Re: sched_setaffinity usability

[Ingo Molnar]

* Ingo Molnar <mingo@xxxxxxx> wrote:

> x86-64 has a VDSO page as well, [...]

hm, i'm not sure this is the case. It does have a vsyscall page but
doesnt fill out AT_SYSINFO. ia64 seems to have something like a vdso,
passed down via AT_SYSINFO.

We could introduce AT_VDSO to standardize this, and switch x86 from
AT_SYSINFO to AT_VDSO, and all architectures that implement the VDSO. 
I.e. something like the draft patch below. (this would also decrease the
size of the auxiliary table - glibc doesnt need to know the exception
header address.).

(this could also put an end to the AT_ bloat - eg. we could even get rid
of some of the constant AT_ values in the future: AT_PAGESZ, AT_CLKTCK,
AT_HWCAP, AT_PHENT and AT_FLAGS, and move them into the VDSO?)

	Ingo

--- linux/include/linux/elf.h.orig
+++ linux/include/linux/elf.h
@@ -162,6 +162,7 @@ typedef __s64	Elf64_Sxword;
 #define AT_PLATFORM 15  /* string identifying CPU for optimizations */
 #define AT_HWCAP  16    /* arch dependent hints at CPU capabilities */
 #define AT_CLKTCK 17	/* frequency at which times() increments */
+#define AT_VDSO   18	/* VDSO address */
 
 #define AT_SECURE 23   /* secure mode boolean */
 
--- linux/include/asm-i386/elf.h.orig
+++ linux/include/asm-i386/elf.h
@@ -132,10 +132,9 @@ extern int dump_task_extended_fpu (struc
 #define VSYSCALL_ENTRY	((unsigned long) &__kernel_vsyscall)
 extern void __kernel_vsyscall;
 
-#define ARCH_DLINFO						\
-do {								\
-		NEW_AUX_ENT(AT_SYSINFO,	VSYSCALL_ENTRY);	\
-		NEW_AUX_ENT(AT_SYSINFO_EHDR, VSYSCALL_BASE);	\
+#define ARCH_DLINFO					\
+do {							\
+	NEW_AUX_ENT(AT_VDSO, VSYSCALL_BASE);		\
 } while (0)
 
 /*
-
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