From 4d048b0255e3dd4fb001c5f1f609fb67463d04d6 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Tue, 10 Jun 2014 14:25:26 -0700 Subject: x86, vdso: Remove one final use of htole16() One final use of the macros from which are not available on older system. In this case we had one sole case of *writing* a littleendian number, but the number is SHN_UNDEF which is the constant zero, so rather than dealing with the general case of littleendian puts here, just document that the constant is zero and be done with it. Reported-and-Tested-by: Andrew Morton Signed-off-by: H. Peter Anvin Cc: Andy Lutomirski Link: http://lkml.kernel.org/r/20140610135051.c3c34165f73d67d218b62bd9@linux-foundation.org --- arch/x86/vdso/vdso2c.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/vdso/vdso2c.h b/arch/x86/vdso/vdso2c.h index 8a074637a576..d9f6f61aef1c 100644 --- a/arch/x86/vdso/vdso2c.h +++ b/arch/x86/vdso/vdso2c.h @@ -116,7 +116,7 @@ static void GOFUNC(void *addr, size_t len, FILE *outfile, const char *name) hdr->e_shoff = 0; hdr->e_shentsize = 0; hdr->e_shnum = 0; - hdr->e_shstrndx = htole16(SHN_UNDEF); + hdr->e_shstrndx = SHN_UNDEF; /* SHN_UNDEF == 0 */ if (!name) { fwrite(addr, load_size, 1, outfile); -- cgit v1.2.3 From 6e8f21584a30ba6ce73cfef34f316d5bf3fadaab Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Thu, 12 Jun 2014 17:53:09 -0700 Subject: x86/vdso/doc: Rename vdso_test.c to vdso_standalone_test_x86.c This thing is hopelessly x86_64-specific: it's an example of how to access the vDSO without any runtime support at all. Signed-off-by: Andy Lutomirski Link: http://lkml.kernel.org/r/3efc170e0e166e15f0150c9fdb37d52488b9c0a4.1402620737.git.luto@amacapital.net Signed-off-by: H. Peter Anvin --- Documentation/vDSO/vdso_standalone_test_x86.c | 111 ++++++++++++++++++++++++++ Documentation/vDSO/vdso_test.c | 111 -------------------------- 2 files changed, 111 insertions(+), 111 deletions(-) create mode 100644 Documentation/vDSO/vdso_standalone_test_x86.c delete mode 100644 Documentation/vDSO/vdso_test.c diff --git a/Documentation/vDSO/vdso_standalone_test_x86.c b/Documentation/vDSO/vdso_standalone_test_x86.c new file mode 100644 index 000000000000..1523f5d681f3 --- /dev/null +++ b/Documentation/vDSO/vdso_standalone_test_x86.c @@ -0,0 +1,111 @@ +/* + * vdso_test.c: Sample code to test parse_vdso.c on x86_64 + * Copyright (c) 2011 Andy Lutomirski + * Subject to the GNU General Public License, version 2 + * + * You can amuse yourself by compiling with: + * gcc -std=gnu99 -nostdlib + * -Os -fno-asynchronous-unwind-tables -flto + * vdso_standalone_test_x86.c parse_vdso.c + * to generate a small binary with no dependencies at all. + */ + +#include +#include +#include +#include + +extern void *vdso_sym(const char *version, const char *name); +extern void vdso_init_from_sysinfo_ehdr(uintptr_t base); +extern void vdso_init_from_auxv(void *auxv); + +/* We need a libc functions... */ +int strcmp(const char *a, const char *b) +{ + /* This implementation is buggy: it never returns -1. */ + while (*a || *b) { + if (*a != *b) + return 1; + if (*a == 0 || *b == 0) + return 1; + a++; + b++; + } + + return 0; +} + +/* ...and two syscalls. This is x86_64-specific. */ +static inline long linux_write(int fd, const void *data, size_t