| Message ID | 20160923012905.GA29985@localhost.localdomain (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 09/23/2016 02:29 AM, Konrad Rzeszutek Wilk wrote: >>> +bool arch_livepatch_symbol_deny(const struct livepatch_elf *elf, >>> + const struct livepatch_elf_sym *sym) >>> +{ >>> +#ifdef CONFIG_ARM_32 >> >> Out of interest, is there any particular reason to use #ifdef rather than >> adding the function in {arm32/arm64}/livepatch.c? > > I updated it be like that: > > From 5fc79e4fc3c0770ee4f6e7e0ed666e593deced65 Mon Sep 17 00:00:00 2001 > From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > Date: Tue, 13 Sep 2016 13:15:07 -0400 > Subject: [PATCH v6] livepatch/arm/x86: Check payload for for unwelcomed > symbols. > > Certain platforms, such as ARM [32|64] add extra mapping symbols > such as $x (for ARM64 instructions), or more interesting to > this patch: $t (for Thumb instructions). These symbols are supposed > to help the final linker to make any adjustments (such as > add an veneer). But more importantly - we do not compile Xen > with any Thumb instructions (which are variable length) - and > if we find these mapping symbols we should disallow such payload. > > Reviewed-by: Julien Grall <julien.grall@arm.com> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>
diff --git a/xen/arch/arm/arm32/livepatch.c b/xen/arch/arm/arm32/livepatch.c index 80f9646..5fc2e63 100644 --- a/xen/arch/arm/arm32/livepatch.c +++ b/xen/arch/arm/arm32/livepatch.c @@ -20,6 +20,19 @@ int arch_livepatch_verify_elf(const struct livepatch_elf *elf) return -EOPNOTSUPP; } +bool arch_livepatch_symbol_deny(const struct livepatch_elf *elf, + const struct livepatch_elf_sym *sym) +{ + /* + * Xen does not use Thumb instructions - and we should not see any of + * them. If we do, abort. + */ + if ( sym->name && sym->name[0] == '$' && sym->name[1] == 't' ) + return ( !sym->name[2] || sym->name[2] == '.' ); + + return false; +} + int arch_livepatch_perform_rela(struct livepatch_elf *elf, const struct livepatch_elf_sec *base, const struct livepatch_elf_sec *rela) diff --git a/xen/arch/arm/arm64/livepatch.c b/xen/arch/arm/arm64/livepatch.c index 0fe73d9..0f25e1e 100644 --- a/xen/arch/arm/arm64/livepatch.c +++ b/xen/arch/arm/arm64/livepatch.c @@ -95,6 +95,13 @@ int arch_livepatch_verify_elf(const struct livepatch_elf *elf) return 0; } +bool arch_livepatch_symbol_deny(const struct livepatch_elf *elf, + const struct livepatch_elf_sym *sym) +{ + /* No special checks on ARM 64. */ + return false; +} + enum aarch64_reloc_op { RELOC_OP_NONE, RELOC_OP_ABS, diff --git a/xen/arch/x86/livepatch.c b/xen/arch/x86/livepatch.c index 7a369a0..9663ef6 100644 --- a/xen/arch/x86/livepatch.c +++ b/xen/arch/x86/livepatch.c @@ -131,6 +131,13 @@ bool arch_livepatch_symbol_ok(const struct livepatch_elf *elf, return true; } +bool arch_livepatch_symbol_deny(const struct livepatch_elf *elf, + const struct livepatch_elf_sym *sym) +{ + /* No special checks on x86. */ + return false; +} + int arch_livepatch_perform_rel(struct livepatch_elf *elf, const struct livepatch_elf_sec *base, const struct livepatch_elf_sec *rela) diff --git a/xen/common/livepatch_elf.c b/xen/common/livepatch_elf.c index dec904a..53b3fba 100644 --- a/xen/common/livepatch_elf.c +++ b/xen/common/livepatch_elf.c @@ -251,6 +251,13 @@ static int elf_get_sym(struct livepatch_elf *elf, const void *data) sym[i].sym = s; sym[i].name = strtab_sec->data + delta; + /* e.g. On ARM we should NEVER see $t* symbols. */ + if ( arch_livepatch_symbol_deny(elf, &sym[i]) ) + { + dprintk(XENLOG_ERR, LIVEPATCH "%s: Symbol '%s' should not be in payload!\n", + elf->name, sym[i].name); + return -EINVAL; + } } elf->nsym = nsym; diff --git a/xen/include/xen/livepatch.h b/xen/include/xen/livepatch.h index e8c67d6..98ec012 100644 --- a/xen/include/xen/livepatch.h +++ b/xen/include/xen/livepatch.h @@ -50,6 +50,8 @@ bool_t is_patch(const void *addr); int arch_livepatch_verify_elf(const struct livepatch_elf *elf); bool arch_livepatch_symbol_ok(const struct livepatch_elf *elf, const struct livepatch_elf_sym *sym); +bool arch_livepatch_symbol_deny(const struct livepatch_elf *elf, + const struct livepatch_elf_sym *sym); int arch_livepatch_perform_rel(struct livepatch_elf *elf, const struct livepatch_elf_sec *base, const struct livepatch_elf_sec *rela);