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From: Arvind Sankar <nivedita@alum.mit.edu>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-efi@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 1/5] x86/boot/compressed/32: Save the output address instead of recalculating it
Date: Sun,  1 Mar 2020 18:05:33 -0500	[thread overview]
Message-ID: <20200301230537.2247550-2-nivedita@alum.mit.edu> (raw)
In-Reply-To: <20200301230537.2247550-1-nivedita@alum.mit.edu>

In preparation for being able to decompress starting at a different
address than startup_32, save the calculated output address instead of
recalculating it later.

We now keep track of three addresses:
	%edx: startup_32 as we were loaded by bootloader
	%ebx: new location of compressed kernel
	%ebp: start of decompression buffer

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
---
 arch/x86/boot/compressed/head_32.S | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 46bbe7ab4adf..894182500606 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -75,11 +75,11 @@ SYM_FUNC_START(startup_32)
  */
 	leal	(BP_scratch+4)(%esi), %esp
 	call	1f
-1:	popl	%ebp
-	subl	$1b, %ebp
+1:	popl	%edx
+	subl	$1b, %edx
 
 	/* Load new GDT */
-	leal	gdt(%ebp), %eax
+	leal	gdt(%edx), %eax
 	movl	%eax, 2(%eax)
 	lgdt	(%eax)
 
@@ -92,13 +92,14 @@ SYM_FUNC_START(startup_32)
 	movl	%eax, %ss
 
 /*
- * %ebp contains the address we are loaded at by the boot loader and %ebx
+ * %edx contains the address we are loaded at by the boot loader and %ebx
  * contains the address where we should move the kernel image temporarily
- * for safe in-place decompression.
+ * for safe in-place decompression. %ebp contains the address that the kernel
+ * will be decompressed to.
  */
 
 #ifdef CONFIG_RELOCATABLE
-	movl	%ebp, %ebx
+	movl	%edx, %ebx
 	movl	BP_kernel_alignment(%esi), %eax
 	decl	%eax
 	addl    %eax, %ebx
@@ -110,10 +111,10 @@ SYM_FUNC_START(startup_32)
 	movl	$LOAD_PHYSICAL_ADDR, %ebx
 1:
 
+	movl	%ebx, %ebp	// Save the output address for later
 	/* Target address to relocate to for decompression */
-	movl    BP_init_size(%esi), %eax
-	subl    $_end, %eax
-	addl    %eax, %ebx
+	addl    BP_init_size(%esi), %ebx
+	subl    $_end, %ebx
 
 	/* Set up the stack */
 	leal	boot_stack_end(%ebx), %esp
@@ -127,7 +128,7 @@ SYM_FUNC_START(startup_32)
  * where decompression in place becomes safe.
  */
 	pushl	%esi
-	leal	(_bss-4)(%ebp), %esi
+	leal	(_bss-4)(%edx), %esi
 	leal	(_bss-4)(%ebx), %edi
 	movl	$(_bss - startup_32), %ecx
 	shrl	$2, %ecx
@@ -196,9 +197,7 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
 				/* push arguments for extract_kernel: */
 	pushl	$z_output_len	/* decompressed length, end of relocs */
 
-	leal	_end(%ebx), %eax
-	subl    BP_init_size(%esi), %eax
-	pushl	%eax		/* output address */
+	pushl	%ebp		/* output address */
 
 	pushl	$z_input_len	/* input_len */
 	leal	input_data(%ebx), %eax
-- 
2.24.1


  reply	other threads:[~2020-03-01 23:05 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-01 23:05 [PATCH 0/5] Minimize the need to move the kernel in the EFI stub Arvind Sankar
2020-03-01 23:05 ` Arvind Sankar [this message]
2020-03-03 19:10   ` [PATCH 1/5] x86/boot/compressed/32: Save the output address instead of recalculating it Ard Biesheuvel
2020-03-01 23:05 ` [PATCH 2/5] efi/x86: Decompress at start of PE image load address Arvind Sankar
2020-03-03  6:28   ` Mika Penttilä
2020-03-03 13:45     ` Arvind Sankar
2020-03-03 19:08   ` Ard Biesheuvel
2020-03-01 23:05 ` [PATCH 3/5] efi/x86: Add kernel preferred address to PE header Arvind Sankar
2020-03-03 19:11   ` Ard Biesheuvel
2020-03-01 23:05 ` [PATCH 4/5] efi/x86: Remove extra headroom for setup block Arvind Sankar
2020-03-02  4:21   ` Mika Penttilä
2020-03-03  4:14     ` Arvind Sankar
2020-03-01 23:05 ` [PATCH 5/5] efi/x86: Don't relocate the kernel unless necessary Arvind Sankar
2020-03-03 19:15   ` Ard Biesheuvel
2020-03-03 22:12 ` [PATCH v2 0/5] Minimize the need to move the kernel in the EFI stub Arvind Sankar
2020-03-03 22:12   ` [PATCH v2 1/5] x86/boot/compressed/32: Save the output address instead of recalculating it Arvind Sankar
2020-03-03 22:12   ` [PATCH v2 2/5] efi/x86: Decompress at start of PE image load address Arvind Sankar
2020-03-03 22:12   ` [PATCH v2 3/5] efi/x86: Add kernel preferred address to PE header Arvind Sankar
2020-03-03 22:12   ` [PATCH v2 4/5] efi/x86: Remove extra headroom for setup block Arvind Sankar
2020-05-11 17:01     ` Mike Lothian
2020-05-11 18:36       ` Arvind Sankar
2020-05-11 21:13         ` Ard Biesheuvel
2020-05-11 22:53           ` Arvind Sankar
2020-05-11 22:58             ` [PATCH] x86/boot: Mark global variables as static Arvind Sankar
2020-05-11 23:12               ` Mike Lothian
2020-05-12 11:05                 ` Ard Biesheuvel
2020-05-22 18:30               ` [tip: efi/urgent] " tip-bot2 for Arvind Sankar
2020-03-03 22:12   ` [PATCH v2 5/5] efi/x86: Don't relocate the kernel unless necessary Arvind Sankar
2020-03-03 23:08     ` Ard Biesheuvel
2020-03-03 23:34       ` Arvind Sankar
2020-03-04  7:30         ` Ard Biesheuvel
2020-03-03 22:26   ` [PATCH v2 0/5] Minimize the need to move the kernel in the EFI stub Ard Biesheuvel

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