The commit fd4363fff3d9 (x86: Introduce int3 (breakpoint)-based instruction
patching) uses the same technique that has been used in ftrace since 08d636b
("ftrace/x86: Have arch x86_64 use breakpoints instead of stop machine")
This patch set merge the two implementations and remove duplicities from
the ftrace side.
+ First four patches improve the generic int3-based framework to be usable
with ftrace. All the changes are based on ideas already used in ftrace.
They are needed to keep the functionality and efficiency.
+ The 5th patch speedups the original ftrace code but it is useful also
with the generic functions.
+ The last three patches modifies different parts of the current
x86-specific ftrace implementation and use the generic functions there.
Changes in v4:
+ reverted one change in text_poke in the first patch as suggested by
Masami Hiramatsu; it means to still call BUG_ON() when the error is
unclear
Changes in v3:
+ use the new text_poke_part only in text_poke_bp_list because it
works only with read-write code
+ update all text_poke functions to return error instead on calling BUG()
+ handle text_poke* function return values whenever they were used
Changes in v2:
+ check for number of CPUs instead of enabling IRQs when syncing CPUs;
suggested by Steven Rostedt, Paul E. McKenney, and Masami Hiramatsu
+ return error codes in text_poke_part and text_poke_bp; needed by ftrace
+ reverted changes in text_poke_bp; it patches only single address again
+ introduce text_poke_bp_iter for patching multiple addresses:
+ uses iterator and callbacks instead of copying data
+ checks old code before patching
+ returns error code and more info about error; needed by ftrace
+ provides recovery mechanism in case of errors
+ update ftrace.c to use the new text_poke_bp_iter
+ split notrace __probe_kernel_read into separate patch because it
is useful for original ftrace code as well
+ rebased on current kernel tip and updated performance statistics;
it started to be slower on idle machine after the commit commit
c229828ca6bc62d6c654 (rcu: Throttle rcu_try_advance_all_cbs() execution)
I tried to switch between 7 tracers: blk, branch, function_graph, wakeup_rt,
irqsoff, function, and nop. Every tracer has also been enabled and disabled.
With 500 cycles, I got these times before the change:
real 18m2.477s 18m8.654s 18m9.196s
user 0m0.008s 0m0.008s 0m0.012s
sys 0m17.316s 0m17.104s 0m17.300s
and after
real 17m19.055s 17m29.200s 17m27.456
user 0m0.052s 0m0.056s 0m0.052s
sys 0m20.236s 0m20.068s 0m20.264s
The patches are against kernel/git/tip/tip.git on top of the commit
af7949e870d4632b Merge branch 'tools/kvm perf fixes'
Petr Mladek (8):
x86: allow to handle errors in text_poke function family
x86: allow to call text_poke_bp during boot
x86: add generic function to modify more calls using int3 framework
x86: speed up int3-based patching using direct write
x86: do not trace __probe_kernel_read
x86: modify ftrace function using the new int3-based framework
x86: patch all traced function calls using the int3-based framework
x86: enable/disable ftrace graph call using new int3-based framework
arch/x86/include/asm/alternative.h | 43 ++-
arch/x86/kernel/alternative.c | 369 +++++++++++++++++++++---
arch/x86/kernel/ftrace.c | 571 ++++++++-----------------------------
arch/x86/kernel/jump_label.c | 11 +-
arch/x86/kernel/kgdb.c | 11 +-
arch/x86/kernel/kprobes/core.c | 10 +-
arch/x86/kernel/kprobes/opt.c | 8 +-
arch/x86/kernel/traps.c | 10 -
include/linux/ftrace.h | 6 -
mm/maccess.c | 2 +-
10 files changed, 527 insertions(+), 514 deletions(-)
--
1.8.4
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