* [PATCH v15 0/6] arm64: expose FAR_EL1 tag bits in siginfo
@ 2020-11-13 2:46 Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 1/6] parisc: Drop parisc special case for __sighandler_t Peter Collingbourne
` (5 more replies)
0 siblings, 6 replies; 8+ messages in thread
From: Peter Collingbourne @ 2020-11-13 2:46 UTC (permalink / raw)
To: Catalin Marinas, Evgenii Stepanov, Kostya Serebryany,
Vincenzo Frascino, Dave Martin, Will Deacon, Oleg Nesterov,
Eric W. Biederman, James E.J. Bottomley
Cc: Peter Collingbourne, Linux ARM, Kevin Brodsky, Andrey Konovalov,
linux-api, Helge Deller, David Spickett
The kernel currently clears the tag bits (i.e. bits 56-63) in the fault
address exposed via siginfo.si_addr and sigcontext.fault_address. However,
the tag bits may be needed by tools in order to accurately diagnose
memory errors, such as HWASan [1] or future tools based on the Memory
Tagging Extension (MTE).
We should not stop clearing these bits in the existing fault address
fields, because there may be existing userspace applications that are
expecting the tag bits to be cleared. Instead, introduce a flag in
sigaction.sa_flags, SA_EXPOSE_TAGBITS, and only expose the tag bits
there if the signal handler has this flag set.
In order to allow userspace to determine whether SA_EXPOSE_TAGBITS
is supported, we first introduce a mechanism for userspace to detect
kernel support for SA_* flags.
The series can be viewed on Gerrit here:
https://linux-review.googlesource.com/id/Ia8876bad8c798e0a32df7c2ce1256c4771c81446
[1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html
Helge Deller (1):
parisc: Drop parisc special case for __sighandler_t
Peter Collingbourne (5):
parisc: start using signal-defs.h
arch: move SA_* definitions to generic headers
signal: clear non-uapi flag bits when passing/returning sa_flags
signal: define the SA_UNSUPPORTED bit in sa_flags
arm64: expose FAR_EL1 tag bits in siginfo
Documentation/arm64/tagged-pointers.rst | 25 ++++++---
arch/alpha/include/uapi/asm/signal.h | 14 -----
arch/arm/include/asm/signal.h | 2 +
arch/arm/include/uapi/asm/signal.h | 27 ++--------
arch/arm64/include/asm/exception.h | 2 +-
arch/arm64/include/asm/system_misc.h | 2 +-
arch/arm64/include/asm/traps.h | 6 +--
arch/arm64/kernel/debug-monitors.c | 5 +-
arch/arm64/kernel/entry-common.c | 2 -
arch/arm64/kernel/ptrace.c | 7 +--
arch/arm64/kernel/sys_compat.c | 5 +-
arch/arm64/kernel/traps.c | 29 ++++++-----
arch/arm64/mm/fault.c | 68 ++++++++++++++-----------
arch/h8300/include/uapi/asm/signal.h | 24 ---------
arch/ia64/include/uapi/asm/signal.h | 24 ---------
arch/m68k/include/uapi/asm/signal.h | 24 ---------
arch/mips/include/uapi/asm/signal.h | 12 -----
arch/parisc/include/asm/signal.h | 2 +
arch/parisc/include/uapi/asm/signal.h | 34 +------------
arch/powerpc/include/uapi/asm/signal.h | 24 ---------
arch/s390/include/uapi/asm/signal.h | 24 ---------
arch/sparc/include/uapi/asm/signal.h | 4 +-
arch/x86/include/uapi/asm/signal.h | 24 ---------
arch/x86/kernel/signal_compat.c | 7 ---
arch/xtensa/include/uapi/asm/signal.h | 24 ---------
include/linux/signal.h | 14 +++++
include/linux/signal_types.h | 12 +++++
include/uapi/asm-generic/signal-defs.h | 57 +++++++++++++++++++++
include/uapi/asm-generic/signal.h | 29 -----------
kernel/signal.c | 39 +++++++++++---
30 files changed, 206 insertions(+), 366 deletions(-)
--
2.29.2.299.gdc1121823c-goog
^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH v15 1/6] parisc: Drop parisc special case for __sighandler_t
2020-11-13 2:46 [PATCH v15 0/6] arm64: expose FAR_EL1 tag bits in siginfo Peter Collingbourne
@ 2020-11-13 2:46 ` Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 2/6] parisc: start using signal-defs.h Peter Collingbourne
` (4 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: Peter Collingbourne @ 2020-11-13 2:46 UTC (permalink / raw)
To: Catalin Marinas, Evgenii Stepanov, Kostya Serebryany,
Vincenzo Frascino, Dave Martin, Will Deacon, Oleg Nesterov,
Eric W. Biederman, James E.J. Bottomley
Cc: Peter Collingbourne, Linux ARM, Kevin Brodsky, Andrey Konovalov,
linux-api, Helge Deller, David Spickett
From: Helge Deller <deller@gmx.de>
I believe we can and *should* drop this parisc-specific typedef for
__sighandler_t when compiling a 64-bit kernel. The reasons:
1. We don't have a 64-bit userspace yet, so nothing (on userspace side)
can break.
2. Inside the Linux kernel, this is only used in kernel/signal.c, in
function kernel_sigaction() where the signal handler is compared against
SIG_IGN. SIG_IGN is defined as (__sighandler_t)1), so only the pointers
are compared.
3. Even when a 64-bit userspace gets added at some point, I think
__sighandler_t should be defined what it is: a function pointer struct.
I compiled kernel/signal.c with and without the patch, and the produced code
is identical in both cases.
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Peter Collingbourne <pcc@google.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Reviewed-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/I21c43f21b264f339e3aa395626af838646f62d97
---
arch/parisc/include/uapi/asm/signal.h | 8 --------
1 file changed, 8 deletions(-)
diff --git a/arch/parisc/include/uapi/asm/signal.h b/arch/parisc/include/uapi/asm/signal.h
index e605197b462c..d9c51769851a 100644
--- a/arch/parisc/include/uapi/asm/signal.h
+++ b/arch/parisc/include/uapi/asm/signal.h
@@ -85,16 +85,8 @@
struct siginfo;
/* Type of a signal handler. */
-#if defined(__LP64__)
-/* function pointers on 64-bit parisc are pointers to little structs and the
- * compiler doesn't support code which changes or tests the address of
- * the function in the little struct. This is really ugly -PB
- */
-typedef char __user *__sighandler_t;
-#else
typedef void __signalfn_t(int);
typedef __signalfn_t __user *__sighandler_t;
-#endif
typedef struct sigaltstack {
void __user *ss_sp;
--
2.29.2.299.gdc1121823c-goog
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH v15 2/6] parisc: start using signal-defs.h
2020-11-13 2:46 [PATCH v15 0/6] arm64: expose FAR_EL1 tag bits in siginfo Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 1/6] parisc: Drop parisc special case for __sighandler_t Peter Collingbourne
@ 2020-11-13 2:46 ` Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 3/6] arch: move SA_* definitions to generic headers Peter Collingbourne
` (3 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: Peter Collingbourne @ 2020-11-13 2:46 UTC (permalink / raw)
To: Catalin Marinas, Evgenii Stepanov, Kostya Serebryany,
Vincenzo Frascino, Dave Martin, Will Deacon, Oleg Nesterov,
Eric W. Biederman, James E.J. Bottomley
Cc: Peter Collingbourne, Linux ARM, Kevin Brodsky, Andrey Konovalov,
linux-api, Helge Deller, David Spickett
We currently include signal-defs.h on all architectures except parisc.
Make parisc fall in line. This will make maintenance easier once the
flag bits are moved here.
Signed-off-by: Peter Collingbourne <pcc@google.com>
Acked-by: Helge Deller <deller@gmx.de>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Link: https://linux-review.googlesource.com/id/If03a5135fb514fe96548fb74610e6c3586a04064
---
arch/parisc/include/uapi/asm/signal.h | 13 +------------
1 file changed, 1 insertion(+), 12 deletions(-)
diff --git a/arch/parisc/include/uapi/asm/signal.h b/arch/parisc/include/uapi/asm/signal.h
index d9c51769851a..9e6f87bc8a73 100644
--- a/arch/parisc/include/uapi/asm/signal.h
+++ b/arch/parisc/include/uapi/asm/signal.h
@@ -68,14 +68,7 @@
#define MINSIGSTKSZ 2048
#define SIGSTKSZ 8192
-
-#define SIG_BLOCK 0 /* for blocking signals */
-#define SIG_UNBLOCK 1 /* for unblocking signals */
-#define SIG_SETMASK 2 /* for setting the signal mask */
-
-#define SIG_DFL ((__sighandler_t)0) /* default signal handling */
-#define SIG_IGN ((__sighandler_t)1) /* ignore signal */
-#define SIG_ERR ((__sighandler_t)-1) /* error return from signal */
+#include <asm-generic/signal-defs.h>
# ifndef __ASSEMBLY__
@@ -84,10 +77,6 @@
/* Avoid too many header ordering problems. */
struct siginfo;
-/* Type of a signal handler. */
-typedef void __signalfn_t(int);
-typedef __signalfn_t __user *__sighandler_t;
-
typedef struct sigaltstack {
void __user *ss_sp;
int ss_flags;
--
2.29.2.299.gdc1121823c-goog
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH v15 3/6] arch: move SA_* definitions to generic headers
2020-11-13 2:46 [PATCH v15 0/6] arm64: expose FAR_EL1 tag bits in siginfo Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 1/6] parisc: Drop parisc special case for __sighandler_t Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 2/6] parisc: start using signal-defs.h Peter Collingbourne
@ 2020-11-13 2:46 ` Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 4/6] signal: clear non-uapi flag bits when passing/returning sa_flags Peter Collingbourne
` (2 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: Peter Collingbourne @ 2020-11-13 2:46 UTC (permalink / raw)
To: Catalin Marinas, Evgenii Stepanov, Kostya Serebryany,
Vincenzo Frascino, Dave Martin, Will Deacon, Oleg Nesterov,
Eric W. Biederman, James E.J. Bottomley
Cc: Peter Collingbourne, Linux ARM, Kevin Brodsky, Andrey Konovalov,
linux-api, Helge Deller, David Spickett, Geert Uytterhoeven
Most architectures with the exception of alpha, mips, parisc and
sparc use the same values for these flags. Move their definitions into
asm-generic/signal-defs.h and allow the architectures with non-standard
values to override them. Also, document the non-standard flag values
in order to make it easier to add new generic flags in the future.
A consequence of this change is that on powerpc and x86, the constants'
values aside from SA_RESETHAND change signedness from unsigned
to signed. This is not expected to impact realistic use of these
constants. In particular the typical use of the constants where they
are or'ed together and assigned to sa_flags (or another int variable)
would not be affected.
Signed-off-by: Peter Collingbourne <pcc@google.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Link: https://linux-review.googlesource.com/id/Ia3849f18b8009bf41faca374e701cdca36974528
---
v14:
- revert unintentional removal of SA_RESTORER on arm as pointed
out by Eric
v11:
- tweak the commit message to point out the change from unsigned
to signed
v10:
- move the comments around and add one for SA_SIGINFO
arch/alpha/include/uapi/asm/signal.h | 14 --------
arch/arm/include/uapi/asm/signal.h | 27 ++-------------
arch/h8300/include/uapi/asm/signal.h | 24 -------------
arch/ia64/include/uapi/asm/signal.h | 24 -------------
arch/m68k/include/uapi/asm/signal.h | 24 -------------
arch/mips/include/uapi/asm/signal.h | 12 -------
arch/parisc/include/uapi/asm/signal.h | 13 -------
arch/powerpc/include/uapi/asm/signal.h | 24 -------------
arch/s390/include/uapi/asm/signal.h | 24 -------------
arch/sparc/include/uapi/asm/signal.h | 4 +--
arch/x86/include/uapi/asm/signal.h | 24 -------------
arch/xtensa/include/uapi/asm/signal.h | 24 -------------
include/uapi/asm-generic/signal-defs.h | 47 ++++++++++++++++++++++++++
include/uapi/asm-generic/signal.h | 29 ----------------
14 files changed, 51 insertions(+), 263 deletions(-)
diff --git a/arch/alpha/include/uapi/asm/signal.h b/arch/alpha/include/uapi/asm/signal.h
index 74c750bf1c1a..a69dd8d080a8 100644
--- a/arch/alpha/include/uapi/asm/signal.h
+++ b/arch/alpha/include/uapi/asm/signal.h
@@ -60,20 +60,6 @@ typedef unsigned long sigset_t;
#define SIGRTMIN 32
#define SIGRTMAX _NSIG
-/*
- * SA_FLAGS values:
- *
- * SA_ONSTACK indicates that a registered stack_t will be used.
