[PATCH v14 8/8] arm64: expose FAR_EL1 tag bits in siginfo
Peter Collingbourne
pcc at google.com
Wed Nov 4 16:18:11 EST 2020
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, create a new pair of
fields in siginfo._sigfault, and store the tag bits of FAR_EL1 there,
together with a mask specifying which bits are valid.
A flag is added to si_faultflags to allow userspace to determine whether
the values in the fields are valid.
[1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html
Signed-off-by: Peter Collingbourne <pcc at google.com>
Link: https://linux-review.googlesource.com/id/Ia8876bad8c798e0a32df7c2ce1256c4771c81446
---
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 | 21 +++++---
arch/arm64/include/asm/exception.h | 2 +-
arch/arm64/include/asm/signal.h | 31 +++++++++++
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/x86/kernel/signal_compat.c | 9 +++-
include/linux/compat.h | 2 +
include/linux/signal.h | 16 ++++++
include/uapi/asm-generic/siginfo.h | 10 ++++
kernel/signal.c | 18 ++++++-
16 files changed, 160 insertions(+), 73 deletions(-)
create mode 100644 arch/arm64/include/asm/signal.h
diff --git a/Documentation/arm64/tagged-pointers.rst b/Documentation/arm64/tagged-pointers.rst
index eab4323609b9..7d07987ad85a 100644
--- a/Documentation/arm64/tagged-pointers.rst
+++ b/Documentation/arm64/tagged-pointers.rst
@@ -53,12 +53,21 @@ 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.
+Non-zero tags are not preserved in the fault address fields
+siginfo.si_addr or sigcontext.fault_address 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 in these fields. One exception to this rule is for
+signals raised in response to watchpoint debug exceptions, where the
+tag information will be preserved.
+
+The fault address tag is preserved in the si_addr_tag_bits field
+of siginfo, which is set for signals raised in response to data aborts
+and instruction aborts. The si_addr_tag_bits_mask field indicates
+which bits of the field are valid. The validity of these fields is
+indicated by the SIFAULTFLAG_ADDR_TAG_BITS flag in siginfo.si_faultflags,
+and the validity of si_faultflags in turn is indicated by the kernel
+indicating support for the sigaction.sa_flags flag SA_FAULTFLAGS.
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/signal.h b/arch/arm64/include/asm/signal.h
new file mode 100644
index 000000000000..67d8e0899e9b
--- /dev/null
+++ b/arch/arm64/include/asm/signal.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARM64_ASM_SIGNAL_H
+#define __ARM64_ASM_SIGNAL_H
+
+#include <uapi/asm/signal.h>
+#include <uapi/asm/siginfo.h>
+
+static inline unsigned long arch_addr_tag_bits_mask(unsigned long sig,
+ unsigned long si_code)
+{
+ /*
+ * For historical reasons, all bits of the fault address are exposed as
+ * address bits for watchpoint exceptions. New architectures should not
+ * follow this practice.
+ */
+ if (sig == SIGTRAP && si_code == TRAP_BRKPT)
+ return 0;
+
+ /*
+ * FAR_EL1[63:60] are UNKNOWN for tag check faults so reflect that in
+ * the tag bits mask. The bits are already being masked out by
+ * do_tag_check_fault so userspace won't see them in si_addr.
+ */
+ if (sig == SIGSEGV && si_code == SEGV_MTESERR)
+ return 0xfUL << 56;
+
+ return 0xffUL << 56;
+}
+#define arch_addr_tag_bits_mask arch_addr_tag_bits_mask
+
+#endif
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/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c
index 222ff6178571..41cbef515b95 100644
--- a/arch/x86/kernel/signal_compat.c
+++ b/arch/x86/kernel/signal_compat.c
@@ -121,8 +121,8 @@ static inline void signal_compat_build_tests(void)
#endif
CHECK_CSI_OFFSET(_sigfault);
- CHECK_CSI_SIZE (_sigfault, 8*sizeof(int));
- CHECK_SI_SIZE (_sigfault, 16*sizeof(int));
+ CHECK_CSI_SIZE (_sigfault, 10*sizeof(int));
+ CHECK_SI_SIZE (_sigfault, 20*sizeof(int));
BUILD_BUG_ON(offsetof(siginfo_t, si_addr) != 0x10);
BUILD_BUG_ON(offsetof(compat_siginfo_t, si_addr) != 0x0C);
@@ -141,6 +141,11 @@ static inline void signal_compat_build_tests(void)
BUILD_BUG_ON(offsetof(siginfo_t, si_faultflags) != 0x48);
BUILD_BUG_ON(offsetof(compat_siginfo_t, si_faultflags) != 0x28);
+ BUILD_BUG_ON(offsetof(siginfo_t, si_addr_tag_bits) != 0x50);
+ BUILD_BUG_ON(offsetof(siginfo_t, si_addr_tag_bits_mask) != 0x58);
+ BUILD_BUG_ON(offsetof(compat_siginfo_t, si_addr_tag_bits) != 0x2C);
+ BUILD_BUG_ON(offsetof(compat_siginfo_t, si_addr_tag_bits_mask) != 0x30);
+
CHECK_CSI_OFFSET(_sigpoll);
CHECK_CSI_SIZE (_sigpoll, 2*sizeof(int));
CHECK_SI_SIZE (_sigpoll, 4*sizeof(int));
diff --git a/include/linux/compat.h b/include/linux/compat.h
index 84d3b72be701..f3c83a6d6623 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -239,6 +239,8 @@ typedef struct compat_siginfo {
compat_uptr_t _pad[6];
};
u32 _faultflags;
+ compat_uptr_t _addr_tag_bits;
+ compat_uptr_t _addr_tag_bits_mask;
} _sigfault;
/* SIGPOLL */
diff --git a/include/linux/signal.h b/include/linux/signal.h
index e9fb05041e7a..7fe7ce1d252e 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -482,4 +482,20 @@ struct seq_file;
extern void render_sigset_t(struct seq_file *, const char *, sigset_t *);
#endif
+#ifndef arch_addr_tag_bits_mask
+/*
+ * Given a signal and si_code which correspond to the _sigfault union member,
+ * if tag bits are present in the fault address which must appear in
+ * si_addr_tag_bits instead of si_addr, this hook must return a bitmask where 1
+ * corresponds to bits appearing in si_addr_tag_bits and 0 corresponds to bits
+ * appearing in si_addr. The value returned by this function will also be
+ * available in si_addr_tag_bits_mask.
