[v6,08/24] xsplice: Add helper elf routines

Message ID	1460000983-28170-9-git-send-email-konrad.wilk@oracle.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <xen-devel-bounces@lists.xen.org> From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> To: xen-devel@lists.xenproject.org, konrad@kernel.org, ross.lagerwall@citrix.com, mpohlack@amazon.de, sasha.levin@oracle.com, andrew.cooper3@citrix.com Date: Wed, 6 Apr 2016 23:49:27 -0400 Message-Id: <1460000983-28170-9-git-send-email-konrad.wilk@oracle.com> In-Reply-To: <1460000983-28170-1-git-send-email-konrad.wilk@oracle.com> References: <1460000983-28170-1-git-send-email-konrad.wilk@oracle.com> Cc: Keir Fraser <keir@xen.org>, Tim Deegan <tim@xen.org>, Ian Jackson <ian.jackson@eu.citrix.com>, Jan Beulich <jbeulich@suse.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Subject: [Xen-devel] [PATCH v6 08/24] xsplice: Add helper elf routines Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" <xen-devel-bounces@lists.xen.org>

diff --git a/xen/common/Makefile b/xen/common/Makefile index 1e4bc70..afd84b6 100644 --- a/xen/common/Makefile +++ b/xen/common/Makefile @@ -59,6 +59,7 @@ obj-y += wait.o obj-$(CONFIG_XENOPROF) += xenoprof.o obj-y += xmalloc_tlsf.o obj-$(CONFIG_XSPLICE) += xsplice.o +obj-$(CONFIG_XSPLICE) += xsplice_elf.o obj-bin-$(CONFIG_X86) += $(foreach n,decompress bunzip2 unxz unlzma unlzo unlz4 earlycpio,$(n).init.o) diff --git a/xen/common/xsplice_elf.c b/xen/common/xsplice_elf.c new file mode 100644 index 0000000..b244d42 --- /dev/null +++ b/xen/common/xsplice_elf.c @@ -0,0 +1,348 @@ +/* + * Copyright (C) 2016 Citrix Systems R&D Ltd. + */ + +#include <xen/errno.h> +#include <xen/lib.h> +#include <xen/xsplice_elf.h> +#include <xen/xsplice.h> + +const struct xsplice_elf_sec *xsplice_elf_sec_by_name(const struct xsplice_elf *elf, + const char *name) +{ + unsigned int i; + + for ( i = 1; i < elf->hdr->e_shnum; i++ ) + { + if ( !strcmp(name, elf->sec[i].name) ) + return &elf->sec[i]; + } + + return NULL; +} + +static int elf_verify_strtab(const struct xsplice_elf_sec *sec) +{ + const Elf_Shdr *s; + const uint8_t *contents; + + s = sec->sec; + + if ( s->sh_type != SHT_STRTAB ) + return -EINVAL; + + if ( !s->sh_size ) + return -EOPNOTSUPP; + + contents = (const uint8_t *)sec->data; + + if ( contents[0] || contents[s->sh_size - 1] ) + return -EINVAL; + + return 0; +} + +static int elf_resolve_sections(struct xsplice_elf *elf, const void *data) +{ + struct xsplice_elf_sec *sec; + unsigned int i; + Elf_Off delta; + int rc; + + /* xsplice_elf_load sanity checked e_shnum. */ + sec = xmalloc_array(struct xsplice_elf_sec, elf->hdr->e_shnum); + if ( !sec ) + { + printk(XENLOG_ERR XSPLICE"%s: Could not allocate memory for section table!\n", + elf->name); + return -ENOMEM; + } + + elf->sec = sec; + + delta = elf->hdr->e_shoff + elf->hdr->e_shnum * elf->hdr->e_shentsize; + if ( delta >= elf->len ) + { + dprintk(XENLOG_DEBUG, XSPLICE "%s: Section table is past end of payload!\n", + elf->name); + return -EINVAL; + } + + for ( i = 1; i < elf->hdr->e_shnum; i++ ) + { + delta = elf->hdr->e_shoff + i * elf->hdr->e_shentsize; + + sec[i].sec = data + delta; + + delta = sec[i].sec->sh_offset; + + /* + * N.B. elf_resolve_section_names, elf_get_sym skip this check as + * we do it here. + */ + if ( delta && (delta + sec[i].sec->sh_size > elf->len) ) + { + dprintk(XENLOG_DEBUG, XSPLICE "%s: Section [%u] data is past end of payload!\n", + elf->name, i); + return -EINVAL; + } + + sec[i].data = data + delta; + /* Name is populated in xsplice_elf_sections_name. */ + sec[i].name = NULL; + + if ( sec[i].sec->sh_type == SHT_SYMTAB ) + { + if ( elf->symtab ) + { + dprintk(XENLOG_DEBUG, XSPLICE "%s: Unsupported multiple symbol tables!