- * SA_RESTART flag to get restarting signals (which were the default long ago)
- * SA_NOCLDSTOP flag to turn off SIGCHLD when children stop.
- * SA_RESETHAND clears the handler when the signal is delivered.
- * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
- * SA_NODEFER prevents the current signal from being masked in the handler.
- *
- * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
- * Unix names RESETHAND and NODEFER respectively.
- */
-
#define SA_ONSTACK 0x00000001
#define SA_RESTART 0x00000002
#define SA_NOCLDSTOP 0x00000004
diff --git a/arch/arm/include/uapi/asm/signal.h b/arch/arm/include/uapi/asm/signal.h
index 9b4185ba4f8a..c9a3ea1d8d41 100644
--- a/arch/arm/include/uapi/asm/signal.h
+++ b/arch/arm/include/uapi/asm/signal.h
@@ -60,33 +60,12 @@ typedef unsigned long sigset_t;
#define SIGSWI 32
/*
- * SA_FLAGS values:
- *
- * SA_NOCLDSTOP flag to turn off SIGCHLD when children stop.
- * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
- * SA_SIGINFO deliver the signal with SIGINFO structs
- * SA_THIRTYTWO delivers the signal in 32-bit mode, even if the task
- * is running in 26-bit.
- * SA_ONSTACK allows alternate signal stacks (see sigaltstack(2)).
- * SA_RESTART flag to get restarting signals (which were the default long ago)
- * SA_NODEFER prevents the current signal from being masked in the handler.
- * SA_RESETHAND clears the handler when the signal is delivered.
- *
- * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
- * Unix names RESETHAND and NODEFER respectively.
+ * SA_THIRTYTWO historically meant deliver the signal in 32-bit mode, even if
+ * the task is running in 26-bit. But since the kernel no longer supports
+ * 26-bit mode, the flag has no effect.
*/
-#define SA_NOCLDSTOP 0x00000001
-#define SA_NOCLDWAIT 0x00000002
-#define SA_SIGINFO 0x00000004
#define SA_THIRTYTWO 0x02000000
#define SA_RESTORER 0x04000000
-#define SA_ONSTACK 0x08000000
-#define SA_RESTART 0x10000000
-#define SA_NODEFER 0x40000000
-#define SA_RESETHAND 0x80000000
-
-#define SA_NOMASK SA_NODEFER
-#define SA_ONESHOT SA_RESETHAND
#define MINSIGSTKSZ 2048
#define SIGSTKSZ 8192
diff --git a/arch/h8300/include/uapi/asm/signal.h b/arch/h8300/include/uapi/asm/signal.h
index e15521037348..2cd0dce2b6a6 100644
--- a/arch/h8300/include/uapi/asm/signal.h
+++ b/arch/h8300/include/uapi/asm/signal.h
@@ -57,30 +57,6 @@ typedef unsigned long sigset_t;
#define SIGRTMIN 32
#define SIGRTMAX _NSIG
-/*
- * SA_FLAGS values:
- *
- * SA_ONSTACK indicates that a registered stack_t will be used.
- * SA_RESTART flag to get restarting signals (which were the default long ago)
- * SA_NOCLDSTOP flag to turn off SIGCHLD when children stop.
- * SA_RESETHAND clears the handler when the signal is delivered.
- * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
- * SA_NODEFER prevents the current signal from being masked in the handler.
- *
- * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
- * Unix names RESETHAND and NODEFER respectively.
- */
-#define SA_NOCLDSTOP 0x00000001
-#define SA_NOCLDWAIT 0x00000002 /* not supported yet */
-#define SA_SIGINFO 0x00000004
-#define SA_ONSTACK 0x08000000
-#define SA_RESTART 0x10000000
-#define SA_NODEFER 0x40000000
-#define SA_RESETHAND 0x80000000
-
-#define SA_NOMASK SA_NODEFER
-#define SA_ONESHOT SA_RESETHAND
-
#define SA_RESTORER 0x04000000
#define MINSIGSTKSZ 2048
diff --git a/arch/ia64/include/uapi/asm/signal.h b/arch/ia64/include/uapi/asm/signal.h
index aa98ff1b9e22..38166a88e4c9 100644
--- a/arch/ia64/include/uapi/asm/signal.h
+++ b/arch/ia64/include/uapi/asm/signal.h
@@ -53,30 +53,6 @@
#define SIGRTMIN 32
#define SIGRTMAX _NSIG
-/*
- * SA_FLAGS values:
- *
- * SA_ONSTACK indicates that a registered stack_t will be used.
- * SA_RESTART flag to get restarting signals (which were the default long ago)
- * SA_NOCLDSTOP flag to turn off SIGCHLD when children stop.
- * SA_RESETHAND clears the handler when the signal is delivered.
- * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
- * SA_NODEFER prevents the current signal from being masked in the handler.
- *
- * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
- * Unix names RESETHAND and NODEFER respectively.
- */
-#define SA_NOCLDSTOP 0x00000001
-#define SA_NOCLDWAIT 0x00000002
-#define SA_SIGINFO 0x00000004
-#define SA_ONSTACK 0x08000000
-#define SA_RESTART 0x10000000
-#define SA_NODEFER 0x40000000
-#define SA_RESETHAND 0x80000000
-
-#define SA_NOMASK SA_NODEFER
-#define SA_ONESHOT SA_RESETHAND
-
#define SA_RESTORER 0x04000000
/*
diff --git a/arch/m68k/include/uapi/asm/signal.h b/arch/m68k/include/uapi/asm/signal.h
index 915cc755a184..4619291df601 100644
--- a/arch/m68k/include/uapi/asm/signal.h
+++ b/arch/m68k/include/uapi/asm/signal.h
@@ -57,30 +57,6 @@ typedef unsigned long sigset_t;
#define SIGRTMIN 32
#define SIGRTMAX _NSIG
-/*
- * SA_FLAGS values:
- *
- * SA_ONSTACK indicates that a registered stack_t will be used.
- * SA_RESTART flag to get restarting signals (which were the default long ago)
- * SA_NOCLDSTOP flag to turn off SIGCHLD when children stop.
- * SA_RESETHAND clears the handler when the signal is delivered.
- * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
- * SA_NODEFER prevents the current signal from being masked in the handler.
- *
- * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
- * Unix names RESETHAND and NODEFER respectively.
- */
-#define SA_NOCLDSTOP 0x00000001
-#define SA_NOCLDWAIT 0x00000002
-#define SA_SIGINFO 0x00000004
-#define SA_ONSTACK 0x08000000
-#define SA_RESTART 0x10000000
-#define SA_NODEFER 0x40000000
-#define SA_RESETHAND 0x80000000
-
-#define SA_NOMASK SA_NODEFER
-#define SA_ONESHOT SA_RESETHAND
-
#define MINSIGSTKSZ 2048
#define SIGSTKSZ 8192
diff --git a/arch/mips/include/uapi/asm/signal.h b/arch/mips/include/uapi/asm/signal.h
index 53104b10aae2..e6c78a15cb2f 100644
--- a/arch/mips/include/uapi/asm/signal.h
+++ b/arch/mips/include/uapi/asm/signal.h
@@ -62,18 +62,6 @@ typedef unsigned long old_sigset_t; /* at least 32 bits */
#define SIGRTMAX _NSIG
/*
- * SA_FLAGS values:
- *
- * SA_ONSTACK indicates that a registered stack_t will be used.
- * SA_RESTART flag to get restarting signals (which were the default long ago)
- * SA_NOCLDSTOP flag to turn off SIGCHLD when children stop.
- * SA_RESETHAND clears the handler when the signal is delivered.
- * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
- * SA_NODEFER prevents the current signal from being masked in the handler.
- *
- * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
- * Unix names RESETHAND and NODEFER respectively.
- *
* SA_RESTORER used to be defined as 0x04000000 but only the O32 ABI ever
* supported its use and no libc was using it, so the entire sa-restorer
* functionality was removed with lmo commit 39bffc12c3580ab for 2.5.48
diff --git a/arch/parisc/include/uapi/asm/signal.h b/arch/parisc/include/uapi/asm/signal.h
index 9e6f87bc8a73..e5a2657477ac 100644
--- a/arch/parisc/include/uapi/asm/signal.h
+++ b/arch/parisc/include/uapi/asm/signal.h
@@ -41,19 +41,6 @@
#define SIGRTMIN 32
#define SIGRTMAX _NSIG
-/*
- * SA_FLAGS values:
- *
- * SA_ONSTACK indicates that a registered stack_t will be used.
- * SA_RESTART flag to get restarting signals (which were the default long ago)
- * SA_NOCLDSTOP flag to turn off SIGCHLD when children stop.
- * SA_RESETHAND clears the handler when the signal is delivered.
- * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
- * SA_NODEFER prevents the current signal from being masked in the handler.
- *
- * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
- * Unix names RESETHAND and NODEFER respectively.
- */
#define SA_ONSTACK 0x00000001
#define SA_RESETHAND 0x00000004
#define SA_NOCLDSTOP 0x00000008
diff --git a/arch/powerpc/include/uapi/asm/signal.h b/arch/powerpc/include/uapi/asm/signal.h
index 85b0a7aa43e7..04873dd311c2 100644
--- a/arch/powerpc/include/uapi/asm/signal.h
+++ b/arch/powerpc/include/uapi/asm/signal.h
@@ -60,30 +60,6 @@ typedef struct {
#define SIGRTMIN 32
#define SIGRTMAX _NSIG
-/*
- * SA_FLAGS values:
- *
- * SA_ONSTACK is not currently supported, but will allow sigaltstack(2).
- * SA_RESTART flag to get restarting signals (which were the default long ago)
- * SA_NOCLDSTOP flag to turn off SIGCHLD when children stop.
- * SA_RESETHAND clears the handler when the signal is delivered.
- * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
- * SA_NODEFER prevents the current signal from being masked in the handler.
- *
- * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
- * Unix names RESETHAND and NODEFER respectively.
- */
-#define SA_NOCLDSTOP 0x00000001U
-#define SA_NOCLDWAIT 0x00000002U
-#define SA_SIGINFO 0x00000004U
-#define SA_ONSTACK 0x08000000U
-#define SA_RESTART 0x10000000U
-#define SA_NODEFER 0x40000000U
-#define SA_RESETHAND 0x80000000U
-
-#define SA_NOMASK SA_NODEFER
-#define SA_ONESHOT SA_RESETHAND
-
#define SA_RESTORER 0x04000000U
#define MINSIGSTKSZ 2048
diff --git a/arch/s390/include/uapi/asm/signal.h b/arch/s390/include/uapi/asm/signal.h
index 9a14a611ed82..0189f326aac5 100644
--- a/arch/s390/include/uapi/asm/signal.h
+++ b/arch/s390/include/uapi/asm/signal.h
@@ -65,30 +65,6 @@ typedef unsigned long sigset_t;
#define SIGRTMIN 32
#define SIGRTMAX _NSIG
-/*
- * SA_FLAGS values:
- *
- * SA_ONSTACK indicates that a registered stack_t will be used.
- * SA_RESTART flag to get restarting signals (which were the default long ago)
- * SA_NOCLDSTOP flag to turn off SIGCHLD when children stop.
- * SA_RESETHAND clears the handler when the signal is delivered.
- * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
- * SA_NODEFER prevents the current signal from being masked in the handler.
- *
- * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
- * Unix names RESETHAND and NODEFER respectively.
- */
-#define SA_NOCLDSTOP 0x00000001
-#define SA_NOCLDWAIT 0x00000002
-#define SA_SIGINFO 0x00000004
-#define SA_ONSTACK 0x08000000
-#define SA_RESTART 0x10000000
-#define SA_NODEFER 0x40000000
-#define SA_RESETHAND 0x80000000
-
-#define SA_NOMASK SA_NODEFER
-#define SA_ONESHOT SA_RESETHAND
-
#define SA_RESTORER 0x04000000
#define MINSIGSTKSZ 2048
diff --git a/arch/sparc/include/uapi/asm/signal.h b/arch/sparc/include/uapi/asm/signal.h
index ff9505923b9a..53758d53ac0e 100644
--- a/arch/sparc/include/uapi/asm/signal.h
+++ b/arch/sparc/include/uapi/asm/signal.h
@@ -137,13 +137,11 @@ struct sigstack {
#define SA_STACK _SV_SSTACK
#define SA_ONSTACK _SV_SSTACK
#define SA_RESTART _SV_INTR
-#define SA_ONESHOT _SV_RESET
+#define SA_RESETHAND _SV_RESET
#define SA_NODEFER 0x20u
#define SA_NOCLDWAIT 0x100u
#define SA_SIGINFO 0x200u
-#define SA_NOMASK SA_NODEFER
-
#define SIG_BLOCK 0x01 /* for blocking signals */
#define SIG_UNBLOCK 0x02 /* for unblocking signals */
#define SIG_SETMASK 0x04 /* for setting the signal mask */
diff --git a/arch/x86/include/uapi/asm/signal.h b/arch/x86/include/uapi/asm/signal.h
index e5745d593dc7..164a22a72984 100644
--- a/arch/x86/include/uapi/asm/signal.h
+++ b/arch/x86/include/uapi/asm/signal.h
@@ -62,30 +62,6 @@ typedef unsigned long sigset_t;
#define SIGRTMIN 32
#define SIGRTMAX _NSIG
-/*
- * SA_FLAGS values:
- *
- * SA_ONSTACK indicates that a registered stack_t will be used.
