Re: [PATCH v3 2/2] ARM: ftrace: Add MODULE_PLTS support

[Ard Biesheuvel]

On 9 March 2018 at 08:54, Alexander Sverdlin
 wrote:
> Hello Ard!
>
> On 09/03/18 09:50, Ard Biesheuvel wrote:
>>> +static u32 fixed_plts[] = {
>>> +   FTRACE_ADDR,
>>> +   MCOUNT_ADDR,
>>> +#ifdef CONFIG_OLD_MCOUNT
>>> +   (unsigned long)ftrace_caller_old,
>>> +   (unsigned long)mcount,
>>> +#endif
>>> +};
>>> +
>> Do we need this stuff in the PLT loader if ftrace is disabled?
>
> You are right, it probably would not even build w/o FTRACE.
> I'll fix it, thanks for looking into this!
>

Also, perhaps you can make the array const (after you put #ifdef's
around all entries)

>>>  static bool in_init(const struct module *mod, unsigned long loc)
>>>  {
>>> return loc - (u32)mod->init_layout.base < mod->init_layout.size;
>>> @@ -31,26 +41,43 @@ u32 get_module_plt(struct module *mod, unsigned long 
>>> loc, Elf32_Addr val)
>>>  {
>>> struct mod_plt_sec *pltsec = !in_init(mod, loc) ? >arch.core :
>>>   >arch.init;
>>> +   int idx;
>>> +   struct plt_entries *plt;
>>> +
>>> +   /* Pre-allocate entries in the first plt */
>>> +   if (!pltsec->plt_count) {
>>> +   plt = (struct plt_entries *)pltsec->plt->sh_addr;
>>> +   for (idx = 0; idx < ARRAY_SIZE(plt->ldr); ++idx)
>>> +   plt->ldr[idx] = PLT_ENT_LDR;
>>> +   memcpy(plt->lit, fixed_plts, sizeof(fixed_plts));
>>> +   pltsec->plt_count = ARRAY_SIZE(fixed_plts);
>>> +   /*
>>> +* cache the address,
>>> +* ELF header is available only during module load
>>> +*/
>>> +   pltsec->plt_ent = plt;
>>> +   }
>>> +   plt = pltsec->plt_ent;
>>>
>>> -   struct plt_entries *plt = (struct plt_entries 
>>> *)pltsec->plt->sh_addr;
>>> -   int idx = 0;
>>> +   idx = ARRAY_SIZE(fixed_plts);
>>> +   while (idx)
>>> +   if (plt->lit[--idx] == val)
>>> +   return (u32)>ldr[idx];
>>>

... and put all this handling in a helper function that only gets
called if ARRAY_SIZE() > 0

AFAICT, that should allow you to leave the rest unchanged.

Re: [PATCH v3 2/2] ARM: ftrace: Add MODULE_PLTS support

[Ard Biesheuvel]

On 9 March 2018 at 08:54, Alexander Sverdlin
 wrote:
> Hello Ard!
>
> On 09/03/18 09:50, Ard Biesheuvel wrote:
>>> +static u32 fixed_plts[] = {
>>> +   FTRACE_ADDR,
>>> +   MCOUNT_ADDR,
>>> +#ifdef CONFIG_OLD_MCOUNT
>>> +   (unsigned long)ftrace_caller_old,
>>> +   (unsigned long)mcount,
>>> +#endif
>>> +};
>>> +
>> Do we need this stuff in the PLT loader if ftrace is disabled?
>
> You are right, it probably would not even build w/o FTRACE.
> I'll fix it, thanks for looking into this!
>

Also, perhaps you can make the array const (after you put #ifdef's
around all entries)

