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Subject[PATCH v9 21/51] powerpc: Deliver SEGV signal on pkey violation
Date
The value of the pkey, whose protection got violated,
is made available in si_pkey field of the siginfo structure.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
---
arch/powerpc/include/asm/bug.h | 1 +
arch/powerpc/kernel/traps.c | 12 ++++++++-
arch/powerpc/mm/fault.c | 55 ++++++++++++++++++++++-----------------
3 files changed, 43 insertions(+), 25 deletions(-)

diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
index 3c04249..97c3847 100644
--- a/arch/powerpc/include/asm/bug.h
+++ b/arch/powerpc/include/asm/bug.h
@@ -133,6 +133,7 @@
extern int do_page_fault(struct pt_regs *, unsigned long, unsigned long);
extern void bad_page_fault(struct pt_regs *, unsigned long, int);
extern void _exception(int, struct pt_regs *, int, unsigned long);
+extern void _exception_pkey(int, struct pt_regs *, int, unsigned long, int);
extern void die(const char *, struct pt_regs *, long);
extern bool die_will_crash(void);

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 13c9dcd..ed1c39b 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -20,6 +20,7 @@
#include <linux/sched/debug.h>
#include <linux/kernel.h>
#include <linux/mm.h>
+#include <linux/pkeys.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
@@ -265,7 +266,9 @@ void user_single_step_siginfo(struct task_struct *tsk,
info->si_addr = (void __user *)regs->nip;
}

-void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr)
+
+void _exception_pkey(int signr, struct pt_regs *regs, int code, unsigned long addr,
+ int key)
{
siginfo_t info;
const char fmt32[] = KERN_INFO "%s[%d]: unhandled signal %d " \
@@ -292,9 +295,16 @@ void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr)
info.si_signo = signr;
info.si_code = code;
info.si_addr = (void __user *) addr;
+ info.si_pkey = key;
+
force_sig_info(signr, &info, current);
}

+void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr)
+{
+ _exception_pkey(signr, regs, code, addr, 0);
+}
+
void system_reset_exception(struct pt_regs *regs)
{
/*
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index dfcd0e4..84523ed 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -107,7 +107,8 @@ static bool store_updates_sp(struct pt_regs *regs)
*/

static int
-__bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code)
+__bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code,
+ int pkey)
{
/*
* If we are in kernel mode, bail out with a SEGV, this will
@@ -117,17 +118,18 @@ static bool store_updates_sp(struct pt_regs *regs)
if (!user_mode(regs))
return SIGSEGV;

- _exception(SIGSEGV, regs, si_code, address);
+ _exception_pkey(SIGSEGV, regs, si_code, address, pkey);

return 0;
}

static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address)
{
- return __bad_area_nosemaphore(regs, address, SEGV_MAPERR);
+ return __bad_area_nosemaphore(regs, address, SEGV_MAPERR, 0);
}

-static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code)
+static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code,
+ int pkey)
{
struct mm_struct *mm = current->mm;

@@ -137,30 +139,18 @@ static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code)
*/
up_read(&mm->mmap_sem);

- return __bad_area_nosemaphore(regs, address, si_code);
+ return __bad_area_nosemaphore(regs, address, si_code, pkey);
}

static noinline int bad_area(struct pt_regs *regs, unsigned long address)
{
- return __bad_area(regs, address, SEGV_MAPERR);
+ return __bad_area(regs, address, SEGV_MAPERR, 0);
}

-static int bad_page_fault_exception(struct pt_regs *regs, unsigned long address,
- int si_code)
+static int bad_key_fault_exception(struct pt_regs *regs, unsigned long address,
+ int pkey)
{
- int sig = SIGBUS;
- int code = BUS_OBJERR;
-
-#ifdef CONFIG_PPC_MEM_KEYS
- if (si_code & DSISR_KEYFAULT) {
- perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
- sig = SIGSEGV;
- code = SEGV_PKUERR;
- }
-#endif /* CONFIG_PPC_MEM_KEYS */
-
- _exception(sig, regs, code, address);
- return 0;
+ return __bad_area_nosemaphore(regs, address, SEGV_PKUERR, pkey);
}

static int do_sigbus(struct pt_regs *regs, unsigned long address,
@@ -411,7 +401,16 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
if (unlikely(page_fault_is_bad(error_code))) {
if (!is_user)
return SIGBUS;
- return bad_page_fault_exception(regs, address, error_code);
+
+ if (error_code & DSISR_KEYFAULT) {
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs,
+ address);
+ return bad_key_fault_exception(regs, address,
+ get_mm_addr_key(current->mm, address));
+ }
+
+ _exception_pkey(SIGBUS, regs, BUS_OBJERR, address, 0);
+ return 0;
}

/* Additional sanity check(s) */
@@ -516,8 +515,16 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
fault = handle_mm_fault(vma, address, flags);

#ifdef CONFIG_PPC_MEM_KEYS
- if (unlikely(fault & VM_FAULT_SIGSEGV))
- return __bad_area(regs, address, SEGV_PKUERR);
+ if (unlikely(fault & VM_FAULT_SIGSEGV)) {
+ /*
+ * The PGD-PDT...PMD-PTE tree may not have been fully setup.
+ * Hence we cannot walk the tree to locate the PTE, to locate
+ * the key. Hence lets use vma_pkey() to get the key; instead
+ * of get_mm_addr_key().
+ */
+ up_read(&current->mm->mmap_sem);
+ return bad_key_fault_exception(regs, address, vma_pkey(vma));
+ }
#endif /* CONFIG_PPC_MEM_KEYS */

major |= fault & VM_FAULT_MAJOR;
--
1.7.1
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