- * SA_RESTART flag to get restarting signals (which were the default long ago)
- * SA_NOCLDSTOP flag to turn off SIGCHLD when children stop.
- * SA_RESETHAND clears the handler when the signal is delivered.
- * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
- * SA_NODEFER prevents the current signal from being masked in the handler.
- *
- * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
- * Unix names RESETHAND and NODEFER respectively.
- */
-#define SA_NOCLDSTOP 0x00000001u
-#define SA_NOCLDWAIT 0x00000002u
-#define SA_SIGINFO 0x00000004u
-#define SA_ONSTACK 0x08000000u
-#define SA_RESTART 0x10000000u
-#define SA_NODEFER 0x40000000u
-#define SA_RESETHAND 0x80000000u
-
-#define SA_NOMASK SA_NODEFER
-#define SA_ONESHOT SA_RESETHAND
-
#define SA_RESTORER 0x04000000
#define MINSIGSTKSZ 2048
diff --git a/arch/xtensa/include/uapi/asm/signal.h b/arch/xtensa/include/uapi/asm/signal.h
index 005dec5bfde4..79ddabaa4e5d 100644
--- a/arch/xtensa/include/uapi/asm/signal.h
+++ b/arch/xtensa/include/uapi/asm/signal.h
@@ -72,30 +72,6 @@ typedef struct {
#define SIGRTMIN 32
#define SIGRTMAX (_NSIG-1)
-/*
- * SA_FLAGS values:
- *
- * SA_ONSTACK indicates that a registered stack_t will be used.
- * SA_RESTART flag to get restarting signals (which were the default long ago)
- * SA_NOCLDSTOP flag to turn off SIGCHLD when children stop.
- * SA_RESETHAND clears the handler when the signal is delivered.
- * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
- * SA_NODEFER prevents the current signal from being masked in the handler.
- *
- * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
- * Unix names RESETHAND and NODEFER respectively.
- */
-#define SA_NOCLDSTOP 0x00000001
-#define SA_NOCLDWAIT 0x00000002 /* not supported yet */
-#define SA_SIGINFO 0x00000004
-#define SA_ONSTACK 0x08000000
-#define SA_RESTART 0x10000000
-#define SA_NODEFER 0x40000000
-#define SA_RESETHAND 0x80000000
-
-#define SA_NOMASK SA_NODEFER
-#define SA_ONESHOT SA_RESETHAND
-
#define SA_RESTORER 0x04000000
#define MINSIGSTKSZ 2048
diff --git a/include/uapi/asm-generic/signal-defs.h b/include/uapi/asm-generic/signal-defs.h
index e9304c95ceea..493953fe319b 100644
--- a/include/uapi/asm-generic/signal-defs.h
+++ b/include/uapi/asm-generic/signal-defs.h
@@ -4,6 +4,53 @@
#include <linux/compiler.h>
+/*
+ * SA_FLAGS values:
+ *
+ * SA_NOCLDSTOP flag to turn off SIGCHLD when children stop.
+ * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
+ * SA_SIGINFO delivers the signal with SIGINFO structs.
+ * SA_ONSTACK indicates that a registered stack_t will be used.
+ * SA_RESTART flag to get restarting signals (which were the default long ago)
+ * SA_NODEFER prevents the current signal from being masked in the handler.
+ * SA_RESETHAND clears the handler when the signal is delivered.
+ *
+ * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
+ * Unix names RESETHAND and NODEFER respectively.
+ *
+ * The following bits are used in architecture-specific SA_* definitions and
+ * should be avoided for new generic flags: 3, 4, 5, 6, 7, 8, 9, 16, 24, 25, 26.
+ */
+#ifndef SA_NOCLDSTOP
+#define SA_NOCLDSTOP 0x00000001
+#endif
+#ifndef SA_NOCLDWAIT
+#define SA_NOCLDWAIT 0x00000002
+#endif
+#ifndef SA_SIGINFO
+#define SA_SIGINFO 0x00000004
+#endif
+#ifndef SA_ONSTACK
+#define SA_ONSTACK 0x08000000
+#endif
+#ifndef SA_RESTART
+#define SA_RESTART 0x10000000
+#endif
+#ifndef SA_NODEFER
+#define SA_NODEFER 0x40000000
+#endif
+#ifndef SA_RESETHAND
+#define SA_RESETHAND 0x80000000
+#endif
+
+#define SA_NOMASK SA_NODEFER
+#define SA_ONESHOT SA_RESETHAND
+
+/*
+ * New architectures should not define the obsolete
+ * SA_RESTORER 0x04000000
+ */
+
#ifndef SIG_BLOCK
#define SIG_BLOCK 0 /* for blocking signals */
#endif
diff --git a/include/uapi/asm-generic/signal.h b/include/uapi/asm-generic/signal.h
index 5c716a952cbe..f634822906e4 100644
--- a/include/uapi/asm-generic/signal.h
+++ b/include/uapi/asm-generic/signal.h
@@ -52,35 +52,6 @@
#define SIGRTMAX _NSIG
#endif
-/*
- * SA_FLAGS values:
- *
- * SA_ONSTACK indicates that a registered stack_t will be used.
- * SA_RESTART flag to get restarting signals (which were the default long ago)
- * SA_NOCLDSTOP flag to turn off SIGCHLD when children stop.
- * SA_RESETHAND clears the handler when the signal is delivered.
- * SA_NOCLDWAIT flag on SIGCHLD to inhibit zombies.
- * SA_NODEFER prevents the current signal from being masked in the handler.
- *
- * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
- * Unix names RESETHAND and NODEFER respectively.
- */
-#define SA_NOCLDSTOP 0x00000001
-#define SA_NOCLDWAIT 0x00000002
-#define SA_SIGINFO 0x00000004
-#define SA_ONSTACK 0x08000000
-#define SA_RESTART 0x10000000
-#define SA_NODEFER 0x40000000
-#define SA_RESETHAND 0x80000000
-
-#define SA_NOMASK SA_NODEFER
-#define SA_ONESHOT SA_RESETHAND
-
-/*
- * New architectures should not define the obsolete
- * SA_RESTORER 0x04000000
- */
-
#if !defined MINSIGSTKSZ || !defined SIGSTKSZ
#define MINSIGSTKSZ 2048
#define SIGSTKSZ 8192
--
2.29.2.299.gdc1121823c-goog
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH v15 4/6] signal: clear non-uapi flag bits when passing/returning sa_flags
2020-11-13 2:46 [PATCH v15 0/6] arm64: expose FAR_EL1 tag bits in siginfo Peter Collingbourne
` (2 preceding siblings ...)
2020-11-13 2:46 ` [PATCH v15 3/6] arch: move SA_* definitions to generic headers Peter Collingbourne
@ 2020-11-13 2:46 ` Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 5/6] signal: define the SA_UNSUPPORTED bit in sa_flags Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 6/6] arm64: expose FAR_EL1 tag bits in siginfo Peter Collingbourne
5 siblings, 0 replies; 8+ messages in thread
From: Peter Collingbourne @ 2020-11-13 2:46 UTC (permalink / raw)
To: Catalin Marinas, Evgenii Stepanov, Kostya Serebryany,
Vincenzo Frascino, Dave Martin, Will Deacon, Oleg Nesterov,
Eric W. Biederman, James E.J. Bottomley
Cc: Peter Collingbourne, Linux ARM, Kevin Brodsky, Andrey Konovalov,
linux-api, Helge Deller, David Spickett
Previously we were not clearing non-uapi flag bits in
sigaction.sa_flags when storing the userspace-provided sa_flags or
when returning them via oldact. Start doing so.
This allows userspace to detect missing support for flag bits and
allows the kernel to use non-uapi bits internally, as we are already
doing in arch/x86 for two flag bits. Now that this change is in
place, we no longer need the code in arch/x86 that was hiding these
bits from userspace, so remove it.
This is technically a userspace-visible behavior change for sigaction, as
the unknown bits returned via oldact.sa_flags are no longer set. However,
we are free to define the behavior for unknown bits exactly because
their behavior is currently undefined, so for now we can define the
meaning of each of them to be "clear the bit in oldact.sa_flags unless
the bit becomes known in the future". Furthermore, this behavior is
consistent with OpenBSD [1], illumos [2] and XNU [3] (FreeBSD [4] and
NetBSD [5] fail the syscall if unknown bits are set). So there is some
precedent for this behavior in other kernels, and in particular in XNU,
which is probably the most popular kernel among those that I looked at,
which means that this change is less likely to be a compatibility issue.
Link: [1] https://github.com/openbsd/src/blob/f634a6a4b5bf832e9c1de77f7894ae2625e74484/sys/kern/kern_sig.c#L278
Link: [2] https://github.com/illumos/illumos-gate/blob/76f19f5fdc974fe5be5c82a556e43a4df93f1de1/usr/src/uts/common/syscall/sigaction.c#L86
Link: [3] https://github.com/apple/darwin-xnu/blob/a449c6a3b8014d9406c2ddbdc81795da24aa7443/bsd/kern/kern_sig.c#L480
Link: [4] https://github.com/freebsd/freebsd/blob/eded70c37057857c6e23fae51f86b8f8f43cd2d0/sys/kern/kern_sig.c#L699
Link: [5] https://github.com/NetBSD/src/blob/3365779becdcedfca206091a645a0e8e22b2946e/sys/kern/sys_sig.c#L473
Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Link: https://linux-review.googlesource.com/id/I35aab6f5be932505d90f3b3450c083b4db1eca86
---
v10:
- rename SA_UAPI_FLAGS -> UAPI_SA_FLAGS
- refactor how we define it to avoid mentioning flags more
than once
arch/arm/include/asm/signal.h | 2 ++
arch/parisc/include/asm/signal.h | 2 ++
arch/x86/kernel/signal_compat.c | 7 -------
include/linux/signal_types.h | 12 ++++++++++++
kernel/signal.c | 10 ++++++++++
5 files changed, 26 insertions(+), 7 deletions(-)
diff --git a/arch/arm/include/asm/signal.h b/arch/arm/include/asm/signal.h
index 65530a042009..430be7774402 100644
--- a/arch/arm/include/asm/signal.h
+++ b/arch/arm/include/asm/signal.h
@@ -17,6 +17,8 @@ typedef struct {
unsigned long sig[_NSIG_WORDS];
} sigset_t;
+#define __ARCH_UAPI_SA_FLAGS (SA_THIRTYTWO | SA_RESTORER)
+
#define __ARCH_HAS_SA_RESTORER
#include <asm/sigcontext.h>
diff --git a/arch/parisc/include/asm/signal.h b/arch/parisc/include/asm/signal.h
index 715c96ba2ec8..30dd1e43ef88 100644
--- a/arch/parisc/include/asm/signal.h
+++ b/arch/parisc/include/asm/signal.h
@@ -21,6 +21,8 @@ typedef struct {
unsigned long sig[_NSIG_WORDS];
} sigset_t;
+#define __ARCH_UAPI_SA_FLAGS _SA_SIGGFAULT
+
#include <asm/sigcontext.h>
#endif /* !__ASSEMBLY */
diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c
index a7f3e12cfbdb..ddfd919be46c 100644
--- a/arch/x86/kernel/signal_compat.c
+++ b/arch/x86/kernel/signal_compat.c
@@ -165,16 +165,9 @@ void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
{
signal_compat_build_tests();
- /* Don't leak in-kernel non-uapi flags to user-space */
- if (oact)
- oact->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
-
if (!act)
return;
- /* Don't let flags to be set from userspace */
- act->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
-
if (in_ia32_syscall())
act->sa.sa_flags |= SA_IA32_ABI;
if (in_x32_syscall())
diff --git a/include/linux/signal_types.h b/include/linux/signal_types.h
index f8a90ae9c6ec..a7887ad84d36 100644
--- a/include/linux/signal_types.h
+++ b/include/linux/signal_types.h
@@ -68,4 +68,16 @@ struct ksignal {
int sig;
};
+#ifndef __ARCH_UAPI_SA_FLAGS
+#ifdef SA_RESTORER
+#define __ARCH_UAPI_SA_FLAGS SA_RESTORER
+#else
+#define __ARCH_UAPI_SA_FLAGS 0
+#endif
+#endif
+
+#define UAPI_SA_FLAGS \
+ (SA_NOCLDSTOP | SA_NOCLDWAIT | SA_SIGINFO | SA_ONSTACK | SA_RESTART | \
+ SA_NODEFER | SA_RESETHAND | __ARCH_UAPI_SA_FLAGS)
+
#endif /* _LINUX_SIGNAL_TYPES_H */
diff --git a/kernel/signal.c b/kernel/signal.c
index ef8f2a28d37c..8f5bd12ee41b 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3985,6 +3985,16 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
if (oact)
*oact = *k;
+ /*
+ * Clear unknown flag bits in order to allow userspace to detect missing
+ * support for flag bits and to allow the kernel to use non-uapi bits
+ * internally.
