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| author | Michael Schmitz <schmitzmic@gmail.com> | 2023-03-01 15:11:07 +1300 |
|---|---|---|
| committer | Geert Uytterhoeven <geert@linux-m68k.org> | 2023-03-06 14:09:42 +0100 |
| commit | e36a82bebbf7da814530d5a179bef9df5934b717 (patch) | |
| tree | fce5898ccbfd0e534a829ffef949efb90f7446f4 /arch/m68k | |
| parent | d4b97925e87eb133e400fe4a482d750c74ce392f (diff) | |
| download | lwn-e36a82bebbf7da814530d5a179bef9df5934b717.tar.gz lwn-e36a82bebbf7da814530d5a179bef9df5934b717.zip | |
m68k: Only force 030 bus error if PC not in exception table
__get_kernel_nofault() does copy data in supervisor mode when
forcing a task backtrace log through /proc/sysrq_trigger.
This is expected cause a bus error exception on e.g. NULL
pointer dereferencing when logging a kernel task has no
workqueue associated. This bus error ought to be ignored.
Our 030 bus error handler is ill equipped to deal with this:
Whenever ssw indicates a kernel mode access on a data fault,
we don't even attempt to handle the fault and instead always
send a SEGV signal (or panic). As a result, the check
for exception handling at the fault PC (buried in
send_sig_fault() which gets called from do_page_fault()
eventually) is never used.
In contrast, both 040 and 060 access error handlers do not
care whether a fault happened on supervisor mode access,
and will call do_page_fault() on those, ultimately honoring
the exception table.
Add a check in bus_error030 to call do_page_fault() in case
we do have an entry for the fault PC in our exception table.
I had attempted a fix for this earlier in 2019 that did rely
on testing pagefault_disabled() (see link below) to achieve
the same thing, but this patch should be more generic.
Tested on 030 Atari Falcon.
Reported-by: Eero Tamminen <oak@helsinkinet.fi>
Link: https://lore.kernel.org/r/alpine.LNX.2.21.1904091023540.25@nippy.intranet
Link: https://lore.kernel.org/r/63130691-1984-c423-c1f2-73bfd8d3dcd3@gmail.com
Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/20230301021107.26307-1-schmitzmic@gmail.com
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Diffstat (limited to 'arch/m68k')
| -rw-r--r-- | arch/m68k/kernel/traps.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/m68k/kernel/traps.c b/arch/m68k/kernel/traps.c index 5c8cba0efc63..a700807c9b6d 100644 --- a/arch/m68k/kernel/traps.c +++ b/arch/m68k/kernel/traps.c @@ -30,6 +30,7 @@ #include <linux/init.h> #include <linux/ptrace.h> #include <linux/kallsyms.h> +#include <linux/extable.h> #include <asm/setup.h> #include <asm/fpu.h> @@ -545,7 +546,8 @@ static inline void bus_error030 (struct frame *fp) errorcode |= 2; if (mmusr & (MMU_I | MMU_WP)) { - if (ssw & 4) { + /* We might have an exception table for this PC */ + if (ssw & 4 && !search_exception_tables(fp->ptregs.pc)) { pr_err("Data %s fault at %#010lx in %s (pc=%#lx)\n", ssw & RW ? "read" : "write", fp->un.fmtb.daddr, |