Re: [PATCH] binfmt_flat: Remove shared library support

Damien Le Moal
2022-04-20T23:37:09Z

On 4/20/22 23:58, Eric W. Biederman wrote:
>

Nit: extra blank line here.

> In a recent discussion[1] it was reported that the binfmt_flat library
> support was only ever used on m68k and even on m68k has not been used
> in a very long time.
>
> The structure of binfmt_flat is different from all of the other binfmt
> implementations becasue of this shared library support and it made

s/becasue/because

> life and code review more effort when I refactored the code in fs/exec.c.
>
> Since in practice the code is dead remove the binfmt_flat shared libarary

s/libarary/library

> support and make maintenance of the code easier.
>
> [1] https://lkml.kernel.org/r/81788b56-5b15-7308-38c7-c7f2502c4e15@linux-m68k.org
> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
> ---
>
> Can the binfmt_flat folks please verify that the shared library support
> really isn't used?

As mentioned in a different email, it is not supported by the toolchains
for riscv.

>
> Was binfmt_flat being enabled on arm and sh the mistake it looks like?
>
> arch/arm/configs/lpc18xx_defconfig | 1 -
> arch/arm/configs/mps2_defconfig | 1 -
> arch/arm/configs/stm32_defconfig | 1 -
> arch/arm/configs/vf610m4_defconfig | 1 -
> arch/sh/configs/rsk7201_defconfig | 1 -
> arch/sh/configs/rsk7203_defconfig | 1 -
> arch/sh/configs/se7206_defconfig | 1 -
> fs/Kconfig.binfmt | 6 -
> fs/binfmt_flat.c | 190 ++++++-----------------------
> 9 files changed, 40 insertions(+), 163 deletions(-)
>
> diff --git a/arch/arm/configs/lpc18xx_defconfig b/arch/arm/configs/lpc18xx_defconfig
> index be882ea0eee4..688c9849eec8 100644
> --- a/arch/arm/configs/lpc18xx_defconfig
> +++ b/arch/arm/configs/lpc18xx_defconfig
> @@ -30,7 +30,6 @@ CONFIG_ARM_APPENDED_DTB=y
> # CONFIG_BLK_DEV_BSG is not set
> CONFIG_BINFMT_FLAT=y
> CONFIG_BINFMT_ZFLAT=y
> -CONFIG_BINFMT_SHARED_FLAT=y
> # CONFIG_COREDUMP is not set
> CONFIG_NET=y
> CONFIG_PACKET=y
> diff --git a/arch/arm/configs/mps2_defconfig b/arch/arm/configs/mps2_defconfig
> index 89f4a6ff30bd..c1e98e33a348 100644
> --- a/arch/arm/configs/mps2_defconfig
> +++ b/arch/arm/configs/mps2_defconfig
> @@ -23,7 +23,6 @@ CONFIG_PREEMPT_VOLUNTARY=y
> CONFIG_ZBOOT_ROM_TEXT=0x0
> CONFIG_ZBOOT_ROM_BSS=0x0
> CONFIG_BINFMT_FLAT=y
> -CONFIG_BINFMT_SHARED_FLAT=y
> # CONFIG_COREDUMP is not set
> # CONFIG_SUSPEND is not set
> CONFIG_NET=y
> diff --git a/arch/arm/configs/stm32_defconfig b/arch/arm/configs/stm32_defconfig
> index 551db328009d..71d6bfcf4551 100644
> --- a/arch/arm/configs/stm32_defconfig
> +++ b/arch/arm/configs/stm32_defconfig
> @@ -28,7 +28,6 @@ CONFIG_ZBOOT_ROM_BSS=0x0
> CONFIG_XIP_KERNEL=y
> CONFIG_XIP_PHYS_ADDR=0x08008000
> CONFIG_BINFMT_FLAT=y
> -CONFIG_BINFMT_SHARED_FLAT=y
> # CONFIG_COREDUMP is not set
> CONFIG_DEVTMPFS=y
> CONFIG_DEVTMPFS_MOUNT=y
> diff --git a/arch/arm/configs/vf610m4_defconfig b/arch/arm/configs/vf610m4_defconfig
> index a89f035c3b01..70fdbfd83484 100644
> --- a/arch/arm/configs/vf610m4_defconfig
> +++ b/arch/arm/configs/vf610m4_defconfig
> @@ -18,7 +18,6 @@ CONFIG_XIP_KERNEL=y
> CONFIG_XIP_PHYS_ADDR=0x0f000080