+ */
+ if (act)
+ act->sa.sa_flags &= UAPI_SA_FLAGS;
+ if (oact)
+ oact->sa.sa_flags &= UAPI_SA_FLAGS;
+
sigaction_compat_abi(act, oact);
if (act) {
--
2.29.2.299.gdc1121823c-goog
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH v15 5/6] signal: define the SA_UNSUPPORTED bit in sa_flags
2020-11-13 2:46 [PATCH v15 0/6] arm64: expose FAR_EL1 tag bits in siginfo Peter Collingbourne
` (3 preceding siblings ...)
2020-11-13 2:46 ` [PATCH v15 4/6] signal: clear non-uapi flag bits when passing/returning sa_flags Peter Collingbourne
@ 2020-11-13 2:46 ` Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 6/6] arm64: expose FAR_EL1 tag bits in siginfo Peter Collingbourne
5 siblings, 0 replies; 8+ messages in thread
From: Peter Collingbourne @ 2020-11-13 2:46 UTC (permalink / raw)
To: Catalin Marinas, Evgenii Stepanov, Kostya Serebryany,
Vincenzo Frascino, Dave Martin, Will Deacon, Oleg Nesterov,
Eric W. Biederman, James E.J. Bottomley
Cc: Peter Collingbourne, Linux ARM, Kevin Brodsky, Andrey Konovalov,
linux-api, Helge Deller, David Spickett
Define a sa_flags bit, SA_UNSUPPORTED, which will never be supported
in the uapi. The purpose of this flag bit is to allow userspace to
distinguish an old kernel that does not clear unknown sa_flags bits
from a kernel that supports every flag bit.
In other words, if userspace does something like:
act.sa_flags |= SA_UNSUPPORTED;
sigaction(SIGSEGV, &act, 0);
sigaction(SIGSEGV, 0, &oldact);
and finds that SA_UNSUPPORTED remains set in oldact.sa_flags, it means
that the kernel cannot be trusted to have cleared unknown flag bits
from sa_flags, so no assumptions about flag bit support can be made.
Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Link: https://linux-review.googlesource.com/id/Ic2501ad150a3a79c1cf27fb8c99be342e9dffbcb
---
v11:
- clarify the commit message
include/uapi/asm-generic/signal-defs.h | 7 +++++++
kernel/signal.c | 6 ++++++
2 files changed, 13 insertions(+)
diff --git a/include/uapi/asm-generic/signal-defs.h b/include/uapi/asm-generic/signal-defs.h
index 493953fe319b..0126ebda4d31 100644
--- a/include/uapi/asm-generic/signal-defs.h
+++ b/include/uapi/asm-generic/signal-defs.h
@@ -14,6 +14,12 @@
* SA_RESTART flag to get restarting signals (which were the default long ago)
* SA_NODEFER prevents the current signal from being masked in the handler.
* SA_RESETHAND clears the handler when the signal is delivered.
+ * SA_UNSUPPORTED is a flag bit that will never be supported. Kernels from
+ * before the introduction of SA_UNSUPPORTED did not clear unknown bits from
+ * sa_flags when read using the oldact argument to sigaction and rt_sigaction,
+ * so this bit allows flag bit support to be detected from userspace while
+ * allowing an old kernel to be distinguished from a kernel that supports every
+ * flag bit.
*
* SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
* Unix names RESETHAND and NODEFER respectively.
@@ -42,6 +48,7 @@
#ifndef SA_RESETHAND
#define SA_RESETHAND 0x80000000
#endif
+#define SA_UNSUPPORTED 0x00000400
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
diff --git a/kernel/signal.c b/kernel/signal.c
index 8f5bd12ee41b..8f34819e80de 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3985,6 +3985,12 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
if (oact)
*oact = *k;
+ /*
+ * Make sure that we never accidentally claim to support SA_UNSUPPORTED,
+ * e.g. by having an architecture use the bit in their uapi.
+ */
+ BUILD_BUG_ON(UAPI_SA_FLAGS & SA_UNSUPPORTED);
+
/*
* Clear unknown flag bits in order to allow userspace to detect missing
* support for flag bits and to allow the kernel to use non-uapi bits
--
2.29.2.299.gdc1121823c-goog
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH v15 6/6] arm64: expose FAR_EL1 tag bits in siginfo
2020-11-13 2:46 [PATCH v15 0/6] arm64: expose FAR_EL1 tag bits in siginfo Peter Collingbourne
` (4 preceding siblings ...)
2020-11-13 2:46 ` [PATCH v15 5/6] signal: define the SA_UNSUPPORTED bit in sa_flags Peter Collingbourne
@ 2020-11-13 2:46 ` Peter Collingbourne
2020-11-13 2:52 ` Peter Collingbourne
5 siblings, 1 reply; 8+ messages in thread
From: Peter Collingbourne @ 2020-11-13 2:46 UTC (permalink / raw)
To: Catalin Marinas, Evgenii Stepanov, Kostya Serebryany,
Vincenzo Frascino, Dave Martin, Will Deacon, Oleg Nesterov,
Eric W. Biederman, James E.J. Bottomley
Cc: Peter Collingbourne, Linux ARM, Kevin Brodsky, Andrey Konovalov,
linux-api, Helge Deller, David Spickett
The kernel currently clears the tag bits (i.e. bits 56-63) in the fault
address exposed via siginfo.si_addr and sigcontext.fault_address. However,
the tag bits may be needed by tools in order to accurately diagnose
memory errors, such as HWASan [1] or future tools based on the Memory
Tagging Extension (MTE).
We should not stop clearing these bits in the existing fault address
fields, because there may be existing userspace applications that are
expecting the tag bits to be cleared. Instead, introduce a flag in
sigaction.sa_flags, SA_EXPOSE_TAGBITS, and only expose the tag bits
there if the signal handler has this flag set.
[1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html
Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/Ia8876bad8c798e0a32df7c2ce1256c4771c81446
---
v15:
- switched to the SA_EXPOSE_TAGBITS approach
proposed by Eric
- rebased to 5.10-rc3
v14:
- fix an inaccuracy in the commit message
- add some comments to arch_addr_tag_bits_mask
v13:
- renamed si_xflags to si_faultflags
- rebased to 5.10-rc2
v12:
- add new fields to signal_compat.c test cases
- rebased to 5.10-rc1
- mask out bits 63:60 for tag check faults
v11:
- add a comment explaining what the arch hook should do
- rename ignored bits to tag bits
v10:
- rename the flag to SIFAULTFLAG_ADDR_IGNORED_BITS
- use an arch hook to specify which bits are ignored, instead
of passing them explicitly
- while refactoring for the arch hook, noticed that my previous
patches missed a case involving cache maintenance instructions,
so expose the tag bits for that signal as well
v9:
- make the ignored bits fields generic
- add some new dependent patches that prepare us to store the
field in such a way that userspace can detect their presence
v8:
- rebase onto 5.8rc2
v7:
- switch to a new siginfo field instead of using sigcontext
- merge the patch back into one since the other patches are now
unnecessary
v6:
- move fault address and fault code into the kernel_siginfo data structure
- split the patch in three since it was getting large and now has
generic and arch-specific parts
v5:
- add padding to fault_addr_top_byte_context in order to ensure the correct
size and preserve sp alignment
v4:
- expose only the tag bits in the context instead of the entire FAR_EL1
- remove mention of the new context from the sigcontext.__reserved[] note
v3:
- add documentation to tagged-pointers.rst
- update comments in sigcontext.h
v2:
- revert changes to hw_breakpoint.c
- rename set_thread_esr to set_thread_far_esr
Documentation/arm64/tagged-pointers.rst | 25 ++++++---
arch/arm64/include/asm/exception.h | 2 +-
arch/arm64/include/asm/system_misc.h | 2 +-
arch/arm64/include/asm/traps.h | 6 +--
arch/arm64/kernel/debug-monitors.c | 5 +-
arch/arm64/kernel/entry-common.c | 2 -
arch/arm64/kernel/ptrace.c | 7 +--
arch/arm64/kernel/sys_compat.c | 5 +-
arch/arm64/kernel/traps.c | 29 ++++++-----
arch/arm64/mm/fault.c | 68 ++++++++++++++-----------
include/linux/signal.h | 14 +++++
include/linux/signal_types.h | 2 +-
include/uapi/asm-generic/signal-defs.h | 3 ++
kernel/signal.c | 23 ++++++---
14 files changed, 116 insertions(+), 77 deletions(-)
diff --git a/Documentation/arm64/tagged-pointers.rst b/Documentation/arm64/tagged-pointers.rst
index eab4323609b9..19d284b70384 100644
--- a/Documentation/arm64/tagged-pointers.rst
+++ b/Documentation/arm64/tagged-pointers.rst
@@ -53,12 +53,25 @@ visibility.
Preserving tags
---------------
-Non-zero tags are not preserved when delivering signals. This means that
-signal handlers in applications making use of tags cannot rely on the
-tag information for user virtual addresses being maintained for fields
-inside siginfo_t. One exception to this rule is for signals raised in
-response to watchpoint debug exceptions, where the tag information will
-be preserved.
+When delivering signals, non-zero tags are not preserved in
+siginfo.si_addr unless the flag SA_EXPOSE_TAGBITS was set in
+sigaction.sa_flags when the signal handler was installed. This means
+that signal handlers in applications making use of tags cannot rely
+on the tag information for user virtual addresses being maintained
+in these fields unless the flag was set.
+
+Due to architecture limitations, bits 63:60 of the fault address
+are not preserved in response to synchronous tag check faults
+(SEGV_MTESERR) even if SA_EXPOSE_TAGBITS was set. Applications should
+treat the values of these bits as undefined in order to accommodate
+future architecture revisions which may preserve the bits.
+
+For signals raised in response to watchpoint debug exceptions, the
+tag information will be preserved regardless of the SA_EXPOSE_TAGBITS
+flag setting.
+
+Non-zero tags are never preserved in sigcontext.fault_address
+regardless of the SA_EXPOSE_TAGBITS flag setting.
