In preparation of making func_desc_t generic, change the ELFv2
version to a struct containing 'addr' element.
This allows using single helpers common to ELFv1 and ELFv2.
Signed-off-by: Christophe Leroy <[email protected]>
---
arch/powerpc/kernel/module_64.c | 32 ++++++++++++++------------------
1 file changed, 14 insertions(+), 18 deletions(-)
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index a89da0ee25e2..b687ef88c4c4 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -33,19 +33,13 @@
#ifdef PPC64_ELF_ABI_v2
/* An address is simply the address of the function. */
-typedef unsigned long func_desc_t;
+typedef struct {
+ unsigned long addr;
+} func_desc_t;
static func_desc_t func_desc(unsigned long addr)
{
- return addr;
-}
-static unsigned long func_addr(unsigned long addr)
-{
- return addr;
-}
-static unsigned long stub_func_addr(func_desc_t func)
-{
- return func;
+ return (func_desc_t){addr};
}
/* PowerPC64 specific values for the Elf64_Sym st_other field. */
@@ -70,14 +64,6 @@ static func_desc_t func_desc(unsigned long addr)
{
return *(struct func_desc *)addr;
}
-static unsigned long func_addr(unsigned long addr)
-{
- return func_desc(addr).addr;
-}
-static unsigned long stub_func_addr(func_desc_t func)
-{
- return func.addr;
-}
static unsigned int local_entry_offset(const Elf64_Sym *sym)
{
return 0;
@@ -93,6 +79,16 @@ void *dereference_module_function_descriptor(struct module *mod, void *ptr)
}
#endif
+static unsigned long func_addr(unsigned long addr)
+{
+ return func_desc(addr).addr;
+}
+
+static unsigned long stub_func_addr(func_desc_t func)
+{
+ return func.addr;
+}
+
#define STUB_MAGIC 0x73747562 /* stub */
/* Like PPC32, we need little trampolines to do > 24-bit jumps (into
--
2.31.1
Excerpts from Christophe Leroy's message of October 17, 2021 10:38 pm:
> In preparation of making func_desc_t generic, change the ELFv2
> version to a struct containing 'addr' element.
>
> This allows using single helpers common to ELFv1 and ELFv2.
>
> Signed-off-by: Christophe Leroy <[email protected]>
> ---
> arch/powerpc/kernel/module_64.c | 32 ++++++++++++++------------------
> 1 file changed, 14 insertions(+), 18 deletions(-)
>
> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
> index a89da0ee25e2..b687ef88c4c4 100644
> --- a/arch/powerpc/kernel/module_64.c
> +++ b/arch/powerpc/kernel/module_64.c
> @@ -33,19 +33,13 @@
> #ifdef PPC64_ELF_ABI_v2
>
> /* An address is simply the address of the function. */
> -typedef unsigned long func_desc_t;
> +typedef struct {
> + unsigned long addr;
> +} func_desc_t;
I'm not quite following why this change is done. I guess it is so you
can move this func_desc_t type into core code, but why do that? Is it
just to avoid using the preprocessor?
On its own this patch looks okay.
Acked-by: Nicholas Piggin <[email protected]>
Le 18/10/2021 à 08:27, Nicholas Piggin a écrit :
> Excerpts from Christophe Leroy's message of October 17, 2021 10:38 pm:
>> In preparation of making func_desc_t generic, change the ELFv2
>> version to a struct containing 'addr' element.
>>
>> This allows using single helpers common to ELFv1 and ELFv2.
>>
>> Signed-off-by: Christophe Leroy <[email protected]>
>
>> ---
>> arch/powerpc/kernel/module_64.c | 32 ++++++++++++++------------------
>> 1 file changed, 14 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
>> index a89da0ee25e2..b687ef88c4c4 100644
>> --- a/arch/powerpc/kernel/module_64.c
>> +++ b/arch/powerpc/kernel/module_64.c
>> @@ -33,19 +33,13 @@
>> #ifdef PPC64_ELF_ABI_v2
>>
>> /* An address is simply the address of the function. */
>> -typedef unsigned long func_desc_t;
>> +typedef struct {
>> + unsigned long addr;
>> +} func_desc_t;
>
> I'm not quite following why this change is done. I guess it is so you
> can move this func_desc_t type into core code, but why do that? Is it
> just to avoid using the preprocessor?
I explained it in patch 7 but yes it probably also deserves some more
explanation here as well.
That's right, it's to avoid having to spread #ifdefs everywhere.
>
> On its own this patch looks okay.
>
> Acked-by: Nicholas Piggin <[email protected]>
>
On Sun, Oct 17, 2021 at 02:38:17PM +0200, Christophe Leroy wrote:
> In preparation of making func_desc_t generic, change the ELFv2
> version to a struct containing 'addr' element.
>
> This allows using single helpers common to ELFv1 and ELFv2.
