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Date: Fri, 29 Jun 2018 22:39:07 +0300
From: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
To: linux-snps-arc@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org,
Vineet Gupta <Vineet.Gupta1@...opsys.com>,
Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
Subject: [PATCH] ARC: prevent showing irrelevant exception info in signal message
We process signals in the end of syscall/exception handler.
It the signal is fatal we print register's content using
show_regs function. show_regs() also prints information about
last exception happened.
In case of multicore system we can catch the situation when we
will print wrong information about exception. See the example:
______________________________
CPU-0: started to handle page fault
CPU-1: sent signal to process, which is executed on CPU-0
CPU-0: ended page fault handle. Started to process signal before
returnig to userspace. Process signal, which is send from
CPU-0. As th signal is fatal we call show_regs().
show_regs() will show information about last exception
which is *page fault* (instead of "trap" which is used for
signals and happened on CPU-0)
So we will get message like this:
/home/waitpid02
potentially unexpected fatal signal 8.
Path: /home/waitpid02
CPU: 0 PID: 100 Comm: waitpid02 Not tainted 4.10.0-rc4 #2
task: 9f11c200 task.stack: 9f3ae000
[ECR ]: 0x00050200 => Invalid Write @ 0x00000000 by insn @ 0x000123ec
[EFA ]: 0x00000000
[BLINK ]: 0x123ea
[ERET ]: 0x123ec
@off 0x123ec in [/home/waitpid02]
VMA: 0x00010000 to 0x00016000
[STAT32]: 0x80080882 : IE U
BTA: 0x000123ea SP: 0x5ffd3db0 FP: 0x00000000
LPS: 0x20031684 LPE: 0x2003169a LPC: 0x00000006
[-----other-info-----]
This message is confusing because it show information about page fault
( [ECR ]: 0x00050200 => Invalid Write ) which is absolutely irrelevant
to signal.
This situation was reproduced with waitpid02 LTP test.
_____________________________
So remove printing information about exceptions from show_regs()
to avoid confusing messages. Print information about exceptions
only in required places instead of show_regs()
Now we don't print information about exceptions if signal is simply
send by another userspace app. So in case of waitpid02 we will print
next message:
_____________________________
./waitpid02
potentially unexpected fatal signal 8.
[STAT32]: 0x80080082 : IE U
BTA: 0x20000fc4 SP: 0x5ff8bd64 FP: 0x00000000
LPS: 0x200524a0 LPE: 0x200524b6 LPC: 0x00000006
[-----other-info-----]
_____________________________
This patch fix
STAR 9001146055: waitpid02: Invalid Write @ 0x00000000 by insn @ 0x000123ec
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
---
arch/arc/include/asm/bug.h | 1 +
arch/arc/kernel/traps.c | 1 +
arch/arc/kernel/troubleshoot.c | 27 ++++++++++++++++++++-------
arch/arc/mm/fault.c | 2 ++
4 files changed, 24 insertions(+), 7 deletions(-)
diff --git a/arch/arc/include/asm/bug.h b/arch/arc/include/asm/bug.h
index 21ec82466d62..b9fd60f7d36b 100644
--- a/arch/arc/include/asm/bug.h
+++ b/arch/arc/include/asm/bug.h
@@ -16,6 +16,7 @@
struct task_struct;
void show_regs(struct pt_regs *regs);
+void show_exception_regs(struct pt_regs *regs);
void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs);
void show_kernel_fault_diag(const char *str, struct pt_regs *regs,
unsigned long address);
diff --git a/arch/arc/kernel/traps.c b/arch/arc/kernel/traps.c
index b123558bf0bb..fe41f0d9488f 100644
--- a/arch/arc/kernel/traps.c
+++ b/arch/arc/kernel/traps.c
@@ -50,6 +50,7 @@ unhandled_exception(const char *str, struct pt_regs *regs, siginfo_t *info)
tsk->thread.fault_address = (__force unsigned int)info->si_addr;
force_sig_info(info->si_signo, info, tsk);
+ show_exception_regs(regs);
} else {
/* If not due to copy_(to|from)_user, we are doomed */
diff --git a/arch/arc/kernel/troubleshoot.c b/arch/arc/kernel/troubleshoot.c
index 783b20354f8b..313aea25e638 100644
--- a/arch/arc/kernel/troubleshoot.c
+++ b/arch/arc/kernel/troubleshoot.c
@@ -170,14 +170,9 @@ static void show_ecr_verbose(struct pt_regs *regs)
}
}
-/************************************************************************
- * API called by rest of kernel
- ***********************************************************************/
-
-void show_regs(struct pt_regs *regs)
+void show_exception_regs(struct pt_regs *regs)
{
struct task_struct *tsk = current;
- struct callee_regs *cregs;
char *buf;
buf = (char *)__get_free_page(GFP_KERNEL);
@@ -190,12 +185,28 @@ void show_regs(struct pt_regs *regs)
show_ecr_verbose(regs);
pr_info("[EFA ]: 0x%08lx\n[BLINK ]: %pS\n[ERET ]: %pS\n",
- current->thread.fault_address,
+ tsk->thread.fault_address,
(void *)regs->blink, (void *)regs->ret);
if (user_mode(regs))
show_faulting_vma(regs->ret, buf); /* faulting code, not data */
+ free_page((unsigned long)buf);
+}
+
+/************************************************************************
+ * API called by rest of kernel
+ ***********************************************************************/
+
+void show_regs(struct pt_regs *regs)
+{
+ struct callee_regs *cregs;
+ char *buf;
+
+ buf = (char *)__get_free_page(GFP_KERNEL);
+ if (!buf)
+ return;
+
pr_info("[STAT32]: 0x%08lx", regs->status32);
#define STS_BIT(r, bit) r->status32 & STATUS_##bit##_MASK ? #bit" " : ""
@@ -238,6 +249,8 @@ void show_kernel_fault_diag(const char *str, struct pt_regs *regs,
/* Show fault description */
pr_info("\n%s\n", str);
+ show_exception_regs(regs);
+
/* Caller and Callee regs */
show_regs(regs);
diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c
index a0b7bd6d030d..7e0e2591bb27 100644
--- a/arch/arc/mm/fault.c
+++ b/arch/arc/mm/fault.c
@@ -200,6 +200,7 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
/* info.si_code has been set above */
info.si_addr = (void __user *)address;
force_sig_info(SIGSEGV, &info, tsk);
+ show_exception_regs(regs);
return;
}
@@ -239,4 +240,5 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
info.si_code = BUS_ADRERR;
info.si_addr = (void __user *)address;
force_sig_info(SIGBUS, &info, tsk);
+ show_exception_regs(regs);
}
--
2.14.4
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