The architecture prevents the use of a tagged PC, so the upper byte will
be set to a sign-extension of bit 55 on exception return.
diff --git a/arch/arm64/include/asm/exception.h b/arch/arm64/include/asm/exception.h
index 99b9383cd036..2a8aa1884d8a 100644
--- a/arch/arm64/include/asm/exception.h
+++ b/arch/arm64/include/asm/exception.h
@@ -32,7 +32,7 @@ static inline u32 disr_to_esr(u64 disr)
}
asmlinkage void enter_from_user_mode(void);
-void do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs);
+void do_mem_abort(unsigned long far, unsigned int esr, struct pt_regs *regs);
void do_undefinstr(struct pt_regs *regs);
void do_bti(struct pt_regs *regs);
asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr);
diff --git a/arch/arm64/include/asm/system_misc.h b/arch/arm64/include/asm/system_misc.h
index 1ab63cfbbaf1..673be2d1263c 100644
--- a/arch/arm64/include/asm/system_misc.h
+++ b/arch/arm64/include/asm/system_misc.h
@@ -22,7 +22,7 @@ void die(const char *msg, struct pt_regs *regs, int err);
struct siginfo;
void arm64_notify_die(const char *str, struct pt_regs *regs,
- int signo, int sicode, void __user *addr,
+ int signo, int sicode, unsigned long far,
int err);
void hook_debug_fault_code(int nr, int (*fn)(unsigned long, unsigned int,
diff --git a/arch/arm64/include/asm/traps.h b/arch/arm64/include/asm/traps.h
index d96dc2c7c09d..54f32a0675df 100644
--- a/arch/arm64/include/asm/traps.h
+++ b/arch/arm64/include/asm/traps.h
@@ -26,9 +26,9 @@ void register_undef_hook(struct undef_hook *hook);
void unregister_undef_hook(struct undef_hook *hook);
void force_signal_inject(int signal, int code, unsigned long address, unsigned int err);
void arm64_notify_segfault(unsigned long addr);
-void arm64_force_sig_fault(int signo, int code, void __user *addr, const char *str);
-void arm64_force_sig_mceerr(int code, void __user *addr, short lsb, const char *str);
-void arm64_force_sig_ptrace_errno_trap(int errno, void __user *addr, const char *str);
+void arm64_force_sig_fault(int signo, int code, unsigned long far, const char *str);
+void arm64_force_sig_mceerr(int code, unsigned long far, short lsb, const char *str);
+void arm64_force_sig_ptrace_errno_trap(int errno, unsigned long far, const char *str);
/*
* Move regs->pc to next instruction and do necessary setup before it
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index fa76151de6ff..4f3661eeb7ec 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -234,9 +234,8 @@ static void send_user_sigtrap(int si_code)
if (interrupts_enabled(regs))
local_irq_enable();
- arm64_force_sig_fault(SIGTRAP, si_code,
- (void __user *)instruction_pointer(regs),
- "User debug trap");
+ arm64_force_sig_fault(SIGTRAP, si_code, instruction_pointer(regs),
+ "User debug trap");
}
static int single_step_handler(unsigned long unused, unsigned int esr,
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 43d4c329775f..dbbddfbf4a72 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -22,7 +22,6 @@ static void notrace el1_abort(struct pt_regs *regs, unsigned long esr)
unsigned long far = read_sysreg(far_el1);
local_daif_inherit(regs);
- far = untagged_addr(far);
do_mem_abort(far, esr, regs);
}
NOKPROBE_SYMBOL(el1_abort);
@@ -114,7 +113,6 @@ static void notrace el0_da(struct pt_regs *regs, unsigned long esr)
user_exit_irqoff();
local_daif_restore(DAIF_PROCCTX);
- far = untagged_addr(far);
do_mem_abort(far, esr, regs);
}
NOKPROBE_SYMBOL(el0_da);
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index f49b349e16a3..8ac487c84e37 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -192,14 +192,11 @@ static void ptrace_hbptriggered(struct perf_event *bp,
break;
}
}
- arm64_force_sig_ptrace_errno_trap(si_errno,
- (void __user *)bkpt->trigger,
+ arm64_force_sig_ptrace_errno_trap(si_errno, bkpt->trigger,
desc);
}
#endif
- arm64_force_sig_fault(SIGTRAP, TRAP_HWBKPT,
- (void __user *)(bkpt->trigger),
- desc);
+ arm64_force_sig_fault(SIGTRAP, TRAP_HWBKPT, bkpt->trigger, desc);
}
/*
diff --git a/arch/arm64/kernel/sys_compat.c b/arch/arm64/kernel/sys_compat.c
index 3c18c2454089..265fe3eb1069 100644
--- a/arch/arm64/kernel/sys_compat.c
+++ b/arch/arm64/kernel/sys_compat.c
@@ -68,7 +68,7 @@ do_compat_cache_op(unsigned long start, unsigned long end, int flags)
*/
long compat_arm_syscall(struct pt_regs *regs, int scno)
{
- void __user *addr;
+ unsigned long addr;
switch (scno) {
/*
@@ -111,8 +111,7 @@ long compat_arm_syscall(struct pt_regs *regs, int scno)
break;
}
- addr = (void __user *)instruction_pointer(regs) -
- (compat_thumb_mode(regs) ? 2 : 4);
+ addr = instruction_pointer(regs) - (compat_thumb_mode(regs) ? 2 : 4);
arm64_notify_die("Oops - bad compat syscall(2)", regs,
SIGILL, ILL_ILLTRP, addr, scno);
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 8af4e0e85736..f4ddbe9ed3f1 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -170,32 +170,32 @@ static void arm64_show_signal(int signo, const char *str)
__show_regs(regs);
}
-void arm64_force_sig_fault(int signo, int code, void __user *addr,
+void arm64_force_sig_fault(int signo, int code, unsigned long far,
const char *str)
{
arm64_show_signal(signo, str);
if (signo == SIGKILL)
force_sig(SIGKILL);
else
- force_sig_fault(signo, code, addr);
+ force_sig_fault(signo, code, (void __user *)far);
}
-void arm64_force_sig_mceerr(int code, void __user *addr, short lsb,
+void arm64_force_sig_mceerr(int code, unsigned long far, short lsb,
const char *str)
{
arm64_show_signal(SIGBUS, str);
- force_sig_mceerr(code, addr, lsb);
+ force_sig_mceerr(code, (void __user *)far, lsb);
}
-void arm64_force_sig_ptrace_errno_trap(int errno, void __user *addr,
+void arm64_force_sig_ptrace_errno_trap(int errno, unsigned long far,
const char *str)
{
arm64_show_signal(SIGTRAP, str);
- force_sig_ptrace_errno_trap(errno, addr);
+ force_sig_ptrace_errno_trap(errno, (void __user *)far);
}
void arm64_notify_die(const char *str, struct pt_regs *regs,
- int signo, int sicode, void __user *addr,
+ int signo, int sicode, unsigned long far,
int err)
{
if (user_mode(regs)) {
@@ -203,7 +203,7 @@ void arm64_notify_die(const char *str, struct pt_regs *regs,
current->thread.fault_address = 0;
current->thread.fault_code = err;
- arm64_force_sig_fault(signo, sicode, addr, str);
+ arm64_force_sig_fault(signo, sicode, far, str);
} else {
die(str, regs, err);
}
@@ -374,7 +374,7 @@ void force_signal_inject(int signal, int code, unsigned long address, unsigned i
signal = SIGKILL;
}
- arm64_notify_die(desc, regs, signal, code, (void __user *)address, err);
+ arm64_notify_die(desc, regs, signal, code, address, err);
}
/*
@@ -385,7 +385,7 @@ void arm64_notify_segfault(unsigned long addr)
int code;
mmap_read_lock(current->mm);
- if (find_vma(current->mm, addr) == NULL)
+ if (find_vma(current->mm, untagged_addr(addr)) == NULL)
code = SEGV_MAPERR;
else
code = SEGV_ACCERR;
@@ -448,12 +448,13 @@ NOKPROBE_SYMBOL(do_ptrauth_fault);
static void user_cache_maint_handler(unsigned int esr, struct pt_regs *regs)
{
- unsigned long address;
+ unsigned long tagged_address, address;
int rt = ESR_ELx_SYS64_ISS_RT(esr);
int crm = (esr & ESR_ELx_SYS64_ISS_CRM_MASK) >> ESR_ELx_SYS64_ISS_CRM_SHIFT;
int ret = 0;
- address = untagged_addr(pt_regs_read_reg(regs, rt));
+ tagged_address = pt_regs_read_reg(regs, rt);
+ address = untagged_addr(tagged_address);
switch (crm) {
case ESR_ELx_SYS64_ISS_CRM_DC_CVAU: /* DC CVAU, gets promoted */
@@ -480,7 +481,7 @@ static void user_cache_maint_handler(unsigned int esr, struct pt_regs *regs)
}
if (ret)
- arm64_notify_segfault(address);
+ arm64_notify_segfault(tagged_address);
else
arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
}
@@ -772,7 +773,7 @@ asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr)
*/
void bad_el0_sync(struct pt_regs *regs, int reason, unsigned int esr)
{
- void __user *pc = (void __user *)instruction_pointer(regs);
+ unsigned long pc = instruction_pointer(regs);
current->thread.fault_address = 0;
current->thread.fault_code = esr;
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 1ee94002801f..c5375cb7763d 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -40,7 +40,7 @@
#include <asm/traps.h>
struct fault_info {
- int (*fn)(unsigned long addr, unsigned int esr,
+ int (*fn)(unsigned long far, unsigned int esr,
struct pt_regs *regs);
int sig;
int code;
@@ -385,8 +385,11 @@ static void set_thread_esr(unsigned long address, unsigned int esr)
current->thread.fault_code = esr;
}
-static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs)
+static void do_bad_area(unsigned long far, unsigned int esr,
+ struct pt_regs *regs)
{
+ unsigned long addr = untagged_addr(far);
+
/*
* If we are in kernel mode at this point, we have no context to
* handle this fault with.
@@ -395,8 +398,7 @@ static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *re
const struct fault_info *inf = esr_to_fault_info(esr);
set_thread_esr(addr, esr);
- arm64_force_sig_fault(inf->sig, inf->code, (void __user *)addr,
- inf->name);
+ arm64_force_sig_fault(inf->sig, inf->code, far, inf->name);
} else {
__do_kernel_fault(addr, esr, regs);
}
@@ -448,7 +450,7 @@ static bool is_write_abort(unsigned int esr)
return (esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM);
}
-static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
+static int __kprobes do_page_fault(unsigned long far, unsigned int esr,
struct pt_regs *regs)
{
const struct fault_info *inf;
@@ -456,6 +458,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
vm_fault_t fault;
unsigned long vm_flags = VM_ACCESS_FLAGS;
unsigned int mm_flags = FAULT_FLAG_DEFAULT;
+ unsigned long addr = untagged_addr(far);
if (kprobe_page_fault(regs, esr))
return 0;
@@ -567,8 +570,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
* We had some memory, but were unable to successfully fix up
* this page fault.
*/
- arm64_force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)addr,
- inf->name);
+ arm64_force_sig_fault(SIGBUS, BUS_ADRERR, far, inf->name);
} else if (fault & (VM_FAULT_HWPOISON_LARGE | VM_FAULT_HWPOISON)) {
unsigned int lsb;
@@ -576,8 +578,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
if (fault & VM_FAULT_HWPOISON_LARGE)
lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
- arm64_force_sig_mceerr(BUS_MCEERR_AR, (void __user *)addr, lsb,
- inf->name);
+ arm64_force_sig_mceerr(BUS_MCEERR_AR, far, lsb, inf->name);
} else {
/*
* Something tried to access memory that isn't in our memory
@@ -585,8 +586,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
*/
arm64_force_sig_fault(SIGSEGV,
fault == VM_FAULT_BADACCESS ? SEGV_ACCERR : SEGV_MAPERR,
- (void __user *)addr,
- inf->name);
+ far, inf->name);
}
return 0;
@@ -596,33 +596,35 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
return 0;
}
-static int __kprobes do_translation_fault(unsigned long addr,
+static int __kprobes do_translation_fault(unsigned long far,
unsigned int esr,
struct pt_regs *regs)
{
+ unsigned long addr = untagged_addr(far);
+
if (is_ttbr0_addr(addr))
- return do_page_fault(addr, esr, regs);
+ return do_page_fault(far, esr, regs);
- do_bad_area(addr, esr, regs);
+ do_bad_area(far, esr, regs);
return 0;
}
-static int do_alignment_fault(unsigned long addr, unsigned int esr,
+static int do_alignment_fault(unsigned long far, unsigned int esr,
struct pt_regs *regs)
{
- do_bad_area(addr, esr, regs);
+ do_bad_area(far, esr, regs);
return 0;
}
-static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs)
+static int do_bad(unsigned long far, unsigned int esr, struct pt_regs *regs)
{
return 1; /* "fault" */
}
-static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
+static int do_sea(unsigned long far, unsigned int esr, struct pt_regs *regs)
{
const struct fault_info *inf;
- void __user *siaddr;
+ unsigned long siaddr;
inf = esr_to_fault_info(esr);
@@ -635,18 +637,23 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
}
if (esr & ESR_ELx_FnV)
- siaddr = NULL;
+ siaddr = 0;
else
- siaddr = (void __user *)addr;
+ siaddr = untagged_addr(far);
arm64_notify_die(inf->name, regs, inf->sig, inf->code, siaddr, esr);
return 0;
}
-static int do_tag_check_fault(unsigned long addr, unsigned int esr,
+static int do_tag_check_fault(unsigned long far, unsigned int esr,
struct pt_regs *regs)
{
- do_bad_area(addr, esr, regs);
+ /*
+ * The architecture specifies that bits 63:60 of FAR_EL1 are UNKNOWN for tag
+ * check faults. Mask them out now so that userspace doesn't see them.
