[RFC PATCH 01/13] fs: binfmt_elf_efpic: add architecture hook elf_arch_finalize_exec

[RFC PATCH 01/13] fs: binfmt_elf_efpic: add architecture hook elf_arch_finalize_exec

[Hajime Tazaki]

FDPIC ELF loader adds an architecture hook at the end of loading
binaries to finalize the mapped memory before moving toward exec
function.  The hook is used by UML under !MMU when translating
syscall/sysenter instructions before calling execve.

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Kees Cook <kees@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-mm@kvack.org
Signed-off-by: Hajime Tazaki <thehajime@gmail.com>
---
 fs/binfmt_elf_fdpic.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 4fe5bb9f1b1f..ab16fdf475b0 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -175,6 +175,12 @@ static int elf_fdpic_fetch_phdrs(struct elf_fdpic_params *params,
 	return 0;
 }
 
+int __weak elf_arch_finalize_exec(struct elf_fdpic_params *exec_params,
+				  struct elf_fdpic_params *interp_params)
+{
+	return 0;
+}
+
 /*****************************************************************************/
 /*
  * load an fdpic binary into various bits of memory
@@ -457,6 +463,10 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm)
 			    dynaddr);
 #endif
 
+	retval = elf_arch_finalize_exec(&exec_params, &interp_params);
+	if (retval)
+		goto error;
+
 	finalize_exec(bprm);
 	/* everything is now ready... get the userspace context ready to roll */
 	entryaddr = interp_params.entry_addr ?: exec_params.entry_addr;
-- 
2.43.0

[RFC PATCH 02/13] x86/um: nommu: elf loader for fdpic

[Hajime Tazaki]

As UML supports CONFIG_MMU=n case, it has to use an alternate ELF
loader, FDPIC ELF loader.  In this commit, we added necessary
definitions in the arch, as UML has not been used so far.  It also
updates Kconfig file to use BINFMT_ELF_FDPIC under !MMU environment.

Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: linux-mm@kvack.org
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Hajime Tazaki <thehajime@gmail.com>
Signed-off-by: Ricardo Koller <ricarkol@google.com>
---
 arch/um/include/asm/mmu.h            |  5 +++++
 arch/um/include/asm/ptrace-generic.h | 17 +++++++++++++++++
 arch/x86/um/asm/elf.h                |  9 +++++++--
 arch/x86/um/asm/module.h             | 19 +------------------
 fs/Kconfig.binfmt                    |  2 +-
 5 files changed, 31 insertions(+), 21 deletions(-)

diff --git a/arch/um/include/asm/mmu.h b/arch/um/include/asm/mmu.h
index a3eaca41ff61..01422b761aa0 100644
--- a/arch/um/include/asm/mmu.h
+++ b/arch/um/include/asm/mmu.h
@@ -14,6 +14,11 @@ typedef struct mm_context {
 	/* Address range in need of a TLB sync */
 	unsigned long sync_tlb_range_from;
 	unsigned long sync_tlb_range_to;
+
+#ifdef CONFIG_BINFMT_ELF_FDPIC
+	unsigned long   exec_fdpic_loadmap;
+	unsigned long   interp_fdpic_loadmap;
+#endif
 } mm_context_t;
 
 #endif
diff --git a/arch/um/include/asm/ptrace-generic.h b/arch/um/include/asm/ptrace-generic.h
index 4696f24d1492..fefa7631394e 100644
--- a/arch/um/include/asm/ptrace-generic.h
+++ b/arch/um/include/asm/ptrace-generic.h
@@ -29,6 +29,12 @@ struct pt_regs {
 
 #define PTRACE_OLDSETOPTIONS 21
 
+#ifdef CONFIG_BINFMT_ELF_FDPIC
+#define PTRACE_GETFDPIC		31
+#define PTRACE_GETFDPIC_EXEC	0
+#define PTRACE_GETFDPIC_INTERP	1
+#endif
+
 struct task_struct;
 
 extern long subarch_ptrace(struct task_struct *child, long request,
@@ -44,6 +50,17 @@ extern void clear_flushed_tls(struct task_struct *task);
 extern int syscall_trace_enter(struct pt_regs *regs);
 extern void syscall_trace_leave(struct pt_regs *regs);
 
+#ifndef CONFIG_MMU
+#include <asm-generic/bug.h>
+
+static inline const struct user_regset_view *task_user_regset_view(
+	struct task_struct *task)
+{
+	WARN_ON_ONCE(true);
+	return 0;
+}
+#endif
+
 #endif
 
 #endif
diff --git a/arch/x86/um/asm/elf.h b/arch/x86/um/asm/elf.h
index 6052200fe925..4f87980bc9e9 100644
--- a/arch/x86/um/asm/elf.h
+++ b/arch/x86/um/asm/elf.h
@@ -8,6 +8,8 @@
 #include <asm/user.h>
 #include <skas.h>
 
