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author | Masami Hiramatsu <mhiramat@redhat.com> | 2010-02-25 14:34:38 +0100 |
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committer | Ingo Molnar <mingo@elte.hu> | 2010-02-25 17:49:26 +0100 |
commit | 3d55cc8a058ee96291d6d45b1e35121b9920eca3 (patch) | |
tree | 716a79a900c013082f02de127e1fae784997ce49 /arch/x86/kernel/alternative.c | |
parent | kprobes/x86: Cleanup save/restore registers (diff) | |
download | linux-3d55cc8a058ee96291d6d45b1e35121b9920eca3.tar.xz linux-3d55cc8a058ee96291d6d45b1e35121b9920eca3.zip |
x86: Add text_poke_smp for SMP cross modifying code
Add generic text_poke_smp for SMP which uses stop_machine()
to synchronize modifying code.
This stop_machine() method is officially described at "7.1.3
Handling Self- and Cross-Modifying Code" on the intel's
software developer's manual 3A.
Since stop_machine() can't protect code against NMI/MCE, this
function can not modify those handlers. And also, this function
is basically for modifying multibyte-single-instruction. For
modifying multibyte-multi-instructions, we need another special
trap & detour code.
This code originaly comes from immediate values with
stop_machine() version. Thanks Jason and Mathieu!
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Anders Kaseorg <andersk@ksplice.com>
Cc: Tim Abbott <tabbott@ksplice.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
LKML-Reference: <20100225133438.6725.80273.stgit@localhost6.localdomain6>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/kernel/alternative.c')
-rw-r--r-- | arch/x86/kernel/alternative.c | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index e63b80e5861c..c41f13c15e8f 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -7,6 +7,7 @@ #include <linux/mm.h> #include <linux/vmalloc.h> #include <linux/memory.h> +#include <linux/stop_machine.h> #include <asm/alternative.h> #include <asm/sections.h> #include <asm/pgtable.h> @@ -570,3 +571,62 @@ void *__kprobes text_poke(void *addr, const void *opcode, size_t len) local_irq_restore(flags); return addr; } + +/* + * Cross-modifying kernel text with stop_machine(). + * This code originally comes from immediate value. + */ +static atomic_t stop_machine_first; +static int wrote_text; + +struct text_poke_params { + void *addr; + const void *opcode; + size_t len; +}; + +static int __kprobes stop_machine_text_poke(void *data) +{ + struct text_poke_params *tpp = data; + + if (atomic_dec_and_test(&stop_machine_first)) { + text_poke(tpp->addr, tpp->opcode, tpp->len); + smp_wmb(); /* Make sure other cpus see that this has run */ + wrote_text = 1; + } else { + while (!wrote_text) + smp_rmb(); + sync_core(); + } + + flush_icache_range((unsigned long)tpp->addr, + (unsigned long)tpp->addr + tpp->len); + return 0; +} + +/** + * text_poke_smp - Update instructions on a live kernel on SMP + * @addr: address to modify + * @opcode: source of the copy + * @len: length to copy + * + * Modify multi-byte instruction by using stop_machine() on SMP. This allows + * user to poke/set multi-byte text on SMP. Only non-NMI/MCE code modifying + * should be allowed, since stop_machine() does _not_ protect code against + * NMI and MCE. + * + * Note: Must be called under get_online_cpus() and text_mutex. + */ +void *__kprobes text_poke_smp(void *addr, const void *opcode, size_t len) +{ + struct text_poke_params tpp; + + tpp.addr = addr; + tpp.opcode = opcode; + tpp.len = len; + atomic_set(&stop_machine_first, 1); + wrote_text = 0; + stop_machine(stop_machine_text_poke, (void *)&tpp, NULL); + return addr; +} + |