+ */
+ far &= (1UL << 60) - 1;
+ do_bad_area(far, esr, regs);
return 0;
}
@@ -717,11 +724,12 @@ static const struct fault_info fault_info[] = {
{ do_bad, SIGKILL, SI_KERNEL, "unknown 63" },
};
-void do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs)
+void do_mem_abort(unsigned long far, unsigned int esr, struct pt_regs *regs)
{
const struct fault_info *inf = esr_to_fault_info(esr);
+ unsigned long addr = untagged_addr(far);
- if (!inf->fn(addr, esr, regs))
+ if (!inf->fn(far, esr, regs))
return;
if (!user_mode(regs)) {
@@ -730,8 +738,7 @@ void do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs)
show_pte(addr);
}
- arm64_notify_die(inf->name, regs,
- inf->sig, inf->code, (void __user *)addr, esr);
+ arm64_notify_die(inf->name, regs, inf->sig, inf->code, addr, esr);
}
NOKPROBE_SYMBOL(do_mem_abort);
@@ -744,8 +751,8 @@ NOKPROBE_SYMBOL(do_el0_irq_bp_hardening);
void do_sp_pc_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs)
{
- arm64_notify_die("SP/PC alignment exception", regs,
- SIGBUS, BUS_ADRALN, (void __user *)addr, esr);
+ arm64_notify_die("SP/PC alignment exception", regs, SIGBUS, BUS_ADRALN,
+ addr, esr);
}
NOKPROBE_SYMBOL(do_sp_pc_abort);
@@ -871,8 +878,7 @@ void do_debug_exception(unsigned long addr_if_watchpoint, unsigned int esr,
arm64_apply_bp_hardening();
if (inf->fn(addr_if_watchpoint, esr, regs)) {
- arm64_notify_die(inf->name, regs,
- inf->sig, inf->code, (void __user *)pc, esr);
+ arm64_notify_die(inf->name, regs, inf->sig, inf->code, pc, esr);
}
debug_exception_exit(regs);
diff --git a/include/linux/signal.h b/include/linux/signal.h
index b256f9c65661..205526c4003a 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -469,4 +469,18 @@ struct seq_file;
extern void render_sigset_t(struct seq_file *, const char *, sigset_t *);
#endif
+#ifndef arch_untagged_si_addr
+/*
+ * Given a fault address and a signal and si_code which correspond to the
+ * _sigfault union member, returns the address that must appear in si_addr if
+ * the signal handler does not have SA_EXPOSE_TAGBITS enabled in sa_flags.
+ */
+static inline void __user *arch_untagged_si_addr(void __user *addr,
+ unsigned long sig,
+ unsigned long si_code)
+{
+ return addr;
+}
+#endif
+
#endif /* _LINUX_SIGNAL_H */
diff --git a/include/linux/signal_types.h b/include/linux/signal_types.h
index a7887ad84d36..68e06c75c5b2 100644
--- a/include/linux/signal_types.h
+++ b/include/linux/signal_types.h
@@ -78,6 +78,6 @@ struct ksignal {
#define UAPI_SA_FLAGS \
(SA_NOCLDSTOP | SA_NOCLDWAIT | SA_SIGINFO | SA_ONSTACK | SA_RESTART | \
- SA_NODEFER | SA_RESETHAND | __ARCH_UAPI_SA_FLAGS)
+ SA_NODEFER | SA_RESETHAND | SA_EXPOSE_TAGBITS | __ARCH_UAPI_SA_FLAGS)
#endif /* _LINUX_SIGNAL_TYPES_H */
diff --git a/include/uapi/asm-generic/signal-defs.h b/include/uapi/asm-generic/signal-defs.h
index 0126ebda4d31..5276bdd4a9e2 100644
--- a/include/uapi/asm-generic/signal-defs.h
+++ b/include/uapi/asm-generic/signal-defs.h
@@ -20,6 +20,8 @@
* so this bit allows flag bit support to be detected from userspace while
* allowing an old kernel to be distinguished from a kernel that supports every
* flag bit.
+ * SA_EXPOSE_TAGBITS exposes an architecture-defined set of tag bits in
+ * siginfo.si_addr.
*
* SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
* Unix names RESETHAND and NODEFER respectively.
@@ -49,6 +51,7 @@
#define SA_RESETHAND 0x80000000
#endif
#define SA_UNSUPPORTED 0x00000400
+#define SA_EXPOSE_TAGBITS 0x00000800
#define SA_NOMASK SA_NODEFER
#define SA_ONESHOT SA_RESETHAND
diff --git a/kernel/signal.c b/kernel/signal.c
index 8f34819e80de..16be62e6d341 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1650,6 +1650,15 @@ void force_sigsegv(int sig)
force_sig(SIGSEGV);
}
+static void __user *get_si_addr(void __user *addr, unsigned long sig,
+ unsigned long si_code)
+{
+ if (current->sighand->action[sig - 1].sa.sa_flags & SA_EXPOSE_TAGBITS)
+ return addr;
+
+ return arch_untagged_si_addr(addr, sig, si_code);
+}
+
int force_sig_fault_to_task(int sig, int code, void __user *addr
___ARCH_SI_TRAPNO(int trapno)
___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr)
@@ -1661,7 +1670,7 @@ int force_sig_fault_to_task(int sig, int code, void __user *addr
info.si_signo = sig;
info.si_errno = 0;
info.si_code = code;
- info.si_addr = addr;
+ info.si_addr = get_si_addr(addr, sig, code);
#ifdef __ARCH_SI_TRAPNO
info.si_trapno = trapno;
#endif
@@ -1693,7 +1702,7 @@ int send_sig_fault(int sig, int code, void __user *addr
info.si_signo = sig;
info.si_errno = 0;
info.si_code = code;
- info.si_addr = addr;
+ info.si_addr = get_si_addr(addr, sig, code);
#ifdef __ARCH_SI_TRAPNO
info.si_trapno = trapno;
#endif
@@ -1714,7 +1723,7 @@ int force_sig_mceerr(int code, void __user *addr, short lsb)
info.si_signo = SIGBUS;
info.si_errno = 0;
info.si_code = code;
- info.si_addr = addr;
+ info.si_addr = get_si_addr(addr, SIGBUS, code);
info.si_addr_lsb = lsb;
return force_sig_info(&info);
}
@@ -1728,7 +1737,7 @@ int send_sig_mceerr(int code, void __user *addr, short lsb, struct task_struct *
info.si_signo = SIGBUS;
info.si_errno = 0;
info.si_code = code;
- info.si_addr = addr;
+ info.si_addr = get_si_addr(addr, SIGBUS, code);
info.si_addr_lsb = lsb;
return send_sig_info(info.si_signo, &info, t);
}
@@ -1742,7 +1751,7 @@ int force_sig_bnderr(void __user *addr, void __user *lower, void __user *upper)
info.si_signo = SIGSEGV;
info.si_errno = 0;
info.si_code = SEGV_BNDERR;
- info.si_addr = addr;
+ info.si_addr = get_si_addr(addr, SIGSEGV, SEGV_BNDERR);
info.si_lower = lower;
info.si_upper = upper;
return force_sig_info(&info);
@@ -1757,7 +1766,7 @@ int force_sig_pkuerr(void __user *addr, u32 pkey)
info.si_signo = SIGSEGV;
info.si_errno = 0;
info.si_code = SEGV_PKUERR;
- info.si_addr = addr;
+ info.si_addr = get_si_addr(addr, SIGSEGV, SEGV_PKUERR);
info.si_pkey = pkey;
return force_sig_info(&info);
}
@@ -1774,7 +1783,7 @@ int force_sig_ptrace_errno_trap(int errno, void __user *addr)
info.si_signo = SIGTRAP;
info.si_errno = errno;
info.si_code = TRAP_HWBKPT;
- info.si_addr = addr;
+ info.si_addr = get_si_addr(addr, SIGTRAP, TRAP_HWBKPT);
return force_sig_info(&info);
}
--
2.29.2.299.gdc1121823c-goog
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH v15 6/6] arm64: expose FAR_EL1 tag bits in siginfo
2020-11-13 2:46 ` [PATCH v15 6/6] arm64: expose FAR_EL1 tag bits in siginfo Peter Collingbourne
@ 2020-11-13 2:52 ` Peter Collingbourne
0 siblings, 0 replies; 8+ messages in thread
From: Peter Collingbourne @ 2020-11-13 2:52 UTC (permalink / raw)
To: Catalin Marinas, Evgenii Stepanov, Kostya Serebryany,
Vincenzo Frascino, Dave Martin, Will Deacon, Oleg Nesterov,
Eric W. Biederman, James E.J. Bottomley
Cc: Linux ARM, Kevin Brodsky, Andrey Konovalov, Linux API,
Helge Deller, David Spickett
On Thu, Nov 12, 2020 at 6:46 PM Peter Collingbourne <pcc@google.com> wrote:
>
> The kernel currently clears the tag bits (i.e. bits 56-63) in the fault
> address exposed via siginfo.si_addr and sigcontext.fault_address. However,
> the tag bits may be needed by tools in order to accurately diagnose
> memory errors, such as HWASan [1] or future tools based on the Memory
> Tagging Extension (MTE).
>
> We should not stop clearing these bits in the existing fault address
> fields, because there may be existing userspace applications that are
> expecting the tag bits to be cleared. Instead, introduce a flag in
> sigaction.sa_flags, SA_EXPOSE_TAGBITS, and only expose the tag bits
> there if the signal handler has this flag set.
>
> [1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html
>
> Signed-off-by: Peter Collingbourne <pcc@google.com>
> Link: https://linux-review.googlesource.com/id/Ia8876bad8c798e0a32df7c2ce1256c4771c81446
> ---
> v15:
> - switched to the SA_EXPOSE_TAGBITS approach
> proposed by Eric
> - rebased to 5.10-rc3
>
> v14:
> - fix an inaccuracy in the commit message
> - add some comments to arch_addr_tag_bits_mask
>
> v13:
> - renamed si_xflags to si_faultflags
> - rebased to 5.10-rc2
>
> v12:
> - add new fields to signal_compat.c test cases
> - rebased to 5.10-rc1
> - mask out bits 63:60 for tag check faults
>
> v11:
> - add a comment explaining what the arch hook should do
> - rename ignored bits to tag bits
>
> v10:
> - rename the flag to SIFAULTFLAG_ADDR_IGNORED_BITS
> - use an arch hook to specify which bits are ignored, instead
> of passing them explicitly
> - while refactoring for the arch hook, noticed that my previous
> patches missed a case involving cache maintenance instructions,
> so expose the tag bits for that signal as well
>
> v9:
> - make the ignored bits fields generic
> - add some new dependent patches that prepare us to store the
> field in such a way that userspace can detect their presence
>
> v8:
> - rebase onto 5.8rc2
>
> v7:
> - switch to a new siginfo field instead of using sigcontext
> - merge the patch back into one since the other patches are now
> unnecessary
>
> v6:
> - move fault address and fault code into the kernel_siginfo data structure
> - split the patch in three since it was getting large and now has
> generic and arch-specific parts
>
> v5:
> - add padding to fault_addr_top_byte_context in order to ensure the correct
> size and preserve sp alignment
>
> v4:
> - expose only the tag bits in the context instead of the entire FAR_EL1
> - remove mention of the new context from the sigcontext.__reserved[] note
>
> v3:
> - add documentation to tagged-pointers.rst
> - update comments in sigcontext.h
>
> v2:
> - revert changes to hw_breakpoint.c
> - rename set_thread_esr to set_thread_far_esr
>
> Documentation/arm64/tagged-pointers.rst | 25 ++++++---
> arch/arm64/include/asm/exception.h | 2 +-
> arch/arm64/include/asm/system_misc.h | 2 +-
> arch/arm64/include/asm/traps.h | 6 +--
> arch/arm64/kernel/debug-monitors.c | 5 +-
> arch/arm64/kernel/entry-common.c | 2 -
> arch/arm64/kernel/ptrace.c | 7 +--
> arch/arm64/kernel/sys_compat.c | 5 +-
> arch/arm64/kernel/traps.c | 29 ++++++-----
> arch/arm64/mm/fault.c | 68 ++++++++++++++-----------
> include/linux/signal.h | 14 +++++
> include/linux/signal_types.h | 2 +-
> include/uapi/asm-generic/signal-defs.h | 3 ++
> kernel/signal.c | 23 ++++++---
> 14 files changed, 116 insertions(+), 77 deletions(-)
I forgot to add the file arch/arm64/include/asm/signal.h to this
patch. Will send a v16 with this fixed. Sorry for the noise.
Peter
>
> diff --git a/Documentation/arm64/tagged-pointers.rst b/Documentation/arm64/tagged-pointers.rst
> index eab4323609b9..19d284b70384 100644
> --- a/Documentation/arm64/tagged-pointers.rst
> +++ b/Documentation/arm64/tagged-pointers.rst
> @@ -53,12 +53,25 @@ visibility.
