| Message ID | 20180406151752.10854-2-christophe.lyon@st.com |
|---|---|
| State | New |
| Headers | show |
| Series | FDPIC ABI for ARM | expand |
On 6 April 2018 at 16:17, Christophe Lyon <christophe.lyon@st.com> wrote: > Adds --enable-fdpic and --disable-fdpic configure options. This > feature is disabled by default, that's why it is not described in the > "Optional features" help section (which are enabled by default if > possible). > > FDPIC ELF objects are identified with e_ident[EI_OSABI] == > ELFOSABI_ARM_FDPIC. If we can identify these ELF objects by looking in the ELF header, why would we want to make this all a configure option that's disabled by default? I think we should just have support for these binaries enabled always. Otherwise it will bitrot because nobody compiles it. thanks -- PMM
On 13/04/2018 17:04, Peter Maydell wrote: > On 6 April 2018 at 16:17, Christophe Lyon <christophe.lyon@st.com> wrote: >> Adds --enable-fdpic and --disable-fdpic configure options. This >> feature is disabled by default, that's why it is not described in the >> "Optional features" help section (which are enabled by default if >> possible). >> >> FDPIC ELF objects are identified with e_ident[EI_OSABI] == >> ELFOSABI_ARM_FDPIC. > > If we can identify these ELF objects by looking in the ELF header, > why would we want to make this all a configure option that's > disabled by default? > > I think we should just have support for these binaries enabled > always. Otherwise it will bitrot because nobody compiles it. > We are relying on a pre-existing CONFIG_USE_FDPIC, which is currently never defined. This was introduced by commit 1af02e83 back in 2011, and indeed if you try to build QEMU with CONFIG_USE_FDPIC, the build fails because elf_is_fdpic() is not defined. We tried to conform to this existing support, but maybe it's already bit-rotten? Do you suggest removing CONFIG_USE_FDPIC? Thanks > thanks > -- PMM > . >
On 16 April 2018 at 08:57, Christophe Lyon <christophe.lyon@st.com> wrote: > On 13/04/2018 17:04, Peter Maydell wrote: >> I think we should just have support for these binaries enabled >> always. Otherwise it will bitrot because nobody compiles it. >> > We are relying on a pre-existing CONFIG_USE_FDPIC, which is currently > never defined. This was introduced by commit 1af02e83 back in 2011, > and indeed if you try to build QEMU with CONFIG_USE_FDPIC, the build fails > because elf_is_fdpic() is not defined. This looks like an excellent demonstration of why we shouldn't hide this feature behind a defaults-to-off #define :-) > Do you suggest removing CONFIG_USE_FDPIC? Yes. Given how old the existing disabled FDPIC code is, I would also suggest you carefully review any of it that you're using... thanks -- PMM
diff --git a/configure b/configure index 4d0e92c..af4c14b 100755 --- a/configure +++ b/configure @@ -451,6 +451,7 @@ jemalloc="no" replication="yes" vxhs="" libxml2="" +fdpic="no" supported_cpu="no" supported_os="no" @@ -1374,6 +1375,10 @@ for opt do ;; --disable-git-update) git_update=no ;; + --disable-fdpic) fdpic="no" + ;; + --enable-fdpic) fdpic="yes" + ;; *) echo "ERROR: unknown option $opt" echo "Try '$0 --help' for more information" @@ -1544,6 +1549,8 @@ Advanced options (experts only): xen pv domain builder --enable-debug-stack-usage track the maximum stack usage of stacks created by qemu_alloc_stack + --disable-fdpic disable loading of FDPIC binary (default) + --enable-fdpic enable loading of FDPIC binary Optional features, enabled with --enable-FEATURE and disabled with --disable-FEATURE, default is enabled if available: @@ -7085,6 +7092,9 @@ fi echo "LDFLAGS+=$ldflags" >> $config_target_mak echo "QEMU_CFLAGS+=$cflags" >> $config_target_mak +if [ "$fdpic" = "yes" ]; then + echo "CONFIG_USE_FDPIC=y" >> $config_target_mak +fi done # for target in $targets diff --git a/include/elf.h b/include/elf.h index c0dc9bb..934dbbd 100644 --- a/include/elf.h +++ b/include/elf.h @@ -1483,6 +1483,7 @@ typedef struct elf64_shdr { #define ELFOSABI_TRU64 10 /* Compaq TRU64 UNIX. */ #define ELFOSABI_MODESTO 11 /* Novell Modesto. */ #define ELFOSABI_OPENBSD 12 /* OpenBSD. */ +#define ELFOSABI_ARM_FDPIC 65 /* ARM FDPIC */ #define ELFOSABI_ARM 97 /* ARM */ #define ELFOSABI_STANDALONE 255 /* Standalone (embedded) application */ diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 23e3495..7ba3795 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -1658,6 +1658,14 @@ static void zero_bss(abi_ulong elf_bss, abi_ulong last_bss, int prot) } #ifdef CONFIG_USE_FDPIC + +#ifdef TARGET_ARM +static int elf_is_fdpic(struct elfhdr *exec) +{ + return exec->e_ident[EI_OSABI] == ELFOSABI_ARM_FDPIC; +} +#endif + static abi_ulong loader_build_fdpic_loadmap(struct image_info *info, abi_ulong sp) { uint16_t n;
Adds --enable-fdpic and --disable-fdpic configure options. This feature is disabled by default, that's why it is not described in the "Optional features" help section (which are enabled by default if possible). FDPIC ELF objects are identified with e_ident[EI_OSABI] == ELFOSABI_ARM_FDPIC. Co-Authored-By: Mickaël Guêné <mickael.guene@st.com> Signed-off-by: Christophe Lyon <christophe.lyon@st.com> -- 2.6.3