Commit-ID: cd0ea35ff5511cde299a61c21a95889b4a71464e Gitweb: http://git.kernel.org/tip/cd0ea35ff5511cde299a61c21a95889b4a71464e Author: Dave Hansen <[email protected]> AuthorDate: Fri, 12 Feb 2016 13:02:12 -0800 Committer: Ingo Molnar <[email protected]> CommitDate: Thu, 18 Feb 2016 09:32:42 +0100
signals, pkeys: Notify userspace about protection key faults A protection key fault is very similar to any other access error. There must be a VMA, etc... We even want to take the same action (SIGSEGV) that we do with a normal access fault. However, we do need to let userspace know that something is different. We do this the same way what we did with SEGV_BNDERR with Memory Protection eXtensions (MPX): define a new SEGV code: SEGV_PKUERR. We add a siginfo field: si_pkey that reveals to userspace which protection key was set on the PTE that we faulted on. There is no other easy way for userspace to figure this out. They could parse smaps but that would be a bit cruel. We share space with in siginfo with _addr_bnd. #BR faults from MPX are completely separate from page faults (#PF) that trigger from protection key violations, so we never need both at the same time. Note that _pkey is a 64-bit value. The current hardware only supports 4-bit protection keys. We do this because there is _plenty_ of space in _sigfault and it is possible that future processors would support more than 4 bits of protection keys. The x86 code to actually fill in the siginfo is in the next patch. Signed-off-by: Dave Hansen <[email protected]> Reviewed-by: Thomas Gleixner <[email protected]> Cc: Al Viro <[email protected]> Cc: Amanieu d'Antras <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Arnd Bergmann <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Palmer Dabbelt <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Richard Weinberger <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Sasha Levin <[email protected]> Cc: Vegard Nossum <[email protected]> Cc: Vladimir Davydov <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- include/uapi/asm-generic/siginfo.h | 17 ++++++++++++----- kernel/signal.c | 4 ++++ 2 files changed, 16 insertions(+), 5 deletions(-) diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h index 1e35520..90384d5 100644 --- a/include/uapi/asm-generic/siginfo.h +++ b/include/uapi/asm-generic/siginfo.h @@ -91,10 +91,15 @@ typedef struct siginfo { int _trapno; /* TRAP # which caused the signal */ #endif short _addr_lsb; /* LSB of the reported address */ - struct { - void __user *_lower; - void __user *_upper; - } _addr_bnd; + union { + /* used when si_code=SEGV_BNDERR */ + struct { + void __user *_lower; + void __user *_upper; + } _addr_bnd; + /* used when si_code=SEGV_PKUERR */ + u64 _pkey; + }; } _sigfault; /* SIGPOLL */ @@ -137,6 +142,7 @@ typedef struct siginfo { #define si_addr_lsb _sifields._sigfault._addr_lsb #define si_lower _sifields._sigfault._addr_bnd._lower #define si_upper _sifields._sigfault._addr_bnd._upper +#define si_pkey _sifields._sigfault._pkey #define si_band _sifields._sigpoll._band #define si_fd _sifields._sigpoll._fd #ifdef __ARCH_SIGSYS @@ -206,7 +212,8 @@ typedef struct siginfo { #define SEGV_MAPERR (__SI_FAULT|1) /* address not mapped to object */ #define SEGV_ACCERR (__SI_FAULT|2) /* invalid permissions for mapped object */ #define SEGV_BNDERR (__SI_FAULT|3) /* failed address bound checks */ -#define NSIGSEGV 3 +#define SEGV_PKUERR (__SI_FAULT|4) /* failed protection key checks */ +#define NSIGSEGV 4 /* * SIGBUS si_codes diff --git a/kernel/signal.c b/kernel/signal.c index 0508544..fe8ed29 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2709,6 +2709,10 @@ int copy_siginfo_to_user(siginfo_t __user *to, const siginfo_t *from) err |= __put_user(from->si_upper, &to->si_upper); } #endif +#ifdef SEGV_PKUERR + if (from->si_signo == SIGSEGV && from->si_code == SEGV_PKUERR) + err |= __put_user(from->si_pkey, &to->si_pkey); +#endif break; case __SI_CHLD: err |= __put_user(from->si_pid, &to->si_pid);
