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From: Peter Zijlstra <peterz@infradead.org>
To: x86@kernel.org, Lai Jiangshan <jiangshanlai@gmail.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Cooper <Andrew.Cooper3@citrix.com>, linux-kernel@vger.kernel.org
Subject: [RFC][PATCH] x86: PUSH_AND_CLEAR_REGS_COMPAT
Date: Sat, 9 Apr 2022 00:38:27 +0200	[thread overview]
Message-ID: <20220408223827.GR2731@worktop.programming.kicks-ass.net> (raw)


How insane?

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/x86/entry/calling.h         | 25 ++++++++----
 arch/x86/entry/entry_64_compat.S | 87 ++--------------------------------------
 2 files changed, 21 insertions(+), 91 deletions(-)

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index a4c061fb7c6e..7f938704da59 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -63,13 +63,15 @@ For 32-bit we have the following conventions - kernel is built with
  * for assembly code:
  */
 
-.macro PUSH_REGS rdx=%rdx rax=%rax save_ret=0
+.macro PUSH_REGS rdx=%rdx rax=%rax save_ret=0 save_rdi=1
 	.if \save_ret
 	pushq	%rsi		/* pt_regs->si */
 	movq	8(%rsp), %rsi	/* temporarily store the return address in %rsi */
 	movq	%rdi, 8(%rsp)	/* pt_regs->di (overwriting original return address) */
 	.else
+	.if \save_rdi
 	pushq   %rdi		/* pt_regs->di */
+	.endif
 	pushq   %rsi		/* pt_regs->si */
 	.endif
 	pushq	\rdx		/* pt_regs->dx */
@@ -92,7 +94,7 @@ For 32-bit we have the following conventions - kernel is built with
 	.endif
 .endm
 
-.macro CLEAR_REGS
+.macro CLEAR_REGS_lo
 	/*
 	 * Sanitize registers of values that a speculation attack might
 	 * otherwise want to exploit. The lower registers are likely clobbered
@@ -101,22 +103,31 @@ For 32-bit we have the following conventions - kernel is built with
 	 */
 	xorl	%edx,  %edx	/* nospec dx  */
 	xorl	%ecx,  %ecx	/* nospec cx  */
+	xorl	%ebx,  %ebx	/* nospec rbx */
+	xorl	%ebp,  %ebp	/* nospec rbp */
+.endm
+
+.macro CLEAR_REGS_hi
 	xorl	%r8d,  %r8d	/* nospec r8  */
 	xorl	%r9d,  %r9d	/* nospec r9  */
 	xorl	%r10d, %r10d	/* nospec r10 */
 	xorl	%r11d, %r11d	/* nospec r11 */
-	xorl	%ebx,  %ebx	/* nospec rbx */
-	xorl	%ebp,  %ebp	/* nospec rbp */
 	xorl	%r12d, %r12d	/* nospec r12 */
 	xorl	%r13d, %r13d	/* nospec r13 */
 	xorl	%r14d, %r14d	/* nospec r14 */
 	xorl	%r15d, %r15d	/* nospec r15 */
+.endm
 
+.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0 save_rdi=1
+	PUSH_REGS rdx=\rdx, rax=\rax, save_ret=\save_ret save_rdi=\save_rdi
+	CLEAR_REGS_lo
+	CLEAR_REGS_hi
 .endm
 
-.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0
-	PUSH_REGS rdx=\rdx, rax=\rax, save_ret=\save_ret
-	CLEAR_REGS
+.macro PUSH_AND_CLEAR_REGS_COMPAT rdx=%rdx rax=%rax save_ret=0 save_rdi=1
+	CLEAR_REGS_hi
+	PUSH_REGS rdx=\rdx, rax=\rax, save_ret=\save_ret save_rdi=\save_rdi
+	CLEAR_REGS_lo
 .endm
 
 .macro POP_REGS pop_rdi=1 skip_r11rcx=0
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 4fdb007cddbd..44a3eaf15de6 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -83,32 +83,7 @@ SYM_INNER_LABEL(entry_SYSENTER_compat_after_hwframe, SYM_L_GLOBAL)
 	movl	%eax, %eax
 
 	pushq	%rax			/* pt_regs->orig_ax */
-	pushq	%rdi			/* pt_regs->di */
-	pushq	%rsi			/* pt_regs->si */
-	pushq	%rdx			/* pt_regs->dx */
-	pushq	%rcx			/* pt_regs->cx */
-	pushq	$-ENOSYS		/* pt_regs->ax */
-	pushq   $0			/* pt_regs->r8  = 0 */
-	xorl	%r8d, %r8d		/* nospec   r8 */
-	pushq   $0			/* pt_regs->r9  = 0 */
-	xorl	%r9d, %r9d		/* nospec   r9 */
-	pushq   $0			/* pt_regs->r10 = 0 */
-	xorl	%r10d, %r10d		/* nospec   r10 */
-	pushq   $0			/* pt_regs->r11 = 0 */
-	xorl	%r11d, %r11d		/* nospec   r11 */
-	pushq   %rbx                    /* pt_regs->rbx */
-	xorl	%ebx, %ebx		/* nospec   rbx */
-	pushq   %rbp                    /* pt_regs->rbp (will be overwritten) */
-	xorl	%ebp, %ebp		/* nospec   rbp */
-	pushq   $0			/* pt_regs->r12 = 0 */
-	xorl	%r12d, %r12d		/* nospec   r12 */
-	pushq   $0			/* pt_regs->r13 = 0 */
-	xorl	%r13d, %r13d		/* nospec   r13 */
-	pushq   $0			/* pt_regs->r14 = 0 */
-	xorl	%r14d, %r14d		/* nospec   r14 */
-	pushq   $0			/* pt_regs->r15 = 0 */
-	xorl	%r15d, %r15d		/* nospec   r15 */
-
+	PUSH_AND_CLEAR_REGS_COMPAT rax=$-ENOSYS
 	UNWIND_HINT_REGS
 