>
> Signed-off-by: Christophe Leroy <[email protected]>
> ---
> arch/powerpc/kernel/module_64.c | 32 ++++++++++++++------------------
> 1 file changed, 14 insertions(+), 18 deletions(-)
>
> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
> index a89da0ee25e2..b687ef88c4c4 100644
> --- a/arch/powerpc/kernel/module_64.c
> +++ b/arch/powerpc/kernel/module_64.c
> @@ -33,19 +33,13 @@
> #ifdef PPC64_ELF_ABI_v2
>
> /* An address is simply the address of the function. */
> -typedef unsigned long func_desc_t;
> +typedef struct {
> + unsigned long addr;
> +} func_desc_t;
>
> static func_desc_t func_desc(unsigned long addr)
> {
> - return addr;
> -}
> -static unsigned long func_addr(unsigned long addr)
> -{
> - return addr;
> -}
> -static unsigned long stub_func_addr(func_desc_t func)
> -{
> - return func;
> + return (func_desc_t){addr};
There's only 1 element in the struct, so okay, but it hurt my eyes a
little. I would have been happier with:
return (func_desc_t){ .addr = addr; };
But of course that also looks bonkers because it starts with "return".
So no matter what I do my eyes bug out. ;)
So it's fine either way. :)
Reviewed-by: Kees Cook <[email protected]>
> }
>
> /* PowerPC64 specific values for the Elf64_Sym st_other field. */
> @@ -70,14 +64,6 @@ static func_desc_t func_desc(unsigned long addr)
> {
> return *(struct func_desc *)addr;
> }
> -static unsigned long func_addr(unsigned long addr)
> -{
> - return func_desc(addr).addr;
> -}
> -static unsigned long stub_func_addr(func_desc_t func)
> -{
> - return func.addr;
> -}
> static unsigned int local_entry_offset(const Elf64_Sym *sym)
> {
> return 0;
> @@ -93,6 +79,16 @@ void *dereference_module_function_descriptor(struct module *mod, void *ptr)
> }
> #endif
>
> +static unsigned long func_addr(unsigned long addr)
> +{
> + return func_desc(addr).addr;
> +}
> +
> +static unsigned long stub_func_addr(func_desc_t func)
> +{
> + return func.addr;
> +}
> +
> #define STUB_MAGIC 0x73747562 /* stub */
>
> /* Like PPC32, we need little trampolines to do > 24-bit jumps (into
> --
> 2.31.1
>
--
Kees Cook
On Thu, Feb 10, 2022 at 04:54:52PM -0800, Kees Cook wrote:
> On Sun, Oct 17, 2021 at 02:38:17PM +0200, Christophe Leroy wrote:
(edited:)
> > +typedef struct {
> > + unsigned long addr;
> > +} func_desc_t;
> >
> > static func_desc_t func_desc(unsigned long addr)
> > {
> > + return (func_desc_t){addr};
> There's only 1 element in the struct, so okay, but it hurt my eyes a
> little. I would have been happier with:
>
> return (func_desc_t){ .addr = addr; };
>
> But of course that also looks bonkers because it starts with "return".
> So no matter what I do my eyes bug out. ;)
The usual way to avoid convoluted constructs is to name more factors.
So:
static func_desc_t func_desc(unsigned long addr)
{
func_desc_t desc = {};
desc.addr = addr;
return desc;
}
Segher
Le 11/02/2022 à 01:54, Kees Cook a écrit :
> On Sun, Oct 17, 2021 at 02:38:17PM +0200, Christophe Leroy wrote:
>> In preparation of making func_desc_t generic, change the ELFv2
>> version to a struct containing 'addr' element.
>>
>> This allows using single helpers common to ELFv1 and ELFv2.
>>
>> Signed-off-by: Christophe Leroy <[email protected]>
>> ---
>> arch/powerpc/kernel/module_64.c | 32 ++++++++++++++------------------
>> 1 file changed, 14 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
>> index a89da0ee25e2..b687ef88c4c4 100644
>> --- a/arch/powerpc/kernel/module_64.c
>> +++ b/arch/powerpc/kernel/module_64.c
>> @@ -33,19 +33,13 @@
>> #ifdef PPC64_ELF_ABI_v2
>>
>> /* An address is simply the address of the function. */
>> -typedef unsigned long func_desc_t;
>> +typedef struct {
>> + unsigned long addr;
>> +} func_desc_t;
>>
>> static func_desc_t func_desc(unsigned long addr)
>> {
>> - return addr;
>> -}
>> -static unsigned long func_addr(unsigned long addr)
>> -{
>> - return addr;
>> -}
>> -static unsigned long stub_func_addr(func_desc_t func)
>> -{
>> - return func;
>> + return (func_desc_t){addr};
>
> There's only 1 element in the struct, so okay, but it hurt my eyes a
> little. I would have been happier with:
>
> return (func_desc_t){ .addr = addr; };
>
> But of course that also looks bonkers because it starts with "return".
> So no matter what I do my eyes bug out. ;)
>
> So it's fine either way. :)
>
> Reviewed-by: Kees Cook <[email protected]>
I am going for:
static func_desc_t func_desc(unsigned long addr)
{
+ func_desc_t desc = {
+ .addr = addr,
+ };
+
+ return desc;
}
Thanks
Christophe