Commit bbf154cc authored by David Howells's avatar David Howells Committed by Linus Torvalds

[PATCH] frv: update the trap tables comment

The attached patch updates the FRV trap tables comment to make it more
appropriate.
Signed-Off-By: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 307035eb
......@@ -17,19 +17,37 @@
###############################################################################
#
# declare the main trap and vector tables
# Declare the main trap and vector tables
#
# - the first instruction in each slot is a branch to the appropriate
# kernel-mode handler routine
# There are six tables:
#
# - the second instruction in each slot is a branch to the debug-mode hardware
# single-step bypass handler - this is called from break.S to deal with the
# CPU stepping in to exception handlers (particular where external interrupts
# are concerned)
# (1) The trap table for debug mode
# (2) The trap table for kernel mode
# (3) The trap table for user mode
#
# - the linker script places the user mode and kernel mode trap tables on to
# the same 8Kb page, so that break.S can be more efficient when performing
# single-step bypass management
# The CPU jumps to an appropriate slot in the appropriate table to perform
# exception processing. We have three different tables for the three
# different CPU modes because there is no hardware differentiation between
# stack pointers for these three modes, and so we have to invent one when
# crossing mode boundaries.
#
# (4) The exception handler vector table
#
# The user and kernel trap tables use the same prologue for normal
# exception processing. The prologue then jumps to the handler in this
# table, as indexed by the exception ID from the TBR.
#
# (5) The fixup table for kernel-trap single-step
# (6) The fixup table for user-trap single-step
#
# Due to the way single-stepping works on this CPU (single-step is not
# disabled when crossing exception boundaries, only when in debug mode),
# we have to catch the single-step event in break.S and jump to the fixup
# routine pointed to by this table.
#
# The linker script places the user mode and kernel mode trap tables on to
# the same 8Kb page, so that break.S can be more efficient when performing
# single-step bypass management
#
###############################################################################
......
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