\n", + elf->name); + return -EOPNOTSUPP; + } + + elf->symtab = &sec[i]; + + /* + * elf->symtab->sec->sh_link would point to the right section + * but we hadn't finished parsing all the sections. + */ + if ( elf->symtab->sec->sh_link > elf->hdr->e_shnum ) + { + dprintk(XENLOG_DEBUG, XSPLICE + "%s: Symbol table idx (%u) to strtab past end (%u)\n", + elf->name, elf->symtab->sec->sh_link, + elf->hdr->e_shnum); + return -EINVAL; + } + } + } + + if ( !elf->symtab ) + { + dprintk(XENLOG_DEBUG, XSPLICE "%s: No symbol table found!\n", + elf->name); + return -EINVAL; + } + + if ( !elf->symtab->sec->sh_size || + elf->symtab->sec->sh_entsize < sizeof(Elf_Sym) ) + { + dprintk(XENLOG_DEBUG, XSPLICE "%s: Symbol table header is corrupted!\n", + elf->name); + return -EINVAL; + } + + /* + * There can be multiple SHT_STRTAB (.shstrtab, .strtab) so pick one + * associated with the symbol table. + */ + elf->strtab = &sec[elf->symtab->sec->sh_link]; + + rc = elf_verify_strtab(elf->strtab); + if ( rc ) + { + dprintk(XENLOG_DEBUG, XSPLICE "%s: String table section is corrupted\n", + elf->name); + } + + return rc; +} + +static int elf_resolve_section_names(struct xsplice_elf *elf, const void *data) +{ + const char *shstrtab; + unsigned int i; + Elf_Off offset, delta; + struct xsplice_elf_sec *sec; + int rc; + + /* + * The elf->sec[0 -> e_shnum] structures have been verified by + * elf_resolve_sections. Find file offset for section string table + * (normally called .shstrtab) + */ + sec = &elf->sec[elf->hdr->e_shstrndx]; + + rc = elf_verify_strtab(sec); + if ( rc ) + { + dprintk(XENLOG_DEBUG, XSPLICE "%s: Section string table is corrupted\n", + elf->name); + return rc; + } + + /* Verified in elf_resolve_sections but just in case. */ + offset = sec->sec->sh_offset; + ASSERT(offset < elf->len && (offset + sec->sec->sh_size <= elf->len)); + + shstrtab = data + offset; + + for ( i = 1; i < elf->hdr->e_shnum; i++ ) + { + delta = elf->sec[i].sec->sh_name; + + if ( delta && delta >= sec->sec->sh_size ) + { + dprintk(XENLOG_DEBUG, XSPLICE "%s: shstrtab [%u] data is past end of payload!\n", + elf->name, i); + return -EINVAL; + } + + elf->sec[i].name = shstrtab + delta; + } + + return 0; +} + +static int elf_get_sym(struct xsplice_elf *elf, const void *data) +{ + const struct xsplice_elf_sec *symtab_sec, *strtab_sec; + struct xsplice_elf_sym *sym; + unsigned int i, delta, offset, nsym; + + symtab_sec = elf->symtab; + strtab_sec = elf->strtab; + + /* Pointers arithmetic to get file offset. */ + offset = strtab_sec->data - data; + + /* Checked already in elf_resolve_sections, but just in case. */ + ASSERT(offset == strtab_sec->sec->sh_offset); + ASSERT(offset < elf->len && (offset + strtab_sec->sec->sh_size <= elf->len)); + + /* symtab_sec->data was computed in elf_resolve_sections. */ + ASSERT((symtab_sec->sec->sh_offset + data) == symtab_sec->data); + + /* No need to check values as elf_resolve_sections did it. */ + nsym = symtab_sec->sec->sh_size / symtab_sec->sec->sh_entsize; + + sym = xmalloc_array(struct xsplice_elf_sym, nsym); + if ( !sym ) + { + printk(XENLOG_ERR XSPLICE "%s: Could not allocate memory for symbols\n", + elf->name); + return -ENOMEM; + } + + /* So we don't leak memory. */ + elf->sym = sym; + + for ( i = 1; i < nsym; i++ ) + { + Elf_Sym *s = &((Elf_Sym *)symtab_sec->data)[i]; + + /* If st->name is STN_UNDEF zero, the check will always be true. */ + delta = s->st_name; + + if ( delta && (delta > strtab_sec->sec->sh_size) ) + { + dprintk(XENLOG_DEBUG, XSPLICE "%s: Symbol [%u] data is past end of payload!\n", + elf->name, i); + return -EINVAL; + } + + sym[i].sym = s; + sym[i].name = data + (delta + offset); + } + elf->nsym = nsym; + + return 0; +} + +static int xsplice_header_check(const struct xsplice_elf *elf) +{ + const Elf_Ehdr *hdr = elf->hdr; + + if ( sizeof(*elf->hdr) > elf->len ) + { + dprintk(XENLOG_DEBUG, XSPLICE "%s: Section header is bigger than payload!