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Date:   Sun, 10 Apr 2022 03:08:28 -0500
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Subject: Re: [RFC PULL] remove arch/h8300
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From:   Rob Landley <rob@landley.net>
To:     Greg Ungerer <gerg@linux-m68k.org>,
        Finn Thain <fthain@linux-m68k.org>
Cc:     Daniel Palmer <daniel@0x0f.com>, Arnd Bergmann <arnd@arndb.de>,
        Christoph Hellwig <hch@infradead.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
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        Damien Le Moal <damien.lemoal@wdc.com>,
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On 4/10/22 02:26, Rob Landley wrote:
>> FWIW this will do it:
>> 
>>      qemu-system-m68k -nographic -machine mcf5208evb -kernel vmlinux
>> 
>> That will boot an m5208evb_defconfig generated vmlinux.
>> But you will need a user space to get a full boot to login/shell.
> 
> No FDPIC support. :(

First stab at switching on CONFIG_BINFMT_FDPIC in the coldfire config and adding
enough stuff to shut up the compiler. Maybe it'll let me load a PIE binary?
Dunno yet, but it compiled a vmlinux that booted to the same panic as the
previous one because I haven't fed it an initramfs yet...

I also had to disable CONFIG_ELF_CORE or else the link died with:

m68k-linux-musl-ld: fs/binfmt_elf_fdpic.o: in function `elf_dump_thread_status':
binfmt_elf_fdpic.c:(.text+0x18): undefined reference to `task_user_regset_view'
make: *** [Makefile:1155: vmlinux] Error 1

But when I did THAT it compiled. :)

diff --git a/arch/m68k/include/asm/elf.h b/arch/m68k/include/asm/elf.h
index 3d387ceaea3f..bcb072396640 100644
--- a/arch/m68k/include/asm/elf.h
+++ b/arch/m68k/include/asm/elf.h
@@ -114,4 +114,6 @@ typedef struct user_m68kfp_struct elf_fpregset_t;

 #define ELF_PLATFORM  (NULL)

+#define ELF_FDPIC_CORE_EFLAGS 0
+
 #endif
diff --git a/arch/m68k/include/asm/mmu.h b/arch/m68k/include/asm/mmu.h
index 5c15aacb1370..6f6d83b731ed 100644
--- a/arch/m68k/include/asm/mmu.h
+++ b/arch/m68k/include/asm/mmu.h
@@ -8,6 +8,10 @@ typedef unsigned long mm_context_t;
 #else
 typedef struct {
 	unsigned long		end_brk;
+#ifdef CONFIG_BINFMT_ELF_FDPIC
+        unsigned long           exec_fdpic_loadmap;
+        unsigned long           interp_fdpic_loadmap;
+#endif
 } mm_context_t;
 #endif

diff --git a/arch/m68k/include/uapi/asm/ptrace.h
b/arch/m68k/include/uapi/asm/ptrace.h
index 19a1b9d0d858..869601381f30 100644
--- a/arch/m68k/include/uapi/asm/ptrace.h
+++ b/arch/m68k/include/uapi/asm/ptrace.h
@@ -71,6 +71,10 @@ struct switch_stack {
 #define PTRACE_SETREGS            13
 #define PTRACE_GETFPREGS          14
 #define PTRACE_SETFPREGS          15
+#define PTRACE_GETFDPIC           31
+
+#define PTRACE_GETFDPIC_EXEC      0
+#define PTRACE_GETFDPIC_INTERP    1

 #define PTRACE_GET_THREAD_AREA    25

diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
index 4d5ae61580aa..073360aa982c 100644
--- a/fs/Kconfig.binfmt
+++ b/fs/Kconfig.binfmt
@@ -45,7 +45,7 @@ config ARCH_USE_GNU_PROPERTY
 config BINFMT_ELF_FDPIC
 	bool "Kernel support for FDPIC ELF binaries"
 	default y if !BINFMT_ELF
-	depends on (ARM || (SUPERH && !MMU))
+	depends on (ARM || (SUPERH && !MMU) || M68K)
 	select ELFCORE
 	help
 	  ELF FDPIC binaries are based on ELF, but allow the individual load


Rob