>>>  static bool in_init(const struct module *mod, unsigned long loc)
>>>  {
>>> return loc - (u32)mod->init_layout.base < mod->init_layout.size;
>>> @@ -31,26 +41,43 @@ u32 get_module_plt(struct module *mod, unsigned long 
>>> loc, Elf32_Addr val)
>>>  {
>>> struct mod_plt_sec *pltsec = !in_init(mod, loc) ? >arch.core :
>>>   >arch.init;
>>> +   int idx;
>>> +   struct plt_entries *plt;
>>> +
>>> +   /* Pre-allocate entries in the first plt */
>>> +   if (!pltsec->plt_count) {
>>> +   plt = (struct plt_entries *)pltsec->plt->sh_addr;
>>> +   for (idx = 0; idx < ARRAY_SIZE(plt->ldr); ++idx)
>>> +   plt->ldr[idx] = PLT_ENT_LDR;
>>> +   memcpy(plt->lit, fixed_plts, sizeof(fixed_plts));
>>> +   pltsec->plt_count = ARRAY_SIZE(fixed_plts);
>>> +   /*
>>> +* cache the address,
>>> +* ELF header is available only during module load
>>> +*/
>>> +   pltsec->plt_ent = plt;
>>> +   }
>>> +   plt = pltsec->plt_ent;
>>>
>>> -   struct plt_entries *plt = (struct plt_entries 
>>> *)pltsec->plt->sh_addr;
>>> -   int idx = 0;
>>> +   idx = ARRAY_SIZE(fixed_plts);
>>> +   while (idx)
>>> +   if (plt->lit[--idx] == val)
>>> +   return (u32)>ldr[idx];
>>>

... and put all this handling in a helper function that only gets
called if ARRAY_SIZE() > 0

AFAICT, that should allow you to leave the rest unchanged.

Re: [PATCH v3 2/2] ARM: ftrace: Add MODULE_PLTS support

[Alexander Sverdlin]

Hello Ard!

On 09/03/18 09:50, Ard Biesheuvel wrote:
>> +static u32 fixed_plts[] = {
>> +   FTRACE_ADDR,
>> +   MCOUNT_ADDR,
>> +#ifdef CONFIG_OLD_MCOUNT
>> +   (unsigned long)ftrace_caller_old,
>> +   (unsigned long)mcount,
>> +#endif
>> +};
>> +
> Do we need this stuff in the PLT loader if ftrace is disabled?

You are right, it probably would not even build w/o FTRACE.
I'll fix it, thanks for looking into this!

>>  static bool in_init(const struct module *mod, unsigned long loc)
>>  {
>> return loc - (u32)mod->init_layout.base < mod->init_layout.size;
>> @@ -31,26 +41,43 @@ u32 get_module_plt(struct module *mod, unsigned long 
>> loc, Elf32_Addr val)
>>  {
>> struct mod_plt_sec *pltsec = !in_init(mod, loc) ? >arch.core :
>>   >arch.init;
>> +   int idx;
>> +   struct plt_entries *plt;
>> +
>> +   /* Pre-allocate entries in the first plt */
>> +   if (!pltsec->plt_count) {
>> +   plt = (struct plt_entries *)pltsec->plt->sh_addr;
>> +   for (idx = 0; idx < ARRAY_SIZE(plt->ldr); ++idx)
>> +   plt->ldr[idx] = PLT_ENT_LDR;
>> +   memcpy(plt->lit, fixed_plts, sizeof(fixed_plts));
>> +   pltsec->plt_count = ARRAY_SIZE(fixed_plts);
>> +   /*
>> +* cache the address,
>> +* ELF header is available only during module load
>> +*/
>> +   pltsec->plt_ent = plt;
>> +   }
>> +   plt = pltsec->plt_ent;
>>
>> -   struct plt_entries *plt = (struct plt_entries *)pltsec->plt->sh_addr;
>> -   int idx = 0;
>> +   idx = ARRAY_SIZE(fixed_plts);
>> +   while (idx)
>> +   if (plt->lit[--idx] == val)
>> +   return (u32)>ldr[idx];
>>
> Same here.

-- 
Best regards,
Alexander Sverdlin.

Re: [PATCH v3 2/2] ARM: ftrace: Add MODULE_PLTS support

[Alexander Sverdlin]

Hello Ard!

On 09/03/18 09:50, Ard Biesheuvel wrote:
>> +static u32 fixed_plts[] = {
>> +   FTRACE_ADDR,
>> +   MCOUNT_ADDR,
>> +#ifdef CONFIG_OLD_MCOUNT
>> +   (unsigned long)ftrace_caller_old,
>> +   (unsigned long)mcount,
>> +#endif
>> +};
>> +
> Do we need this stuff in the PLT loader if ftrace is disabled?

You are right, it probably would not even build w/o FTRACE.
I'll fix it, thanks for looking into this!