+ */
+static inline unsigned long arch_addr_tag_bits_mask(unsigned long sig,
+ unsigned long si_code)
+{
+ return 0;
+}
+#endif
+
#endif /* _LINUX_SIGNAL_H */
diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h
index 10a55aed9ede..df196ad74238 100644
--- a/include/uapi/asm-generic/siginfo.h
+++ b/include/uapi/asm-generic/siginfo.h
@@ -97,6 +97,8 @@ union __sifields {
#ifdef __LP64__
__u32 _pad2; /* to be used if we add another 32-bit field */
#endif
+ unsigned long _addr_tag_bits;
+ unsigned long _addr_tag_bits_mask;
} _sigfault;
/* SIGPOLL */
@@ -159,6 +161,8 @@ typedef struct siginfo {
#define si_addr_lsb _sifields._sigfault._addr_lsb
/* si_faultflags is only valid if 0 < si_code < SI_KERNEL */
#define si_faultflags _sifields._sigfault._faultflags
+#define si_addr_tag_bits _sifields._sigfault._addr_tag_bits
+#define si_addr_tag_bits_mask _sifields._sigfault._addr_tag_bits_mask
#define si_lower _sifields._sigfault._addr_bnd._lower
#define si_upper _sifields._sigfault._addr_bnd._upper
#define si_pkey _sifields._sigfault._addr_pkey._pkey
@@ -301,6 +305,12 @@ typedef struct siginfo {
#define EMT_TAGOVF 1 /* tag overflow */
#define NSIGEMT 1
+/*
+ * SIGILL, SIGFPE, SIGSEGV, SIGBUS, SIGTRAP, SIGEMT si_faultflags
+ */
+#define SIFAULTFLAG_ADDR_TAG_BITS 1
+/* si_addr_tag_bits{,_mask} fields valid */
+
/*
* sigevent definitions
*
diff --git a/kernel/signal.c b/kernel/signal.c
index 1fd1f0d12174..aa69dd312bd5 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1653,11 +1653,16 @@ void force_sigsegv(int sig)
static void set_sigfault_common_fields(struct kernel_siginfo *info, int sig,
int code, void __user *addr)
{
+ unsigned long addr_long = (unsigned long)addr;
+ unsigned long tag_bits_mask = arch_addr_tag_bits_mask(sig, code);
+
info->si_signo = sig;
info->si_errno = 0;
info->si_code = code;
- info->si_addr = addr;
- info->si_faultflags = 0;
+ info->si_addr = (void __user *)(addr_long & ~tag_bits_mask);
+ info->si_faultflags = SIFAULTFLAG_ADDR_TAG_BITS;
+ info->si_addr_tag_bits = addr_long & tag_bits_mask;
+ info->si_addr_tag_bits_mask = tag_bits_mask;
}
int force_sig_fault_to_task(int sig, int code, void __user *addr
@@ -3272,6 +3277,13 @@ void copy_siginfo_to_external32(struct compat_siginfo *to,
to->si_trapno = from->si_trapno;
#endif
to->si_faultflags = from->si_faultflags;
+ /*
+ * These assignments involve a truncation, but as with si_addr
+ * they will be derived from a 32-bit fault address so we
+ * should not expect any truncation in practice.
+ */
+ to->si_addr_tag_bits = from->si_addr_tag_bits;
+ to->si_addr_tag_bits_mask = from->si_addr_tag_bits_mask;
}
switch (layout) {
@@ -3348,6 +3360,8 @@ static int post_copy_siginfo_from_user32(kernel_siginfo_t *to,
to->si_trapno = from->si_trapno;
#endif
to->si_faultflags = from->si_faultflags;
+ to->si_addr_tag_bits = from->si_addr_tag_bits;
+ to->si_addr_tag_bits_mask = from->si_addr_tag_bits_mask;
}
switch (layout) {
--
2.29.1.341.ge80a0c044ae-goog
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