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160 lines
6.1 KiB
Diff
160 lines
6.1 KiB
Diff
# commit 122b66defdb9e4ded3ccc5c2b290f0520c6fa3cd
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# Author: Ulrich Weigand <Ulrich.Weigand@de.ibm.com>
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# Date: Wed Dec 4 06:52:40 2013 -0600
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#
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# PowerPC64 ELFv2 ABI 3/6: PLT local entry point optimization
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#
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# This is a follow-on to the previous patch to support the ELFv2 ABI in the
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# dynamic loader, split off into its own patch since it is just an optional
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# optimization.
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#
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# In the ELFv2 ABI, most functions define both a global and a local entry
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# point; the local entry requires r2 to be already set up by the caller
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# to point to the callee's TOC; while the global entry does not require
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# the caller to know about the callee's TOC, but it needs to set up r12
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# to the callee's entry point address.
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#
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# Now, when setting up a PLT slot, the dynamic linker will usually need
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# to enter the target function's global entry point. However, if the
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# linker can prove that the target function is in the same DSO as the
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# PLT slot itself, and the whole DSO only uses a single TOC (which the
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# linker will let ld.so know via a DT_PPC64_OPT entry), then it is
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# possible to actually enter the local entry point address into the
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# PLT slot, for a slight improvement in performance.
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#
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# Note that this uncovered a problem on the first call via _dl_runtime_resolve,
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# because that routine neglected to restore the caller's TOC before calling
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# the target function for the first time, since it assumed that function
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# would always reload its own TOC anyway ...
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#
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diff -urN glibc-2.17-c758a686/elf/elf.h glibc-2.17-c758a686/elf/elf.h
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--- glibc-2.17-c758a686/elf/elf.h 2014-05-29 14:08:44.000000000 -0500
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+++ glibc-2.17-c758a686/elf/elf.h 2014-05-29 14:08:44.000000000 -0500
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@@ -2273,8 +2273,19 @@
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#define DT_PPC64_GLINK (DT_LOPROC + 0)
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#define DT_PPC64_OPD (DT_LOPROC + 1)
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#define DT_PPC64_OPDSZ (DT_LOPROC + 2)
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+#define DT_PPC64_OPT (DT_LOPROC + 3)
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#define DT_PPC64_NUM 3
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+/* PowerPC64 specific values for the DT_PPC64_OPT Dyn entry. */
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+#define PPC64_OPT_TLS 1
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+#define PPC64_OPT_MULTI_TOC 2
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+
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+/* PowerPC64 specific values for the Elf64_Sym st_other field. */
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+#define STO_PPC64_LOCAL_BIT 5
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+#define STO_PPC64_LOCAL_MASK (7 << STO_PPC64_LOCAL_BIT)
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+#define PPC64_LOCAL_ENTRY_OFFSET(other) \
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+ (((1 << (((other) & STO_PPC64_LOCAL_MASK) >> STO_PPC64_LOCAL_BIT)) >> 2) << 2)
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+
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/* ARM specific declarations */
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diff -urN glibc-2.17-c758a686/sysdeps/powerpc/powerpc64/dl-machine.h glibc-2.17-c758a686/sysdeps/powerpc/powerpc64/dl-machine.h
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--- glibc-2.17-c758a686/sysdeps/powerpc/powerpc64/dl-machine.h 2014-05-29 14:08:40.000000000 -0500
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+++ glibc-2.17-c758a686/sysdeps/powerpc/powerpc64/dl-machine.h 2014-05-29 14:08:44.000000000 -0500
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@@ -425,6 +425,42 @@
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return lazy;
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}
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+#if _CALL_ELF == 2
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+/* If the PLT entry whose reloc is 'reloc' resolves to a function in
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+ the same object, return the target function's local entry point
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+ offset if usable. */
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+static inline Elf64_Addr __attribute__ ((always_inline))
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+ppc64_local_entry_offset (struct link_map *map, lookup_t sym_map,
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+ const Elf64_Rela *reloc)
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+{
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+ const Elf64_Sym *symtab;
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+ const Elf64_Sym *sym;
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+
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+ /* If the target function is in a different object, we cannot
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+ use the local entry point. */
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+ if (sym_map != map)
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+ return 0;
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+
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+ /* If the linker inserted multiple TOCs, we cannot use the