>>  static bool in_init(const struct module *mod, unsigned long loc)
>>  {
>> return loc - (u32)mod->init_layout.base < mod->init_layout.size;
>> @@ -31,26 +41,43 @@ u32 get_module_plt(struct module *mod, unsigned long 
>> loc, Elf32_Addr val)
>>  {
>> struct mod_plt_sec *pltsec = !in_init(mod, loc) ? >arch.core :
>>   >arch.init;
>> +   int idx;
>> +   struct plt_entries *plt;
>> +
>> +   /* Pre-allocate entries in the first plt */
>> +   if (!pltsec->plt_count) {
>> +   plt = (struct plt_entries *)pltsec->plt->sh_addr;
>> +   for (idx = 0; idx < ARRAY_SIZE(plt->ldr); ++idx)
>> +   plt->ldr[idx] = PLT_ENT_LDR;
>> +   memcpy(plt->lit, fixed_plts, sizeof(fixed_plts));
>> +   pltsec->plt_count = ARRAY_SIZE(fixed_plts);
>> +   /*
>> +* cache the address,
>> +* ELF header is available only during module load
>> +*/
>> +   pltsec->plt_ent = plt;
>> +   }
>> +   plt = pltsec->plt_ent;
>>
>> -   struct plt_entries *plt = (struct plt_entries *)pltsec->plt->sh_addr;
>> -   int idx = 0;
>> +   idx = ARRAY_SIZE(fixed_plts);
>> +   while (idx)
>> +   if (plt->lit[--idx] == val)
>> +   return (u32)>ldr[idx];
>>
> Same here.

-- 
Best regards,
Alexander Sverdlin.

Re: [PATCH v3 2/2] ARM: ftrace: Add MODULE_PLTS support

[Ard Biesheuvel]

