From 040425f849b959ed903610cc028e0996d921f9ca Mon Sep 17 00:00:00 2001 From: Alex Bennée Date: Fri, 3 Apr 2020 20:11:39 +0100 Subject: elf-ops: bail out if we have no function symbols It's perfectly possible to have no function symbols in your elf file and if we do the undefined behaviour sanitizer rightly complains about us passing NULL to qsort. Check nsyms before we go ahead. While we are at it lets drop the unchecked return value and cleanup the fail leg by use of g_autoptr. Another fix was proposed 101 weeks ago in: Message-Id: 20180421232120.22208-1-f4bug@amsat.org Signed-off-by: Alex Bennée Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Richard Henderson Message-Id: <20200403191150.863-2-alex.bennee@linaro.org> --- include/hw/elf_ops.h | 48 +++++++++++++++++++++++++----------------------- 1 file changed, 25 insertions(+), 23 deletions(-) (limited to 'include') diff --git a/include/hw/elf_ops.h b/include/hw/elf_ops.h index a1411bfcab..e0bb47bb67 100644 --- a/include/hw/elf_ops.h +++ b/include/hw/elf_ops.h @@ -104,19 +104,21 @@ static int glue(symcmp, SZ)(const void *s0, const void *s1) : ((sym0->st_value > sym1->st_value) ? 1 : 0); } -static int glue(load_symbols, SZ)(struct elfhdr *ehdr, int fd, int must_swab, - int clear_lsb, symbol_fn_t sym_cb) +static void glue(load_symbols, SZ)(struct elfhdr *ehdr, int fd, int must_swab, + int clear_lsb, symbol_fn_t sym_cb) { - struct elf_shdr *symtab, *strtab, *shdr_table = NULL; - struct elf_sym *syms = NULL; + struct elf_shdr *symtab, *strtab; + g_autofree struct elf_shdr *shdr_table = NULL; + g_autofree struct elf_sym *syms = NULL; + g_autofree char *str = NULL; struct syminfo *s; int nsyms, i; - char *str = NULL; shdr_table = load_at(fd, ehdr->e_shoff, sizeof(struct elf_shdr) * ehdr->e_shnum); - if (!shdr_table) - return -1; + if (!shdr_table) { + return ; + } if (must_swab) { for (i = 0; i < ehdr->e_shnum; i++) { @@ -125,23 +127,25 @@ static int glue(load_symbols, SZ)(struct elfhdr *ehdr, int fd, int must_swab, } symtab = glue(find_section, SZ)(shdr_table, ehdr->e_shnum, SHT_SYMTAB); - if (!symtab) - goto fail; + if (!symtab) { + return; + } syms = load_at(fd, symtab->sh_offset, symtab->sh_size); - if (!syms) - goto fail; + if (!syms) { + return; + } nsyms = symtab->sh_size / sizeof(struct elf_sym); /* String table */ if (symtab->sh_link >= ehdr->e_shnum) { - goto fail; + return; } strtab = &shdr_table[symtab->sh_link]; str = load_at(fd, strtab->sh_offset, strtab->sh_size); if (!str) { - goto fail; + return; } i = 0; @@ -170,8 +174,13 @@ static int glue(load_symbols, SZ)(struct elfhdr *ehdr, int fd, int must_swab, } i++; } - syms = g_realloc(syms, nsyms * sizeof(*syms)); + /* check we have symbols left */ + if (nsyms == 0) { + return; + } + + syms = g_realloc(syms, nsyms * sizeof(*syms)); qsort(syms, nsyms, sizeof(*syms), glue(symcmp, SZ)); for (i = 0; i < nsyms - 1; i++) { if (syms[i].st_size == 0) { @@ -182,18 +191,11 @@ static int glue(load_symbols, SZ)(struct elfhdr *ehdr, int fd, int must_swab, /* Commit */ s = g_malloc0(sizeof(*s)); s->lookup_symbol = glue(lookup_symbol, SZ); - glue(s->disas_symtab.elf, SZ) = syms; + glue(s->disas_symtab.elf, SZ) = g_steal_pointer(&syms); s->disas_num_syms = nsyms; - s->disas_strtab = str; + s->disas_strtab = g_steal_pointer(&str); s->next = syminfos; syminfos = s; - g_free(shdr_table); - return 0; - fail: - g_free(syms); - g_free(str); - g_free(shdr_table); - return -1; } static int glue(elf_reloc, SZ)(struct elfhdr *ehdr, int fd, int must_swab, -- cgit v1.2.3-55-g7522 From 01ef6b9e4e4e84b106b7f934354eada8fe36674f Mon Sep 17 00:00:00 2001 From: Alex Bennée Date: Fri, 3 Apr 2020 20:11:46 +0100 Subject: linux-user: factor out reading of /proc/self/maps Unfortunately reading /proc/self/maps is still considered the gold standard for a process finding out about it's own memory layout. As we will want this data in other contexts soon factor out the code to read and parse the data. Rather than just blindly copying the existing sscanf based code we use a more modern glib version of the parsing code to make a more general purpose map structure. Signed-off-by: Alex Bennée Message-Id: <20200403191150.863-9-alex.bennee@linaro.org> --- include/qemu/selfmap.h | 44 ++++++++++++++++++++++++++++ linux-user/syscall.c | 58 ++++++++++++++++++------------------- util/Makefile.objs | 1 + util/selfmap.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 151 insertions(+), 30 deletions(-) create mode 100644 include/qemu/selfmap.h create mode 100644 util/selfmap.c (limited to 'include') diff --git a/include/qemu/selfmap.h b/include/qemu/selfmap.h new file mode 100644 index 0000000000..8382c4c779 --- /dev/null +++ b/include/qemu/selfmap.h @@ -0,0 +1,44 @@ +/* + * Utility functions to read our own memory map + * + * Copyright (c) 2020 Linaro Ltd + * + * SPDX-License-Identifier: GPL-2.0-or-later + */ + +#ifndef _SELFMAP_H_ +#define _SELFMAP_H_ + +typedef struct { + unsigned long start; + unsigned long end; + + /* flags */ + bool is_read; + bool is_write; + bool is_exec; + bool is_priv; + + unsigned long offset; + gchar *dev; + uint64_t inode; + gchar *path; +} MapInfo; + + +/** + * read_self_maps: + * + * Read /proc/self/maps and return a list of MapInfo structures. + */ +GSList *read_self_maps(void); + +/** + * free_self_maps: + * @info: a GSlist + * + * Free a list of MapInfo structures. + */ +void free_self_maps(GSList *info); + +#endif /* _SELFMAP_H_ */ diff --git a/linux-user/syscall.c b/linux-user/syscall.c index b679bc6b13..5f11787294 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -117,6 +117,7 @@ #include "qemu.h" #include "qemu/guest-random.h" +#include "qemu/selfmap.h" #include "user/syscall-trace.h" #include "qapi/error.h" #include "fd-trans.h" @@ -7232,45 +7233,45 @@ static int open_self_maps(void *cpu_env, int fd) { CPUState *cpu = env_cpu((CPUArchState *)cpu_env); TaskState *ts = cpu->opaque; - FILE *fp; - char *line = NULL; - size_t len = 0; - ssize_t read; + GSList *map_info = read_self_maps(); + GSList *s; - fp = fopen("/proc/self/maps", "r"); - if (fp == NULL) { - return -1; - } + for (s = map_info; s; s = g_slist_next(s)) { + MapInfo *e = (MapInfo *) s->data; - while ((read = getline(&line, &len, fp)) != -1) { - int fields, dev_maj, dev_min, inode; - uint64_t min, max, offset; - char flag_r, flag_w, flag_x, flag_p; - char path[512] = ""; - fields = sscanf(line, "%"PRIx64"-%"PRIx64" %c%c%c%c %"PRIx64" %x:%x %d" - " %512s", &min, &max, &flag_r, &flag_w, &flag_x, - &flag_p, &offset, &dev_maj, &dev_min, &inode, path); - - if ((fields < 10) || (fields > 11)) { - continue; - } - if (h2g_valid(min)) { + if (h2g_valid(e->start)) { + unsigned long min = e->start; + unsigned long max = e->end; int flags = page_get_flags(h2g(min)); - max = h2g_valid(max - 1) ? max : (uintptr_t)g2h(GUEST_ADDR_MAX) + 1; + const char *path; + + max = h2g_valid(max - 1) ? + max : (uintptr_t) g2h(GUEST_ADDR_MAX) + 1; + if (page_check_range(h2g(min), max - min, flags) == -1) { continue; } + if (h2g(min) == ts->info->stack_limit) { - pstrcpy(path, sizeof(path), " [stack]"); + path = " [stack]"; + } else { + path = e->path; } + dprintf(fd, TARGET_ABI_FMT_ptr "-" TARGET_ABI_FMT_ptr - " %c%c%c%c %08" PRIx64 " %02x:%02x %d %s%s\n", - h2g(min), h2g(max - 1) + 1, flag_r, flag_w, - flag_x, flag_p, offset, dev_maj, dev_min, inode, - path[0] ? " " : "", path); + " %c%c%c%c %08" PRIx64 " %s %"PRId64" %s%s\n", + h2g(min), h2g(max - 1) + 1, + e->is_read ? 'r' : '-', + e->is_write ? 'w' : '-', + e->is_exec ? 'x' : '-', + e->is_priv ? 'p' : '-', + (uint64_t) e->offset, e->dev, e->inode, + path ? " " : "", path ? path : ""); } } + free_self_maps(map_info); + #ifdef TARGET_VSYSCALL_PAGE /* * We only support execution from the vsyscall page. @@ -7281,9 +7282,6 @@ static int open_self_maps(void *cpu_env, int fd) TARGET_VSYSCALL_PAGE, TARGET_VSYSCALL_PAGE + TARGET_PAGE_SIZE); #endif - free(line); - fclose(fp); - return 0; } diff --git a/util/Makefile.objs b/util/Makefile.objs index 6718a38b61..fe339c2636 100644 --- a/util/Makefile.objs +++ b/util/Makefile.objs @@ -63,3 +63,4 @@ util-obj-y += guest-random.o util-obj-$(CONFIG_GIO) += dbus.o dbus.o-cflags = $(GIO_CFLAGS) dbus.o-libs = $(GIO_LIBS) +util-obj-$(CONFIG_USER_ONLY) += selfmap.o diff --git a/util/selfmap.c b/util/selfmap.c new file mode 100644 index 0000000000..2ec99dfdda --- /dev/null +++ b/util/selfmap.c @@ -0,0 +1,78 @@ +/* + * Utility function to get QEMU's own process map + * + * Copyright (c) 2020 Linaro Ltd + * + * SPDX-License-Identifier: GPL-2.0-or-later + */ + +#include "qemu/osdep.h" +#include "qemu/cutils.h" +#include "qemu/selfmap.h" + +GSList *read_self_maps(void) +{ + gchar *maps; + GSList *map_info = NULL; + + if (g_file_get_contents("/proc/self/maps", &maps, NULL, NULL)) { + gchar **lines = g_strsplit(maps, "\n", 0); + int i, entries = g_strv_length(lines); + + for (i = 0; i < entries; i++) { + gchar **fields = g_strsplit(lines[i], " ", 6); + if (g_strv_length(fields) > 4) { + MapInfo *e = g_new0(MapInfo, 1); + int errors; + const char *end; + + errors = qemu_strtoul(fields[0], &end, 16, &e->start); + errors += qemu_strtoul(end + 1, NULL, 16, &e->end); + + e->is_read = fields[1][0] == 'r'; + e->is_write = fields[1][1] == 'w'; + e->is_exec = fields[1][2] == 'x'; + e->is_priv = fields[1][3] == 'p'; + + errors += qemu_strtoul(fields[2], NULL, 16, &e->offset); + e->dev = g_strdup(fields[3]); + errors += qemu_strtou64(fields[4], NULL, 10, &e->inode); + + /* + * The last field may have leading spaces which we + * need to strip. + */ + if (g_strv_length(fields) == 6) { + e->path = g_strdup(g_strchug(fields[5])); + } + map_info = g_slist_prepend(map_info, e); + } + + g_strfreev(fields); + } + g_strfreev(lines); + g_free(maps); + } + + /* ensure the map data is in the same order we collected it */ + return g_slist_reverse(map_info); +} + +/** + * free_self_maps: + * @info: a GSlist + * + * Free a list of MapInfo structures. + */ +static void free_info(gpointer data) +{ + MapInfo *e = (MapInfo *) data; + g_free(e->dev); + g_free(e->path); + g_free(e); +} + +void free_self_maps(GSList *info) +{ + g_slist_free_full(info, &free_info); +} -- cgit v1.2.3-55-g7522