len) +{ + + long ret; + asm volatile ("syscall" : "=a" (ret) : "a" (__NR_write), + "D" (fd), "S" (data), "d" (len) : + "cc", "memory", "rcx", + "r8", "r9", "r10", "r11" ); + return ret; +} + +static inline void linux_exit(int code) +{ + asm volatile ("syscall" : : "a" (__NR_exit), "D" (code)); +} + +void to_base10(char *lastdig, uint64_t n) +{ + while (n) { + *lastdig = (n % 10) + '0'; + n /= 10; + lastdig--; + } +} + +__attribute__((externally_visible)) void c_main(void **stack) +{ + /* Parse the stack */ + long argc = (long)*stack; + stack += argc + 2; + + /* Now we're pointing at the environment. Skip it. */ + while(*stack) + stack++; + stack++; + + /* Now we're pointing at auxv. Initialize the vDSO parser. */ + vdso_init_from_auxv((void *)stack); + + /* Find gettimeofday. */ + typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz); + gtod_t gtod = (gtod_t)vdso_sym("LINUX_2.6", "__vdso_gettimeofday"); + + if (!gtod) + linux_exit(1); + + struct timeval tv; + long ret = gtod(&tv, 0); + + if (ret == 0) { + char buf[] = "The time is .000000\n"; + to_base10(buf + 31, tv.tv_sec); + to_base10(buf + 38, tv.tv_usec); + linux_write(1, buf, sizeof(buf) - 1); + } else { + linux_exit(ret); + } + + linux_exit(0); +} + +/* + * This is the real entry point. It passes the initial stack into + * the C entry point. + */ +asm ( + ".text\n" + ".global _start\n" + ".type _start,@function\n" + "_start:\n\t" + "mov %rsp,%rdi\n\t" + "jmp c_main" + ); diff --git a/Documentation/vDSO/vdso_test.c b/Documentation/vDSO/vdso_test.c deleted file mode 100644 index fff633432dff..000000000000 --- a/Documentation/vDSO/vdso_test.c +++ /dev/null @@ -1,111 +0,0 @@ -/* - * vdso_test.c: Sample code to test parse_vdso.c on x86_64 - * Copyright (c) 2011 Andy Lutomirski - * Subject to the GNU General Public License, version 2 - * - * You can amuse yourself by compiling with: - * gcc -std=gnu99 -nostdlib - * -Os -fno-asynchronous-unwind-tables -flto - * vdso_test.c parse_vdso.c -o vdso_test - * to generate a small binary with no dependencies at all. - */ - -#include -#include -#include -#include - -extern void *vdso_sym(const char *version, const char *name); -extern void vdso_init_from_sysinfo_ehdr(uintptr_t base); -extern void vdso_init_from_auxv(void *auxv); - -/* We need a libc functions... */ -int strcmp(const char *a, const char *b) -{ - /* This implementation is buggy: it never returns -1. */ - while (*a || *b) { - if (*a != *b) - return 1; - if (*a == 0 || *b == 0) - return 1; - a++; - b++; - } - - return 0; -} - -/* ...and two syscalls. This is x86_64-specific. */ -static inline long linux_write(int fd, const void *data, size_t len) -{ - - long ret; - asm volatile ("syscall" : "=a" (ret) : "a" (__NR_write), - "D" (fd), "S" (data), "d" (len) : - "cc", "memory", "rcx", - "r8", "r9", "r10", "r11" ); - return ret; -} - -static inline void linux_exit(int code) -{ - asm volatile ("syscall" : : "a" (__NR_exit), "D" (code)); -} - -void to_base10(char *lastdig, uint64_t n) -{ - while (n) { - *lastdig = (n % 10) + '0'; - n /= 10; - lastdig--; - } -} - -__attribute__((externally_visible)) void c_main(void **stack) -{ - /* Parse the stack */ - long argc = (long)*stack; - stack += argc + 2; - - /* Now we're pointing at the environment. Skip it. */ - while(*stack) - stack++; - stack++; - - /* Now we're pointing at auxv. Initialize the vDSO parser. */ - vdso_init_from_auxv((void *)stack); - - /* Find gettimeofday. */ - typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz); - gtod_t gtod = (gtod_t)vdso_sym("LINUX_2.6", "__vdso_gettimeofday"); - - if (!gtod) - linux_exit(1); - - struct timeval tv; - long ret = gtod(&tv, 0); - - if (ret == 0) { - char buf[] = "The time is .000000\n"; - to_base10(buf + 31, tv.tv_sec); - to_base10(buf + 38, tv.tv_usec); - linux_write(1, buf, sizeof(buf) - 1); - } else { - linux_exit(ret); - } - - linux_exit(0); -} - -/* - * This is the real entry point. It passes the initial stack into - * the C entry point. - */ -asm ( - ".text\n" - ".global _start\n" - ".type _start,@function\n" - "_start:\n\t" - "mov %rsp,%rdi\n\t" - "jmp c_main" - ); -- cgit v1.2.3 From 4ebbefd6b93c34d6da0d950b1d2e0dcca2f1e6ef Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Thu, 12 Jun 2014 17:53:10 -0700 Subject: x86/vdso/doc: Make vDSO examples more portable This adds a new vdso_test.c that's written entirely in C. It also makes all of the vDSO examples work on 32-bit x86. Cc: Stefani Seibold Signed-off-by: Andy Lutomirski Link: http://lkml.kernel.org/r/62b701fc44b79f118ac2b2d64d19965fc5c291fb.1402620737.git.luto@amacapital.net Signed-off-by: H. Peter Anvin --- Documentation/vDSO/parse_vdso.c | 67 ++++++++++++++++----------- Documentation/vDSO/vdso_standalone_test_x86.c | 45 ++++++++++++------ Documentation/vDSO/vdso_test.c | 52 +++++++++++++++++++++ 3 files changed, 123 insertions(+), 41 deletions(-) create mode 100644 Documentation/vDSO/vdso_test.c diff --git a/Documentation/vDSO/parse_vdso.c b/Documentation/vDSO/parse_vdso.c index 85870208edcf..1dbb4b87268f 100644 --- a/Documentation/vDSO/parse_vdso.c +++ b/Documentation/vDSO/parse_vdso.c @@ -1,6 +1,6 @@ /* * parse_vdso.c: Linux reference vDSO parser - * Written by Andrew Lutomirski, 2011. + * Written by Andrew Lutomirski, 2011-2014. * * This code is meant to be linked in to various programs that run on Linux. * As such, it is available with as few restrictions as possible. This file @@ -11,13 +11,14 @@ * it starts a program. It works equally well in statically and dynamically * linked binaries. * - * This code is tested on x86_64. In principle it should work on any 64-bit + * This code is tested on x86. In principle it should work on any * architecture that has a vDSO. */ #include #include #include +#include #include /* @@ -45,11 +46,18 @@ extern void *vdso_sym(const char *version, const char *name); /* And here's the code. */ - -#ifndef __x86_64__ -# error Not yet ported to non-x86_64 architectures +#ifndef ELF_BITS +# if ULONG_MAX > 0xffffffffUL +# define ELF_BITS 64 +# else +# define ELF_BITS 32 +# endif #endif +#define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x +#define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x) +#define ELF(x) ELF_BITS_XFORM(ELF_BITS, x) + static struct vdso_info { bool valid; @@ -59,14 +67,14 @@ static struct vdso_info uintptr_t load_offset; /* load_addr - recorded vaddr */ /* Symbol table */ - Elf64_Sym *symtab; + ELF(Sym) *symtab; const char *symstrings; - Elf64_Word *bucket, *chain; - Elf64_Word