Hi Alexander,

On 9 March 2018 at 08:41, Alexander Sverdlin
 wrote:
> Teach ftrace_make_call() and ftrace_make_nop() about PLTs.
> Teach PLT code about FTRACE and all its callbacks.
> Otherwise the following might happen:
>
> [ cut here ]
> WARNING: CPU: 14 PID: 2265 at .../arch/arm/kernel/insn.c:14 
> __arm_gen_branch+0x83/0x8c()
> ...
> Hardware name: LSI Axxia AXM55XX
> [] (unwind_backtrace) from [] (show_stack+0x11/0x14)
> [] (show_stack) from [] (dump_stack+0x81/0xa8)
> [] (dump_stack) from [] (warn_slowpath_common+0x69/0x90)
> [] (warn_slowpath_common) from [] 
> (warn_slowpath_null+0x17/0x1c)
> [] (warn_slowpath_null) from [] 
> (__arm_gen_branch+0x83/0x8c)
> [] (__arm_gen_branch) from [] (ftrace_make_nop+0xf/0x24)
> [] (ftrace_make_nop) from [] 
> (ftrace_process_locs+0x27b/0x3e8)
> [] (ftrace_process_locs) from [] 
> (load_module+0x11e9/0x1a44)
> [] (load_module) from [] (SyS_finit_module+0x59/0x84)
> [] (SyS_finit_module) from [] (ret_fast_syscall+0x1/0x18)
> ---[ end trace e1b64ced7a89adcc ]---
> [ cut here ]
> WARNING: CPU: 14 PID: 2265 at .../kernel/trace/ftrace.c:1979 
> ftrace_bug+0x1b1/0x234()
> ...
> Hardware name: LSI Axxia AXM55XX
> [] (unwind_backtrace) from [] (show_stack+0x11/0x14)
> [] (show_stack) from [] (dump_stack+0x81/0xa8)
> [] (dump_stack) from [] (warn_slowpath_common+0x69/0x90)
> [] (warn_slowpath_common) from [] 
> (warn_slowpath_null+0x17/0x1c)
> [] (warn_slowpath_null) from [] (ftrace_bug+0x1b1/0x234)
> [] (ftrace_bug) from [] (ftrace_process_locs+0x285/0x3e8)
> [] (ftrace_process_locs) from [] 
> (load_module+0x11e9/0x1a44)
> [] (load_module) from [] (SyS_finit_module+0x59/0x84)
> [] (SyS_finit_module) from [] (ret_fast_syscall+0x1/0x18)
> ---[ end trace e1b64ced7a89adcd ]---
> ftrace failed to modify [] 0xe9ef7006
> actual: 02:f0:3b:fa
> ftrace record flags: 0
> (0) expected tramp: c0314265
>
> Signed-off-by: Alexander Sverdlin 
> ---
>  arch/arm/include/asm/ftrace.h |  3 +++
>  arch/arm/include/asm/module.h |  1 +
>  arch/arm/kernel/ftrace.c  | 62 
> ---
>  arch/arm/kernel/module-plts.c | 53 +++-
>  4 files changed, 97 insertions(+), 22 deletions(-)
>
> diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
> index 9e842ff..faeb6b1 100644
> --- a/arch/arm/include/asm/ftrace.h
> +++ b/arch/arm/include/asm/ftrace.h
> @@ -19,6 +19,9 @@ struct dyn_arch_ftrace {
>  #ifdef CONFIG_OLD_MCOUNT
> boolold_mcount;
>  #endif
> +#ifdef CONFIG_ARM_MODULE_PLTS
> +   struct module *mod;
> +#endif
>  };
>
>  static inline unsigned long ftrace_call_adjust(unsigned long addr)
> diff --git a/arch/arm/include/asm/module.h b/arch/arm/include/asm/module.h
> index 6996405..e3d7a51 100644
> --- a/arch/arm/include/asm/module.h
> +++ b/arch/arm/include/asm/module.h
> @@ -30,6 +30,7 @@ struct plt_entries {
>
>  struct mod_plt_sec {
> struct elf32_shdr   *plt;
> +   struct plt_entries  *plt_ent;
> int plt_count;
>  };
>
> diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
> index 5617932..b55355f 100644
> --- a/arch/arm/kernel/ftrace.c
> +++ b/arch/arm/kernel/ftrace.c
> @@ -98,6 +98,19 @@ int ftrace_arch_code_modify_post_process(void)
>
>  static unsigned long ftrace_call_replace(unsigned long pc, unsigned long 
> addr)
>  {
> +   s32 offset = addr - pc;
> +   s32 blim = 0xfe08;
> +   s32 flim = 0x0204;
> +
> +   if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
> +   blim = 0xff04;
> +   flim = 0x0102;
> +   }
> +
> +   if (IS_ENABLED(CONFIG_ARM_MODULE_PLTS) &&
> +   (offset < blim || offset > flim))
> +   return 0;
> +
> return arm_gen_branch_link(pc, addr);
>  }
>
> @@ -166,10 +179,22 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned 
> long addr)
>  {
> unsigned long new, old;
> unsigned long ip = rec->ip;
> +   unsigned long aaddr = adjust_address(rec, addr);
>
> old = ftrace_nop_replace(rec);
>
> -   new = ftrace_call_replace(ip, adjust_address(rec, addr));
> +   new = ftrace_call_replace(ip, aaddr);
> +
> +#ifdef CONFIG_ARM_MODULE_PLTS
> +   if (!new) {
> +   struct module *mod = rec->arch.mod;
> +
> +   if (mod) {
> +   aaddr = get_module_plt(mod, ip, aaddr);
> +   new = ftrace_call_replace(ip, aaddr);
> +   }
> +   }
> +#endif
>
> return ftrace_modify_code(rec->ip, old, new, true);
>  }
> @@ -199,20 +224,39 @@ int ftrace_make_nop(struct module *mod,
> unsigned long new;
> int ret;
>
> -   old = ftrace_call_replace(ip, adjust_address(rec, addr));
> -   new = ftrace_nop_replace(rec);
> -   ret = ftrace_modify_code(ip, old, new, true);
> +#ifdef CONFIG_ARM_MODULE_PLTS
> +

Re: [PATCH v3 2/2] ARM: ftrace: Add MODULE_PLTS support

[Ard Biesheuvel]