\n", + elf->name); + return -EINVAL; + } + + if ( !IS_ELF(*hdr) ) + { + printk(XENLOG_ERR XSPLICE "%s: Not an ELF payload!\n", elf->name); + return -EINVAL; + } + + if ( hdr->e_ident[EI_CLASS] != ELFCLASS64 || + hdr->e_ident[EI_DATA] != ELFDATA2LSB || + hdr->e_ident[EI_OSABI] != ELFOSABI_SYSV || + hdr->e_type != ET_REL || + hdr->e_phnum != 0 ) + { + printk(XENLOG_ERR XSPLICE "%s: Invalid ELF payload!\n", elf->name); + return -EOPNOTSUPP; + } + + if ( elf->hdr->e_shstrndx == SHN_UNDEF ) + { + dprintk(XENLOG_DEBUG, XSPLICE "%s: Section name idx is undefined!?\n", + elf->name); + return -EINVAL; + } + + /* Check that section name index is within the sections. */ + if ( elf->hdr->e_shstrndx >= elf->hdr->e_shnum ) + { + dprintk(XENLOG_DEBUG, XSPLICE "%s: Section name idx (%u) is past end of sections (%u)!\n", + elf->name, elf->hdr->e_shstrndx, elf->hdr->e_shnum); + return -EINVAL; + } + + if ( elf->hdr->e_shnum > 64 ) + { + dprintk(XENLOG_DEBUG, XSPLICE "%s: Too many (%u) sections!\n", + elf->name, elf->hdr->e_shnum); + return -EINVAL; + } + + return 0; +} + +int xsplice_elf_load(struct xsplice_elf *elf, const void *data) +{ + int rc; + + elf->hdr = data; + + rc = xsplice_header_check(elf); + if ( rc ) + return rc; + + rc = elf_resolve_sections(elf, data); + if ( rc ) + return rc; + + rc = elf_resolve_section_names(elf, data); + if ( rc ) + return rc; + + rc = elf_get_sym(elf, data); + if ( rc ) + return rc; + + return 0; +} + +void xsplice_elf_free(struct xsplice_elf *elf) +{ + xfree(elf->sec); + elf->sec = NULL; + xfree(elf->sym); + elf->sym = NULL; + elf->nsym = 0; + elf->name = NULL; + elf->len = 0; +} + +/* + * Local variables: + * mode: C + * c-file-style: "BSD" + * c-basic-offset: 4 + * tab-width: 4 + * indent-tabs-mode: nil + * End: + */ diff --git a/xen/include/xen/xsplice.h b/xen/include/xen/xsplice.h index 5c84851..00482d0 100644 --- a/xen/include/xen/xsplice.h +++ b/xen/include/xen/xsplice.h @@ -10,6 +10,9 @@ struct xen_sysctl_xsplice_op; #ifdef CONFIG_XSPLICE +/* Convenience define for printk. */ +#define XSPLICE "xsplice: " + int xsplice_op(struct xen_sysctl_xsplice_op *); #else diff --git a/xen/include/xen/xsplice_elf.h b/xen/include/xen/xsplice_elf.h new file mode 100644 index 0000000..3231639 --- /dev/null +++ b/xen/include/xen/xsplice_elf.h @@ -0,0 +1,51 @@ +/* + * Copyright (C) 2016 Citrix Systems R&D Ltd. + */ + +#ifndef __XEN_XSPLICE_ELF_H__ +#define __XEN_XSPLICE_ELF_H__ + +#include <xen/types.h> +#include <xen/elfstructs.h> + +/* The following describes an Elf file as consumed by xSplice. */ +struct xsplice_elf_sec { + const Elf_Shdr *sec; /* Hooked up in elf_resolve_sections.*/ + const char *name; /* Human readable name hooked in + elf_resolve_section_names. */ + const void *data; /* Pointer to the section (done by + elf_resolve_sections). */ +}; + +struct xsplice_elf_sym { + Elf_Sym *sym; + const char *name; +}; + +struct xsplice_elf { + const char *name; /* Pointer to payload->name. */ + size_t len; /* Length of the ELF file. */ + const Elf_Ehdr *hdr; /* ELF file. */ + struct xsplice_elf_sec *sec; /* Array of sections, allocated by us. */ + struct xsplice_elf_sym *sym; /* Array of symbols , allocated by us. */ + unsigned int nsym; + const struct xsplice_elf_sec *symtab;/* Pointer to .symtab section - aka to sec[x]. */ + const struct xsplice_elf_sec *strtab;/* Pointer to .strtab section - aka to sec[y]. */ +}; + +const struct xsplice_elf_sec *xsplice_elf_sec_by_name(const struct xsplice_elf *elf, + const char *name); +int xsplice_elf_load(struct xsplice_elf *elf, const void *data); +void xsplice_elf_free(struct xsplice_elf *elf); + +#endif /* __XEN_XSPLICE_ELF_H__ */ + +/* + * Local variables: + * mode: C + * c-file-style: "BSD" + * c-basic-offset: 4 + * tab-width: 4 + * indent-tabs-mode: nil + * End: + */

[v6,08/24] xsplice: Add helper elf routines

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