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Subject[PATCH 3/7] x86/boot/compressed/64: Setup IDT in startup_32 boot path
Date
From: Joerg Roedel <jroedel@suse.de>

This boot path needs exception handling when it is used with SEV-ES.
Setup an IDT and provide a helper function to write IDT entries for
use in 32-bit protected mode.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/boot/compressed/head_64.S | 73 +++++++++++++++++++++++++++++-
1 file changed, 72 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index c59c80ca546d..8deeec78cdb4 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -116,6 +116,11 @@ SYM_FUNC_START(startup_32)
lretl
1:

+#ifdef CONFIG_AMD_MEM_ENCRYPT
+ /* Setup Exception handling for SEV-ES */
+ call startup32_load_idt
+#endif
+
/* Make sure cpu supports long mode. */
call verify_cpu
testl %eax, %eax
@@ -528,7 +533,6 @@ SYM_FUNC_END_ALIAS(efi_stub_entry)

.text
SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
-
/*
* Clear BSS (stack is currently empty)
*/
@@ -701,6 +705,19 @@ SYM_DATA_START(boot_idt)
.endr
SYM_DATA_END_LABEL(boot_idt, SYM_L_GLOBAL, boot_idt_end)

+#ifdef CONFIG_AMD_MEM_ENCRYPT
+SYM_DATA_START(boot32_idt_desc)
+ .word boot32_idt_end - boot32_idt - 1
+ .long 0
+SYM_DATA_END(boot32_idt_desc)
+ .balign 8
+SYM_DATA_START(boot32_idt)
+ .rept 32
+ .quad 0
+ .endr
+SYM_DATA_END_LABEL(boot32_idt, SYM_L_GLOBAL, boot32_idt_end)
+#endif
+
#ifdef CONFIG_EFI_STUB
SYM_DATA(image_offset, .long 0)
#endif
@@ -793,6 +810,60 @@ SYM_DATA_START_LOCAL(loaded_image_proto)
SYM_DATA_END(loaded_image_proto)
#endif

+#ifdef CONFIG_AMD_MEM_ENCRYPT
+ __HEAD
+ .code32
+/*
+ * Write an IDT entry into boot32_idt
+ *
+ * Parameters:
+ *
+ * %eax: Handler address
+ * %edx: Vector number
+ *
+ * Physical offset is expected in %ebp
+ */
+SYM_FUNC_START(startup32_set_idt_entry)
+ push %ebx
+ push %ecx
+
+ /* IDT entry address to %ebx */
+ leal rva(boot32_idt)(%ebp), %ebx
+ shl $3, %edx
+ addl %edx, %ebx
+
+ /* Build IDT entry, lower 4 bytes */
+ movl %eax, %edx
+ andl $0x0000ffff, %edx
+ movl $__KERNEL32_CS, %ecx
+ shl $16, %ecx
+ orl %ecx, %edx
+
+ /* Store lower 4 bytes to IDT */
+ movl %edx, (%ebx)
+
+ /* Build IDT entry, upper 4 bytes */
+ movl %eax, %edx
+ andl $0xffff0000, %edx
+ orl $0x00008e00, %edx
+
+ /* Store upper 4 bytes to IDT */
+ movl %edx, 4(%ebx)
+
+ pop %ecx
+ pop %ebx
+ ret
+SYM_FUNC_END(startup32_set_idt_entry)
+
+SYM_FUNC_START(startup32_load_idt)
+ /* Load IDT */
+ leal rva(boot32_idt)(%ebp), %eax
+ movl %eax, rva(boot32_idt_desc+2)(%ebp)
+ lidt rva(boot32_idt_desc)(%ebp)
+
+ ret
+SYM_FUNC_END(startup32_load_idt)
+#endif
/*
* Stack and heap for uncompression
*/
--
2.30.0
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