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From: Arvind Sankar <nivedita@alum.mit.edu>
To: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	Michael Matz <matz@suse.de>
Subject: [PATCH v2] x86/boot: Use 32-bit (zero-extended) move for z_output_len
Date: Tue, 11 Feb 2020 12:33:33 -0500	[thread overview]
Message-ID: <20200211173333.1722739-1-nivedita@alum.mit.edu> (raw)
In-Reply-To: <20200211161739.GE32279@zn.tnic>

z_output_len is the size of the decompressed payload (i.e. vmlinux +
vmlinux.relocs) and is generated as an unsigned 32-bit quantity by
mkpiggy.c.

The current movq $z_output_len, %r9 instruction generates a
sign-extended move to %r9. Using movl $z_output_len, %r9d will instead
zero-extend into %r9, which is appropriate for an unsigned 32-bit
quantity. This is also what we already do for z_input_len, the size of
the compressed payload.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
---
v2: Improve commit message

 arch/x86/boot/compressed/head_64.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 1f1f6c8139b3..03369246a4ff 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -484,7 +484,7 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
 	leaq	input_data(%rip), %rdx  /* input_data */
 	movl	$z_input_len, %ecx	/* input_len */
 	movq	%rbp, %r8		/* output target address */
-	movq	$z_output_len, %r9	/* decompressed length, end of relocs */
+	movl	$z_output_len, %r9d	/* decompressed length, end of relocs */
 	call	extract_kernel		/* returns kernel location in %rax */
 	popq	%rsi
 
-- 
2.24.1


  reply	other threads:[~2020-02-11 17:33 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-07 19:44 [PATCH 1/3] x86/boot/compressed/32: Simplify calculation of output address Arvind Sankar
2020-01-07 19:44 ` [PATCH 2/3] x86/boot/compressed/64: Use leal to initialize boot stack pointer Arvind Sankar
2020-02-12 12:04   ` [tip: x86/boot] x86/boot/compressed/64: Use LEA " tip-bot2 for Arvind Sankar
2020-01-07 19:44 ` [PATCH 3/3] x86/boot/compressed/64: Use 32-bit move for z_output_len Arvind Sankar
2020-02-11 16:17   ` Borislav Petkov
2020-02-11 17:33     ` Arvind Sankar [this message]
2020-02-11 18:15       ` [PATCH v2] x86/boot: Use 32-bit (zero-extended) " Borislav Petkov
2020-02-11 19:27         ` Arvind Sankar
2020-02-12  9:47           ` Borislav Petkov
2020-02-12 12:04       ` [tip: x86/boot] x86/boot/compressed/64: Use 32-bit (zero-extended) MOV " tip-bot2 for Arvind Sankar
2020-01-23 11:04 ` [tip: x86/asm] x86/boot: Simplify calculation of output address tip-bot2 for Arvind Sankar

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