path: root/arch/x86
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authorJoerg Roedel <jroedel@suse.de>2018-07-18 11:40:40 +0200
committerThomas Gleixner <tglx@linutronix.de>2018-07-20 01:11:36 +0200
commita6b744f3ce9d017dd86b28355de2d8e0d36496d4 (patch)
treee2fcd05628125b68ba6da8d71958fa69839f6064 /arch/x86
parentae2e565bc6aaee3f3db420fec5fdd39755c9813e (diff)
x86/entry/32: Load task stack from x86_tss.sp1 in SYSENTER handler
x86_tss.sp0 will be used to point to the entry stack later to use it as a trampoline stack for other kernel entry points besides SYSENTER. So store the real task stack pointer in x86_tss.sp1, which is otherwise unused by the hardware, as Linux doesn't make use of Ring 1. Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Pavel Machek <pavel@ucw.cz> Cc: "H . Peter Anvin" <hpa@zytor.com> Cc: linux-mm@kvack.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Brian Gerst <brgerst@gmail.com> Cc: David Laight <David.Laight@aculab.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Eduardo Valentin <eduval@amazon.com> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Will Deacon <will.deacon@arm.com> Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Waiman Long <llong@redhat.com> Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca> Cc: joro@8bytes.org Link: https://lkml.kernel.org/r/1531906876-13451-4-git-send-email-joro@8bytes.org
Diffstat (limited to 'arch/x86')
2 files changed, 9 insertions, 2 deletions
diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c
index 15b3f45b69cd..82826f2275cc 100644
--- a/arch/x86/kernel/asm-offsets_32.c
+++ b/arch/x86/kernel/asm-offsets_32.c
@@ -46,9 +46,14 @@ void foo(void)
OFFSET(saved_context_gdt_desc, saved_context, gdt_desc);
- /* Offset from the entry stack to task stack stored in TSS */
+ /*
+ * Offset from the entry stack to task stack stored in TSS. Kernel entry
+ * happens on the per-cpu entry-stack, and the asm code switches to the
+ * task-stack pointer stored in x86_tss.sp1, which is a copy of
+ * task->thread.sp0 where entry code can find it.
+ */
- offsetof(struct cpu_entry_area, tss.x86_tss.sp0) -
+ offsetof(struct cpu_entry_area, tss.x86_tss.sp1) -
offsetofend(struct cpu_entry_area, entry_stack_page.stack));
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 0ae659de21eb..ec62cc77388d 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -290,6 +290,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
(unsigned long)task_stack_page(next_p) +
+ /* SYSENTER reads the task-stack from tss.sp1 */
+ this_cpu_write(cpu_tss_rw.x86_tss.sp1, next_p->thread.sp0);
* Restore %gs if needed (which is common)