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