> CONFIG_BINFMT_FLAT=y
> CONFIG_BINFMT_ZFLAT=y
> -CONFIG_BINFMT_SHARED_FLAT=y
> # CONFIG_SUSPEND is not set
> # CONFIG_UEVENT_HELPER is not set
> # CONFIG_STANDALONE is not set
> diff --git a/arch/sh/configs/rsk7201_defconfig b/arch/sh/configs/rsk7201_defconfig
> index e41526120be1..619c18699459 100644
> --- a/arch/sh/configs/rsk7201_defconfig
> +++ b/arch/sh/configs/rsk7201_defconfig
> @@ -25,7 +25,6 @@ CONFIG_CMDLINE_OVERWRITE=y
> CONFIG_CMDLINE="console=ttySC0,115200 earlyprintk=serial ignore_loglevel"
> CONFIG_BINFMT_FLAT=y
> CONFIG_BINFMT_ZFLAT=y
> -CONFIG_BINFMT_SHARED_FLAT=y
> CONFIG_PM=y
> CONFIG_CPU_IDLE=y
> # CONFIG_STANDALONE is not set
> diff --git a/arch/sh/configs/rsk7203_defconfig b/arch/sh/configs/rsk7203_defconfig
> index 6af08fa1ddf8..5a54e2b883f0 100644
> --- a/arch/sh/configs/rsk7203_defconfig
> +++ b/arch/sh/configs/rsk7203_defconfig
> @@ -30,7 +30,6 @@ CONFIG_CMDLINE_OVERWRITE=y
> CONFIG_CMDLINE="console=ttySC0,115200 earlyprintk=serial ignore_loglevel"
> CONFIG_BINFMT_FLAT=y
> CONFIG_BINFMT_ZFLAT=y
> -CONFIG_BINFMT_SHARED_FLAT=y
> CONFIG_PM=y
> CONFIG_CPU_IDLE=y
> CONFIG_NET=y
> diff --git a/arch/sh/configs/se7206_defconfig b/arch/sh/configs/se7206_defconfig
> index 601d062250d1..122216123e63 100644
> --- a/arch/sh/configs/se7206_defconfig
> +++ b/arch/sh/configs/se7206_defconfig
> @@ -40,7 +40,6 @@ CONFIG_CMDLINE_OVERWRITE=y
> CONFIG_CMDLINE="console=ttySC3,115200 ignore_loglevel earlyprintk=serial"
> CONFIG_BINFMT_FLAT=y
> CONFIG_BINFMT_ZFLAT=y
> -CONFIG_BINFMT_SHARED_FLAT=y
> CONFIG_BINFMT_MISC=y
> CONFIG_NET=y
> CONFIG_PACKET=y
> diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
> index 21c6332fa785..32dff7ba3dda 100644
> --- a/fs/Kconfig.binfmt
> +++ b/fs/Kconfig.binfmt
> @@ -142,12 +142,6 @@ config BINFMT_ZFLAT
> help
> Support FLAT format compressed binaries
>
> -config BINFMT_SHARED_FLAT
> - bool "Enable shared FLAT support"
> - depends on BINFMT_FLAT
> - help
> - Support FLAT shared libraries
> -
> config HAVE_AOUT
> def_bool n
>
> diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
> index 0ad2c7bbaddd..82e4412a9665 100644
> --- a/fs/binfmt_flat.c
> +++ b/fs/binfmt_flat.c
> @@ -68,11 +68,7 @@
> #define RELOC_FAILED 0xff00ff01 /* Relocation incorrect somewhere */
> #define UNLOADED_LIB 0x7ff000ff /* Placeholder for unused library */
>
> -#ifdef CONFIG_BINFMT_SHARED_FLAT
> -#define MAX_SHARED_LIBS (4)
> -#else
> -#define MAX_SHARED_LIBS (1)
> -#endif
> +#define MAX_SHARED_LIBS (1)
>
> #ifdef CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET
> #define DATA_START_OFFSET_WORDS (0)
> @@ -92,10 +88,6 @@ struct lib_info {
> } lib_list[MAX_SHARED_LIBS];
> };
>
> -#ifdef CONFIG_BINFMT_SHARED_FLAT
> -static int load_flat_shared_library(int id, struct lib_info *p);
> -#endif
> -
> static int load_flat_binary(struct linux_binprm *);
>
> static struct linux_binfmt flat_format = {
> @@ -307,51 +299,18 @@ static int decompress_exec(struct linux_binprm *bprm, loff_t fpos, char *dst,
> /****************************************************************************/
>
> static unsigned long
> -calc_reloc(unsigned long r, struct lib_info *p, int curid, int internalp)