nbucket, nchain; + ELF(Word) *bucket, *chain; + ELF(Word) nbucket, nchain; /* Version table */ - Elf64_Versym *versym; - Elf64_Verdef *verdef; + ELF(Versym) *versym; + ELF(Verdef) *verdef; } vdso_info; /* Straight from the ELF specification. */ @@ -92,9 +100,14 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base) vdso_info.load_addr = base; - Elf64_Ehdr *hdr = (Elf64_Ehdr*)base; - Elf64_Phdr *pt = (Elf64_Phdr*)(vdso_info.load_addr + hdr->e_phoff); - Elf64_Dyn *dyn = 0; + ELF(Ehdr) *hdr = (ELF(Ehdr)*)base; + if (hdr->e_ident[EI_CLASS] != + (ELF_BITS == 32 ? ELFCLASS32 : ELFCLASS64)) { + return; /* Wrong ELF class -- check ELF_BITS */ + } + + ELF(Phdr) *pt = (ELF(Phdr)*)(vdso_info.load_addr + hdr->e_phoff); + ELF(Dyn) *dyn = 0; /* * We need two things from the segment table: the load offset @@ -108,7 +121,7 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base) + (uintptr_t)pt[i].p_offset - (uintptr_t)pt[i].p_vaddr; } else if (pt[i].p_type == PT_DYNAMIC) { - dyn = (Elf64_Dyn*)(base + pt[i].p_offset); + dyn = (ELF(Dyn)*)(base + pt[i].p_offset); } } @@ -118,7 +131,7 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base) /* * Fish out the useful bits of the dynamic table. */ - Elf64_Word *hash = 0; + ELF(Word) *hash = 0; vdso_info.symstrings = 0; vdso_info.symtab = 0; vdso_info.versym = 0; @@ -131,22 +144,22 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base) + vdso_info.load_offset); break; case DT_SYMTAB: - vdso_info.symtab = (Elf64_Sym *) + vdso_info.symtab = (ELF(Sym) *) ((uintptr_t)dyn[i].d_un.d_ptr + vdso_info.load_offset); break; case DT_HASH: - hash = (Elf64_Word *) + hash = (ELF(Word) *) ((uintptr_t)dyn[i].d_un.d_ptr + vdso_info.load_offset); break; case DT_VERSYM: - vdso_info.versym = (Elf64_Versym *) + vdso_info.versym = (ELF(Versym) *) ((uintptr_t)dyn[i].d_un.d_ptr + vdso_info.load_offset); break; case DT_VERDEF: - vdso_info.verdef = (Elf64_Verdef *) + vdso_info.verdef = (ELF(Verdef) *) ((uintptr_t)dyn[i].d_un.d_ptr + vdso_info.load_offset); break; @@ -168,8 +181,8 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base) vdso_info.valid = true; } -static bool vdso_match_version(Elf64_Versym ver, - const char *name, Elf64_Word hash) +static bool vdso_match_version(ELF(Versym) ver, + const char *name, ELF(Word) hash) { /* * This is a helper function to check if the version indexed by @@ -188,7 +201,7 @@ static bool vdso_match_version(Elf64_Versym ver, /* First step: find the version definition */ ver &= 0x7fff; /* Apparently bit 15 means "hidden" */ - Elf64_Verdef *def = vdso_info.verdef; + ELF(Verdef) *def = vdso_info.verdef; while(true) { if ((def->vd_flags & VER_FLG_BASE) == 0 && (def->vd_ndx & 0x7fff) == ver) @@ -197,11 +210,11 @@ static bool vdso_match_version(Elf64_Versym ver, if (def->vd_next == 0) return false; /* No definition. */ - def = (Elf64_Verdef *)((char *)def + def->vd_next); + def = (ELF(Verdef) *)((char *)def + def->vd_next); } /* Now figure out whether it matches. */ - Elf64_Verdaux *aux = (Elf64_Verdaux*)((char *)def + def->vd_aux); + ELF(Verdaux) *aux = (ELF(Verdaux)*)((char *)def + def->vd_aux); return def->vd_hash == hash && !strcmp(name, vdso_info.symstrings + aux->vda_name); } @@ -213,10 +226,10 @@ void *vdso_sym(const char *version, const char *name) return 0; ver_hash = elf_hash(version); - Elf64_Word