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livepatch: Use the default ftrace_ops instead of REGS when ARGS is available

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When CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS is available, the ftrace call
will be able to set the ip of the calling function. This will improve the
performance of live kernel patching where it does not need all the regs to
be stored just to change the instruction pointer.

If all archs that support live kernel patching also support
HAVE_DYNAMIC_FTRACE_WITH_ARGS, then the architecture specific function
klp_arch_set_pc() could be made generic.

It is possible that an arch can support HAVE_DYNAMIC_FTRACE_WITH_ARGS but
not HAVE_DYNAMIC_FTRACE_WITH_REGS and then have access to live patching.

Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: live-patching@vger.kernel.org
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2020-10-28 17:15:27 -04:00
parent 02a474ca26
commit 2860cd8a23
8 changed files with 29 additions and 9 deletions
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2
kernel/livepatch/Kconfig
View file

@ -6,7 +6,7 @@ config HAVE_LIVEPATCH
config LIVEPATCH
bool "Kernel Live Patching"
depends on DYNAMIC_FTRACE_WITH_REGS
depends on DYNAMIC_FTRACE_WITH_REGS || DYNAMIC_FTRACE_WITH_ARGS
depends on MODULES
depends on SYSFS
depends on KALLSYMS_ALL

9
kernel/livepatch/patch.c
View file

@ -42,7 +42,6 @@ static void notrace klp_ftrace_handler(unsigned long ip,
struct ftrace_ops *fops,
struct ftrace_regs *fregs)
{
struct pt_regs *regs = ftrace_get_regs(fregs);
struct klp_ops *ops;
struct klp_func *func;
int patch_state;
@ -118,7 +117,7 @@ static void notrace klp_ftrace_handler(unsigned long ip,
if (func->nop)
goto unlock;
klp_arch_set_pc(regs, (unsigned long)func->new_func);
klp_arch_set_pc(fregs, (unsigned long)func->new_func);
unlock:
preempt_enable_notrace();
@ -200,8 +199,10 @@ static int klp_patch_func(struct klp_func *func)
return -ENOMEM;
ops->fops.func = klp_ftrace_handler;
ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
FTRACE_OPS_FL_DYNAMIC |
ops->fops.flags = FTRACE_OPS_FL_DYNAMIC |
#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
FTRACE_OPS_FL_SAVE_REGS |
#endif
FTRACE_OPS_FL_IPMODIFY |
FTRACE_OPS_FL_PERMANENT;