[PATCH] x86, signals: add missing signal_compat code for x86 features

[Dave Hansen]

Sending this out early so folks can have a look.  I haven't let
it run through a full set of tests, so buyer beware, but it would
have a hard time hurting anything other than the already-broken
32-bit compat signal code.

---

From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>

The 32-bit siginfo is a different binary format than the 64-bit
one.  So, when running 32-bit binaries on 64-bit kernels, we have
to convert the kernel's 64-bit version to a 32-bit version that
userspace can grok.

We've added a few features to siginfo over the past few years and
neglected to add them to arch/x86/kernel/signal_compat.c:

   1. The si_addr_lsb used in SIGBUS's sent for machine checks
   2. The upper/lower bounds for MPX SIGSEGV faults
   3. The protection key for pkey faults

I caught this with some protection keys unit tests and realized
it affected a few more features.

This was tested only with my protection keys patch that looks
for a proper value in si_pkey.  I didn't actually test the machine
check or MPX code.

Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: linux-edac@xxxxxxxxxxxxxxx
Cc: x86@xxxxxxxxxx
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
---

 b/arch/x86/include/asm/compat.h   |   11 +++++++++++
 b/arch/x86/kernel/signal_compat.c |   13 +++++++++++++
 2 files changed, 24 insertions(+)

diff -puN arch/x86/include/asm/compat.h~add-signal-compat-for-mpx-pkeys arch/x86/include/asm/compat.h
--- a/arch/x86/include/asm/compat.h~add-signal-compat-for-mpx-pkeys	2016-05-18 15:29:27.238736544 -0700
+++ b/arch/x86/include/asm/compat.h	2016-05-18 15:29:27.243736772 -0700
@@ -40,6 +40,7 @@ typedef s32		compat_long_t;
 typedef s64 __attribute__((aligned(4))) compat_s64;
 typedef u32		compat_uint_t;
 typedef u32		compat_ulong_t;
+typedef u32		compat_u32;
 typedef u64 __attribute__((aligned(4))) compat_u64;
 typedef u32		compat_uptr_t;
 
@@ -181,6 +182,16 @@ typedef struct compat_siginfo {
 		/* SIGILL, SIGFPE, SIGSEGV, SIGBUS */
 		struct {
 			unsigned int _addr;	/* faulting insn/memory ref. */
+			short int _addr_lsb;	/* Valid LSB of the reported address. */
+			union {
+				/* used when si_code=SEGV_BNDERR */
+				struct {
+					compat_uptr_t _lower;
+					compat_uptr_t _upper;
+				} _addr_bnd;
+				/* used when si_code=SEGV_PKUERR */
+				compat_u32 _pkey;
+			};
 		} _sigfault;
 
 		/* SIGPOLL */
diff -puN arch/x86/kernel/signal_compat.c~add-signal-compat-for-mpx-pkeys arch/x86/kernel/signal_compat.c
--- a/arch/x86/kernel/signal_compat.c~add-signal-compat-for-mpx-pkeys	2016-05-18 15:29:27.240736635 -0700
+++ b/arch/x86/kernel/signal_compat.c	2016-05-18 16:54:54.366568908 -0700
@@ -32,6 +32,19 @@ int copy_siginfo_to_user32(compat_siginf
 					  &to->_sifields._pad[0]);
 			switch (from->si_code >> 16) {
 			case __SI_FAULT >> 16:
+		                if (from->si_signo == SIGBUS &&
+		                    (from->si_code == BUS_MCEERR_AR ||
+				     from->si_code == BUS_MCEERR_AO))
+					put_user_ex(from->si_addr_lsb, &to->si_addr_lsb);
+
+				if (from->si_signo == SIGSEGV) {
+				       	if (from->si_code == SEGV_BNDERR) {
+						put_user_ex(from->si_lower, &to->si_lower);
+						put_user_ex(from->si_upper, &to->si_upper);
+					}
+				       	if (from->si_code == SEGV_PKUERR)
+						put_user_ex(from->si_pkey, &to->si_pkey);
+				}
 				break;
 			case __SI_SYS >> 16:
 				put_user_ex(from->si_syscall, &to->si_syscall);
_