chain = vdso_info.bucket[elf_hash(name) % vdso_info.nbucket]; + ELF(Word) chain = vdso_info.bucket[elf_hash(name) % vdso_info.nbucket]; for (; chain != STN_UNDEF; chain = vdso_info.chain[chain]) { - Elf64_Sym *sym = &vdso_info.symtab[chain]; + ELF(Sym) *sym = &vdso_info.symtab[chain]; /* Check for a defined global or weak function w/ right name. */ if (ELF64_ST_TYPE(sym->st_info) != STT_FUNC) @@ -243,7 +256,7 @@ void *vdso_sym(const char *version, const char *name) void vdso_init_from_auxv(void *auxv) { - Elf64_auxv_t *elf_auxv = auxv; + ELF(auxv_t) *elf_auxv = auxv; for (int i = 0; elf_auxv[i].a_type != AT_NULL; i++) { if (elf_auxv[i].a_type == AT_SYSINFO_EHDR) { diff --git a/Documentation/vDSO/vdso_standalone_test_x86.c b/Documentation/vDSO/vdso_standalone_test_x86.c index 1523f5d681f3..d46240265c50 100644 --- a/Documentation/vDSO/vdso_standalone_test_x86.c +++ b/Documentation/vDSO/vdso_standalone_test_x86.c @@ -1,13 +1,14 @@ /* - * vdso_test.c: Sample code to test parse_vdso.c on x86_64 - * Copyright (c) 2011 Andy Lutomirski + * vdso_test.c: Sample code to test parse_vdso.c on x86 + * Copyright (c) 2011-2014 Andy Lutomirski * Subject to the GNU General Public License, version 2 * * You can amuse yourself by compiling with: * gcc -std=gnu99 -nostdlib - * -Os -fno-asynchronous-unwind-tables -flto + * -Os -fno-asynchronous-unwind-tables -flto -lgcc_s * vdso_standalone_test_x86.c parse_vdso.c - * to generate a small binary with no dependencies at all. + * to generate a small binary. On x86_64, you can omit -lgcc_s + * if you want the binary to be completely standalone. */ #include @@ -35,21 +36,31 @@ int strcmp(const char *a, const char *b) return 0; } -/* ...and two syscalls. This is x86_64-specific. */ -static inline long linux_write(int fd, const void *data, size_t len) +/* ...and two syscalls. This is x86-specific. */ +static inline long x86_syscall3(long nr, long a0, long a1, long a2) { - long ret; - asm volatile ("syscall" : "=a" (ret) : "a" (__NR_write), - "D" (fd), "S" (data), "d" (len) : +#ifdef __x86_64__ + asm volatile ("syscall" : "=a" (ret) : "a" (nr), + "D" (a0), "S" (a1), "d" (a2) : "cc", "memory", "rcx", "r8", "r9", "r10", "r11" ); +#else + asm volatile ("int $0x80" : "=a" (ret) : "a" (nr), + "b" (a0), "c" (a1), "d" (a2) : + "cc", "memory" ); +#endif return ret; } +static inline long linux_write(int fd, const void *data, size_t len) +{ + return x86_syscall3(__NR_write, fd, (long)data, (long)len); +} + static inline void linux_exit(int code) { - asm volatile ("syscall" : : "a" (__NR_exit), "D" (code)); + x86_syscall3(__NR_exit, code, 0, 0); } void to_base10(char *lastdig, uint64_t n) @@ -104,8 +115,14 @@ __attribute__((externally_visible)) void c_main(void **stack) asm ( ".text\n" ".global _start\n" - ".type _start,@function\n" - "_start:\n\t" - "mov %rsp,%rdi\n\t" - "jmp c_main" + ".type _start,@function\n" + "_start:\n\t" +#ifdef __x86_64__ + "mov %rsp,%rdi\n\t" + "jmp c_main" +#else + "push %esp\n\t" + "call c_main\n\t" + "int $3" +#endif ); diff --git a/Documentation/vDSO/vdso_test.c b/Documentation/vDSO/vdso_test.c new file mode 100644 index 000000000000..8daeb7d7032c --- /dev/null +++ b/Documentation/vDSO/vdso_test.c @@ -0,0 +1,52 @@ +/* + * vdso_test.c: Sample code to