 	cld
@@ -225,35 +200,7 @@ SYM_INNER_LABEL(entry_SYSCALL_compat_safe_stack, SYM_L_GLOBAL)
 SYM_INNER_LABEL(entry_SYSCALL_compat_after_hwframe, SYM_L_GLOBAL)
 	movl	%eax, %eax		/* discard orig_ax high bits */
 	pushq	%rax			/* pt_regs->orig_ax */
-	pushq	%rdi			/* pt_regs->di */
-	pushq	%rsi			/* pt_regs->si */
-	xorl	%esi, %esi		/* nospec   si */
-	pushq	%rdx			/* pt_regs->dx */
-	xorl	%edx, %edx		/* nospec   dx */
-	pushq	%rbp			/* pt_regs->cx (stashed in bp) */
-	xorl	%ecx, %ecx		/* nospec   cx */
-	pushq	$-ENOSYS		/* pt_regs->ax */
-	pushq   $0			/* pt_regs->r8  = 0 */
-	xorl	%r8d, %r8d		/* nospec   r8 */
-	pushq   $0			/* pt_regs->r9  = 0 */
-	xorl	%r9d, %r9d		/* nospec   r9 */
-	pushq   $0			/* pt_regs->r10 = 0 */
-	xorl	%r10d, %r10d		/* nospec   r10 */
-	pushq   $0			/* pt_regs->r11 = 0 */
-	xorl	%r11d, %r11d		/* nospec   r11 */
-	pushq   %rbx                    /* pt_regs->rbx */
-	xorl	%ebx, %ebx		/* nospec   rbx */
-	pushq   %rbp                    /* pt_regs->rbp (will be overwritten) */
-	xorl	%ebp, %ebp		/* nospec   rbp */
-	pushq   $0			/* pt_regs->r12 = 0 */
-	xorl	%r12d, %r12d		/* nospec   r12 */
-	pushq   $0			/* pt_regs->r13 = 0 */
-	xorl	%r13d, %r13d		/* nospec   r13 */
-	pushq   $0			/* pt_regs->r14 = 0 */
-	xorl	%r14d, %r14d		/* nospec   r14 */
-	pushq   $0			/* pt_regs->r15 = 0 */
-	xorl	%r15d, %r15d		/* nospec   r15 */
-
+	PUSH_AND_CLEAR_REGS_COMPAT rax=$-ENOSYS
 	UNWIND_HINT_REGS
 
 	movq	%rsp, %rdi
@@ -381,35 +328,7 @@ SYM_CODE_START(entry_INT80_compat)
 	pushq	1*8(%rdi)		/* regs->orig_ax */
 	pushq	(%rdi)			/* pt_regs->di */
 .Lint80_keep_stack:
-
-	pushq	%rsi			/* pt_regs->si */
-	xorl	%esi, %esi		/* nospec   si */
-	pushq	%rdx			/* pt_regs->dx */
-	xorl	%edx, %edx		/* nospec   dx */
-	pushq	%rcx			/* pt_regs->cx */
-	xorl	%ecx, %ecx		/* nospec   cx */
-	pushq	$-ENOSYS		/* pt_regs->ax */
-	pushq   %r8			/* pt_regs->r8 */
-	xorl	%r8d, %r8d		/* nospec   r8 */
-	pushq   %r9			/* pt_regs->r9 */
-	xorl	%r9d, %r9d		/* nospec   r9 */
-	pushq   %r10			/* pt_regs->r10*/
-	xorl	%r10d, %r10d		/* nospec   r10 */
-	pushq   %r11			/* pt_regs->r11 */
-	xorl	%r11d, %r11d		/* nospec   r11 */
-	pushq   %rbx                    /* pt_regs->rbx */
-	xorl	%ebx, %ebx		/* nospec   rbx */
-	pushq   %rbp                    /* pt_regs->rbp */
-	xorl	%ebp, %ebp		/* nospec   rbp */
-	pushq   %r12                    /* pt_regs->r12 */
-	xorl	%r12d, %r12d		/* nospec   r12 */
-	pushq   %r13                    /* pt_regs->r13 */
-	xorl	%r13d, %r13d		/* nospec   r13 */
-	pushq   %r14                    /* pt_regs->r14 */
-	xorl	%r14d, %r14d		/* nospec   r14 */
-	pushq   %r15                    /* pt_regs->r15 */
-	xorl	%r15d, %r15d		/* nospec   r15 */
-
+	PUSH_AND_CLEAR_REGS save_rdi=0
 	UNWIND_HINT_REGS
 
 	cld

             reply	other threads:[~2022-04-08 22:38 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-08 22:38 Peter Zijlstra [this message]
2022-04-08 23:14 ` [RFC][PATCH] x86: PUSH_AND_CLEAR_REGS_COMPAT Peter Zijlstra
2022-04-09  2:00   ` Josh Poimboeuf
2022-04-10 15:20   ` Brian Gerst

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