[tip:x86/asm] x86/asm: Make sure verify_cpu() has a good stack

[tip-bot for Borislav Petkov]

Commit-ID:  91ed140d6c1e168b11bbbddac4f6066f40a0c6b5
Gitweb: http://git.kernel.org/tip/91ed140d6c1e168b11bbbddac4f6066f40a0c6b5
Author: Borislav Petkov 
AuthorDate: Thu, 31 Mar 2016 16:21:02 +0200
Committer:  Ingo Molnar 
CommitDate: Wed, 13 Apr 2016 11:52:19 +0200

x86/asm: Make sure verify_cpu() has a good stack

04633df0c43d ("x86/cpu: Call verify_cpu() after having entered long mode too")
added the call to verify_cpu() for sanitizing CPU configuration.

The latter uses the stack minimally and it can happen that we land in
startup_64() directly from a 64-bit bootloader. Then we want to use our
own, known good stack.

Do that.

APs don't need this as the trampoline sets up a stack for them.

Reported-by: Tom Lendacky 
Signed-off-by: Borislav Petkov 
Cc: Brian Gerst 
Cc: Linus Torvalds 
Cc: Mika Penttilä 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1459434062-31055-1-git-send-email...@alien8.de
Signed-off-by: Ingo Molnar 
---
 arch/x86/kernel/head_64.S | 8 
 include/asm-generic/vmlinux.lds.h | 4 +++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 3de91a7..5df831e 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -65,6 +65,14 @@ startup_64:
 * tables and then reload them.
 */
 
+   /*
+* Setup stack for verify_cpu(). "-8" because stack_start is defined
+* this way, see below. Our best guess is a NULL ptr for stack
+* termination heuristics and we don't want to break anything which
+* might depend on it (kgdb, ...).
+*/
+   leaq(__end_init_task - 8)(%rip), %rsp
+
/* Sanitize CPU configuration */
call verify_cpu
 
diff --git a/include/asm-generic/vmlinux.lds.h 
b/include/asm-generic/vmlinux.lds.h
index 339125b..6a67ab9 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -245,7 +245,9 @@
 
 #define INIT_TASK_DATA(align)  \
. = ALIGN(align);   \
-   *(.data..init_task)
+   VMLINUX_SYMBOL(__start_init_task) = .;  \
+   *(.data..init_task) \
+   VMLINUX_SYMBOL(__end_init_task) = .;
 
 /*
  * Read only Data

[tip:x86/asm] x86/asm: Make sure verify_cpu() has a good stack

[tip-bot for Borislav Petkov]

Commit-ID:  91ed140d6c1e168b11bbbddac4f6066f40a0c6b5
Gitweb: http://git.kernel.org/tip/91ed140d6c1e168b11bbbddac4f6066f40a0c6b5
Author: Borislav Petkov 
AuthorDate: Thu, 31 Mar 2016 16:21:02 +0200
Committer:  Ingo Molnar 
CommitDate: Wed, 13 Apr 2016 11:52:19 +0200

x86/asm: Make sure verify_cpu() has a good stack

04633df0c43d ("x86/cpu: Call verify_cpu() after having entered long mode too")
added the call to verify_cpu() for sanitizing CPU configuration.

The latter uses the stack minimally and it can happen that we land in
startup_64() directly from a 64-bit bootloader. Then we want to use our
own, known good stack.

Do that.

APs don't need this as the trampoline sets up a stack for them.

Reported-by: Tom Lendacky 
Signed-off-by: Borislav Petkov 
Cc: Brian Gerst 
Cc: Linus Torvalds 
Cc: Mika Penttilä 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1459434062-31055-1-git-send-email...@alien8.de
Signed-off-by: Ingo Molnar 
---
 arch/x86/kernel/head_64.S | 8 
 include/asm-generic/vmlinux.lds.h | 4 +++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 3de91a7..5df831e 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -65,6 +65,14 @@ startup_64:
 * tables and then reload them.
 */
 
+   /*
+* Setup stack for verify_cpu(). "-8" because stack_start is defined
+* this way, see below. Our best guess is a NULL ptr for stack
+* termination heuristics and we don't want to break anything which
+* might depend on it (kgdb, ...).
+*/
+   leaq(__end_init_task - 8)(%rip), %rsp
+
/* Sanitize CPU configuration */
call verify_cpu
 
diff --git a/include/asm-generic/vmlinux.lds.h 
b/include/asm-generic/vmlinux.lds.h
index 339125b..6a67ab9 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -245,7 +245,9 @@
 
 #define INIT_TASK_DATA(align)  \
. = ALIGN(align);   \
-   *(.data..init_task)
+   VMLINUX_SYMBOL(__start_init_task) = .;  \
+   *(.data..init_task) \
+   VMLINUX_SYMBOL(__end_init_task) = .;
 
 /*
  * Read only Data