> +calc_reloc(unsigned long r, struct lib_info *p)
> {
> unsigned long addr;
> - int id;
> unsigned long start_brk;
> unsigned long start_data;
> unsigned long text_len;
> unsigned long start_code;
>
> -#ifdef CONFIG_BINFMT_SHARED_FLAT
> - if (r == 0)
> - id = curid; /* Relocs of 0 are always self referring */
> - else {
> - id = (r >> 24) & 0xff; /* Find ID for this reloc */
> - r &= 0x00ffffff; /* Trim ID off here */
> - }
> - if (id >= MAX_SHARED_LIBS) {
> - pr_err("reference 0x%lx to shared library %d", r, id);
> - goto failed;
> - }
> - if (curid != id) {
> - if (internalp) {
> - pr_err("reloc address 0x%lx not in same module "
> - "(%d != %d)", r, curid, id);
> - goto failed;
> - } else if (!p->lib_list[id].loaded &&
> - load_flat_shared_library(id, p) < 0) {
> - pr_err("failed to load library %d", id);
> - goto failed;
> - }
> - /* Check versioning information (i.e. time stamps) */
> - if (p->lib_list[id].build_date && p->lib_list[curid].build_date &&
> - p->lib_list[curid].build_date < p->lib_list[id].build_date) {
> - pr_err("library %d is younger than %d", id, curid);
> - goto failed;
> - }
> - }
> -#else
> - id = 0;
> -#endif
> -
> - start_brk = p->lib_list[id].start_brk;
> - start_data = p->lib_list[id].start_data;
> - start_code = p->lib_list[id].start_code;
> - text_len = p->lib_list[id].text_len;
> + start_brk = p->lib_list[0].start_brk;
> + start_data = p->lib_list[0].start_data;
> + start_code = p->lib_list[0].start_code;
> + text_len = p->lib_list[0].text_len;
>
> if (r > start_brk - start_data + text_len) {
> pr_err("reloc outside program 0x%lx (0 - 0x%lx/0x%lx)",
> @@ -419,7 +378,7 @@ static void old_reloc(unsigned long rl)
> /****************************************************************************/
>
> static int load_flat_file(struct linux_binprm *bprm,
> - struct lib_info *libinfo, int id, unsigned long *extra_stack)
> + struct lib_info *libinfo, unsigned long *extra_stack)
> {
> struct flat_hdr *hdr;
> unsigned long textpos, datapos, realdatastart;
> @@ -471,14 +430,6 @@ static int load_flat_file(struct linux_binprm *bprm,
> goto err;
> }
>
> - /* Don't allow old format executables to use shared libraries */
> - if (rev == OLD_FLAT_VERSION && id != 0) {
> - pr_err("shared libraries are not available before rev 0x%lx\n",
> - FLAT_VERSION);
> - ret = -ENOEXEC;
> - goto err;
> - }
> -
> /*
> * fix up the flags for the older format, there were all kinds
> * of endian hacks, this only works for the simple cases
> @@ -529,15 +480,13 @@ static int load_flat_file(struct linux_binprm *bprm,
> }
>
> /* Flush all traces of the currently running executable */
> - if (id == 0) {
> - ret = begin_new_exec(bprm);
> - if (ret)
> - goto err;
> + ret = begin_new_exec(bprm);
> + if (ret)
> + goto err;
>
> - /* OK, This is the point of no return */
> - set_personality(PER_LINUX_32BIT);
> - setup_new_exec(bprm);
> - }
> + /* OK, This is the point of no return */
> + set_personality(PER_LINUX_32BIT);
> + setup_new_exec(bprm);
>
> /*
> * calculate the extra space we need to map in
> @@ -717,42 +666,40 @@ static int load_flat_file(struct linux_binprm *bprm,