test parse_vdso.c + * Copyright (c) 2014 Andy Lutomirski + * Subject to the GNU General Public License, version 2 + * + * Compile with: + * gcc -std=gnu99 vdso_test.c parse_vdso.c + * + * Tested on x86, 32-bit and 64-bit. It may work on other architectures, too. + */ + +#include +#include +#include +#include +#include + +extern void *vdso_sym(const char *version, const char *name); +extern void vdso_init_from_sysinfo_ehdr(uintptr_t base); +extern void vdso_init_from_auxv(void *auxv); + +int main(int argc, char **argv) +{ + unsigned long sysinfo_ehdr = getauxval(AT_SYSINFO_EHDR); + if (!sysinfo_ehdr) { + printf("AT_SYSINFO_EHDR is not present!\n"); + return 0; + } + + vdso_init_from_sysinfo_ehdr(getauxval(AT_SYSINFO_EHDR)); + + /* Find gettimeofday. */ + typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz); + gtod_t gtod = (gtod_t)vdso_sym("LINUX_2.6", "__vdso_gettimeofday"); + + if (!gtod) { + printf("Could not find __vdso_gettimeofday\n"); + return 1; + } + + struct timeval tv; + long ret = gtod(&tv, 0); + + if (ret == 0) { + printf("The time is %lld.%06lld\n", + (long long)tv.tv_sec, (long long)tv.tv_usec); + } else { + printf("__vdso_gettimeofday failed\n"); + } + + return 0; +} -- cgit v1.2.3 From b4b31f6101433e4b8ee73779b69b935af07682f8 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Thu, 12 Jun 2014 17:53:11 -0700 Subject: x86/vdso: Add PUT_LE to store little-endian values Add PUT_LE() by analogy with GET_LE() to write littleendian values in addition to reading them. Signed-off-by: Andy Lutomirski Link: http://lkml.kernel.org/r/3d9b27e92745b27b6fda1b9a98f70dc9c1246c7a.1402620737.git.luto@amacapital.net Signed-off-by: H. Peter Anvin --- arch/x86/vdso/vdso2c.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/arch/x86/vdso/vdso2c.c b/arch/x86/vdso/vdso2c.c index 450ac6eaf613..7a6bf50f9165 100644 --- a/arch/x86/vdso/vdso2c.c +++ b/arch/x86/vdso/vdso2c.c @@ -54,7 +54,7 @@ static void fail(const char *format, ...) } /* - * Evil macros to do a little-endian read. + * Evil macros for little-endian reads and writes */ #define GLE(x, bits, ifnot) \ __builtin_choose_expr( \ @@ -62,11 +62,24 @@ static void fail(const char *format, ...) (__typeof__(*(x)))get_unaligned_le##bits(x), ifnot) extern void bad_get_le(void); -#define LAST_LE(x) \ +#define LAST_GLE(x) \ __builtin_choose_expr(sizeof(*(x)) == 1, *(x), bad_get_le()) #define GET_LE(x) \ - GLE(x, 64, GLE(x, 32, GLE(x, 16, LAST_LE(x)))) + GLE(x, 64, GLE(x, 32, GLE(x, 16, LAST_GLE(x)))) + +#define PLE(x, val, bits, ifnot) \ + __builtin_choose_expr( \ + (sizeof(*(x)) == bits/8), \ + put_unaligned_le##bits((val), (x)), ifnot) + +extern void bad_put_le(void); +#define LAST_PLE(x, val) \ + __builtin_choose_expr(sizeof(*(x)) == 1, *(x) = (val), bad_put_le()) + +#define PUT_LE(x, val) \ + PLE(x, val, 64, PLE(x, val, 32, PLE(x, val, 16, LAST_PLE(x, val)))) + #define NSYMS (sizeof(required_syms) / sizeof(required_syms[0])) -- cgit v1.2.3 From e0bf7b86dace87eccdabdd66d2769ccad19cb81c Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Thu, 12 Jun 2014 17:53:12 -0700 Subject: x86/vdso: Hack to keep 64-bit Go programs working The Go runtime has a buggy vDSO parser that currently segfaults. This writes an empty SHT_DYNSYM entry that causes Go's runtime to