Hi Alexander,

On 9 March 2018 at 08:41, Alexander Sverdlin
 wrote:
> Teach ftrace_make_call() and ftrace_make_nop() about PLTs.
> Teach PLT code about FTRACE and all its callbacks.
> Otherwise the following might happen:
>
> [ cut here ]
> WARNING: CPU: 14 PID: 2265 at .../arch/arm/kernel/insn.c:14 
> __arm_gen_branch+0x83/0x8c()
> ...
> Hardware name: LSI Axxia AXM55XX
> [] (unwind_backtrace) from [] (show_stack+0x11/0x14)
> [] (show_stack) from [] (dump_stack+0x81/0xa8)
> [] (dump_stack) from [] (warn_slowpath_common+0x69/0x90)
> [] (warn_slowpath_common) from [] 
> (warn_slowpath_null+0x17/0x1c)
> [] (warn_slowpath_null) from [] 
> (__arm_gen_branch+0x83/0x8c)
> [] (__arm_gen_branch) from [] (ftrace_make_nop+0xf/0x24)
> [] (ftrace_make_nop) from [] 
> (ftrace_process_locs+0x27b/0x3e8)
> [] (ftrace_process_locs) from [] 
> (load_module+0x11e9/0x1a44)
> [] (load_module) from [] (SyS_finit_module+0x59/0x84)
> [] (SyS_finit_module) from [] (ret_fast_syscall+0x1/0x18)
> ---[ end trace e1b64ced7a89adcc ]---
> [ cut here ]
> WARNING: CPU: 14 PID: 2265 at .../kernel/trace/ftrace.c:1979 
> ftrace_bug+0x1b1/0x234()
> ...
> Hardware name: LSI Axxia AXM55XX
> [] (unwind_backtrace) from [] (show_stack+0x11/0x14)
> [] (show_stack) from [] (dump_stack+0x81/0xa8)
> [] (dump_stack) from [] (warn_slowpath_common+0x69/0x90)
> [] (warn_slowpath_common) from [] 
> (warn_slowpath_null+0x17/0x1c)
> [] (warn_slowpath_null) from [] (ftrace_bug+0x1b1/0x234)
> [] (ftrace_bug) from [] (ftrace_process_locs+0x285/0x3e8)
> [] (ftrace_process_locs) from [] 
> (load_module+0x11e9/0x1a44)
> [] (load_module) from [] (SyS_finit_module+0x59/0x84)
> [] (SyS_finit_module) from [] (ret_fast_syscall+0x1/0x18)
> ---[ end trace e1b64ced7a89adcd ]---
> ftrace failed to modify [] 0xe9ef7006
> actual: 02:f0:3b:fa
> ftrace record flags: 0
> (0) expected tramp: c0314265
>
> Signed-off-by: Alexander Sverdlin 
> ---
>  arch/arm/include/asm/ftrace.h |  3 +++
>  arch/arm/include/asm/module.h |  1 +
>  arch/arm/kernel/ftrace.c  | 62 
> ---
>  arch/arm/kernel/module-plts.c | 53 +++-
>  4 files changed, 97 insertions(+), 22 deletions(-)
>
> diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
> index 9e842ff..faeb6b1 100644
> --- a/arch/arm/include/asm/ftrace.h
> +++ b/arch/arm/include/asm/ftrace.h
> @@ -19,6 +19,9 @@ struct dyn_arch_ftrace {
>  #ifdef CONFIG_OLD_MCOUNT
> boolold_mcount;
>  #endif
> +#ifdef CONFIG_ARM_MODULE_PLTS
> +   struct module *mod;
> +#endif
>  };
>
>  static inline unsigned long ftrace_call_adjust(unsigned long addr)
> diff --git a/arch/arm/include/asm/module.h b/arch/arm/include/asm/module.h
> index 6996405..e3d7a51 100644
> --- a/arch/arm/include/asm/module.h
> +++ b/arch/arm/include/asm/module.h
> @@ -30,6 +30,7 @@ struct plt_entries {
>
>  struct mod_plt_sec {
> struct elf32_shdr   *plt;
> +   struct plt_entries  *plt_ent;
> int plt_count;
>  };
>
> diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
> index 5617932..b55355f 100644
> --- a/arch/arm/kernel/ftrace.c
> +++ b/arch/arm/kernel/ftrace.c
> @@ -98,6 +98,19 @@ int ftrace_arch_code_modify_post_process(void)
>
>  static unsigned long ftrace_call_replace(unsigned long pc, unsigned long 
> addr)
>  {
> +   s32 offset = addr - pc;
> +   s32 blim = 0xfe08;
> +   s32 flim = 0x0204;
> +
> +   if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
> +   blim = 0xff04;
> +   flim = 0x0102;
> +   }
> +
> +   if (IS_ENABLED(CONFIG_ARM_MODULE_PLTS) &&
> +   (offset < blim || offset > flim))
> +   return 0;
> +
> return arm_gen_branch_link(pc, addr);
>  }
>
> @@ -166,10 +179,22 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned 
> long addr)
>  {
> unsigned long new, old;
> unsigned long ip = rec->ip;
> +   unsigned long aaddr = adjust_address(rec, addr);
>
> old = ftrace_nop_replace(rec);
>
> -   new = ftrace_call_replace(ip, adjust_address(rec, addr));
> +   new = ftrace_call_replace(ip, aaddr);
> +
> +#ifdef CONFIG_ARM_MODULE_PLTS
> +   if (!new) {
> +   struct module *mod = rec->arch.mod;
> +
> +   if (mod) {
> +   aaddr = get_module_plt(mod, ip, aaddr);
> +   new = ftrace_call_replace(ip, aaddr);
> +   }
> +   }
> +#endif
>
> return ftrace_modify_code(rec->ip, old, new, true);
>  }
> @@ -199,20 +224,39 @@ int ftrace_make_nop(struct module *mod,
> unsigned long new;
> int ret;
>
> -   old = ftrace_call_replace(ip, adjust_address(rec, addr));
> -   new = ftrace_nop_replace(rec);
> -   ret = ftrace_modify_code(ip, old, new, true);
> +#ifdef CONFIG_ARM_MODULE_PLTS
> +   /* mod is only supplied during module loading */
> + 

