Le 14/02/2022 à 16:25, Naveen N. Rao a écrit :
> Christophe Leroy wrote:
>> Implement CONFIG_DYNAMIC_FTRACE_WITH_ARGS. It accelerates the call
>> of livepatching.
>>
>> Also note that powerpc being the last one to convert to
>> CONFIG_DYNAMIC_FTRACE_WITH_ARGS, it will now be possible to remove
>> klp_arch_set_pc() on all architectures.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
>> ---
>> arch/powerpc/Kconfig | 1 +
>> arch/powerpc/include/asm/ftrace.h | 17 +++++++++++++++++
>> arch/powerpc/include/asm/livepatch.h | 4 +---
>> 3 files changed, 19 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index cdac2115eb00..e2b1792b2aae 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -210,6 +210,7 @@ config PPC
>> select HAVE_DEBUG_KMEMLEAK
>> select HAVE_DEBUG_STACKOVERFLOW
>> select HAVE_DYNAMIC_FTRACE
>> + select HAVE_DYNAMIC_FTRACE_WITH_ARGS if MPROFILE_KERNEL || PPC32
>> select HAVE_DYNAMIC_FTRACE_WITH_REGS if MPROFILE_KERNEL || PPC32
>> select HAVE_EBPF_JIT
>> select HAVE_EFFICIENT_UNALIGNED_ACCESS if !(CPU_LITTLE_ENDIAN
>> && POWER7_CPU)
>> diff --git a/arch/powerpc/include/asm/ftrace.h
>> b/arch/powerpc/include/asm/ftrace.h
>> index b3f6184f77ea..45c3d6f11daa 100644
>> --- a/arch/powerpc/include/asm/ftrace.h
>> +++ b/arch/powerpc/include/asm/ftrace.h
>> @@ -22,6 +22,23 @@ static inline unsigned long
>> ftrace_call_adjust(unsigned long addr)
>> struct dyn_arch_ftrace {
>> struct module *mod;
>> };
>> +
>> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
>> +struct ftrace_regs {
>> + struct pt_regs regs;
>> +};
>> +
>> +static __always_inline struct pt_regs *arch_ftrace_get_regs(struct
>> ftrace_regs *fregs)
>> +{
>> + return &fregs->regs;
>> +}
>
> I think this is wrong. We need to differentiate between ftrace_caller()
> and ftrace_regs_caller() here, and only return pt_regs if coming in
> through ftrace_regs_caller() (i.e., FL_SAVE_REGS is set).
Not sure I follow you.
This is based on 5740a7c71ab6 ("s390/ftrace: add
HAVE_DYNAMIC_FTRACE_WITH_ARGS support")
It's all the point of HAVE_DYNAMIC_FTRACE_WITH_ARGS, have the regs also
with ftrace_caller().
Sure you only have the params, but that's the same on s390, so what did
I miss ?
>
>> +
>> +static __always_inline void ftrace_instruction_pointer_set(struct
>> ftrace_regs *fregs,
>> + unsigned long ip)
>> +{
>> + regs_set_return_ip(&fregs->regs, ip);
>
> Should we use that helper here? regs_set_return_ip() also updates some
> other state related to taking interrupts and I don't think it makes
> sense for use with ftrace.
>
Today we have:
static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned
long ip)
{
struct pt_regs *regs = ftrace_get_regs(fregs);
regs_set_return_ip(regs, ip);
}
Which like x86 and s390 becomes:
static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned
long ip)
{
ftrace_instruction_pointer_set(fregs, ip);
}
That's the reason why I've been using regs_set_return_ip(). Do you think
it was wrong to use regs_set_return_ip() in klp_arch_set_pc() ?
That was added by 59dc5bfca0cb ("powerpc/64s: avoid reloading (H)SRR
registers if they are still valid")
Christophe
