diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h')
| -rw-r--r-- | sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h | 32 |
1 files changed, 26 insertions, 6 deletions
diff --git a/sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h b/sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h index ba54de4eb0..31dd15ecc4 100644 --- a/sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h +++ b/sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h @@ -41,12 +41,32 @@ extern void *__vdso_sigtramp32; extern void *__vdso_sigtramp_rt32; #endif -/* 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)) +#if (defined(__PPC64__) || defined(__powerpc64__)) && _CALL_ELF != 2 +/* 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. */ +#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 |