Messages in this thread | | | Subject | Re: [PATCH v4 1/2] binfmt_flat: allow not offsetting data start | From | Greg Ungerer <> | Date | Sat, 17 Apr 2021 14:52:05 +1000 |
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On 17/4/21 11:10 am, Damien Le Moal wrote: > Commit 2217b9826246 ("binfmt_flat: revert "binfmt_flat: don't offset > the data start"") restored offsetting the start of the data section by > a number of words defined by MAX_SHARED_LIBS. As a result, since > MAX_SHARED_LIBS is never 0, a gap between the text and data sections > always exists. For architectures which cannot support a such gap > between the text and data sections (e.g. riscv nommu), flat binary > programs cannot be executed. > > To allow an architecture to request no data start offset to allow for > contiguous text and data sections for binaries flagged with > FLAT_FLAG_RAM, introduce the new config option > CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET. Using this new option, the > macro DATA_START_OFFSET_WORDS is conditionally defined in binfmt_flat.c > to MAX_SHARED_LIBS for architectures tolerating or needing the data > start offset (CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET disabled case) > and to 0 when CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET is enabled. > DATA_START_OFFSET_WORDS is used in load_flat_file() to calculate the > data section length and start position. > > Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> > --- > fs/Kconfig.binfmt | 3 +++ > fs/binfmt_flat.c | 19 ++++++++++++++----- > 2 files changed, 17 insertions(+), 5 deletions(-) > > diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt > index c6f1c8c1934e..06fb7a93a1bd 100644 > --- a/fs/Kconfig.binfmt > +++ b/fs/Kconfig.binfmt > @@ -112,6 +112,9 @@ config BINFMT_FLAT_ARGVP_ENVP_ON_STACK > config BINFMT_FLAT_OLD_ALWAYS_RAM > bool > > +config BINFMT_FLAT_NO_DATA_START_OFFSET > + bool > + > config BINFMT_FLAT_OLD > bool "Enable support for very old legacy flat binaries" > depends on BINFMT_FLAT > diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c > index b9c658e0548e..1dc68dfba3e0 100644 > --- a/fs/binfmt_flat.c > +++ b/fs/binfmt_flat.c > @@ -74,6 +74,12 @@ > #define MAX_SHARED_LIBS (1) > #endif > > +#ifdef CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET > +#define DATA_START_OFFSET_WORDS (0) > +#else > +#define DATA_START_OFFSET_WORDS (MAX_SHARED_LIBS) > +#endif > + > struct lib_info { > struct { > unsigned long start_code; /* Start of text segment */ > @@ -560,6 +566,7 @@ static int load_flat_file(struct linux_binprm *bprm, > * it all together. > */ > if (!IS_ENABLED(CONFIG_MMU) && !(flags & (FLAT_FLAG_RAM|FLAT_FLAG_GZIP))) { > +
Random white space change... Don't worry about re-spinning though, I will just edit this chunk out.
> /* > * this should give us a ROM ptr, but if it doesn't we don't > * really care > @@ -576,7 +583,8 @@ static int load_flat_file(struct linux_binprm *bprm, > goto err; > } > > - len = data_len + extra + MAX_SHARED_LIBS * sizeof(unsigned long); > + len = data_len + extra + > + DATA_START_OFFSET_WORDS * sizeof(unsigned long); > len = PAGE_ALIGN(len); > realdatastart = vm_mmap(NULL, 0, len, > PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, 0); > @@ -591,7 +599,7 @@ static int load_flat_file(struct linux_binprm *bprm, > goto err; > } > datapos = ALIGN(realdatastart + > - MAX_SHARED_LIBS * sizeof(unsigned long), > + DATA_START_OFFSET_WORDS * sizeof(unsigned long), > FLAT_DATA_ALIGN); > > pr_debug("Allocated data+bss+stack (%u bytes): %lx\n", > @@ -622,7 +630,8 @@ static int load_flat_file(struct linux_binprm *bprm, > memp_size = len; > } else { > > - len = text_len + data_len + extra + MAX_SHARED_LIBS * sizeof(u32); > + len = text_len + data_len + extra + > + DATA_START_OFFSET_WORDS * sizeof(u32); > len = PAGE_ALIGN(len); > textpos = vm_mmap(NULL, 0, len, > PROT_READ | PROT_EXEC | PROT_WRITE, MAP_PRIVATE, 0); > @@ -638,7 +647,7 @@ static int load_flat_file(struct linux_binprm *bprm, > > realdatastart = textpos + ntohl(hdr->data_start); > datapos = ALIGN(realdatastart + > - MAX_SHARED_LIBS * sizeof(u32), > + DATA_START_OFFSET_WORDS * sizeof(u32), > FLAT_DATA_ALIGN); > > reloc = (__be32 __user *) > @@ -714,7 +723,7 @@ static int load_flat_file(struct linux_binprm *bprm, > ret = result; > pr_err("Unable to read code+data+bss, errno %d\n", ret); > vm_munmap(textpos, text_len + data_len + extra + > - MAX_SHARED_LIBS * sizeof(u32)); > + DATA_START_OFFSET_WORDS * sizeof(u32)); > goto err; > } > } >
Thanks, otherwise looks good.
Acked-by: Greg Ungerer <gerg@linux-m68k.org>
I will push this into my m68knommu tree, for-next branch. I just carry the flat format changes in that tree now to make my life easier.
Regards Greg
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