malfunction by thinking that the vDSO is empty rather than malfunctioning by running off the end and segfaulting. This affects x86-64 only as far as we know, so we do not need this for the i386 and x32 vdsos. Signed-off-by: Andy Lutomirski Link: http://lkml.kernel.org/r/d10618176c4bd39b457a5e85c497295c90cab1bc.1402620737.git.luto@amacapital.net Signed-off-by: H. Peter Anvin --- arch/x86/vdso/Makefile | 18 ++++++++++-------- arch/x86/vdso/vdso-fakesections.c | 32 ++++++++++++++++++++++++++++++++ arch/x86/vdso/vdso2c.h | 23 ++++++++++++++++++----- 3 files changed, 60 insertions(+), 13 deletions(-) create mode 100644 arch/x86/vdso/vdso-fakesections.c 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 + +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); -- cgit v1.2.3 From a934fb5bc9cd1260be89272cfb7a6c9dc71974d7 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Thu, 12 Jun 2014 08:28:10 -0700 Subject: x86/vdso: Fix vdso_install "make vdso_install" installs unstripped versions of the vdso objects for the benefit of the debugger. This was broken by checkin: 6f121e548f83 x86, vdso: Reimplement vdso.so preparation in build-time C The filenames are different now, so update the Makefile to cope. This still installs the 64-bit vdso as vdso64.so. We believe this will be okay, as the only known user is a patched gdb which is known to use build-ids, but if it turns out to be a problem we may have to add a link. Inspired by a patch from Sam Ravnborg. Acked-by: Sam Ravnborg Reported-by: Josh Boyer Tested-by: Josh Boyer Signed-off-by: Andy Lutomirski Link: http://lkml.kernel.org/r/b10299edd8ba98d17e07dafcd895b8ecf4d99eff.1402586707.git.luto@amacapital.net Signed-off-by: H. Peter Anvin --- arch/x86/vdso/Makefile | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/arch/x86/vdso/Makefile b/arch/x86/vdso/Makefile index ba6fc2757ee4..3c0809a0631f 100644 --- a/arch/x86/vdso/Makefile +++ b/arch/x86/vdso/Makefile @@ -9,11 +9,6 @@ VDSOX32-$(CONFIG_X86_X32_ABI) := y VDSO32-$(CONFIG_X86_32) := y VDSO32-$(CONFIG_COMPAT) := y -vdso-install-$(VDSO64-y) += vdso.so -vdso-install-$(VDSOX32-y) += vdsox32.so -vdso-install-$(VDSO32-y) += $(vdso32-images) - - # files to link into the vdso vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o vdso-fakesections.o vobjs-nox32 := vdso-fakesections.o @@ -178,15 +173,20 @@ VDSO_LDFLAGS = -fPIC -shared $(call cc-ldoption, -Wl$(comma)--hash-style=sysv) \ GCOV_PROFILE := n # -# Install the unstripped copy of vdso*.so listed in $(vdso-install-y). +# Install the unstripped copies of vdso*.so. # -quiet_cmd_vdso_install = INSTALL $@ - cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@ -$(vdso-install-y): %.so: $(obj)/%.so.dbg FORCE +quiet_cmd_vdso_install = INSTALL $(@:install_%=%) + cmd_vdso_install = cp $< $(MODLIB)/vdso/$(@:install_%=%) + +vdso_img_insttargets := $(vdso_img_sodbg:%.dbg=install_%) + +$(MODLIB)/vdso: FORCE @mkdir -p $(MODLIB)/vdso + +$(vdso_img_insttargets): install_%: $(obj)/%.dbg $(MODLIB)/vdso FORCE $(call cmd,vdso_install) -PHONY += vdso_install $(vdso-install-y) -vdso_install: $(vdso-install-y) +PHONY += vdso_install $(vdso_img_insttargets) +vdso_install: $(vdso_img_insttargets) FORCE clean-files := vdso32-syscall* vdso32-sysenter* vdso32-int80* -- cgit v1.2.3