff --git a/lib/x86/setup.c b/lib/x86/setup.c
index dd2b916..367c13f 100644
--- a/lib/x86/setup.c
+++ b/lib/x86/setup.c
@@ -169,8 +169,27 @@  void setup_multiboot(struct mbi_bootinfo *bi)
 
 #ifdef CONFIG_EFI
 
-/* From x86/efi/efistart64.S */
-extern void load_gdt_tss(size_t tss_offset);
+static void setup_segments64(void)
+{
+	/* Update data segments */
+	write_ds(KERNEL_DS);
+	write_es(KERNEL_DS);
+	write_fs(KERNEL_DS);
+	write_gs(KERNEL_DS);
+	write_ss(KERNEL_DS);
+
+	/*
+	 * Update the code segment by putting it on the stack before the return
+	 * address, then doing a far return: this will use the new code segment
+	 * along with the address.
+	 */
+	asm volatile("pushq %1\n\t"
+		"lea 1f(%%rip), %0\n\t"
+		"pushq %0\n\t"
+		"lretq\n\t"
+		"1:"
+		:: "r" ((u64)KERNEL_DS), "i" (KERNEL_CS));
+}
 
 static efi_status_t setup_memory_allocator(efi_bootinfo_t *efi_bootinfo)
 {
@@ -275,6 +294,8 @@  static void setup_gdt_tss(void)
 	/* 64-bit setup_tss does not use the stacktop argument.  */
 	tss_offset = setup_tss(NULL);
 	load_gdt_tss(tss_offset);
+
+	setup_segments64();
 }
 
 efi_status_t setup_efi(efi_bootinfo_t *efi_bootinfo)
diff --git a/x86/efi/efistart64.S b/x86/efi/efistart64.S
index 98cc965..b94c5ab 100644
--- a/x86/efi/efistart64.S
+++ b/x86/efi/efistart64.S
@@ -26,33 +26,6 @@  ptl4:
 .code64
 .text
 
-.globl load_gdt_tss
-load_gdt_tss:
-	/* Load GDT */
-	lgdt gdt_descr(%rip)
-
-	/* Load TSS */
-	mov %rdi, %rax
-	ltr %ax
-
-	/* Update data segments */
-	mov $0x10, %ax /* 3rd entry in gdt64: 32/64-bit data segment */
-	mov %ax, %ds
-	mov %ax, %es
-	mov %ax, %fs
-	mov %ax, %gs
-	mov %ax, %ss
-
-	/*
-	 * Update the code segment by putting it on the stack before the return
-	 * address, then doing a far return: this will use the new code segment
-	 * along with the address.
-	 */
-	popq %rdi
-	pushq $0x08 /* 2nd entry in gdt64: 64-bit code segment */
-	pushq %rdi
-	lretq
-
 .code16
 
 .globl rm_trampoline