Commit-ID: 91ed140d6c1e168b11bbbddac4f6066f40a0c6b5
Gitweb: http://git.kernel.org/tip/91ed140d6c1e168b11bbbddac4f6066f40a0c6b5
Author: Borislav Petkov <bp@xxxxxxx>
AuthorDate: Thu, 31 Mar 2016 16:21:02 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
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 <thomas.lendacky@xxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mika Penttilä <mika.penttila@xxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1459434062-31055-1-git-send-email-bp@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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
--
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