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This patch implements CONFIG_DEBUG_RODATA, allowing
the kernel text section to be marked read-only in
order to catch bugs that write over the kernel. This
requires mapping the kernel code, plus up to 4MB, using
pages instead of sections, which can increase TLB
pressure.
The kernel is normally mapped using 1MB section entries
in the first level page table, and the first level page
table is copied into every mm. This prevents marking
the kernel text read-only, because the 1MB section
entries are too large granularity to separate the init
section, which is reused as read-write memory after
init, and the kernel text section. Also, the top level
page table for every process would need to be updated,
which is not possible to do safely and efficiently on SMP.
To solve both problems, allow alloc_init_pte to overwrite
an existing section entry with a fully-populated second
level page table. When CONFIG_DEBUG_RODATA is set, all
the section entries that overlap the kernel text section
will be replaced with page mappings. The kernel always
uses a pair of 2MB-aligned 1MB sections, so up to 2MB
of memory before and after the kernel may end up page
mapped.
When the top level page tables are copied into each
process the second level page tables are not copied,
leaving a single second level page table that will
affect all processes on all cpus. To mark a page
read-only, the second level page table is located using
the pointer in the first level page table for the
current process, and the supervisor RO bit is flipped
atomically. Once all pages have been updated, all TLBs
are flushed to ensure the changes are visible on all
cpus.
If CONFIG_DEBUG_RODATA is not set, the kernel will be
mapped using the normal 1MB section entries.
Change-Id: I94fae337f882c2e123abaf8e1082c29cd5d483c6
Signed-off-by: Colin Cross <ccross@android.com>
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Commit 722b3c74695377d11d18a52f3da08114d37f3f37 modified x86 ftrace to
avoid tracing all functions called from irqs when function graph was
used with a filter. Port the same fix to ARM.
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Extract out the instruction generation code so that it can be used
for jump labels too.
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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As commit 592201a9f15 (ARM: Thumb-2: Support Thumb-2 in undefined
instruction handler) says:
32-bit Thumb instructions are specified in the form:
((first_half << 16 ) | second_half)
which matches the layout used by the ARM ARM.
Convert the ftrace code to use the same format to avoid the usage of
different formats in kernel code.
Acked-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Before replacing an instruction, the ftrace code determines what the old
instruction should be and verifies that that's what's really there in
memory before replacing it. This is useful if for example a bug in
mcountrecord causes it to record wrong locations.
However, in cases where we replace call sites in entry-common.S, these
checks are not needed. For these, we currently just memcpy() the memory
content and then "verify" it -- this is quite useless and can be
removed.
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Support the graph tracer + dynamic ftrace combination on ARM.
Signed-off-by: Rabin Vincent <rabin@rab.in>
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Cc: Tim Bird <tim.bird@am.sony.com>
[rabin@rab.in: rebase on top of latest code,
keep code in ftrace.c instead of separate file,
check for ftrace_graph_entry also]
Signed-off-by: Rabin Vincent <rabin@rab.in>
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Handle the different nop and call instructions for Thumb-2. Also, we
need to adjust the recorded mcount_loc addresses because they have the
lsb set.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org> [recordmcount.pl change]
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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This adds mcount recording and updates dynamic ftrace for ARM to work
with the new ftrace dyamic tracing implementation. It also adds support
for the mcount format used by newer ARM compilers.
With dynamic tracing, mcount() is implemented as a nop. Callsites are
patched on startup with nops, and dynamically patched to call to the
ftrace_caller() routine as needed.
Acked-by: Steven Rostedt <rostedt@goodmis.org> [recordmcount.pl change]
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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/tmp/ccJ3ssZW.s: Assembler messages:
/tmp/ccJ3ssZW.s:1952: Error: can't resolve `.text' {.text section} - `.LFB1077'
This is caused because:
.section .data
.section .text
.section .text
.previous
does not return us to the .text section, but the .data section; this
makes use of .previous dangerous if the ordering of previous sections
is not known.
Fix up the other users of .previous; .pushsection and .popsection are
a safer pairing to use than .section and .previous.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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... not kstop_machine. Add a note that irqs are disabled.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
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The arch dependent function ftrace_mcount_set was only used by the daemon
start up code. This patch removes it.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Record the address of the mcount call-site. Currently all archs except sparc64
record the address of the instruction following the mcount call-site. Some
general cleanups are entailed. Storing mcount addresses in rec->ip enables
looking them up in the kprobe hash table later on to check if they're kprobe'd.
Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: davem@davemloft.net
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Remove the unneeded function ftrace_ip_converted().
Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Core ftrace support for the ARM architecture, which includes support
for dynamic function tracing.
Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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