diff options
| -rw-r--r-- | arch/x86/vdso/Makefile | 18 | ||||
| -rw-r--r-- | arch/x86/vdso/vdso-fakesections.c | 32 | ||||
| -rw-r--r-- | arch/x86/vdso/vdso2c.h | 23 |
3 files changed, 60 insertions, 13 deletions
diff --git a/arch/x86/vdso/Makefile b/arch/x86/vdso/Makefile index 9769df094035..ba6fc2757ee4 100644 --- a/arch/x86/vdso/Makefile +++ b/arch/x86/vdso/Makefile @@ -15,12 +15,8 @@ vdso-install-$(VDSO32-y) += $(vdso32-images) # files to link into the vdso -vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o - -vobjs-$(VDSOX32-y) += $(vobjx32s-compat) - -# Filter out x32 objects. -vobj64s := $(filter-out $(vobjx32s-compat),$(vobjs-y)) +vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o vdso-fakesections.o +vobjs-nox32 := vdso-fakesections.o # files to link into kernel obj-y += vma.o @@ -34,7 +30,7 @@ vdso_img-$(VDSO32-y) += 32-sysenter obj-$(VDSO32-y) += vdso32-setup.o -vobjs := $(foreach F,$(vobj64s),$(obj)/$F) +vobjs := $(foreach F,$(vobjs-y),$(obj)/$F) $(obj)/vdso.o: $(obj)/vdso.so @@ -104,7 +100,13 @@ VDSO_LDFLAGS_vdsox32.lds = -Wl,-m,elf32_x86_64 \ -Wl,-z,max-page-size=4096 \ -Wl,-z,common-page-size=4096 -vobjx32s-y := $(vobj64s:.o=-x32.o) +# 64-bit objects to re-brand as x32 +vobjs64-for-x32 := $(filter-out $(vobjs-nox32),$(vobjs-y)) + +# x32-rebranded versions +vobjx32s-y := $(vobjs64-for-x32:.o=-x32.o) + +# same thing, but in the output directory vobjx32s := $(foreach F,$(vobjx32s-y),$(obj)/$F) # Convert 64bit object file to x32 for x32 vDSO. diff --git a/arch/x86/vdso/vdso-fakesections.c b/arch/x86/vdso/vdso-fakesections.c new file mode 100644 index 000000000000..cb8a8d72c24b --- /dev/null +++ b/arch/x86/vdso/vdso-fakesections.c @@ -0,0 +1,32 @@ +/* + * Copyright 2014 Andy Lutomirski + * Subject to the GNU Public License, v.2 + * + * Hack to keep broken Go programs working. + * + * The Go runtime had a couple of bugs: it would read the section table to try + * to figure out how many dynamic symbols there were (it shouldn't have looked + * at the section table at all) and, if there were no SHT_SYNDYM section table + * entry, it would use an uninitialized value for the number of symbols. As a + * workaround, we supply a minimal section table. vdso2c will adjust the + * in-memory image so that "vdso_fake_sections" becomes the section table. + * + * The bug was introduced by: + * https://code.google.com/p/go/source/detail?r=56ea40aac72b (2012-08-31) + * and is being addressed in the Go runtime in this issue: + * https://code.google.com/p/go/issues/detail?id=8197 + */ + +#ifndef __x86_64__ +#error This hack is specific to the 64-bit vDSO +#endif + +#include <linux/elf.h> + +extern const __visible struct elf64_shdr vdso_fake_sections[]; +const __visible struct elf64_shdr vdso_fake_sections[] = { + { + .sh_type = SHT_DYNSYM, + .sh_entsize = sizeof(Elf64_Sym), + } +}; diff --git a/arch/x86/vdso/vdso2c.h b/arch/x86/vdso/vdso2c.h index d9f6f61aef1c..c6eefaf389b9 100644 --- a/arch/x86/vdso/vdso2c.h +++ b/arch/x86/vdso/vdso2c.h @@ -18,6 +18,8 @@ static void GOFUNC(void *addr, size_t len, FILE *outfile, const char *name) const char *secstrings; uint64_t syms[NSYMS] = {}; + uint64_t fake_sections_value = 0, fake_sections_size = 0; + Elf_Phdr *pt = (Elf_Phdr *)(addr + GET_LE(&hdr->e_phoff)); /* Walk the segment table. */ @@ -84,6 +86,7 @@ static void GOFUNC(void *addr, size_t len, FILE *outfile, const char *name) GET_LE(&symtab_hdr->sh_entsize) * i; const char *name = addr + GET_LE(&strtab_hdr->sh_offset) + GET_LE(&sym->st_name); + for (k = 0; k < NSYMS; k++) { if (!strcmp(name, required_syms[k])) { if (syms[k]) { @@ -93,6 +96,13 @@ static void GOFUNC(void *addr, size_t len, FILE *outfile, const char *name) syms[k] = GET_LE(&sym->st_value); } } + + if (!strcmp(name, "vdso_fake_sections")) { + if (fake_sections_value) + fail("duplicate vdso_fake_sections\n"); + fake_sections_value = GET_LE(&sym->st_value); + fake_sections_size = GET_LE(&sym->st_size); + } } /* Validate mapping addresses. */ @@ -112,11 +122,14 @@ static void GOFUNC(void *addr, size_t len, FILE *outfile, const char *name) if (syms[sym_end_mapping] % 4096) fail("end_mapping must be a multiple of 4096\n"); - /* Remove sections. */ - hdr->e_shoff = 0; - hdr->e_shentsize = 0; - hdr->e_shnum = 0; - hdr->e_shstrndx = SHN_UNDEF; /* SHN_UNDEF == 0 */ + /* Remove sections or use fakes */ + if (fake_sections_size % sizeof(Elf_Shdr)) + fail("vdso_fake_sections size is not a multiple of %ld\n", + (long)sizeof(Elf_Shdr)); + PUT_LE(&hdr->e_shoff, fake_sections_value); + PUT_LE(&hdr->e_shentsize, fake_sections_value ? sizeof(Elf_Shdr) : 0); + PUT_LE(&hdr->e_shnum, fake_sections_size / sizeof(Elf_Shdr)); + PUT_LE(&hdr->e_shstrndx, SHN_UNDEF); if (!name) { fwrite(addr, load_size, 1, outfile); |