> Preserving tags
> ---------------
>
> -Non-zero tags are not preserved when delivering signals. This means that
> -signal handlers in applications making use of tags cannot rely on the
> -tag information for user virtual addresses being maintained for fields
> -inside siginfo_t. One exception to this rule is for signals raised in
> -response to watchpoint debug exceptions, where the tag information will
> -be preserved.
> +When delivering signals, non-zero tags are not preserved in
> +siginfo.si_addr unless the flag SA_EXPOSE_TAGBITS was set in
> +sigaction.sa_flags when the signal handler was installed. This means
> +that signal handlers in applications making use of tags cannot rely
> +on the tag information for user virtual addresses being maintained
> +in these fields unless the flag was set.
> +
> +Due to architecture limitations, bits 63:60 of the fault address
> +are not preserved in response to synchronous tag check faults
> +(SEGV_MTESERR) even if SA_EXPOSE_TAGBITS was set. Applications should
> +treat the values of these bits as undefined in order to accommodate
> +future architecture revisions which may preserve the bits.
> +
> +For signals raised in response to watchpoint debug exceptions, the
> +tag information will be preserved regardless of the SA_EXPOSE_TAGBITS
> +flag setting.
> +
> +Non-zero tags are never preserved in sigcontext.fault_address
> +regardless of the SA_EXPOSE_TAGBITS flag setting.
>
> The architecture prevents the use of a tagged PC, so the upper byte will
> be set to a sign-extension of bit 55 on exception return.
> diff --git a/arch/arm64/include/asm/exception.h b/arch/arm64/include/asm/exception.h
> index 99b9383cd036..2a8aa1884d8a 100644
> --- a/arch/arm64/include/asm/exception.h
> +++ b/arch/arm64/include/asm/exception.h
> @@ -32,7 +32,7 @@ static inline u32 disr_to_esr(u64 disr)
> }
>
> asmlinkage void enter_from_user_mode(void);
> -void do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs);
> +void do_mem_abort(unsigned long far, unsigned int esr, struct pt_regs *regs);
> void do_undefinstr(struct pt_regs *regs);
> void do_bti(struct pt_regs *regs);
> asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr);
> diff --git a/arch/arm64/include/asm/system_misc.h b/arch/arm64/include/asm/system_misc.h
> index 1ab63cfbbaf1..673be2d1263c 100644
> --- a/arch/arm64/include/asm/system_misc.h
> +++ b/arch/arm64/include/asm/system_misc.h
> @@ -22,7 +22,7 @@ void die(const char *msg, struct pt_regs *regs, int err);
>
> struct siginfo;
> void arm64_notify_die(const char *str, struct pt_regs *regs,
> - int signo, int sicode, void __user *addr,
> + int signo, int sicode, unsigned long far,
> int err);
>
> void hook_debug_fault_code(int nr, int (*fn)(unsigned long, unsigned int,
> diff --git a/arch/arm64/include/asm/traps.h b/arch/arm64/include/asm/traps.h
> index d96dc2c7c09d..54f32a0675df 100644
> --- a/arch/arm64/include/asm/traps.h
> +++ b/arch/arm64/include/asm/traps.h
> @@ -26,9 +26,9 @@ void register_undef_hook(struct undef_hook *hook);
> void unregister_undef_hook(struct undef_hook *hook);
> void force_signal_inject(int signal, int code, unsigned long address, unsigned int err);
> void arm64_notify_segfault(unsigned long addr);
> -void arm64_force_sig_fault(int signo, int code, void __user *addr, const char *str);
> -void arm64_force_sig_mceerr(int code, void __user *addr, short lsb, const char *str);
> -void arm64_force_sig_ptrace_errno_trap(int errno, void __user *addr, const char *str);
> +void arm64_force_sig_fault(int signo, int code, unsigned long far, const char *str);
> +void arm64_force_sig_mceerr(int code, unsigned long far, short lsb, const char *str);
> +void arm64_force_sig_ptrace_errno_trap(int errno, unsigned long far, const char *str);
>
> /*
> * Move regs->pc to next instruction and do necessary setup before it
> diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
> index fa76151de6ff..4f3661eeb7ec 100644
> --- a/arch/arm64/kernel/debug-monitors.c
> +++ b/arch/arm64/kernel/debug-monitors.c
> @@ -234,9 +234,8 @@ static void send_user_sigtrap(int si_code)
> if (interrupts_enabled(regs))
> local_irq_enable();
>
> - arm64_force_sig_fault(SIGTRAP, si_code,
> - (void __user *)instruction_pointer(regs),
> - "User debug trap");
> + arm64_force_sig_fault(SIGTRAP, si_code, instruction_pointer(regs),
> + "User debug trap");
> }
>
> static int single_step_handler(unsigned long unused, unsigned int esr,
> diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
> index 43d4c329775f..dbbddfbf4a72 100644
> --- a/arch/arm64/kernel/entry-common.c
> +++ b/arch/arm64/kernel/entry-common.c
> @@ -22,7 +22,6 @@ static void notrace el1_abort(struct pt_regs *regs, unsigned long esr)
> unsigned long far = read_sysreg(far_el1);
>
> local_daif_inherit(regs);
> - far = untagged_addr(far);
> do_mem_abort(far, esr, regs);
> }
> NOKPROBE_SYMBOL(el1_abort);
> @@ -114,7 +113,6 @@ static void notrace el0_da(struct pt_regs *regs, unsigned long esr)
>
> user_exit_irqoff();
> local_daif_restore(DAIF_PROCCTX);
> - far = untagged_addr(far);
> do_mem_abort(far, esr, regs);
> }
> NOKPROBE_SYMBOL(el0_da);
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index f49b349e16a3..8ac487c84e37 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -192,14 +192,11 @@ static void ptrace_hbptriggered(struct perf_event *bp,
> break;
> }
> }
> - arm64_force_sig_ptrace_errno_trap(si_errno,
> - (void __user *)bkpt->trigger,
> + arm64_force_sig_ptrace_errno_trap(si_errno, bkpt->trigger,
> desc);
> }
> #endif
> - arm64_force_sig_fault(SIGTRAP, TRAP_HWBKPT,
> - (void __user *)(bkpt->trigger),
> - desc);
> + arm64_force_sig_fault(SIGTRAP, TRAP_HWBKPT, bkpt->trigger, desc);
> }
>
> /*
> diff --git a/arch/arm64/kernel/sys_compat.c b/arch/arm64/kernel/sys_compat.c
> index 3c18c2454089..265fe3eb1069 100644
> --- a/arch/arm64/kernel/sys_compat.c
> +++ b/arch/arm64/kernel/sys_compat.c
> @@ -68,7 +68,7 @@ do_compat_cache_op(unsigned long start, unsigned long end, int flags)
> */
> long compat_arm_syscall(struct pt_regs *regs, int scno)
> {
> - void __user *addr;
> + unsigned long addr;
>
> switch (scno) {
> /*
> @@ -111,8 +111,7 @@ long compat_arm_syscall(struct pt_regs *regs, int scno)
> break;
> }
>
> - addr = (void __user *)instruction_pointer(regs) -
> - (compat_thumb_mode(regs) ? 2 : 4);
> + addr = instruction_pointer(regs) - (compat_thumb_mode(regs) ? 2 : 4);
>
> arm64_notify_die("Oops - bad compat syscall(2)", regs,
> SIGILL, ILL_ILLTRP, addr, scno);
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index 8af4e0e85736..f4ddbe9ed3f1 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -170,32 +170,32 @@ static void arm64_show_signal(int signo, const char *str)
> __show_regs(regs);
> }
>
> -void arm64_force_sig_fault(int signo, int code, void __user *addr,
> +void arm64_force_sig_fault(int signo, int code, unsigned long far,
> const char *str)
> {
> arm64_show_signal(signo, str);
> if (signo == SIGKILL)
> force_sig(SIGKILL);
> else
> - force_sig_fault(signo, code, addr);
> + force_sig_fault(signo, code, (void __user *)far);
> }
>
> -void arm64_force_sig_mceerr(int code, void __user *addr, short lsb,
> +void arm64_force_sig_mceerr(int code, unsigned long far, short lsb,
> const char *str)
> {
> arm64_show_signal(SIGBUS, str);
> - force_sig_mceerr(code, addr, lsb);
> + force_sig_mceerr(code, (void __user *)far, lsb);
> }
>
> -void arm64_force_sig_ptrace_errno_trap(int errno, void __user *addr,
> +void arm64_force_sig_ptrace_errno_trap(int errno, unsigned long far,
> const char *str)
> {
> arm64_show_signal(SIGTRAP, str);
> - force_sig_ptrace_errno_trap(errno, addr);
> + force_sig_ptrace_errno_trap(errno, (void __user *)far);
> }
>
> void arm64_notify_die(const char *str, struct pt_regs *regs,
> - int signo, int sicode, void __user *addr,
> + int signo, int sicode, unsigned long far,
> int err)
> {
> if (user_mode(regs)) {
> @@ -203,7 +203,7 @@ void arm64_notify_die(const char *str, struct pt_regs *regs,
> current->thread.fault_address = 0;
> current->thread.fault_code = err;
>
> - arm64_force_sig_fault(signo, sicode, addr, str);
> + arm64_force_sig_fault(signo, sicode, far, str);
> } else {
> die(str, regs, err);
> }
> @@ -374,7 +374,7 @@ void force_signal_inject(int signal, int code, unsigned long address, unsigned i
> signal = SIGKILL;
> }
>
> - arm64_notify_die(desc, regs, signal, code, (void __user *)address, err);
> + arm64_notify_die(desc, regs, signal, code, address, err);
> }
>
> /*
> @@ -385,7 +385,7 @@ void arm64_notify_segfault(unsigned long addr)
> int code;
>
> mmap_read_lock(current->mm);
> - if (find_vma(current->mm, addr) == NULL)
> + if (find_vma(current->mm, untagged_addr(addr)) == NULL)
> code = SEGV_MAPERR;
> else
> code = SEGV_ACCERR;
> @@ -448,12 +448,13 @@ NOKPROBE_SYMBOL(do_ptrauth_fault);
>
> static void user_cache_maint_handler(unsigned int esr, struct pt_regs *regs)
> {
> - unsigned long address;
> + unsigned long tagged_address, address;
> int rt = ESR_ELx_SYS64_ISS_RT(esr);
> int crm = (esr & ESR_ELx_SYS64_ISS_CRM_MASK) >> ESR_ELx_SYS64_ISS_CRM_SHIFT;
> int ret = 0;
>
> - address = untagged_addr(pt_regs_read_reg(regs, rt));
> + tagged_address = pt_regs_read_reg(regs, rt);
> + address = untagged_addr(tagged_address);
>
> switch (crm) {
> case ESR_ELx_SYS64_ISS_CRM_DC_CVAU: /* DC CVAU, gets promoted */
> @@ -480,7 +481,7 @@ static void user_cache_maint_handler(unsigned int esr, struct pt_regs *regs)
> }
>
> if (ret)
> - arm64_notify_segfault(address);
> + arm64_notify_segfault(tagged_address);
> else
> arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
> }
> @@ -772,7 +773,7 @@ asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr)
> */
> void bad_el0_sync(struct pt_regs *regs, int reason, unsigned int esr)
> {
> - void __user *pc = (void __user *)instruction_pointer(regs);
> + unsigned long pc = instruction_pointer(regs);
>
> current->thread.fault_address = 0;
> current->thread.fault_code = esr;
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index 1ee94002801f..c5375cb7763d 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -40,7 +40,7 @@
> #include <asm/traps.h>
>
> struct fault_info {
> - int (*fn)(unsigned long addr, unsigned int esr,
> + int (*fn)(unsigned long far, unsigned int esr,
> struct pt_regs *regs);
> int sig;
> int code;
> @@ -385,8 +385,11 @@ static void set_thread_esr(unsigned long address, unsigned int esr)
> current->thread.fault_code = esr;
> }
>
> -static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs)
> +static void do_bad_area(unsigned long far, unsigned int esr,
> + struct pt_regs *regs)
> {
> + unsigned long addr = untagged_addr(far);
> +
> /*
> * If we are in kernel mode at this point, we have no context to
> * handle this fault with.
> @@ -395,8 +398,7 @@ static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *re
> const struct fault_info *inf = esr_to_fault_info(esr);
>
> set_thread_esr(addr, esr);
> - arm64_force_sig_fault(inf->sig, inf->code, (void __user *)addr,
> - inf->name);
> + arm64_force_sig_fault(inf->sig, inf->code, far, inf->name);
> } else {
> __do_kernel_fault(addr, esr, regs);
> }
> @@ -448,7 +450,7 @@ static bool is_write_abort(unsigned int esr)
> return (esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM);
> }
>
> -static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
> +static int __kprobes do_page_fault(unsigned long far, unsigned int esr,
> struct pt_regs *regs)
> {
> const struct fault_info *inf;
> @@ -456,6 +458,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
> vm_fault_t fault;
> unsigned long vm_flags = VM_ACCESS_FLAGS;
> unsigned int mm_flags = FAULT_FLAG_DEFAULT;
> + unsigned long addr = untagged_addr(far);
>
> if (kprobe_page_fault(regs, esr))
> return 0;
> @@ -567,8 +570,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
> * We had some memory, but were unable to successfully fix up
> * this page fault.