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+ local entry point. */
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+ if (map->l_info[DT_PPC64(OPT)]
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+ && (map->l_info[DT_PPC64(OPT)]->d_un.d_val & PPC64_OPT_MULTI_TOC))
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+ return 0;
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+
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+ /* Otherwise, we can use the local entry point. Retrieve its offset
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+ from the symbol's ELF st_other field. */
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+ symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
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+ sym = &symtab[ELFW(R_SYM) (reloc->r_info)];
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+
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+ /* If the target function is an ifunc then the local entry offset is
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+ for the resolver, not the final destination. */
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+ if (__builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC, 0))
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+ return 0;
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+
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+ return PPC64_LOCAL_ENTRY_OFFSET (sym->st_other);
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+}
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+#endif
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+
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/* Change the PLT entry whose reloc is 'reloc' to call the actual
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routine. */
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static inline Elf64_Addr __attribute__ ((always_inline))
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@@ -471,6 +507,7 @@
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PPC_DCBST (&plt->fd_func);
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PPC_ISYNC;
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#else
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+ finaladdr += ppc64_local_entry_offset (map, sym_map, reloc);
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*reloc_addr = finaladdr;
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#endif
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@@ -478,7 +515,9 @@
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}
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static inline void __attribute__ ((always_inline))
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-elf_machine_plt_conflict (Elf64_Addr *reloc_addr, Elf64_Addr finaladdr)
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+elf_machine_plt_conflict (struct link_map *map, lookup_t sym_map,
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+ const Elf64_Rela *reloc,
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+ Elf64_Addr *reloc_addr, Elf64_Addr finaladdr)
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{
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#if _CALL_ELF != 2
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Elf64_FuncDesc *plt = (Elf64_FuncDesc *) reloc_addr;
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@@ -492,6 +531,7 @@
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PPC_DCBST (&plt->fd_toc);
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PPC_SYNC;
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#else
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+ finaladdr += ppc64_local_entry_offset (map, sym_map, reloc);
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*reloc_addr = finaladdr;
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#endif
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}
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@@ -641,7 +681,7 @@
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/* Fall thru */
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case R_PPC64_JMP_SLOT:
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#ifdef RESOLVE_CONFLICT_FIND_MAP
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- elf_machine_plt_conflict (reloc_addr, value);
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+ elf_machine_plt_conflict (map, sym_map, reloc, reloc_addr, value);
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#else
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elf_machine_fixup_plt (map, sym_map, reloc, reloc_addr, value);
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#endif
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diff -urN glibc-2.17-c758a686/sysdeps/powerpc/powerpc64/dl-trampoline.S glibc-2.17-c758a686/sysdeps/powerpc/powerpc64/dl-trampoline.S
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--- glibc-2.17-c758a686/sysdeps/powerpc/powerpc64/dl-trampoline.S 2014-05-29 14:08:40.000000000 -0500
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+++ glibc-2.17-c758a686/sysdeps/powerpc/powerpc64/dl-trampoline.S 2014-05-29 14:08:44.000000000 -0500
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@@ -74,6 +74,10 @@
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/* Prepare for calling the function returned by fixup. */
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PPC64_LOAD_FUNCPTR r3
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ld r3,INT_PARMS+0(r1)
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+#if _CALL_ELF == 2
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+/* Restore the caller's TOC in case we jump to a local entry point. */
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+ ld r2,FRAME_SIZE+40(r1)
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+#endif
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/* Unwind the stack frame, and jump. */
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addi r1,r1,FRAME_SIZE
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bctr
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@@ -321,6 +325,10 @@
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/* Prepare for calling the function returned by fixup. */
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PPC64_LOAD_FUNCPTR r3
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ld r3,INT_PARMS+0(r1)
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+#if _CALL_ELF == 2
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+/* Restore the caller's TOC in case we jump to a local entry point. */
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+ ld r2,FRAME_SIZE+40(r1)
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+#endif
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/* Load the floating point registers. */
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lfd fp1,FPR_PARMS+0(r1)
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lfd fp2,FPR_PARMS+8(r1)
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