126 lines
4.7 KiB
Diff
126 lines
4.7 KiB
Diff
From: Alan Modra <amodra@gmail.com>
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Date: Fri, 15 Jan 2016 20:52:22 +1100
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Subject: powerpc: Simplify module TOC handling
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Origin: https://git.kernel.org/linus/c153693d7eb9eeb28478aa2deaaf0b4e7b5ff5e9
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PowerPC64 uses the symbol .TOC. much as other targets use
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_GLOBAL_OFFSET_TABLE_. It identifies the value of the GOT pointer (or in
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powerpc parlance, the TOC pointer). Global offset tables are generally
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local to an executable or shared library, or in the kernel, module. Thus
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it does not make sense for a module to resolve a relocation against
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.TOC. to the kernel's .TOC. value. A module has its own .TOC., and
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indeed the powerpc64 module relocation processing ignores the kernel
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value of .TOC. and instead calculates a module-local value.
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This patch removes code involved in exporting the kernel .TOC., tweaks
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modpost to ignore an undefined .TOC., and the module loader to twiddle
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the section symbol so that .TOC. isn't seen as undefined.
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Note that if the kernel was compiled with -msingle-pic-base then ELFv2
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would not have function global entry code setting up r2. In that case
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the module call stubs would need to be modified to set up r2 using the
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kernel .TOC. value, requiring some of this code to be reinstated.
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mpe: Furthermore a change in binutils master (not yet released) causes
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the current way we handle the TOC to no longer work when building with
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MODVERSIONS=y and RELOCATABLE=n. The symptom is that modules can not be
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loaded due to there being no version found for TOC.
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Cc: stable@vger.kernel.org # 3.16+
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Signed-off-by: Alan Modra <amodra@gmail.com>
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Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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---
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arch/powerpc/kernel/misc_64.S | 28 ----------------------------
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arch/powerpc/kernel/module_64.c | 12 +++++++++---
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scripts/mod/modpost.c | 3 ++-
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3 files changed, 11 insertions(+), 32 deletions(-)
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diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
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index db475d41b57a..f28754c497e5 100644
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--- a/arch/powerpc/kernel/misc_64.S
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+++ b/arch/powerpc/kernel/misc_64.S
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@@ -701,31 +701,3 @@ _GLOBAL(kexec_sequence)
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li r5,0
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blr /* image->start(physid, image->start, 0); */
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#endif /* CONFIG_KEXEC */
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-
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-#ifdef CONFIG_MODULES
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-#if defined(_CALL_ELF) && _CALL_ELF == 2
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-
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-#ifdef CONFIG_MODVERSIONS
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-.weak __crc_TOC.
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-.section "___kcrctab+TOC.","a"
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-.globl __kcrctab_TOC.
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-__kcrctab_TOC.:
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- .llong __crc_TOC.
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-#endif
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-
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-/*
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- * Export a fake .TOC. since both modpost and depmod will complain otherwise.
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- * Both modpost and depmod strip the leading . so we do the same here.
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- */
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-.section "__ksymtab_strings","a"
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-__kstrtab_TOC.:
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- .asciz "TOC."
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-
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-.section "___ksymtab+TOC.","a"
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-/* This symbol name is important: it's used by modpost to find exported syms */
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-.globl __ksymtab_TOC.
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-__ksymtab_TOC.:
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- .llong 0 /* .value */
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- .llong __kstrtab_TOC.
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-#endif /* ELFv2 */
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-#endif /* MODULES */
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diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
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index 59663af9315f..ac64ffdb52c8 100644
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--- a/arch/powerpc/kernel/module_64.c
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+++ b/arch/powerpc/kernel/module_64.c
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@@ -326,7 +326,10 @@ static void dedotify_versions(struct modversion_info *vers,
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}
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}
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-/* Undefined symbols which refer to .funcname, hack to funcname (or .TOC.) */
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+/*
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+ * Undefined symbols which refer to .funcname, hack to funcname. Make .TOC.
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+ * seem to be defined (value set later).
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+ */
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static void dedotify(Elf64_Sym *syms, unsigned int numsyms, char *strtab)
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{
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unsigned int i;
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@@ -334,8 +337,11 @@ static void dedotify(Elf64_Sym *syms, unsigned int numsyms, char *strtab)
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for (i = 1; i < numsyms; i++) {
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if (syms[i].st_shndx == SHN_UNDEF) {
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char *name = strtab + syms[i].st_name;
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- if (name[0] == '.')
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+ if (name[0] == '.') {
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+ if (strcmp(name+1, "TOC.") == 0)
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+ syms[i].st_shndx = SHN_ABS;
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memmove(name, name+1, strlen(name));
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+ }
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}
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}
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}
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@@ -351,7 +357,7 @@ static Elf64_Sym *find_dot_toc(Elf64_Shdr *sechdrs,
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numsyms = sechdrs[symindex].sh_size / sizeof(Elf64_Sym);
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for (i = 1; i < numsyms; i++) {
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- if (syms[i].st_shndx == SHN_UNDEF
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+ if (syms[i].st_shndx == SHN_ABS
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&& strcmp(strtab + syms[i].st_name, "TOC.") == 0)
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return &syms[i];
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}
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diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
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index e080746e1a6b..48958d3cec9e 100644
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--- a/scripts/mod/modpost.c
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+++ b/scripts/mod/modpost.c
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@@ -594,7 +594,8 @@ static int ignore_undef_symbol(struct elf_info *info, const char *symname)
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if (strncmp(symname, "_restgpr0_", sizeof("_restgpr0_") - 1) == 0 ||
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strncmp(symname, "_savegpr0_", sizeof("_savegpr0_") - 1) == 0 ||
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strncmp(symname, "_restvr_", sizeof("_restvr_") - 1) == 0 ||
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- strncmp(symname, "_savevr_", sizeof("_savevr_") - 1) == 0)
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+ strncmp(symname, "_savevr_", sizeof("_savevr_") - 1) == 0 ||
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+ strcmp(symname, ".TOC.") == 0)
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return 1;
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/* Do not ignore this symbol */
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return 0;
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