| From | Ingo Molnar <> | Subject | [PATCH 31/43] x86/mm/kaiser: Map entry stack variable | Date | Fri, 24 Nov 2017 18:23:59 +0100 |
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From: Dave Hansen <dave.hansen@linux.intel.com>
There are times where the kernel is entered but there is no safe stack, like at SYSCALL entry. To obtain a safe stack, we have to clobber %rsp and store the clobbered value in 'rsp_scratch'.
Map this to userspace to allow us to do this stack switch before the CR3 switch.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Cc: linux-mm@kvack.org Cc: luto@kernel.org Cc: michael.schwarz@iaik.tugraz.at Cc: moritz.lipp@iaik.tugraz.at Cc: richard.fellner@student.tugraz.at Link: https://lkml.kernel.org/r/20171123003459.C0FF167A@viggo.jf.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/kernel/process_64.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index bafe65b08697..9a0220aa2bf9 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -59,7 +59,7 @@ #include <asm/unistd_32_ia32.h> #endif -__visible DEFINE_PER_CPU(unsigned long, rsp_scratch); +__visible DEFINE_PER_CPU_USER_MAPPED(unsigned long, rsp_scratch); /* Prints also some state that isn't saved in the pt_regs */ void __show_regs(struct pt_regs *regs, int all) -- 2.14.1
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