[PATCH v3 2/2] ARM: ftrace: Add MODULE_PLTS support

[Alexander Sverdlin]

Teach ftrace_make_call() and ftrace_make_nop() about PLTs.
Teach PLT code about FTRACE and all its callbacks.
Otherwise the following might happen:

[ cut here ]
WARNING: CPU: 14 PID: 2265 at .../arch/arm/kernel/insn.c:14 
__arm_gen_branch+0x83/0x8c()
...
Hardware name: LSI Axxia AXM55XX
[] (unwind_backtrace) from [] (show_stack+0x11/0x14)
[] (show_stack) from [] (dump_stack+0x81/0xa8)
[] (dump_stack) from [] (warn_slowpath_common+0x69/0x90)
[] (warn_slowpath_common) from [] 
(warn_slowpath_null+0x17/0x1c)
[] (warn_slowpath_null) from [] (__arm_gen_branch+0x83/0x8c)
[] (__arm_gen_branch) from [] (ftrace_make_nop+0xf/0x24)
[] (ftrace_make_nop) from [] 
(ftrace_process_locs+0x27b/0x3e8)
[] (ftrace_process_locs) from [] (load_module+0x11e9/0x1a44)
[] (load_module) from [] (SyS_finit_module+0x59/0x84)
[] (SyS_finit_module) from [] (ret_fast_syscall+0x1/0x18)
---[ end trace e1b64ced7a89adcc ]---
[ cut here ]
WARNING: CPU: 14 PID: 2265 at .../kernel/trace/ftrace.c:1979 
ftrace_bug+0x1b1/0x234()
...
Hardware name: LSI Axxia AXM55XX
[] (unwind_backtrace) from [] (show_stack+0x11/0x14)
[] (show_stack) from [] (dump_stack+0x81/0xa8)
[] (dump_stack) from [] (warn_slowpath_common+0x69/0x90)
[] (warn_slowpath_common) from [] 
(warn_slowpath_null+0x17/0x1c)
[] (warn_slowpath_null) from [] (ftrace_bug+0x1b1/0x234)
[] (ftrace_bug) from [] (ftrace_process_locs+0x285/0x3e8)
[] (ftrace_process_locs) from [] (load_module+0x11e9/0x1a44)
[] (load_module) from [] (SyS_finit_module+0x59/0x84)
[] (SyS_finit_module) from [] (ret_fast_syscall+0x1/0x18)
---[ end trace e1b64ced7a89adcd ]---
ftrace failed to modify [] 0xe9ef7006
actual: 02:f0:3b:fa
ftrace record flags: 0
(0) expected tramp: c0314265

Signed-off-by: Alexander Sverdlin 
---
 arch/arm/include/asm/ftrace.h |  3 +++
 arch/arm/include/asm/module.h |  1 +
 arch/arm/kernel/ftrace.c  | 62 ---
 arch/arm/kernel/module-plts.c | 53 +++-
 4 files changed, 97 insertions(+), 22 deletions(-)

diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
index 9e842ff..faeb6b1 100644
--- a/arch/arm/include/asm/ftrace.h
+++ b/arch/arm/include/asm/ftrace.h
@@ -19,6 +19,9 @@ struct dyn_arch_ftrace {
 #ifdef CONFIG_OLD_MCOUNT
boolold_mcount;
 #endif
+#ifdef CONFIG_ARM_MODULE_PLTS
+   struct module *mod;
+#endif
 };
 
 static inline unsigned long ftrace_call_adjust(unsigned long addr)
diff --git a/arch/arm/include/asm/module.h b/arch/arm/include/asm/module.h
index 6996405..e3d7a51 100644
--- a/arch/arm/include/asm/module.h
+++ b/arch/arm/include/asm/module.h
@@ -30,6 +30,7 @@ struct plt_entries {
 
 struct mod_plt_sec {
struct elf32_shdr   *plt;
+   struct plt_entries  *plt_ent;
int plt_count;
 };
 
