powerpc64: Implement TLS using PC-relative addressing
Commit Message
As the TOC pointer becomes optional on POWER, TLS access has to be
modified in order to use PC-relative addressing instead of depending on
the TOC pointer availability.
This patch also changes old TLS code to use the new syntax. It's a
purely aesthetical change: the old code still works and the new syntax
helps to move the argument setup instruction away from the call, which
is not used in an inline assembly.
Suggested-by: Alan Modra <amodra@gmail.com>
---
sysdeps/powerpc/mod-tlsopt-powerpc.c | 7 ++++
sysdeps/powerpc/powerpc64/tls-macros.h | 54 ++++++++++++++++++++++----
2 files changed, 53 insertions(+), 8 deletions(-)
Comments
* Tulio Magno Quites Machado Filho via Libc-alpha:
> diff --git a/sysdeps/powerpc/mod-tlsopt-powerpc.c b/sysdeps/powerpc/mod-tlsopt-powerpc.c
> index ee0db12a73..5856dab60b 100644
> --- a/sysdeps/powerpc/mod-tlsopt-powerpc.c
> +++ b/sysdeps/powerpc/mod-tlsopt-powerpc.c
> @@ -24,7 +24,14 @@ tls_get_addr_opt_test (void)
> tls_index *tls_arg;
> #ifdef __powerpc64__
> register unsigned long thread_pointer __asm__ ("r13");
> + /* PC-relative addressing is available when compiling with -mpcrel.
> + The first releases of GCC 10 do support -mpcrel, but do not export
> + __PCREL__. */
> +# if defined(__PCREL__) || __GNUC__ <= 10 && defined(_ARCH_PWR10)
> + asm ("pla %0,foo@got@tlsgd@pcrel" : "=r" (tls_arg));
> +# else
> asm ("addi %0,2,foo@got@tlsgd" : "=r" (tls_arg));
> +# endif
Should this check for binutils support for @pcrel? Or won't GCC enable
_ARCH_PWR10 in this case?
Thanks,
Florian
On Sep 30 2020, Tulio Magno Quites Machado Filho via Libc-alpha wrote:
> diff --git a/sysdeps/powerpc/mod-tlsopt-powerpc.c b/sysdeps/powerpc/mod-tlsopt-powerpc.c
> index ee0db12a73..5856dab60b 100644
> --- a/sysdeps/powerpc/mod-tlsopt-powerpc.c
> +++ b/sysdeps/powerpc/mod-tlsopt-powerpc.c
> @@ -24,7 +24,14 @@ tls_get_addr_opt_test (void)
> tls_index *tls_arg;
> #ifdef __powerpc64__
> register unsigned long thread_pointer __asm__ ("r13");
> + /* PC-relative addressing is available when compiling with -mpcrel.
> + The first releases of GCC 10 do support -mpcrel, but do not export
> + __PCREL__. */
> +# if defined(__PCREL__) || __GNUC__ <= 10 && defined(_ARCH_PWR10)
Space after defined, and remove the parens.
Andreas.
On Thu, Oct 01, 2020 at 10:49:43AM +0200, Florian Weimer wrote:
> * Tulio Magno Quites Machado Filho via Libc-alpha:
>
> > diff --git a/sysdeps/powerpc/mod-tlsopt-powerpc.c b/sysdeps/powerpc/mod-tlsopt-powerpc.c
> > index ee0db12a73..5856dab60b 100644
> > --- a/sysdeps/powerpc/mod-tlsopt-powerpc.c
> > +++ b/sysdeps/powerpc/mod-tlsopt-powerpc.c
> > @@ -24,7 +24,14 @@ tls_get_addr_opt_test (void)
> > tls_index *tls_arg;
> > #ifdef __powerpc64__
> > register unsigned long thread_pointer __asm__ ("r13");
> > + /* PC-relative addressing is available when compiling with -mpcrel.
> > + The first releases of GCC 10 do support -mpcrel, but do not export
> > + __PCREL__. */
> > +# if defined(__PCREL__) || __GNUC__ <= 10 && defined(_ARCH_PWR10)
> > + asm ("pla %0,foo@got@tlsgd@pcrel" : "=r" (tls_arg));
> > +# else
> > asm ("addi %0,2,foo@got@tlsgd" : "=r" (tls_arg));
> > +# endif
>
> Should this check for binutils support for @pcrel? Or won't GCC enable
> _ARCH_PWR10 in this case?
