[PATCH v2 09/10] binfmt_flat: add MMU-specific support

[Nicolas Pitre]

Not much else to do at this point except for the different stack setups.

SuperH and Xtensa could be added to the allowed list if they implement
__put_user_unaligned() and __get_user_unaligned().

Signed-off-by: Nicolas Pitre <n...@linaro.org>
---
 fs/Kconfig.binfmt |  3 ++-
 fs/binfmt_flat.c  | 16 +++++++++++++---
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
index 72c03354c1..4c09d93d95 100644
--- a/fs/Kconfig.binfmt
+++ b/fs/Kconfig.binfmt
@@ -89,7 +89,8 @@ config BINFMT_SCRIPT
 
 config BINFMT_FLAT
        bool "Kernel support for flat binaries"
-       depends on !MMU && (!FRV || BROKEN)
+       depends on !MMU || ARM || M68K
+       depends on !FRV || BROKEN
        help
          Support uClinux FLAT format binaries.
 
diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 3221ed9d7c..4cb0c4b6ae 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -546,7 +546,7 @@ static int load_flat_file(struct linux_binprm * bprm,
         * case,  and then the fully copied to RAM case which lumps
         * it all together.
         */
-       if ((flags & (FLAT_FLAG_RAM|FLAT_FLAG_GZIP)) == 0) {
+       if (!IS_ENABLED(CONFIG_MMU) && !(flags & 
(FLAT_FLAG_RAM|FLAT_FLAG_GZIP))) {
                /*
                 * this should give us a ROM ptr,  but if it doesn't we don't
                 * really care
@@ -687,7 +687,9 @@ static int load_flat_file(struct linux_binprm * bprm,
                 */
                current->mm->start_brk = datapos + data_len + bss_len;
                current->mm->brk = (current->mm->start_brk + 3) & ~3;
+#ifndef CONFIG_MMU
                current->mm->context.end_brk = memp + memp_size - stack_len;
+#endif
        }
 
        if (flags & FLAT_FLAG_KTRACE) {
@@ -878,7 +880,7 @@ static int load_flat_binary(struct linux_binprm * bprm)
 {
        struct lib_info libinfo;
        struct pt_regs *regs = current_pt_regs();
-       unsigned long stack_len;
+       unsigned long stack_len = 0;
        unsigned long start_addr;
        int res;
        int i, j;
@@ -892,7 +894,9 @@ static int load_flat_binary(struct linux_binprm * bprm)
         * pedantic and include space for the argv/envp array as it may have
         * a lot of entries.
         */
-       stack_len = PAGE_SIZE * MAX_ARG_PAGES - bprm->p;  /* the strings */
+#ifndef CONFIG_MMU
+       stack_len += PAGE_SIZE * MAX_ARG_PAGES - bprm->p; /* the strings */
+#endif
        stack_len += (bprm->argc + 1) * sizeof(char *);   /* the argv array */
        stack_len += (bprm->envc + 1) * sizeof(char *);   /* the envp array */
        stack_len = ALIGN(stack_len, FLAT_STACK_ALIGN);
@@ -920,6 +924,11 @@ static int load_flat_binary(struct linux_binprm * bprm)
 
        set_binfmt(&flat_format);
 
+#ifdef CONFIG_MMU
+       res = setup_arg_pages(bprm, STACK_TOP, EXSTACK_DEFAULT);
+       if (!res)
+               res = create_flat_tables(bprm, bprm->p);
+#else
        /* Stash our initial stack pointer into the mm structure */
        current->mm->start_stack =
                ((current->mm->context.end_brk + stack_len + 3) & ~3) - 4;
@@ -929,6 +938,7 @@ static int load_flat_binary(struct linux_binprm * bprm)
        res = transfer_args_to_stack(bprm, &current->mm->start_stack);
        if (!res)
                res = create_flat_tables(bprm, current->mm->start_stack);
+#endif
        if (res)
                return res;
 
-- 
2.7.4