Please disregard the patch below. Further testing shows that it does not
completely solve the problem. In particular, when line-wrap also produces
vertical scrolling. I think the recursive console_putc call may have to
go.
On Fri, 7 Mar 2025, Finn Thain wrote:
When long lines are sent to the debug console on the framebuffer, the
right-most column is lost. Fix this by subtracting 1 from the column
count before comparing it with console_struct_cur_column, as the latter
counts from zero.
Linewrap is handled with a recursive call to console_putc, but this
alters the console_struct_cur_row global. Store the old value before
calling console_putc, so the right-most character gets rendered on the
correct line.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxx>
---
arch/m68k/kernel/head.S | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/m68k/kernel/head.S b/arch/m68k/kernel/head.S
index 852255cf60de..9c60047764d0 100644
--- a/arch/m68k/kernel/head.S
+++ b/arch/m68k/kernel/head.S
@@ -3583,11 +3583,16 @@ L(console_not_home):
movel %a0@(Lconsole_struct_cur_column),%d0
addql #1,%a0@(Lconsole_struct_cur_column)
movel %a0@(Lconsole_struct_num_columns),%d1
+ subil #1,%d1
cmpl %d1,%d0
jcs 1f
- console_putc #'\n' /* recursion is OK! */
+ /* recursion will alter console_struct so load d1 register first */
+ movel %a0@(Lconsole_struct_cur_row),%d1
+ console_putc #'\n'
+ jmp 2f
1:
movel %a0@(Lconsole_struct_cur_row),%d1
+2:
/*
* At this point we make a shift in register usage