> text_len -= sizeof(struct flat_hdr); /* the real code len */
>
> /* The main program needs a little extra setup in the task structure */
> - if (id == 0) {
> - current->mm->start_code = start_code;
> - current->mm->end_code = end_code;
> - current->mm->start_data = datapos;
> - current->mm->end_data = datapos + data_len;
> - /*
> - * set up the brk stuff, uses any slack left in data/bss/stack
> - * allocation. We put the brk after the bss (between the bss
> - * and stack) like other platforms.
> - * Userspace code relies on the stack pointer starting out at
> - * an address right at the end of a page.
> - */
> - current->mm->start_brk = datapos + data_len + bss_len;
> - current->mm->brk = (current->mm->start_brk + 3) & ~3;
> + current->mm->start_code = start_code;
> + current->mm->end_code = end_code;
> + current->mm->start_data = datapos;
> + current->mm->end_data = datapos + data_len;
> + /*
> + * set up the brk stuff, uses any slack left in data/bss/stack
> + * allocation. We put the brk after the bss (between the bss
> + * and stack) like other platforms.
> + * Userspace code relies on the stack pointer starting out at
> + * an address right at the end of a page.
> + */
> + 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;
> + current->mm->context.end_brk = memp + memp_size - stack_len;
> #endif
> - }
>
> if (flags & FLAT_FLAG_KTRACE) {
> pr_info("Mapping is %lx, Entry point is %x, data_start is %x\n",
> textpos, 0x00ffffff&ntohl(hdr->entry), ntohl(hdr->data_start));
> pr_info("%s %s: TEXT=%lx-%lx DATA=%lx-%lx BSS=%lx-%lx\n",
> - id ? "Lib" : "Load", bprm->filename,
> + "Load", bprm->filename,
> start_code, end_code, datapos, datapos + data_len,
> datapos + data_len, (datapos + data_len + bss_len + 3) & ~3);
> }
>
> /* Store the current module values into the global library structure */
> - libinfo->lib_list[id].start_code = start_code;
> - libinfo->lib_list[id].start_data = datapos;
> - libinfo->lib_list[id].start_brk = datapos + data_len + bss_len;
> - libinfo->lib_list[id].text_len = text_len;
> - libinfo->lib_list[id].loaded = 1;
> - libinfo->lib_list[id].entry = (0x00ffffff & ntohl(hdr->entry)) + textpos;
> - libinfo->lib_list[id].build_date = ntohl(hdr->build_date);
> + libinfo->lib_list[0].start_code = start_code;
> + libinfo->lib_list[0].start_data = datapos;
> + libinfo->lib_list[0].start_brk = datapos + data_len + bss_len;
> + libinfo->lib_list[0].text_len = text_len;
> + libinfo->lib_list[0].loaded = 1;
> + libinfo->lib_list[0].entry = (0x00ffffff & ntohl(hdr->entry)) + textpos;
> + libinfo->lib_list[0].build_date = ntohl(hdr->build_date);
>
> /*
> * We just load the allocations into some temporary memory to
> @@ -774,7 +721,7 @@ static int load_flat_file(struct linux_binprm *bprm,
> if (rp_val == 0xffffffff)
> break;
> if (rp_val) {
> - addr = calc_reloc(rp_val, libinfo, id, 0);
> + addr = calc_reloc(rp_val, libinfo);
> if (addr == RELOC_FAILED) {
> ret = -ENOEXEC;
> goto err;
> @@ -810,7 +757,7 @@ static int load_flat_file(struct linux_binprm *bprm,
> return -EFAULT;
> relval = ntohl(tmp);
> addr = flat_get_relocate_addr(relval);
> - rp = (u32 __user *)calc_reloc(addr, libinfo, id, 1);
