Messages in this thread | | | From | Damien Le Moal <> | Subject | Re: [PATCH v4 1/2] binfmt_flat: allow not offsetting data start | Date | Thu, 22 Apr 2021 12:00:32 +0000 |
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On 2021/04/18 11:38, Greg Ungerer wrote: > > > On 17/4/21 2:54 pm, Damien Le Moal wrote: >> On 2021/04/17 13:52, Greg Ungerer wrote: >>> >>> 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. >> >> Oops. Sorry about that. I should have better checked :) >> >>> >>> >>>> /* >>>> * 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. >> >> Great. Thanks ! >> Are you taking both patches or should Plamer take the riscv Kconfig change >> through his tree ? > > I am happy to take both. > Palmer?
Palmer,
Ping !
-- Damien Le Moal Western Digital Research
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