From: Andy Lutomirski <luto@kernel.org>
To: x86@kernel.org
Cc: linux-kernel@vger.kernel.org,
Andrew Cooper <andrew.cooper3@citrix.com>,
Juergen Gross <jgross@suse.com>,
Andy Lutomirski <luto@kernel.org>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Stefano Stabellini <sstabellini@kernel.org>,
xen-devel@lists.xenproject.org
Subject: [PATCH 3/6] x86/entry/64/compat: Fix Xen PV SYSENTER frame setup
Date: Fri, 26 Jun 2020 10:21:13 -0700 [thread overview]
Message-ID: <947880c41ade688ff4836f665d0c9fcaa9bd1201.1593191971.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1593191971.git.luto@kernel.org>
The SYSENTER frame setup was nonsense. It worked by accident
because the normal code into which the Xen asm jumped
(entry_SYSENTER_32/compat) threw away SP without touching the stack.
entry_SYSENTER_compat was recently modified such that it relied on
having a valid stack pointer, so now the Xen asm needs to invoke it
with a valid stack.
Fix it up like SYSCALL: use the Xen-provided frame and skip the bare
metal prologue.
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: xen-devel@lists.xenproject.org
Fixes: 1c3e5d3f60e2 ("x86/entry: Make entry_64_compat.S objtool clean")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/entry/entry_64_compat.S | 1 +
arch/x86/xen/xen-asm_64.S | 20 ++++++++++++++++----
2 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 7b9d8150f652..381a6de7de9c 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -79,6 +79,7 @@ SYM_CODE_START(entry_SYSENTER_compat)
pushfq /* pt_regs->flags (except IF = 0) */
pushq $__USER32_CS /* pt_regs->cs */
pushq $0 /* pt_regs->ip = 0 (placeholder) */
+SYM_INNER_LABEL(entry_SYSENTER_compat_after_hwframe, SYM_L_GLOBAL)
pushq %rax /* pt_regs->orig_ax */
pushq %rdi /* pt_regs->di */
pushq %rsi /* pt_regs->si */
diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S
index 5d252aaeade8..e1e1c7eafa60 100644
--- a/arch/x86/xen/xen-asm_64.S
+++ b/arch/x86/xen/xen-asm_64.S
@@ -161,10 +161,22 @@ SYM_FUNC_END(xen_syscall32_target)
/* 32-bit compat sysenter target */
SYM_FUNC_START(xen_sysenter_target)
- mov 0*8(%rsp), %rcx
- mov 1*8(%rsp), %r11
- mov 5*8(%rsp), %rsp
- jmp entry_SYSENTER_compat
+ /*
+ * NB: Xen is polite and clears TF from EFLAGS for us. This means
+ * that we don't need to guard against single step exceptions here.
+ */
+ popq %rcx
+ popq %r11
+
+ /*
+ * Neither Xen nor the kernel really knows what the old SS and
+ * CS were. The kernel expects __USER32_DS and __USER32_CS, so
+ * report those values even though Xen will guess its own values.
+ */
+ movq $__USER32_DS, 4*8(%rsp)
+ movq $__USER32_CS, 1*8(%rsp)
+
+ jmp entry_SYSENTER_compat_after_hwframe
SYM_FUNC_END(xen_sysenter_target)
#else /* !CONFIG_IA32_EMULATION */
--
2.25.4
WARNING: multiple messages have this Message-ID (diff)
From: Andy Lutomirski <luto@kernel.org>
To: x86@kernel.org
Cc: Juergen Gross <jgross@suse.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Andrew Cooper <andrew.cooper3@citrix.com>,
linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
xen-devel@lists.xenproject.org,
Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: [PATCH 3/6] x86/entry/64/compat: Fix Xen PV SYSENTER frame setup
Date: Fri, 26 Jun 2020 10:21:13 -0700 [thread overview]
Message-ID: <947880c41ade688ff4836f665d0c9fcaa9bd1201.1593191971.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1593191971.git.luto@kernel.org>
The SYSENTER frame setup was nonsense. It worked by accident
because the normal code into which the Xen asm jumped
(entry_SYSENTER_32/compat) threw away SP without touching the stack.
entry_SYSENTER_compat was recently modified such that it relied on
having a valid stack pointer, so now the Xen asm needs to invoke it
with a valid stack.
Fix it up like SYSCALL: use the Xen-provided frame and skip the bare
metal prologue.
