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[PATCH v6 11/21] arm64: ilp32: introduce binfmt_ilp32.c

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  [PATCH v6 11/21] arm64: ilp32: introduce binfmt_ilp32.c Yury Norov <ynorov@caviumnetworks.com> - 2016-01-08 00:40 +0100
    Re: [PATCH v6 11/21] arm64: ilp32: introduce binfmt_ilp32.c Yury Norov <ynorov@caviumnetworks.com> - 2016-01-08 00:50 +0100
    Re: [PATCH v6 11/21] arm64: ilp32: introduce binfmt_ilp32.c Arnd Bergmann <arnd@arndb.de> - 2016-01-08 10:10 +0100
      Re: [PATCH v6 11/21] arm64: ilp32: introduce binfmt_ilp32.c Yury Norov <ynorov@caviumnetworks.com> - 2016-01-12 17:50 +0100
        Re: [PATCH v6 11/21] arm64: ilp32: introduce binfmt_ilp32.c Arnd Bergmann <arnd@arndb.de> - 2016-01-13 00:10 +0100

#1304009 — [PATCH v6 11/21] arm64: ilp32: introduce binfmt_ilp32.c

to handle ILP32 binaries

Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
---
 arch/arm64/kernel/Makefile       |  1 +
 arch/arm64/kernel/binfmt_ilp32.c | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+)
 create mode 100644 arch/arm64/kernel/binfmt_ilp32.c

diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index f1b798a..ad7158c 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -28,6 +28,7 @@ $(obj)/%.stub.o: $(obj)/%.o FORCE
 arm64-obj-$(CONFIG_AARCH32_EL0)		+= sys32.o kuser32.o signal32.o 	\
 					   sys_compat.o entry32.o		\
 					   ../../arm/kernel/opcodes.o binfmt_elf32.o
+arm64-obj-$(CONFIG_ARM64_ILP32)		+= binfmt_ilp32.o
 arm64-obj-$(CONFIG_FUNCTION_TRACER)	+= ftrace.o entry-ftrace.o
 arm64-obj-$(CONFIG_MODULES)		+= arm64ksyms.o module.o
 arm64-obj-$(CONFIG_PERF_EVENTS)		+= perf_regs.o perf_callchain.o
diff --git a/arch/arm64/kernel/binfmt_ilp32.c b/arch/arm64/kernel/binfmt_ilp32.c
new file mode 100644
index 0000000..02a7a6c
--- /dev/null
+++ b/arch/arm64/kernel/binfmt_ilp32.c
@@ -0,0 +1,21 @@
+/*
+ * Support for ILP32 Linux/aarch64 ELF binaries.
+ */
+
+/* AARCH64 ILP32 EABI. */
+#define compat_elf_check_arch(x)	(((x)->e_machine == EM_AARCH64)	\
+					&& (x)->e_ident[EI_CLASS] == ELFCLASS32)
+
+#define COMPAT_SET_PERSONALITY(ex)					\
+do {									\
+	set_thread_flag(TIF_32BIT_AARCH64);				\
+	clear_thread_flag(TIF_32BIT);					\
+} while (0)
+
+#define COMPAT_ARCH_DLINFO						\
+do {									\
+	NEW_AUX_ENT(AT_SYSINFO_EHDR,					\
+		    (elf_addr_t)(long)current->mm->context.vdso);	\
+} while (0)
+
+#include "../../../fs/compat_binfmt_elf.c"
-- 
2.5.0

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#1304026

On Fri, Jan 08, 2016 at 02:34:29AM +0300, Yury Norov wrote:
> to handle ILP32 binaries
> 
> Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
> ---
[...]
> diff --git a/arch/arm64/kernel/binfmt_ilp32.c b/arch/arm64/kernel/binfmt_ilp32.c
> new file mode 100644
> index 0000000..02a7a6c
> --- /dev/null
> +++ b/arch/arm64/kernel/binfmt_ilp32.c
> @@ -0,0 +1,21 @@
> +/*
> + * Support for ILP32 Linux/aarch64 ELF binaries.
> + */
> +
> +/* AARCH64 ILP32 EABI. */
> +#define compat_elf_check_arch(x)	(((x)->e_machine == EM_AARCH64)	\
> +					&& (x)->e_ident[EI_CLASS] == ELFCLASS32)
> +

Not sure about this. Originally it was just:
        #define compat_elf_check_arch(x)	(((x)->e_machine == EM_AARCH64)	\

But how than distinguish aarch64 and aarch64/ilp32 elfs? 

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#1304289

On Friday 08 January 2016 02:34:29 Yury Norov wrote:
> +
> +#include "../../../fs/compat_binfmt_elf.c"
> 

This is the wrong file, you have to include fs/binfmt_elf.c, otherwise
you pick up the same definitions that you have for the other one.

Alternatively, you can also change binfmt_elf32.c to include fs/binfmt_elf.c
and use fs/compat_binfmt_elf.c here if that makes the code nicer, you
just can use the compat file for both or things get ugly because of
the extra indirections.

	Arnd

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#1307619

On Fri, Jan 08, 2016 at 10:08:44AM +0100, Arnd Bergmann wrote:
> On Friday 08 January 2016 02:34:29 Yury Norov wrote:
> > +
> > +#include "../../../fs/compat_binfmt_elf.c"
> > 
> 
> This is the wrong file, you have to include fs/binfmt_elf.c, otherwise
> you pick up the same definitions that you have for the other one.
> 

I chose compat as it's how it wokrs now. It redefines some types like
user_long_t, and I think it's neccessary for ILP32, as for aarch32.

> Alternatively, you can also change binfmt_elf32.c to include fs/binfmt_elf.c
> and use fs/compat_binfmt_elf.c here if that makes the code nicer, you
> just can use the compat file for both or things get ugly because of
> the extra indirections.
> 
> 	Arnd

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#1307907

On Tuesday 12 January 2016 19:46:41 Yury Norov wrote:
> On Fri, Jan 08, 2016 at 10:08:44AM +0100, Arnd Bergmann wrote:
> > On Friday 08 January 2016 02:34:29 Yury Norov wrote:
> > > +
> > > +#include "../../../fs/compat_binfmt_elf.c"
> > > 
> > 
> > This is the wrong file, you have to include fs/binfmt_elf.c, otherwise
> > you pick up the same definitions that you have for the other one.
> > 
> 
> I chose compat as it's how it wokrs now. It redefines some types like
> user_long_t, and I think it's neccessary for ILP32, as for aarch32.

I really think the double indirection adds way too much complexity
here, it makes it rather hard to understand what is going on, and
that leads to bugs.

fs/compat_binfmt_elf.c is not doing much at all, and most of it is not
actually needed if you just make a copy of that file and fill in the
data as needed. Some of the overrides (ELF_ARCH, ELF_PLATFORM, ELF_NREG,
ELF_HWCAP, ELF_HWCAP2) are identical between ilp32 and lp64 modes
for arm64, but are different for arm32 compat, so you don't even have
to override them at all.

	Arnd

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