> */
> - arm64_force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)addr,
> - inf->name);
> + arm64_force_sig_fault(SIGBUS, BUS_ADRERR, far, inf->name);
> } else if (fault & (VM_FAULT_HWPOISON_LARGE | VM_FAULT_HWPOISON)) {
> unsigned int lsb;
>
> @@ -576,8 +578,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
> if (fault & VM_FAULT_HWPOISON_LARGE)
> lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
>
> - arm64_force_sig_mceerr(BUS_MCEERR_AR, (void __user *)addr, lsb,
> - inf->name);
> + arm64_force_sig_mceerr(BUS_MCEERR_AR, far, lsb, inf->name);
> } else {
> /*
> * Something tried to access memory that isn't in our memory
> @@ -585,8 +586,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
> */
> arm64_force_sig_fault(SIGSEGV,
> fault == VM_FAULT_BADACCESS ? SEGV_ACCERR : SEGV_MAPERR,
> - (void __user *)addr,
> - inf->name);
> + far, inf->name);
> }
>
> return 0;
> @@ -596,33 +596,35 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
> return 0;
> }
>
> -static int __kprobes do_translation_fault(unsigned long addr,
> +static int __kprobes do_translation_fault(unsigned long far,
> unsigned int esr,
> struct pt_regs *regs)
> {
> + unsigned long addr = untagged_addr(far);
> +
> if (is_ttbr0_addr(addr))
> - return do_page_fault(addr, esr, regs);
> + return do_page_fault(far, esr, regs);
>
> - do_bad_area(addr, esr, regs);
> + do_bad_area(far, esr, regs);
> return 0;
> }
>
> -static int do_alignment_fault(unsigned long addr, unsigned int esr,
> +static int do_alignment_fault(unsigned long far, unsigned int esr,
> struct pt_regs *regs)
> {
> - do_bad_area(addr, esr, regs);
> + do_bad_area(far, esr, regs);
> return 0;
> }
>
> -static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs)
> +static int do_bad(unsigned long far, unsigned int esr, struct pt_regs *regs)
> {
> return 1; /* "fault" */
> }
>
> -static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
> +static int do_sea(unsigned long far, unsigned int esr, struct pt_regs *regs)
> {
> const struct fault_info *inf;
> - void __user *siaddr;
> + unsigned long siaddr;
>
> inf = esr_to_fault_info(esr);
>
> @@ -635,18 +637,23 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
> }
>
> if (esr & ESR_ELx_FnV)
> - siaddr = NULL;
> + siaddr = 0;
> else
> - siaddr = (void __user *)addr;
> + siaddr = untagged_addr(far);
> arm64_notify_die(inf->name, regs, inf->sig, inf->code, siaddr, esr);
>
> return 0;
> }
>
> -static int do_tag_check_fault(unsigned long addr, unsigned int esr,
> +static int do_tag_check_fault(unsigned long far, unsigned int esr,
> struct pt_regs *regs)
> {
> - do_bad_area(addr, esr, regs);
> + /*
> + * The architecture specifies that bits 63:60 of FAR_EL1 are UNKNOWN for tag
> + * check faults. Mask them out now so that userspace doesn't see them.
> + */
> + far &= (1UL << 60) - 1;
> + do_bad_area(far, esr, regs);
> return 0;
> }
>
> @@ -717,11 +724,12 @@ static const struct fault_info fault_info[] = {
> { do_bad, SIGKILL, SI_KERNEL, "unknown 63" },
> };
>
> -void do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs)
> +void do_mem_abort(unsigned long far, unsigned int esr, struct pt_regs *regs)
> {
> const struct fault_info *inf = esr_to_fault_info(esr);
> + unsigned long addr = untagged_addr(far);
>
> - if (!inf->fn(addr, esr, regs))
> + if (!inf->fn(far, esr, regs))
> return;
>
> if (!user_mode(regs)) {
> @@ -730,8 +738,7 @@ void do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs)
> show_pte(addr);
> }
>
> - arm64_notify_die(inf->name, regs,
> - inf->sig, inf->code, (void __user *)addr, esr);
> + arm64_notify_die(inf->name, regs, inf->sig, inf->code, addr, esr);
> }
> NOKPROBE_SYMBOL(do_mem_abort);
>
> @@ -744,8 +751,8 @@ NOKPROBE_SYMBOL(do_el0_irq_bp_hardening);
>
> void do_sp_pc_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs)
> {
> - arm64_notify_die("SP/PC alignment exception", regs,
> - SIGBUS, BUS_ADRALN, (void __user *)addr, esr);
> + arm64_notify_die("SP/PC alignment exception", regs, SIGBUS, BUS_ADRALN,
> + addr, esr);
> }
> NOKPROBE_SYMBOL(do_sp_pc_abort);
>
> @@ -871,8 +878,7 @@ void do_debug_exception(unsigned long addr_if_watchpoint, unsigned int esr,
> arm64_apply_bp_hardening();
>
> if (inf->fn(addr_if_watchpoint, esr, regs)) {
> - arm64_notify_die(inf->name, regs,
> - inf->sig, inf->code, (void __user *)pc, esr);
> + arm64_notify_die(inf->name, regs, inf->sig, inf->code, pc, esr);
> }
>
> debug_exception_exit(regs);
> diff --git a/include/linux/signal.h b/include/linux/signal.h
> index b256f9c65661..205526c4003a 100644
> --- a/include/linux/signal.h
> +++ b/include/linux/signal.h
> @@ -469,4 +469,18 @@ struct seq_file;
> extern void render_sigset_t(struct seq_file *, const char *, sigset_t *);
> #endif
>
> +#ifndef arch_untagged_si_addr
> +/*
> + * Given a fault address and a signal and si_code which correspond to the
> + * _sigfault union member, returns the address that must appear in si_addr if
> + * the signal handler does not have SA_EXPOSE_TAGBITS enabled in sa_flags.
> + */
> +static inline void __user *arch_untagged_si_addr(void __user *addr,
> + unsigned long sig,
> + unsigned long si_code)
> +{
> + return addr;
> +}
> +#endif
> +
> #endif /* _LINUX_SIGNAL_H */
> diff --git a/include/linux/signal_types.h b/include/linux/signal_types.h
> index a7887ad84d36..68e06c75c5b2 100644
> --- a/include/linux/signal_types.h
> +++ b/include/linux/signal_types.h
> @@ -78,6 +78,6 @@ struct ksignal {
>
> #define UAPI_SA_FLAGS \
> (SA_NOCLDSTOP | SA_NOCLDWAIT | SA_SIGINFO | SA_ONSTACK | SA_RESTART | \
> - SA_NODEFER | SA_RESETHAND | __ARCH_UAPI_SA_FLAGS)
> + SA_NODEFER | SA_RESETHAND | SA_EXPOSE_TAGBITS | __ARCH_UAPI_SA_FLAGS)
>
> #endif /* _LINUX_SIGNAL_TYPES_H */
> diff --git a/include/uapi/asm-generic/signal-defs.h b/include/uapi/asm-generic/signal-defs.h
> index 0126ebda4d31..5276bdd4a9e2 100644
> --- a/include/uapi/asm-generic/signal-defs.h
> +++ b/include/uapi/asm-generic/signal-defs.h
> @@ -20,6 +20,8 @@
> * so this bit allows flag bit support to be detected from userspace while
> * allowing an old kernel to be distinguished from a kernel that supports every
> * flag bit.
> + * SA_EXPOSE_TAGBITS exposes an architecture-defined set of tag bits in
> + * siginfo.si_addr.
> *
> * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single
> * Unix names RESETHAND and NODEFER respectively.
> @@ -49,6 +51,7 @@
> #define SA_RESETHAND 0x80000000
> #endif
> #define SA_UNSUPPORTED 0x00000400
> +#define SA_EXPOSE_TAGBITS 0x00000800
>
> #define SA_NOMASK SA_NODEFER
> #define SA_ONESHOT SA_RESETHAND
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 8f34819e80de..16be62e6d341 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -1650,6 +1650,15 @@ void force_sigsegv(int sig)
> force_sig(SIGSEGV);
> }
>
> +static void __user *get_si_addr(void __user *addr, unsigned long sig,
> + unsigned long si_code)
> +{
> + if (current->sighand->action[sig - 1].sa.sa_flags & SA_EXPOSE_TAGBITS)
> + return addr;
> +
> + return arch_untagged_si_addr(addr, sig, si_code);
> +}
> +
> int force_sig_fault_to_task(int sig, int code, void __user *addr
> ___ARCH_SI_TRAPNO(int trapno)
> ___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr)
> @@ -1661,7 +1670,7 @@ int force_sig_fault_to_task(int sig, int code, void __user *addr
> info.si_signo = sig;
> info.si_errno = 0;
> info.si_code = code;
> - info.si_addr = addr;
> + info.si_addr = get_si_addr(addr, sig, code);
> #ifdef __ARCH_SI_TRAPNO
> info.si_trapno = trapno;
> #endif
> @@ -1693,7 +1702,7 @@ int send_sig_fault(int sig, int code, void __user *addr
> info.si_signo = sig;
> info.si_errno = 0;
> info.si_code = code;
> - info.si_addr = addr;
> + info.si_addr = get_si_addr(addr, sig, code);
> #ifdef __ARCH_SI_TRAPNO
> info.si_trapno = trapno;
> #endif
> @@ -1714,7 +1723,7 @@ int force_sig_mceerr(int code, void __user *addr, short lsb)
> info.si_signo = SIGBUS;
> info.si_errno = 0;
> info.si_code = code;
> - info.si_addr = addr;
> + info.si_addr = get_si_addr(addr, SIGBUS, code);
> info.si_addr_lsb = lsb;
> return force_sig_info(&info);
> }
> @@ -1728,7 +1737,7 @@ int send_sig_mceerr(int code, void __user *addr, short lsb, struct task_struct *
> info.si_signo = SIGBUS;
> info.si_errno = 0;
> info.si_code = code;
> - info.si_addr = addr;
> + info.si_addr = get_si_addr(addr, SIGBUS, code);
> info.si_addr_lsb = lsb;
> return send_sig_info(info.si_signo, &info, t);
> }
> @@ -1742,7 +1751,7 @@ int force_sig_bnderr(void __user *addr, void __user *lower, void __user *upper)
> info.si_signo = SIGSEGV;
> info.si_errno = 0;
> info.si_code = SEGV_BNDERR;
> - info.si_addr = addr;
> + info.si_addr = get_si_addr(addr, SIGSEGV, SEGV_BNDERR);
> info.si_lower = lower;
> info.si_upper = upper;
> return force_sig_info(&info);
> @@ -1757,7 +1766,7 @@ int force_sig_pkuerr(void __user *addr, u32 pkey)
> info.si_signo = SIGSEGV;
> info.si_errno = 0;
> info.si_code = SEGV_PKUERR;
> - info.si_addr = addr;
> + info.si_addr = get_si_addr(addr, SIGSEGV, SEGV_PKUERR);
> info.si_pkey = pkey;
> return force_sig_info(&info);
> }
> @@ -1774,7 +1783,7 @@ int force_sig_ptrace_errno_trap(int errno, void __user *addr)
> info.si_signo = SIGTRAP;
> info.si_errno = errno;
> info.si_code = TRAP_HWBKPT;
> - info.si_addr = addr;
> + info.si_addr = get_si_addr(addr, SIGTRAP, TRAP_HWBKPT);
> return force_sig_info(&info);
> }
>
> --
> 2.29.2.299.gdc1121823c-goog
>
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2020-11-13 2:52 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-11-13 2:46 [PATCH v15 0/6] arm64: expose FAR_EL1 tag bits in siginfo Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 1/6] parisc: Drop parisc special case for __sighandler_t Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 2/6] parisc: start using signal-defs.h Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 3/6] arch: move SA_* definitions to generic headers Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 4/6] signal: clear non-uapi flag bits when passing/returning sa_flags Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 5/6] signal: define the SA_UNSUPPORTED bit in sa_flags Peter Collingbourne
2020-11-13 2:46 ` [PATCH v15 6/6] arm64: expose FAR_EL1 tag bits in siginfo Peter Collingbourne
2020-11-13 2:52 ` Peter Collingbourne
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