On Tue, Jul 11, 2023, at 9:07 AM, Greg Ungerer wrote:
> Add support for enabling and using the binfmt_elf_fdpic program loader
> on RISC-V platforms. The most important change is to setup registers
> during program load to pass the mapping addresses to the new process.
>
> One of the interesting features of the elf-fdpic loader is that it
> also allows appropriately compiled ELF format binaries to be loaded on
> nommu systems. Appropriate being those compiled with -pie.
>
> Signed-off-by: Greg Ungerer <gerg@xxxxxxxxxx>
> ---
> v1->v2: rebase onto linux-6.5-rc1
> increment PTRACE_GETFDPIC value to keep it unique
>
> arch/riscv/include/asm/elf.h | 11 ++++++++++-
> arch/riscv/include/asm/mmu.h | 4 ++++
> arch/riscv/include/uapi/asm/ptrace.h | 5 +++++
> fs/Kconfig.binfmt | 2 +-
> 4 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/include/asm/elf.h b/arch/riscv/include/asm/elf.h
> index c24280774caf..c33fe923ef6d 100644
> --- a/arch/riscv/include/asm/elf.h
> +++ b/arch/riscv/include/asm/elf.h
> @@ -41,6 +41,7 @@ extern bool compat_elf_check_arch(Elf32_Ehdr *hdr);
> #define compat_elf_check_arch compat_elf_check_arch
>
> #define CORE_DUMP_USE_REGSET
> +#define ELF_FDPIC_CORE_EFLAGS 0
> #define ELF_EXEC_PAGESIZE (PAGE_SIZE)
>
> /*
> @@ -69,6 +70,13 @@ extern bool compat_elf_check_arch(Elf32_Ehdr *hdr);
> #define ELF_HWCAP riscv_get_elf_hwcap()
> extern unsigned long elf_hwcap;
>
> +#define ELF_FDPIC_PLAT_INIT(_r, _exec_map_addr, _interp_map_addr,
> dynamic_addr) \
> + do { \
> + (_r)->a1 = _exec_map_addr; \
> + (_r)->a2 = _interp_map_addr; \
> + (_r)->a3 = dynamic_addr; \
> + } while (0)
> +
This should probably be left empty for now; it will be defined by the
ELF FDPIC ABI when that is done, and shouldn't be used by normal ELF
binaries. I'd ask if there's a reason it starts at a1 instead of a0,
but it seems idiosyncratic on all arches that have full FDPIC support.
-s
> /*
> * This yields a string that ld.so will use to load implementation
> * specific libraries for optimization. This is more specific in
> @@ -78,7 +86,6 @@ extern unsigned long elf_hwcap;
>
> #define COMPAT_ELF_PLATFORM (NULL)
>
> -#ifdef CONFIG_MMU
> #define ARCH_DLINFO \
> do { \
> /* \
> @@ -115,6 +122,8 @@ do { \
> else \
> NEW_AUX_ENT(AT_IGNORE, 0); \
> } while (0)
> +
> +#ifdef CONFIG_MMU
> #define ARCH_HAS_SETUP_ADDITIONAL_PAGES
> struct linux_binprm;
> extern int arch_setup_additional_pages(struct linux_binprm *bprm,
> diff --git a/arch/riscv/include/asm/mmu.h b/arch/riscv/include/asm/mmu.h
> index 0099dc116168..355504b37f8e 100644
> --- a/arch/riscv/include/asm/mmu.h
> +++ b/arch/riscv/include/asm/mmu.h
> @@ -20,6 +20,10 @@ typedef struct {
> /* A local icache flush is needed before user execution can resume. */
> cpumask_t icache_stale_mask;
> #endif
> +#ifdef CONFIG_BINFMT_ELF_FDPIC
> + unsigned long exec_fdpic_loadmap;
> + unsigned long interp_fdpic_loadmap;
> +#endif
> } mm_context_t;
>
> void __init create_pgd_mapping(pgd_t *pgdp, uintptr_t va, phys_addr_t
> pa,
> diff --git a/arch/riscv/include/uapi/asm/ptrace.h
> b/arch/riscv/include/uapi/asm/ptrace.h
> index e17c550986a6..30f6d6537adc 100644
> --- a/arch/riscv/include/uapi/asm/ptrace.h
> +++ b/arch/riscv/include/uapi/asm/ptrace.h
> @@ -10,6 +10,11 @@
>
> #include <linux/types.h>
>
> +#define PTRACE_GETFDPIC 33
> +
> +#define PTRACE_GETFDPIC_EXEC 0
> +#define PTRACE_GETFDPIC_INTERP 1
> +
> /*
> * User-mode register state for core dumps, ptrace, sigcontext
> *
> diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
> index 93539aac0e5b..f5693164ca9a 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 || SUPERH || XTENSA) && !MMU)
> + depends on ARM || ((M68K || RISCV || SUPERH || XTENSA) && !MMU)
> select ELFCORE
> help
> ELF FDPIC binaries are based on ELF, but allow the individual load
> --
> 2.25.1
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/linux-riscv