> + rp = (u32 __user *)calc_reloc(addr, libinfo);
> if (rp == (u32 __user *)RELOC_FAILED) {
> ret = -ENOEXEC;
> goto err;
> @@ -833,7 +780,7 @@ static int load_flat_file(struct linux_binprm *bprm,
> */
> addr = ntohl((__force __be32)addr);
> }
> - addr = calc_reloc(addr, libinfo, id, 0);
> + addr = calc_reloc(addr, libinfo);
> if (addr == RELOC_FAILED) {
> ret = -ENOEXEC;
> goto err;
> @@ -861,7 +808,7 @@ static int load_flat_file(struct linux_binprm *bprm,
> /* zero the BSS, BRK and stack areas */
> if (clear_user((void __user *)(datapos + data_len), bss_len +
> (memp + memp_size - stack_len - /* end brk */
> - libinfo->lib_list[id].start_brk) + /* start brk */
> + libinfo->lib_list[0].start_brk) + /* start brk */
> stack_len))
> return -EFAULT;
>
> @@ -871,49 +818,6 @@ static int load_flat_file(struct linux_binprm *bprm,
> }
>
>
> -/****************************************************************************/
> -#ifdef CONFIG_BINFMT_SHARED_FLAT
> -
> -/*
> - * Load a shared library into memory. The library gets its own data
> - * segment (including bss) but not argv/argc/environ.
> - */
> -
> -static int load_flat_shared_library(int id, struct lib_info *libs)
> -{
> - /*
> - * This is a fake bprm struct; only the members "buf", "file" and
> - * "filename" are actually used.
> - */
> - struct linux_binprm bprm;
> - int res;
> - char buf[16];
> - loff_t pos = 0;
> -
> - memset(&bprm, 0, sizeof(bprm));
> -
> - /* Create the file name */
> - sprintf(buf, "/lib/lib%d.so", id);
> -
> - /* Open the file up */
> - bprm.filename = buf;
> - bprm.file = open_exec(bprm.filename);
> - res = PTR_ERR(bprm.file);
> - if (IS_ERR(bprm.file))
> - return res;
> -
> - res = kernel_read(bprm.file, bprm.buf, BINPRM_BUF_SIZE, &pos);
> -
> - if (res >= 0)
> - res = load_flat_file(&bprm, libs, id, NULL);
> -
> - allow_write_access(bprm.file);
> - fput(bprm.file);
> -
> - return res;
> -}
> -
> -#endif /* CONFIG_BINFMT_SHARED_FLAT */
> /****************************************************************************/
>
> /*
> @@ -946,7 +850,7 @@ static int load_flat_binary(struct linux_binprm *bprm)
> stack_len += (bprm->envc + 1) * sizeof(char *); /* the envp array */
> stack_len = ALIGN(stack_len, FLAT_STACK_ALIGN);
>
> - res = load_flat_file(bprm, &libinfo, 0, &stack_len);
> + res = load_flat_file(bprm, &libinfo, &stack_len);
> if (res < 0)
> return res;
>
> @@ -991,20 +895,6 @@ static int load_flat_binary(struct linux_binprm *bprm)
> */
> start_addr = libinfo.lib_list[0].entry;
>
> -#ifdef CONFIG_BINFMT_SHARED_FLAT
> - for (i = MAX_SHARED_LIBS-1; i > 0; i--) {
> - if (libinfo.lib_list[i].loaded) {
> - /* Push previos first to call address */
> - unsigned long __user *sp;
> - current->mm->start_stack -= sizeof(unsigned long);
> - sp = (unsigned long __user *)current->mm->start_stack;
> - if (put_user(start_addr, sp))
> - return -EFAULT;
> - start_addr = libinfo.lib_list[i].entry;
> - }
> - }
> -#endif
> -
> #ifdef FLAT_PLAT_INIT
> FLAT_PLAT_INIT(regs);
> #endif

Apart from the typos mentioned above, looks OK to me.

Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

--
Damien Le Moal
Western Digital Research