[tip:x86/urgent] x86/mm/kcore: Add vsyscall page to /proc/kcore conditionally

[tip-bot for Jia Zhang]

Commit-ID:  cd026ca2861e7f384d677626a483da797c76b9da
Gitweb:     https://git.kernel.org/tip/cd026ca2861e7f384d677626a483da797c76b9da
Author:     Jia Zhang <zhang.jia@xxxxxxxxxxxxxxxxx>
AuthorDate: Mon, 12 Feb 2018 22:44:54 +0800
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 13 Feb 2018 09:15:59 +0100

x86/mm/kcore: Add vsyscall page to /proc/kcore conditionally

The vsyscall page should be visible only if vsyscall=emulate/native when dumping /proc/kcore.

Signed-off-by: Jia Zhang <zhang.jia@xxxxxxxxxxxxxxxxx>
Reviewed-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: jolsa@xxxxxxxxxx
Link: http://lkml.kernel.org/r/1518446694-21124-3-git-send-email-zhang.jia@xxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/mm/init_64.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 6aa33d1..8ba9c31 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1193,7 +1193,8 @@ void __init mem_init(void)
 	register_page_bootmem_info();
 
 	/* Register memory areas for /proc/kcore */
-	kclist_add(&kcore_vsyscall, (void *)VSYSCALL_ADDR, PAGE_SIZE, KCORE_USER);
+	if (get_gate_vma(&init_mm))
+		kclist_add(&kcore_vsyscall, (void *)VSYSCALL_ADDR, PAGE_SIZE, KCORE_USER);
 
 	mem_init_print_info(NULL);
 }