| Message ID | 20221028143346.183569-3-sv@linux.ibm.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | objtool: Enable and implement --mcount option on powerpc | expand |
Le 28/10/2022 à 16:33, Sathvika Vasireddy a écrit : > In a subsequent patch, we would want to annotate powerpc assembly functions > with SYM_FUNC_START_LOCAL macro. This macro depends on __ALIGN macro. > > The default expansion of __ALIGN macro is: > #define __ALIGN .align 4,0x90 > > So, override __ALIGN and __ALIGN_STR macros to use the same alignment as > that of the existing _GLOBAL macro. Also, do not pad with 0x90, because > repeated 0x90s are not a nop or trap on powerpc. By the way, do we know what the instruction 0x90909090 is on powerpc ? Is that something valid or not ? > > Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> > Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> > Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu> > Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> > Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com> > --- > arch/powerpc/include/asm/linkage.h | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/powerpc/include/asm/linkage.h b/arch/powerpc/include/asm/linkage.h > index b71b9582e754..b88d1d2cf304 100644 > --- a/arch/powerpc/include/asm/linkage.h > +++ b/arch/powerpc/include/asm/linkage.h > @@ -4,6 +4,9 @@ > > #include <asm/types.h> > > +#define __ALIGN .align 2 > +#define __ALIGN_STR ".align 2" > + > #ifdef CONFIG_PPC64_ELF_ABI_V1 > #define cond_syscall(x) \ > asm ("\t.weak " #x "\n\t.set " #x ", sys_ni_syscall\n" \
Christophe Leroy <christophe.leroy@csgroup.eu> writes: > Le 28/10/2022 à 16:33, Sathvika Vasireddy a écrit : >> In a subsequent patch, we would want to annotate powerpc assembly functions >> with SYM_FUNC_START_LOCAL macro. This macro depends on __ALIGN macro. >> >> The default expansion of __ALIGN macro is: >> #define __ALIGN .align 4,0x90 >> >> So, override __ALIGN and __ALIGN_STR macros to use the same alignment as >> that of the existing _GLOBAL macro. Also, do not pad with 0x90, because >> repeated 0x90s are not a nop or trap on powerpc. > > By the way, do we know what the instruction 0x90909090 is on powerpc ? > Is that something valid or not ? According to objdump it's: stw r4,-28528(r16) cheers
On Wed, Nov 02, 2022 at 12:35:07PM +0000, Christophe Leroy wrote: > > > Le 28/10/2022 à 16:33, Sathvika Vasireddy a écrit : > > In a subsequent patch, we would want to annotate powerpc assembly functions > > with SYM_FUNC_START_LOCAL macro. This macro depends on __ALIGN macro. > > > > The default expansion of __ALIGN macro is: > > #define __ALIGN .align 4,0x90 > > > > So, override __ALIGN and __ALIGN_STR macros to use the same alignment as > > that of the existing _GLOBAL macro. Also, do not pad with 0x90, because > > repeated 0x90s are not a nop or trap on powerpc. > > By the way, do we know what the instruction 0x90909090 is on powerpc ? > Is that something valid or not ? Please also look at the version that's in tip/x86/core (and next). This stuff should be gone now. include/linux/linkage.h now reads like: #ifndef __ALIGN #define __ALIGN .balign CONFIG_FUNCTION_ALIGNMENT #define __ALIGN_STR __stringify(__ALIGN) #endif
Hi Peter, On 03/11/22 14:18, Peter Zijlstra wrote: > On Wed, Nov 02, 2022 at 12:35:07PM +0000, Christophe Leroy wrote: >> >> Le 28/10/2022 à 16:33, Sathvika Vasireddy a écrit : >>> In a subsequent patch, we would want to annotate powerpc assembly functions >>> with SYM_FUNC_START_LOCAL macro. This macro depends on __ALIGN macro. >>> >>> The default expansion of __ALIGN macro is: >>> #define __ALIGN .align 4,0x90 >>> >>> So, override __ALIGN and __ALIGN_STR macros to use the same alignment as >>> that of the existing _GLOBAL macro. Also, do not pad with 0x90, because >>> repeated 0x90s are not a nop or trap on powerpc. >> By the way, do we know what the instruction 0x90909090 is on powerpc ? >> Is that something valid or not ? > Please also look at the version that's in tip/x86/core (and next). This > stuff should be gone now. > > include/linux/linkage.h now reads like: > > #ifndef __ALIGN > #define __ALIGN .balign CONFIG_FUNCTION_ALIGNMENT > #define __ALIGN_STR __stringify(__ALIGN) > #endif Since the above mentioned changes are not a part of powerpc/merge branch yet, I am retaining this patch for this merge cycle and will post a cleanup patch (to move to using FUNCTION_ALIGNMENT_4B) after the next -rc1. Thanks, Sathvika
diff --git a/arch/powerpc/include/asm/linkage.h b/arch/powerpc/include/asm/linkage.h index b71b9582e754..b88d1d2cf304 100644 --- a/arch/powerpc/include/asm/linkage.h +++ b/arch/powerpc/include/asm/linkage.h @@ -4,6 +4,9 @@ #include <asm/types.h> +#define __ALIGN .align 2 +#define __ALIGN_STR ".align 2" + #ifdef CONFIG_PPC64_ELF_ABI_V1 #define cond_syscall(x) \ asm ("\t.weak " #x "\n\t.set " #x ", sys_ni_syscall\n" \
In a subsequent patch, we would want to annotate powerpc assembly functions with SYM_FUNC_START_LOCAL macro. This macro depends on __ALIGN macro. The default expansion of __ALIGN macro is: #define __ALIGN .align 4,0x90 So, override __ALIGN and __ALIGN_STR macros to use the same alignment as that of the existing _GLOBAL macro. Also, do not pad with 0x90, because repeated 0x90s are not a nop or trap on powerpc. Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com> --- arch/powerpc/include/asm/linkage.h | 3 +++ 1 file changed, 3 insertions(+)