Right, gcc doesn't support power10 without the requisite binutils
support. In any case, this file is only used when running the
testsuite so it hardly seems worth the bother of configure checks.
The patch looks good to me.
@@ -24,7 +24,14 @@ tls_get_addr_opt_test (void)
tls_index *tls_arg;
#ifdef __powerpc64__
register unsigned long thread_pointer __asm__ ("r13");
+ /* PC-relative addressing is available when compiling with -mpcrel.
+ The first releases of GCC 10 do support -mpcrel, but do not export
+ __PCREL__. */
+# if defined(__PCREL__) || __GNUC__ <= 10 && defined(_ARCH_PWR10)
+ asm ("pla %0,foo@got@tlsgd@pcrel" : "=r" (tls_arg));
+# else
asm ("addi %0,2,foo@got@tlsgd" : "=r" (tls_arg));
+# endif
#else
register unsigned long thread_pointer __asm__ ("r2");
asm ("bcl 20,31,1f\n1:\t"
@@ -9,20 +9,56 @@
: "=b" (__result) ); \
__result; \
})
-/* PowerPC64 Initial Exec TLS access. */
-#define TLS_IE(x) \
+
+/* PC-relative addressing is available when compiling with -mpcrel.
+ The first releases of GCC 10 do support -mpcrel, but do not export
+ __PCREL__. */
+#if defined(__PCREL__) || __GNUC__ <= 10 && defined(_ARCH_PWR10)
+/* PowerPC64 Initial Exec TLS access, PC-relative addressing. */
+# define TLS_IE(x) \
({ int * __result; \
- asm ("ld %0," #x "@got@tprel(2)\n\t" \
- "add %0,%0," #x "@tls" \
+ asm ("pld %0," #x "@got@tprel@pcrel\n\t" \
+ "add %0,%0," #x "@tls@pcrel" \
: "=r" (__result) ); \
__result; \
})
+/* PowerPC64 Local Dynamic TLS access, PC-relative addressing. */
+# define TLS_LD(x) \
+ ({ int * __result; \
+ asm ("pla 3, " #x "@got@tlsld@pcrel\n\t" \
+ "bl __tls_get_addr@notoc(" #x "@tlsld)\n\t" \
+ "addis %0,3," #x "@dtprel@ha\n\t" \
+ "addi %0,%0," #x "@dtprel@l" \
+ : "=b" (__result) : \
+ : "3", __TLS_CALL_CLOBBERS); \
+ __result; \
+ })
+
+/* PowerPC64 General Dynamic TLS access, PC-relative addressing. */
+# define TLS_GD(x) \
+ ({ register int *__result __asm__ ("r3"); \
+ asm ("pla 3," #x "@got@tlsgd@pcrel\n\t" \
+ "bl __tls_get_addr@notoc(" #x "@tlsgd)" \
+ : "=r" (__result) : \
+ : __TLS_CALL_CLOBBERS); \
+ __result; \
+ })
+#else
+/* PowerPC64 Initial Exec TLS access. */
+# define TLS_IE(x) \
+ ({ int * __result; \
+ asm ("ld %0," #x "@got@tprel(2)\n\t" \
+ "add %0,%0," #x "@tls" \
+ : "=r" (__result) ); \
+ __result; \
+ })
+
/* PowerPC64 Local Dynamic TLS access. */
-#define TLS_LD(x) \
+# define TLS_LD(x) \
({ int * __result; \
asm ("addi 3,2," #x "@got@tlsld\n\t" \
- "bl __tls_get_addr\n\t" \
+ "bl __tls_get_addr(" #x "@tlsld)\n\t" \
"nop \n\t" \
"addis %0,3," #x "@dtprel@ha\n\t" \
"addi %0,%0," #x "@dtprel@l" \
@@ -30,13 +66,15 @@
: "3", __TLS_CALL_CLOBBERS); \
__result; \
})
+
/* PowerPC64 General Dynamic TLS access. */
-#define TLS_GD(x) \
+# define TLS_GD(x) \
({ register int *__result __asm__ ("r3"); \
asm ("addi 3,2," #x "@got@tlsgd\n\t" \
- "bl __tls_get_addr\n\t" \
+ "bl __tls_get_addr(" #x "@tlsgd)\n\t" \
"nop " \
: "=r" (__result) : \
: __TLS_CALL_CLOBBERS); \
__result; \
})
+#endif