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: xen-devel@lists.xenproject.org
Fixes: 1c3e5d3f60e2 ("x86/entry: Make entry_64_compat.S objtool clean")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/entry/entry_64_compat.S | 1 +
arch/x86/xen/xen-asm_64.S | 20 ++++++++++++++++----
2 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 7b9d8150f652..381a6de7de9c 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -79,6 +79,7 @@ SYM_CODE_START(entry_SYSENTER_compat)
pushfq /* pt_regs->flags (except IF = 0) */
pushq $__USER32_CS /* pt_regs->cs */
pushq $0 /* pt_regs->ip = 0 (placeholder) */
+SYM_INNER_LABEL(entry_SYSENTER_compat_after_hwframe, SYM_L_GLOBAL)
pushq %rax /* pt_regs->orig_ax */
pushq %rdi /* pt_regs->di */
pushq %rsi /* pt_regs->si */
diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S
index 5d252aaeade8..e1e1c7eafa60 100644
--- a/arch/x86/xen/xen-asm_64.S
+++ b/arch/x86/xen/xen-asm_64.S
@@ -161,10 +161,22 @@ SYM_FUNC_END(xen_syscall32_target)
/* 32-bit compat sysenter target */
SYM_FUNC_START(xen_sysenter_target)
- mov 0*8(%rsp), %rcx
- mov 1*8(%rsp), %r11
- mov 5*8(%rsp), %rsp
- jmp entry_SYSENTER_compat
+ /*
+ * NB: Xen is polite and clears TF from EFLAGS for us. This means
+ * that we don't need to guard against single step exceptions here.
+ */
+ popq %rcx
+ popq %r11
+
+ /*
+ * Neither Xen nor the kernel really knows what the old SS and
+ * CS were. The kernel expects __USER32_DS and __USER32_CS, so
+ * report those values even though Xen will guess its own values.
+ */
+ movq $__USER32_DS, 4*8(%rsp)
+ movq $__USER32_CS, 1*8(%rsp)
+
+ jmp entry_SYSENTER_compat_after_hwframe
SYM_FUNC_END(xen_sysenter_target)
#else /* !CONFIG_IA32_EMULATION */
--
2.25.4
next prev parent reply other threads:[~2020-06-26 17:21 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-26 17:21 [PATCH 0/6] x86/entry: Fixes Andy Lutomirski
2020-06-26 17:21 ` [PATCH 1/6] x86/entry: Assert that syscalls are on the right stack Andy Lutomirski
2020-07-01 8:04 ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
2020-07-06 14:34 ` [PATCH] x86/entry: Mark check_user_regs() noinstr Peter Zijlstra
2020-06-26 17:21 ` [PATCH 2/6] x86/entry: Move SYSENTER's regs->sp and regs->flags fixups into C Andy Lutomirski
2020-07-01 8:04 ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
2020-06-26 17:21 ` Andy Lutomirski [this message]
2020-06-26 17:21 ` [PATCH 3/6] x86/entry/64/compat: Fix Xen PV SYSENTER frame setup Andy Lutomirski
2020-06-28 2:47 ` Boris Ostrovsky
2020-06-28 2:47 ` Boris Ostrovsky
2020-07-01 8:04 ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
2020-07-01 15:42 ` [PATCH 3/6] " Brian Gerst
2020-07-01 15:42 ` Brian Gerst
2020-07-01 18:39 ` Andy Lutomirski
2020-07-01 18:39 ` Andy Lutomirski
2020-07-02 12:54 ` Thomas Gleixner
2020-07-02 12:54 ` Thomas Gleixner
2020-06-26 17:21 ` [PATCH 4/6] selftests/x86/syscall_nt: Add more flag combinations Andy Lutomirski
2020-07-01 8:04 ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
2020-06-26 17:21 ` [PATCH 5/6] selftests/x86/syscall_nt: Clear weird flags after each test Andy Lutomirski
2020-07-01 8:04 ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
2020-06-26 17:21 ` [PATCH 6/6] selftests/x86: Consolidate and fix get/set_eflags() helpers Andy Lutomirski
2020-07-01 8:04 ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=947880c41ade688ff4836f665d0c9fcaa9bd1201.1593191971.git.luto@kernel.org \
--to=luto@kernel.org \
--cc=andrew.cooper3@citrix.com \
--cc=boris.ostrovsky@oracle.com \
--cc=jgross@suse.com \
--cc=linux-kernel@vger.kernel.org \
--cc=sstabellini@kernel.org \
--cc=x86@kernel.org \
--cc=xen-devel@lists.xenproject.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.