linux-kernel - [PATCH v2] arch: define weak abort

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Message-Id: <1513118956-8718-1-git-send-email-sudipm.mukherjee@gmail.com>
Date:   Tue, 12 Dec 2017 22:49:16 +0000
From:   Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Subject: [PATCH v2] arch: define weak abort

gcc toggle -fisolate-erroneous-paths-dereference (default at -O2
onwards) isolates faulty code paths such as null pointer access, divide
by zero etc. If gcc port doesnt implement __builtin_trap, an abort() is
generated which causes kernel link error.

In this case, gcc is generating abort due to 'divide by zero' in
lib/mpi/mpih-div.c.

Currently 'frv' and 'arc' are failing. Previously other arch was also
broken like m32r was fixed by d22e3d69ee1a ("m32r: fix build failure").

Lets define this weak function which is common for all arch and fix the
problem permanently. We can even remove the arch specific 'abort' after
this is done.

Cc: Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@...il.com>
---

Hi Alexey,
I was thinking of sending the m32r revert patch in few days. My m32r
builds are having a little problem and should be fixed by this weekend.
I can not test m32r before that. We can also send a patch to remove the
same code in arm and unicore32.

 kernel/exit.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/exit.c b/kernel/exit.c
index af6c245..90c6869 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1759,3 +1759,11 @@ long kernel_wait4(pid_t upid, int __user *stat_addr, int options,
 	return -EFAULT;
 }
 #endif
+
+__weak void abort(void)
+{
+	BUG();
+
+	/* if that doesn't kill us, halt */
+	panic("Oops failed to kill thread");
+}
-- 
1.9.1