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#
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# commit 76a9b9986141b1a7d9fd290c349d27fcee780c7a
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# Author: Adhemerval Zanella <azanella@linux.vnet.ibm.com>
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# Date: Thu Nov 7 05:34:22 2013 -0600
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#
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# PowerPC: Fix vDSO missing ODP entries
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#
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# This patch fixes the vDSO symbol used directed in IFUNC resolver where
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# they do not have an associated ODP entry leading to undefined behavior
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# in some cases. It adds an artificial OPD static entry to such cases
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# and set its TOC to non 0 to avoid triggering lazy resolutions.
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#
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diff -urN glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h
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--- glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h 2015-01-15 16:05:08.853681325 -0500
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+++ glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h 2015-01-15 16:06:11.451747716 -0500
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@@ -34,12 +34,32 @@
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extern void *__vdso_time;
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-/* This macro is needed for PPC64 to return a skeleton OPD entry of a vDSO
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- symbol. This works because _dl_vdso_vsym always return the function
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- address, and no vDSO symbols use the TOC or chain pointers from the OPD
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- so we can allow them to be garbage. */
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-#if defined(__PPC64__) || defined(__powerpc64__)
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-#define VDSO_IFUNC_RET(value) ((void *) &(value))
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+/* The correct solution is for _dl_vdso_vsym to return the address of the OPD
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+ for the kernel VDSO function. That address would then be stored in the
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+ __vdso_* variables and returned as the result of the IFUNC resolver function.
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+ Yet, the kernel does not contain any OPD entries for the VDSO functions
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+ (incomplete implementation). However, PLT relocations for IFUNCs still expect
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+ the address of an OPD to be returned from the IFUNC resolver function (since
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+ PLT entries on PPC64 are just copies of OPDs). The solution for now is to
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+ create an artificial static OPD for each VDSO function returned by a resolver
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+ function. The TOC value is set to a non-zero value to avoid triggering lazy
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+ symbol resolution via .glink0/.plt0 for a zero TOC (requires thread-safe PLT
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+ sequences) when the dynamic linker isn't prepared for it e.g. RTLD_NOW. None
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+ of the kernel VDSO routines use the TOC or AUX values so any non-zero value
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+ will work. Note that function pointer comparisons will not use this artificial
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+ static OPD since those are resolved via ADDR64 relocations and will point at
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+ the non-IFUNC default OPD for the symbol. Lastly, because the IFUNC relocations
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+ are processed immediately at startup the resolver functions and this code need
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+ not be thread-safe, but if the caller writes to a PLT slot it must do so in a
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+ thread-safe manner with all the required barriers. */
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+#if (defined(__PPC64__) || defined(__powerpc64__)) && _CALL_ELF != 2
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+#define VDSO_IFUNC_RET(value) \
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+ ({ \
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+ static Elf64_FuncDesc vdso_opd = { .fd_toc = ~0x0 }; \
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+ vdso_opd.fd_func = (Elf64_Addr)value; \
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+ &vdso_opd; \
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+ })
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+
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#else
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#define VDSO_IFUNC_RET(value) ((void *) (value))
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#endif
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diff -urN glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/gettimeofday.c glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/gettimeofday.c
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--- glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/gettimeofday.c 2015-01-15 16:05:08.912679502 -0500
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+++ glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/gettimeofday.c 2015-01-15 16:06:11.451747716 -0500
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@@ -21,6 +21,7 @@
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# include <dl-vdso.h>
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# include <bits/libc-vdso.h>
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+# include <dl-machine.h>
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void *gettimeofday_ifunc (void) __asm__ ("__gettimeofday");
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diff -urN glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/time.c glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/time.c
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--- glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/time.c 2015-01-15 16:05:08.912679502 -0500
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+++ glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/time.c 2015-01-15 16:06:11.451747716 -0500
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@@ -20,7 +20,9 @@
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# include <time.h>
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# include <sysdep.h>
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+# include <dl-vdso.h>
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# include <bits/libc-vdso.h>
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+# include <dl-machine.h>
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void *time_ifunc (void) asm ("time");
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