| Message ID | 0576fd5c74440ad0250f16ac6609ecf587812456.1500319216.git.thomas.lendacky@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
* Tom Lendacky <thomas.lendacky@amd.com> wrote: > Create a new function attribute, __nostackp, that can used to turn off > stack protection on a per function basis. > > Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> > --- > include/linux/compiler-gcc.h | 2 ++ > include/linux/compiler.h | 4 ++++ > 2 files changed, 6 insertions(+) > > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h > index cd4bbe8..682063b 100644 > --- a/include/linux/compiler-gcc.h > +++ b/include/linux/compiler-gcc.h > @@ -166,6 +166,8 @@ > > #if GCC_VERSION >= 40100 > # define __compiletime_object_size(obj) __builtin_object_size(obj, 0) > + > +#define __nostackp __attribute__((__optimize__("no-stack-protector"))) > #endif > > #if GCC_VERSION >= 40300 > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index 219f82f..63cbca1 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -470,6 +470,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s > #define __visible > #endif > > +#ifndef __nostackp > +#define __nostackp > +#endif So I changed this from the hard to read and ambiguous "__nostackp" abbreviation (does it mean 'no stack pointer?') to "__nostackprotector", plus added this detail to the changelog: | ( This is needed by the SME in-place kernel memory encryption feature, | which activates encryption in its sme_enable() function and thus changes the | visible value of the stack protection cookie on function return. ) Agreed? Thanks, Ingo
On 7/18/2017 4:36 AM, Ingo Molnar wrote: > > * Tom Lendacky <thomas.lendacky@amd.com> wrote: > >> Create a new function attribute, __nostackp, that can used to turn off >> stack protection on a per function basis. >> >> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> >> --- >> include/linux/compiler-gcc.h | 2 ++ >> include/linux/compiler.h | 4 ++++ >> 2 files changed, 6 insertions(+) >> >> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h >> index cd4bbe8..682063b 100644 >> --- a/include/linux/compiler-gcc.h >> +++ b/include/linux/compiler-gcc.h >> @@ -166,6 +166,8 @@ >> >> #if GCC_VERSION >= 40100 >> # define __compiletime_object_size(obj) __builtin_object_size(obj, 0) >> + >> +#define __nostackp __attribute__((__optimize__("no-stack-protector"))) >> #endif >> >> #if GCC_VERSION >= 40300 >> diff --git a/include/linux/compiler.h b/include/linux/compiler.h >> index 219f82f..63cbca1 100644 >> --- a/include/linux/compiler.h >> +++ b/include/linux/compiler.h >> @@ -470,6 +470,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s >> #define __visible >> #endif >> >> +#ifndef __nostackp >> +#define __nostackp >> +#endif > > So I changed this from the hard to read and ambiguous "__nostackp" abbreviation > (does it mean 'no stack pointer?') to "__nostackprotector", plus added this detail > to the changelog: > > | ( This is needed by the SME in-place kernel memory encryption feature, > | which activates encryption in its sme_enable() function and thus changes the > | visible value of the stack protection cookie on function return. ) > > Agreed? Hi Ingo, I debugged this to needing "__nostackprotector" because sme_enable() is called very early in the boot process before everything is properly setup to fully support stack protection when KASLR is enabled. Without this attribute the call to sme_enable() would fail even if encryption was disabled with the "mem_encrypt=off" command line option. If KASLR wasn't enabled, then everything worked fine without the "__nostackprotector" attribute, encryption enabled or not. The stack protection support is activated because of the 16-byte character buffer in the sme_enable() routine. I think we'll find that if a character buffer greater than 8 bytes is added to, for example, __startup_64, then this attribute will need to be added to that routine. Thanks, Tom > > Thanks, > > Ingo >
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index cd4bbe8..682063b 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -166,6 +166,8 @@ #if GCC_VERSION >= 40100 # define __compiletime_object_size(obj) __builtin_object_size(obj, 0) + +#define __nostackp __attribute__((__optimize__("no-stack-protector"))) #endif #if GCC_VERSION >= 40300 diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 219f82f..63cbca1 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -470,6 +470,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s #define __visible #endif +#ifndef __nostackp +#define __nostackp +#endif + /* * Assume alignment of return value. */
Create a new function attribute, __nostackp, that can used to turn off stack protection on a per function basis. Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> --- include/linux/compiler-gcc.h | 2 ++ include/linux/compiler.h | 4 ++++ 2 files changed, 6 insertions(+)