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index 5617932..b55355f 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -98,6 +98,19 @@ int ftrace_arch_code_modify_post_process(void)
 
 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
 {
+   s32 offset = addr - pc;
+   s32 blim = 0xfe08;
+   s32 flim = 0x0204;
+
+   if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
+   blim = 0xff04;
+   flim = 0x0102;
+   }
+
+   if (IS_ENABLED(CONFIG_ARM_MODULE_PLTS) &&
+   (offset < blim || offset > flim))
+   return 0;
+
return arm_gen_branch_link(pc, addr);
 }
 
@@ -166,10 +179,22 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned 
long addr)
 {
unsigned long new, old;
unsigned long ip = rec->ip;
+   unsigned long aaddr = adjust_address(rec, addr);
 
old = ftrace_nop_replace(rec);
 
-   new = ftrace_call_replace(ip, adjust_address(rec, addr));
+   new = ftrace_call_replace(ip, aaddr);
+
+#ifdef CONFIG_ARM_MODULE_PLTS
+   if (!new) {
+   struct module *mod = rec->arch.mod;
+
+   if (mod) {
+   aaddr = get_module_plt(mod, ip, aaddr);
+   new = ftrace_call_replace(ip, aaddr);
+   }
+   }
+#endif
 
return ftrace_modify_code(rec->ip, old, new, true);
 }
@@ -199,20 +224,39 @@ int ftrace_make_nop(struct module *mod,
unsigned long new;
int ret;
 
-   old = ftrace_call_replace(ip, adjust_address(rec, addr));
-   new = ftrace_nop_replace(rec);
-   ret = ftrace_modify_code(ip, old, new, true);
+#ifdef CONFIG_ARM_MODULE_PLTS
+   /* mod is only supplied during module loading */
+   if (!mod)
+   mod = rec->arch.mod;
+   else
+   rec->arch.mod = mod;
+#endif
 
-#ifdef CONFIG_OLD_MCOUNT
-   if (ret == -EINVAL && addr == MCOUNT_ADDR) {
-   rec->arch.old_mcount = true;
+   for (;;) {
+   unsigned long aaddr = 

[PATCH v3 2/2] ARM: ftrace: Add MODULE_PLTS support

[Alexander Sverdlin]

Teach ftrace_make_call() and ftrace_make_nop() about PLTs.
Teach PLT code about FTRACE and all its callbacks.
Otherwise the following might happen:

[ cut here ]
WARNING: CPU: 14 PID: 2265 at .../arch/arm/kernel/insn.c:14 
__arm_gen_branch+0x83/0x8c()
...
Hardware name: LSI Axxia AXM55XX
[] (unwind_backtrace) from [] (show_stack+0x11/0x14)
[] (show_stack) from [] (dump_stack+0x81/0xa8)
[] (dump_stack) from [] (warn_slowpath_common+0x69/0x90)
[] (warn_slowpath_common) from [] 
(warn_slowpath_null+0x17/0x1c)
[] (warn_slowpath_null) from [] (__arm_gen_branch+0x83/0x8c)
[] (__arm_gen_branch) from [] (ftrace_make_nop+0xf/0x24)
[] (ftrace_make_nop) from [] 
(ftrace_process_locs+0x27b/0x3e8)
[] (ftrace_process_locs) from [] (load_module+0x11e9/0x1a44)
[] (load_module) from [] (SyS_finit_module+0x59/0x84)
[] (SyS_finit_module) from [] (ret_fast_syscall+0x1/0x18)
---[ end trace e1b64ced7a89adcc ]---
[ cut here ]
WARNING: CPU: 14 PID: 2265 at .../kernel/trace/ftrace.c:1979 
ftrace_bug+0x1b1/0x234()
...
Hardware name: LSI Axxia AXM55XX
[] (unwind_backtrace) from [] (show_stack+0x11/0x14)
[] (show_stack) from [] (dump_stack+0x81/0xa8)
[] (dump_stack) from [] (warn_slowpath_common+0x69/0x90)
[] (warn_slowpath_common) from [] 
(warn_slowpath_null+0x17/0x1c)
[] (warn_slowpath_null) from [] (ftrace_bug+0x1b1/0x234)
[] (ftrace_bug) from [] (ftrace_process_locs+0x285/0x3e8)
[] (ftrace_process_locs) from [] (load_module+0x11e9/0x1a44)
[] (load_module) from [] (SyS_finit_module+0x59/0x84)
[] (SyS_finit_module) from [] (ret_fast_syscall+0x1/0x18)
---[ end trace e1b64ced7a89adcd ]---
ftrace failed to modify [] 0xe9ef7006
actual: 02:f0:3b:fa
ftrace record flags: 0
(0) expected tramp: c0314265

