path: root/sys-kernel/linux-image-redcore-lts/files/4.19-revert-patches-causing-instant-reboot.patch

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 8169e8b7a4dc..12915511be61 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -305,48 +305,13 @@ ENTRY(startup_64)
 	/* Set up the stack */
 	leaq	boot_stack_end(%rbx), %rsp
 
-	/*
-	 * paging_prepare() and cleanup_trampoline() below can have GOT
-	 * references. Adjust the table with address we are running at.
-	 *
-	 * Zero RAX for adjust_got: the GOT was not adjusted before;
-	 * there's no adjustment to undo.
-	 */
-	xorq	%rax, %rax
-
-	/*
-	 * Calculate the address the binary is loaded at and use it as
-	 * a GOT adjustment.
-	 */
-	call	1f
-1:	popq	%rdi
-	subq	$1b, %rdi
-
-	call	adjust_got
-
 	/*
 	 * At this point we are in long mode with 4-level paging enabled,
-	 * but we might want to enable 5-level paging or vice versa.
-	 *
-	 * The problem is that we cannot do it directly. Setting or clearing
-	 * CR4.LA57 in long mode would trigger #GP. So we need to switch off
-	 * long mode and paging first.
-	 *
-	 * We also need a trampoline in lower memory to switch over from
-	 * 4- to 5-level paging for cases when the bootloader puts the kernel
-	 * above 4G, but didn't enable 5-level paging for us.
-	 *
-	 * The same trampoline can be used to switch from 5- to 4-level paging
-	 * mode, like when starting 4-level paging kernel via kexec() when
-	 * original kernel worked in 5-level paging mode.
-	 *
-	 * For the trampoline, we need the top page table to reside in lower
-	 * memory as we don't have a way to load 64-bit values into CR3 in
-	 * 32-bit mode.
+	 * but we want to enable 5-level paging.
 	 *
-	 * We go though the trampoline even if we don't have to: if we're
-	 * already in a desired paging mode. This way the trampoline code gets
-	 * tested on every boot.
+	 * The problem is that we cannot do it directly. Setting LA57 in
+	 * long mode would trigger #GP. So we need to switch off long mode
+	 * first.
 	 */
 
 	/* Make sure we have GDT with 32-bit code segment */
@@ -371,32 +336,40 @@ ENTRY(startup_64)
 	/* Save the trampoline address in RCX */
 	movq	%rax, %rcx
 
+	/* Check if we need to enable 5-level paging */
+	cmpq	$0, %rdx
+	jz	lvl5
+
+	/* Clear additional page table */
+	leaq	lvl5_pgtable(%rbx), %rdi
+	xorq	%rax, %rax
+	movq	$(PAGE_SIZE/8), %rcx
+	rep	stosq
+
 	/*
-	 * Load the address of trampoline_return() into RDI.
-	 * It will be used by the trampoline to return to the main code.
+	 * Setup current CR3 as the first and only entry in a new top level
+	 * page table.
 	 */
-	leaq	trampoline_return(%rip), %rdi
+	movq	%cr3, %rdi
+	leaq	0x7 (%rdi), %rax
+	movq	%rax, lvl5_pgtable(%rbx)
 
 	/* Switch to compatibility mode (CS.L = 0 CS.D = 1) via far return */
 	pushq	$__KERNEL32_CS
-	leaq	TRAMPOLINE_32BIT_CODE_OFFSET(%rax), %rax
+	leaq	compatible_mode(%rip), %rax
 	pushq	%rax
 	lretq
-trampoline_return:
+lvl5:
 	/* Restore the stack, the 32-bit trampoline uses its own stack */
 	leaq	boot_stack_end(%rbx), %rsp
 
 	/*
 	 * cleanup_trampoline() would restore trampoline memory.
 	 *
-	 * RDI is address of the page table to use instead of page table
-	 * in trampoline memory (if required).
-	 *
 	 * RSI holds real mode data and needs to be preserved across
 	 * this function call.
 	 */
 	pushq	%rsi
-	leaq	top_pgtable(%rbx), %rdi
 	call	cleanup_trampoline
 	popq	%rsi
 
@@ -404,21 +377,6 @@ trampoline_return:
 	pushq	$0
 	popfq
 
-	/*
-	 * Previously we've adjusted the GOT with address the binary was
-	 * loaded at. Now we need to re-adjust for relocation address.
-	 *
-	 * Calculate the address the binary is loaded at, so that we can
-	 * undo the previous GOT adjustment.
-	 */
-	call	1f
-1:	popq	%rax
-	subq	$1b, %rax
-
-	/* The new adjustment is the relocation address */
-	movq	%rbx, %rdi
-	call	adjust_got
-
 /*
  * Copy the compressed kernel to the end of our buffer
  * where decompression in place becomes safe.
@@ -519,6 +477,19 @@ relocated:
 	shrq	$3, %rcx
 	rep	stosq
 
+/*
+ * Adjust our own GOT
+ */
+	leaq	_got(%rip), %rdx
+	leaq	_egot(%rip), %rcx
+1:
+	cmpq	%rcx, %rdx
+	jae	2f
+	addq	%rbx, (%rdx)
+	addq	$8, %rdx
+	jmp	1b
+2:
+	
 /*
  * Do the extraction, and jump to the new kernel..
  */
@@ -537,36 +508,9 @@ relocated:
  */
 	jmp	*%rax
 
