Patch "kaiser: fix compile error without vsyscall" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

kaiser: fix compile error without vsyscall

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kaiser-fix-compile-error-without-vsyscall.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Date: Tue, 13 Feb 2018 16:45:20 +0100
To: Greg KH <[email protected]>
From: Hugh Dickins <[email protected]>
Subject: kaiser: fix compile error without vsyscall

From: Hugh Dickins <[email protected]>

Tobias noticed a compile error on 4.4.115, and it's the same on 4.9.80:
arch/x86/mm/kaiser.c: In function ‘kaiser_init’:
arch/x86/mm/kaiser.c:348:8: error: ‘vsyscall_pgprot’ undeclared
(first use in this function)

It seems like his combination of kernel options doesn't work for KAISER. X86_VSYSCALL_EMULATION is not set on his system, while LEGACY_VSYSCALL is set to NONE (LEGACY_VSYSCALL_NONE=y). He managed to get things compiling again, by moving the 'extern unsigned long vsyscall_pgprot' outside of the preprocessor statement. This works because the optimizer removes that code (vsyscall_enabled() is always false) - and that's how it was done in some older backports.

---
 arch/x86/include/asm/vsyscall.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -13,7 +13,6 @@ extern void map_vsyscall(void);
  */
 extern bool emulate_vsyscall(struct pt_regs *regs, unsigned long address);
 extern bool vsyscall_enabled(void);
-extern unsigned long vsyscall_pgprot;
 #else
 static inline void map_vsyscall(void) {}
 static inline bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)

@@ -22,5 +21,6 @@ static inline bool emulate_vsyscall(stru
 }
 static inline bool vsyscall_enabled(void) { return false; }
 #endif
+extern unsigned long vsyscall_pgprot;
 
 #endif /* _ASM_X86_VSYSCALL_H */

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/media-hdpvr-fix-an-error-handling-path-in-hdpvr_probe.patch queue-4.9/media-dvb-usb-v2-lmedm04-move-ts2020-attach-to-dm04_lme2510_tuner.patch queue-4.9/kaiser-fix-compile-error-without-vsyscall.patch queue-4.9/usb-gadget-uvc-missing-files-for-configfs-interface.patch queue-4.9/dmaengine-dmatest-fix-container_of-member-in-dmatest_callback.patch queue-4.9/cifs-fix-missing-put_xid-in-cifs_file_strict_mmap.patch queue-4.9/cifs-fix-autonegotiate-security-settings-mismatch.patch queue-4.9/sched-rt-use-container_of-to-get-root-domain-in-rto_push_irq_work_func.patch queue-4.9/posix-timer-properly-check-sigevent-sigev_notify.patch queue-4.9/media-dvb-usb-v2-lmedm04-improve-logic-checking-of-warm-start.patch queue-4.9/powerpc-pseries-include-linux-types.h-in-asm-hvcall.h.patch queue-4.9/cifs-zero-sensitive-data-when-freeing.patch queue-4.9/sched-rt-up-the-root-domain-ref-count-when-passing-it-around-via-ipis.patch queue-4.9/dccp-cve-2017-8824-use-after-free-in-dccp-code.patch