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kprobes/x86: Support kprobes jump optimization on x86

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Introduce x86 arch-specific optimization code, which supports
both of x86-32 and x86-64.

This code also supports safety checking, which decodes whole of
a function in which probe is inserted, and checks following
conditions before optimization:
 - The optimized instructions which will be replaced by a jump instruction
   don't straddle the function boundary.
 - There is no indirect jump instruction, because it will jumps into
   the address range which is replaced by jump operand.
 - There is no jump/loop instruction which jumps into the address range
   which is replaced by jump operand.
 - Don't optimize kprobes if it is in functions into which fixup code will
   jumps.

This uses text_poke_multibyte() which doesn't support modifying
code on NMI/MCE handler. However, since kprobes itself doesn't
support NMI/MCE code probing, it's not a problem.

Changes in v9:
 - Use *_text_reserved() for checking the probe can be optimized.
 - Verify jump address range is in 2G range when preparing slot.
 - Backup original code when switching optimized buffer, instead of
   preparing buffer, because there can be int3 of other probes in
   preparing phase.
 - Check kprobe is disabled in arch_check_optimized_kprobe().
 - Strictly check indirect jump opcodes (ff /4, ff /5).

Changes in v6:
 - Split stop_machine-based jump patching code.
 - Update comments and coding style.

Changes in v5:
 - Introduce stop_machine-based jump replacing.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
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: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
LKML-Reference: <20100225133446.6725.78994.stgit@localhost6.localdomain6>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Masami Hiramatsu
2010-02-25 08:34:46 -05:00
committed by Ingo Molnar
parent 3d55cc8a05
commit c0f7ac3a9e
3 changed files with 441 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
arch/x86/include/asm/kprobes.h
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@ -33,6 +33,9 @@ struct kprobe;
typedef u8 kprobe_opcode_t;
#define BREAKPOINT_INSTRUCTION 0xcc
#define RELATIVEJUMP_OPCODE 0xe9
#define RELATIVEJUMP_SIZE 5
#define RELATIVECALL_OPCODE 0xe8
#define RELATIVE_ADDR_SIZE 4
#define MAX_INSN_SIZE 16
#define MAX_STACK_SIZE 64
#define MIN_STACK_SIZE(ADDR) \
@ -44,6 +47,17 @@ typedef u8 kprobe_opcode_t;
#define flush_insn_slot(p) do { } while (0)
/* optinsn template addresses */
extern kprobe_opcode_t optprobe_template_entry;
extern kprobe_opcode_t optprobe_template_val;
extern kprobe_opcode_t optprobe_template_call;
extern kprobe_opcode_t optprobe_template_end;
#define MAX_OPTIMIZED_LENGTH (MAX_INSN_SIZE + RELATIVE_ADDR_SIZE)
#define MAX_OPTINSN_SIZE \
(((unsigned long)&optprobe_template_end - \
(unsigned long)&optprobe_template_entry) + \
MAX_OPTIMIZED_LENGTH + RELATIVEJUMP_SIZE)
extern const int kretprobe_blacklist_size;
void arch_remove_kprobe(struct kprobe *p);
@ -64,6 +78,21 @@ struct arch_specific_insn {
int boostable;
};
struct arch_optimized_insn {
/* copy of the original instructions */
kprobe_opcode_t copied_insn[RELATIVE_ADDR_SIZE];
/* detour code buffer */
kprobe_opcode_t *insn;
/* the size of instructions copied to detour code buffer */
size_t size;
};
/* Return true (!0) if optinsn is prepared for optimization. */
static inline int arch_prepared_optinsn(struct arch_optimized_insn *optinsn)
{
return optinsn->size;
}
struct prev_kprobe {
struct kprobe *kp;
unsigned long status;