+#define ELF_FDPIC_CORE_EFLAGS  0
+
 #ifdef CONFIG_X86_32
 
 #define R_386_NONE	0
@@ -188,8 +190,11 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm,
 
 extern unsigned long um_vdso_addr;
 #define AT_SYSINFO_EHDR 33
-#define ARCH_DLINFO	NEW_AUX_ENT(AT_SYSINFO_EHDR, um_vdso_addr)
-
+#define ARCH_DLINFO						\
+do {								\
+	NEW_AUX_ENT(AT_SYSINFO_EHDR, um_vdso_addr);		\
+	NEW_AUX_ENT(AT_MINSIGSTKSZ, 0);			\
+} while (0)
 #endif
 
 typedef unsigned long elf_greg_t;
diff --git a/arch/x86/um/asm/module.h b/arch/x86/um/asm/module.h
index a3b061d66082..4f7be1481979 100644
--- a/arch/x86/um/asm/module.h
+++ b/arch/x86/um/asm/module.h
@@ -2,23 +2,6 @@
 #ifndef __UM_MODULE_H
 #define __UM_MODULE_H
 
-/* UML is simple */
-struct mod_arch_specific
-{
-};
-
-#ifdef CONFIG_X86_32
-
-#define Elf_Shdr Elf32_Shdr
-#define Elf_Sym Elf32_Sym
-#define Elf_Ehdr Elf32_Ehdr
-
-#else
-
-#define Elf_Shdr Elf64_Shdr
-#define Elf_Sym Elf64_Sym
-#define Elf_Ehdr Elf64_Ehdr
-
-#endif
+#include <asm-generic/module.h>
 
 #endif
diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
index bd2f530e5740..419ba0282806 100644
--- a/fs/Kconfig.binfmt
+++ b/fs/Kconfig.binfmt
@@ -58,7 +58,7 @@ config ARCH_USE_GNU_PROPERTY
 config BINFMT_ELF_FDPIC
 	bool "Kernel support for FDPIC ELF binaries"
 	default y if !BINFMT_ELF
-	depends on ARM || ((M68K || RISCV || SUPERH || XTENSA) && !MMU)
+	depends on ARM || ((M68K || RISCV || SUPERH || UML || XTENSA) && !MMU)
 	select ELFCORE
 	help
 	  ELF FDPIC binaries are based on ELF, but allow the individual load
-- 
2.43.0

Re: [RFC PATCH 02/13] x86/um: nommu: elf loader for fdpic

[Johannes Berg]

On Thu, 2024-10-24 at 21:09 +0900, Hajime Tazaki wrote:
> 
> +#ifndef CONFIG_MMU
> +#include <asm-generic/bug.h>

Not sure that makes so much sense in the middle of the file, no harm
always having it?
> 
> +static inline const struct user_regset_view *task_user_regset_view(
> +	struct task_struct *task)

What happened to indentation here ;-)

static inline const ..... *
task_user_regset_view(....)

would be far easier to read.

> +++ b/arch/x86/um/asm/module.h
> @@ -2,23 +2,6 @@
>  #ifndef __UM_MODULE_H
>  #define __UM_MODULE_H
>  
> -/* UML is simple */
> -struct mod_arch_specific
> -{
> -};
> -
> -#ifdef CONFIG_X86_32
> -
> -#define Elf_Shdr Elf32_Shdr
> -#define Elf_Sym Elf32_Sym
> -#define Elf_Ehdr Elf32_Ehdr
> -
> -#else
> -
> -#define Elf_Shdr Elf64_Shdr
> -#define Elf_Sym Elf64_Sym
> -#define Elf_Ehdr Elf64_Ehdr
> -
> -#endif
> +#include <asm-generic/module.h>
>  
>  #endif

That seems like a worthwhile cleanup on its own, but you should be able
to just remove the file entirely?

johannes

Re: [RFC PATCH 02/13] x86/um: nommu: elf loader for fdpic

[Hajime Tazaki]

Hello Johannes,

On Fri, 25 Oct 2024 17:56:51 +0900,
Johannes Berg wrote:
> 
> On Thu, 2024-10-24 at 21:09 +0900, Hajime Tazaki wrote:
> > 
> > +#ifndef CONFIG_MMU
> > +#include <asm-generic/bug.h>
> 
> Not sure that makes so much sense in the middle of the file, no harm
> always having it?

agree.

> > +static inline const struct user_regset_view *task_user_regset_view(
> > +	struct task_struct *task)
> 
> What happened to indentation here ;-)
> 
> static inline const ..... *
> task_user_regset_view(....)
> 
> would be far easier to read.

fine, will fix it in the next revision.

> > +++ b/arch/x86/um/asm/module.h
> > @@ -2,23 +2,6 @@
> >  #ifndef __UM_MODULE_H
> >  #define __UM_MODULE_H
> >  
> > -/* UML is simple */
> > -struct mod_arch_specific
> > -{
> > -};
> > -
> > -#ifdef CONFIG_X86_32
> > -
> > -#define Elf_Shdr Elf32_Shdr
> > -#define Elf_Sym Elf32_Sym
> > -#define Elf_Ehdr Elf32_Ehdr
> > -
> > -#else
> > -
> > -#define Elf_Shdr Elf64_Shdr
> > -#define Elf_Sym Elf64_Sym
> > -#define Elf_Ehdr Elf64_Ehdr
> > -
> > -#endif
> > +#include <asm-generic/module.h>
> >  
> >  #endif
> 
> That seems like a worthwhile cleanup on its own, but you should be able
> to just remove the file entirely?

agree. will add module.h to arch/um/include/asm/Kbuild.

-- Hajime