Signed-off-by: Alexander Sverdlin 
---
 arch/arm/include/asm/ftrace.h |  3 +++
 arch/arm/include/asm/module.h |  1 +
 arch/arm/kernel/ftrace.c  | 62 ---
 arch/arm/kernel/module-plts.c | 53 +++-
 4 files changed, 97 insertions(+), 22 deletions(-)

diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
index 9e842ff..faeb6b1 100644
--- a/arch/arm/include/asm/ftrace.h
+++ b/arch/arm/include/asm/ftrace.h
@@ -19,6 +19,9 @@ struct dyn_arch_ftrace {
 #ifdef CONFIG_OLD_MCOUNT
boolold_mcount;
 #endif
+#ifdef CONFIG_ARM_MODULE_PLTS
+   struct module *mod;
+#endif
 };
 
 static inline unsigned long ftrace_call_adjust(unsigned long addr)
diff --git a/arch/arm/include/asm/module.h b/arch/arm/include/asm/module.h
index 6996405..e3d7a51 100644
--- a/arch/arm/include/asm/module.h
+++ b/arch/arm/include/asm/module.h
@@ -30,6 +30,7 @@ struct plt_entries {
 
 struct mod_plt_sec {
struct elf32_shdr   *plt;
+   struct plt_entries  *plt_ent;
int plt_count;
 };
 
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index 5617932..b55355f 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -98,6 +98,19 @@ int ftrace_arch_code_modify_post_process(void)
 
 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
 {
+   s32 offset = addr - pc;
+   s32 blim = 0xfe08;
+   s32 flim = 0x0204;
+
+   if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
+   blim = 0xff04;
+   flim = 0x0102;
+   }
+
+   if (IS_ENABLED(CONFIG_ARM_MODULE_PLTS) &&
+   (offset < blim || offset > flim))
+   return 0;
+
return arm_gen_branch_link(pc, addr);
 }
 
@@ -166,10 +179,22 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned 
long addr)
 {
unsigned long new, old;
unsigned long ip = rec->ip;
+   unsigned long aaddr = adjust_address(rec, addr);
 
old = ftrace_nop_replace(rec);
 
-   new = ftrace_call_replace(ip, adjust_address(rec, addr));
+   new = ftrace_call_replace(ip, aaddr);
+
+#ifdef CONFIG_ARM_MODULE_PLTS
+   if (!new) {
+   struct module *mod = rec->arch.mod;
+
+   if (mod) {
+   aaddr = get_module_plt(mod, ip, aaddr);
+   new = ftrace_call_replace(ip, aaddr);
+   }
+   }
+#endif
 
return ftrace_modify_code(rec->ip, old, new, true);
 }
@@ -199,20 +224,39 @@ int ftrace_make_nop(struct module *mod,
unsigned long new;
int ret;
 
-   old = ftrace_call_replace(ip, adjust_address(rec, addr));
-   new = ftrace_nop_replace(rec);
-   ret = ftrace_modify_code(ip, old, new, true);
+#ifdef CONFIG_ARM_MODULE_PLTS
+   /* mod is only supplied during module loading */
+   if (!mod)
+   mod = rec->arch.mod;
+   else
+   rec->arch.mod = mod;
+#endif
 
-#ifdef CONFIG_OLD_MCOUNT
-   if (ret == -EINVAL && addr == MCOUNT_ADDR) {
-   rec->arch.old_mcount = true;
+   for (;;) {
+   unsigned long aaddr = adjust_address(rec, addr);
+
+