-/*
- * Adjust the global offset table
- *
- * RAX is the previous adjustment of the table to undo (use 0 if it's the
- * first time we touch GOT).
- * RDI is the new adjustment to apply.
- */
-adjust_got:
-	/* Walk through the GOT adding the address to the entries */
-	leaq	_got(%rip), %rdx
-	leaq	_egot(%rip), %rcx
-1:
-	cmpq	%rcx, %rdx
-	jae	2f
-	subq	%rax, (%rdx)	/* Undo previous adjustment */
-	addq	%rdi, (%rdx)	/* Apply the new adjustment */
-	addq	$8, %rdx
-	jmp	1b
-2:
-	ret
-
 	.code32
-/*
- * This is the 32-bit trampoline that will be copied over to low memory.
- *
- * RDI contains the return address (might be above 4G).
- * ECX contains the base address of the trampoline memory.
- * Non zero RDX on return means we need to enable 5-level paging.
- */
 ENTRY(trampoline_32bit_src)
+compatible_mode:
 	/* Set up data and stack segments */
 	movl	$__KERNEL_DS, %eax
 	movl	%eax, %ds
@@ -580,61 +524,33 @@ ENTRY(trampoline_32bit_src)
 	btrl	$X86_CR0_PG_BIT, %eax
 	movl	%eax, %cr0
 
-	/* Check what paging mode we want to be in after the trampoline */
-	cmpl	$0, %edx
-	jz	1f
+	/* Point CR3 to 5-level paging */
+	leal	lvl5_pgtable(%ebx), %eax
+	movl	%eax, %cr3
 
-	/* We want 5-level paging: don't touch CR3 if it already points to 5-level page tables */
+	/* Enable PAE and LA57 mode */
 	movl	%cr4, %eax
-	testl	$X86_CR4_LA57, %eax
-	jnz	3f
-	jmp	2f
-1:
-	/* We want 4-level paging: don't touch CR3 if it already points to 4-level page tables */
-	movl	%cr4, %eax
-	testl	$X86_CR4_LA57, %eax
-	jz	3f
-2:
-	/* Point CR3 to the trampoline's new top level page table */
-	leal	TRAMPOLINE_32BIT_PGTABLE_OFFSET(%ecx), %eax
-	movl	%eax, %cr3
-3:
-	/* Enable PAE and LA57 (if required) paging modes */
-	movl	$X86_CR4_PAE, %eax
-	cmpl	$0, %edx
-	jz	1f
-	orl	$X86_CR4_LA57, %eax
-1:
+	orl	$(X86_CR4_PAE | X86_CR4_LA57), %eax
 	movl	%eax, %cr4
 
-	/* Calculate address of paging_enabled() once we are executing in the trampoline */
-	leal	paging_enabled - trampoline_32bit_src + TRAMPOLINE_32BIT_CODE_OFFSET(%ecx), %eax
+	/* Calculate address we are running at */
+	call	1f
+1:	popl	%edi
+	subl	$1b, %edi
 
-	/* Prepare the stack for far return to Long Mode */
+	/* Prepare stack for far return to Long Mode */
 	pushl	$__KERNEL_CS
-	pushl	%eax
+	leal	lvl5(%edi), %eax
+	push	%eax
 
-	/* Enable paging again */
+	/* Enable paging back */
 	movl	$(X86_CR0_PG | X86_CR0_PE), %eax
 	movl	%eax, %cr0
 
 	lret
 
-	.code64
-paging_enabled:
-	/* Return from the trampoline */
-	jmp	*%rdi
-
-	/*
-         * The trampoline code has a size limit.
-         * Make sure we fail to compile if the trampoline code grows
-         * beyond TRAMPOLINE_32BIT_CODE_SIZE bytes.
-	 */
-	.org	trampoline_32bit_src + TRAMPOLINE_32BIT_CODE_SIZE
-
-	.code32
 no_longmode:
-	/* This isn't an x86-64 CPU, so hang intentionally, we cannot continue */
+	/* This isn't an x86-64 CPU so hang */
 1:
 	hlt
 	jmp     1b
@@ -695,10 +611,5 @@ boot_stack_end:
 	.balign 4096
 pgtable:
 	.fill BOOT_PGT_SIZE, 1, 0
-
-/*
- * The page table is going to be used instead of page table in the trampoline
- * memory.
- */
-top_pgtable:
+lvl5_pgtable:
 	.fill PAGE_SIZE, 1, 0
diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c
index a362fa0b849c..32af1cbcd903 100644
--- a/arch/x86/boot/compressed/pgtable_64.c
+++ b/arch/x86/boot/compressed/pgtable_64.c
@@ -22,6 +22,14 @@ struct paging_config {
 /* Buffer to preserve trampoline memory */
 static char trampoline_save[TRAMPOLINE_32BIT_SIZE];
 
+/*
+ * The page table is going to be used instead of page table in the trampoline
+ * memory.
+ *
+ * It must not be in BSS as BSS is cleared after cleanup_trampoline().
+ */
+static char top_pgtable[PAGE_SIZE] __aligned(PAGE_SIZE) __section(.data);
+
 /*
  * Trampoline address will be printed by extract_kernel() for debugging
  * purposes.
@@ -126,7 +134,7 @@ struct paging_config paging_prepare(void)
 	return paging_config;
 }
 
-void cleanup_trampoline(void *pgtable)
+void cleanup_trampoline(void)
 {
 	void *trampoline_pgtable;
 
@@ -137,8 +145,8 @@ void cleanup_trampoline(void *pgtable)
 	 * if it's there.
 	 */
 	if ((void *)__native_read_cr3() == trampoline_pgtable) {
-		memcpy(pgtable, trampoline_pgtable, PAGE_SIZE);
-		native_write_cr3((unsigned long)pgtable);
+		memcpy(top_pgtable, trampoline_pgtable, PAGE_SIZE);
+		native_write_cr3((unsigned long)top_pgtable);
 	}
 
 	/* Restore trampoline memory */