| Message ID | 1463746166-15601-1-git-send-email-thuth@redhat.com |
|---|---|
| State | Accepted |
| Headers | show |
Thomas Huth <thuth@redhat.com> writes: > When I tried to abort the net-snk TFTP boot by pressing ESC > a couple of times, I sometimes noticed that SLOF ended up > with a negative stack depth counter. After doing some closer > investigation, I disovered that the problem can be reproduced > by simply pressing "ESC ESC RETURN" at the SLOF prompt. > > The problem is in the code in accept.fs: If an ESC character is > found in the input stream, the "handle-ESC" function is called. > This reads in the next input character with "key", and if it > does not match 0x5b or 0x4f, it calls "handle-meta" for further > handling. handle-meta consumes the value from "key" on the stack > to use it as an index into a jump table, thus the stack is empty > now. If the index was a 0x1b (due to the second ESC character), > the function handle-CSI is called. But that function expects > another value as index for a jump table on the stack, and since > the stack was already empty, we end up with a negative stack > depth here. > Apparently, handle-meta should call a function instead that > uses "key" to get another character from the input stream, > before calling the handle-CSI function. > > Signed-off-by: Thomas Huth <thuth@redhat.com> Tested-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com> > --- > slof/fs/accept.fs | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/slof/fs/accept.fs b/slof/fs/accept.fs > index 7e8e271..cb6f2fa 100644 > --- a/slof/fs/accept.fs > +++ b/slof/fs/accept.fs > @@ -295,6 +295,10 @@ TABLE-EXECUTE handle-CSI > 0 , 0 , 0 , 0 , > 0 , 0 , 0 , 0 , > > +: handle-CSI-key > + key 1f and handle-CSI > +; > + > TABLE-EXECUTE handle-meta > 0 , 0 , 0 , 0 , > 0 , 0 , 0 , 0 , > @@ -302,7 +306,7 @@ TABLE-EXECUTE handle-meta > 0 , 0 , 0 , ' handle-fn , > 0 , 0 , 0 , 0 , > 0 , 0 , 0 , 0 , > -0 , 0 , 0 , ' handle-CSI , > +0 , 0 , 0 , ' handle-CSI-key , > 0 , 0 , 0 , 0 , > > : handle-ESC-O > -- > 1.8.3.1
On 20/05/16 22:09, Thomas Huth wrote: > When I tried to abort the net-snk TFTP boot by pressing ESC > a couple of times, I sometimes noticed that SLOF ended up > with a negative stack depth counter. After doing some closer > investigation, I disovered that the problem can be reproduced > by simply pressing "ESC ESC RETURN" at the SLOF prompt. > > The problem is in the code in accept.fs: If an ESC character is > found in the input stream, the "handle-ESC" function is called. > This reads in the next input character with "key", and if it > does not match 0x5b or 0x4f, it calls "handle-meta" for further > handling. handle-meta consumes the value from "key" on the stack > to use it as an index into a jump table, thus the stack is empty > now. If the index was a 0x1b (due to the second ESC character), > the function handle-CSI is called. But that function expects > another value as index for a jump table on the stack, and since > the stack was already empty, we end up with a negative stack > depth here. > Apparently, handle-meta should call a function instead that > uses "key" to get another character from the input stream, > before calling the handle-CSI function. > > Signed-off-by: Thomas Huth <thuth@redhat.com> Thanks, applied. > --- > slof/fs/accept.fs | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/slof/fs/accept.fs b/slof/fs/accept.fs > index 7e8e271..cb6f2fa 100644 > --- a/slof/fs/accept.fs > +++ b/slof/fs/accept.fs > @@ -295,6 +295,10 @@ TABLE-EXECUTE handle-CSI > 0 , 0 , 0 , 0 , > 0 , 0 , 0 , 0 , > > +: handle-CSI-key > + key 1f and handle-CSI > +; > + > TABLE-EXECUTE handle-meta > 0 , 0 , 0 , 0 , > 0 , 0 , 0 , 0 , > @@ -302,7 +306,7 @@ TABLE-EXECUTE handle-meta > 0 , 0 , 0 , ' handle-fn , > 0 , 0 , 0 , 0 , > 0 , 0 , 0 , 0 , > -0 , 0 , 0 , ' handle-CSI , > +0 , 0 , 0 , ' handle-CSI-key , > 0 , 0 , 0 , 0 , > > : handle-ESC-O >
diff --git a/slof/fs/accept.fs b/slof/fs/accept.fs index 7e8e271..cb6f2fa 100644 --- a/slof/fs/accept.fs +++ b/slof/fs/accept.fs @@ -295,6 +295,10 @@ TABLE-EXECUTE handle-CSI 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , +: handle-CSI-key + key 1f and handle-CSI +; + TABLE-EXECUTE handle-meta 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , @@ -302,7 +306,7 @@ TABLE-EXECUTE handle-meta 0 , 0 , 0 , ' handle-fn , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , -0 , 0 , 0 , ' handle-CSI , +0 , 0 , 0 , ' handle-CSI-key , 0 , 0 , 0 , 0 , : handle-ESC-O
When I tried to abort the net-snk TFTP boot by pressing ESC a couple of times, I sometimes noticed that SLOF ended up with a negative stack depth counter. After doing some closer investigation, I disovered that the problem can be reproduced by simply pressing "ESC ESC RETURN" at the SLOF prompt. The problem is in the code in accept.fs: If an ESC character is found in the input stream, the "handle-ESC" function is called. This reads in the next input character with "key", and if it does not match 0x5b or 0x4f, it calls "handle-meta" for further handling. handle-meta consumes the value from "key" on the stack to use it as an index into a jump table, thus the stack is empty now. If the index was a 0x1b (due to the second ESC character), the function handle-CSI is called. But that function expects another value as index for a jump table on the stack, and since the stack was already empty, we end up with a negative stack depth here. Apparently, handle-meta should call a function instead that uses "key" to get another character from the input stream, before calling the handle-CSI function. Signed-off-by: Thomas Huth <thuth@redhat.com> --- slof/fs/accept.fs | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)