[uClinux-dev] Re: [PATCH 1/2 v2] FLAT: split the stack data alignments
Jivin Mike Frysinger lays it down ... The stack and data have different alignment requirements, so don't force them to wear the same shoe. Increase the data alignment to match that which the elf2flt linker script has always been using: 0x20 bytes. Not only does this bring the kernel loader in line with the toolchain, but it also fixes a swath of gcc tests which try to force larger alignment values but randomly fail when the FLAT loader fails to deliver. Signed-off-by: Mike Frysinger vap...@gentoo.org Acked-by: David McCullough david_mccullo...@mcafee.com Cheers, Davidm --- v2 - split changes document better fs/binfmt_flat.c | 23 +++ 1 files changed, 15 insertions(+), 8 deletions(-) diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c index 49566c1..b865622 100644 --- a/fs/binfmt_flat.c +++ b/fs/binfmt_flat.c @@ -56,15 +56,22 @@ #endif /* - * User data (stack, data section and bss) needs to be aligned - * for the same reasons as SLAB memory is, and to the same amount. - * Avoid duplicating architecture specific code by using the same - * macro as with SLAB allocation: + * User data (data section and bss) needs to be aligned. + * We pick 0x20 here because it is the max value elf2flt has always + * used in producing FLAT files, and because it seems to be large + * enough to make all the gcc alignment related tests happy. + */ +#define FLAT_DATA_ALIGN (0x20) + +/* + * User data (stack) also needs to be aligned. + * Here we can be a bit looser than the data sections since this + * needs to only meet arch ABI requirements. */ #ifdef ARCH_SLAB_MINALIGN -#define FLAT_DATA_ALIGN (ARCH_SLAB_MINALIGN) +#define FLAT_STACK_ALIGN (ARCH_SLAB_MINALIGN) #else -#define FLAT_DATA_ALIGN (sizeof(void *)) +#define FLAT_STACK_ALIGN (sizeof(void *)) #endif #define RELOC_FAILED 0xff00ff01 /* Relocation incorrect somewhere */ @@ -129,7 +136,7 @@ static unsigned long create_flat_tables( sp = (unsigned long *)p; sp -= (envc + argc + 2) + 1 + (flat_argvp_envp_on_stack() ? 2 : 0); - sp = (unsigned long *) ((unsigned long)sp -FLAT_DATA_ALIGN); + sp = (unsigned long *) ((unsigned long)sp -FLAT_STACK_ALIGN); argv = sp + 1 + (flat_argvp_envp_on_stack() ? 2 : 0); envp = argv + (argc + 1); @@ -876,7 +883,7 @@ static int load_flat_binary(struct linux_binprm * bprm, struct pt_regs * regs) stack_len = TOP_OF_ARGS - bprm-p; /* the strings */ stack_len += (bprm-argc + 1) * sizeof(char *); /* the argv array */ stack_len += (bprm-envc + 1) * sizeof(char *); /* the envp array */ - stack_len += FLAT_DATA_ALIGN - 1; /* reserve for upcoming alignment */ + stack_len += FLAT_STACK_ALIGN - 1; /* reserve for upcoming alignment */ res = load_flat_file(bprm, libinfo, 0, stack_len); if (IS_ERR_VALUE(res)) -- 1.7.1 -- David McCullough, david_mccullo...@mcafee.com, Ph:+61 734352815 McAfee - SnapGear http://www.mcafee.com http://www.uCdot.org ___ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
[uClinux-dev] Re: [PATCH 1/2 v2] FLAT: split the stack data alignments
Mike Frysinger wrote: The stack and data have different alignment requirements, so don't force them to wear the same shoe. Increase the data alignment to match that which the elf2flt linker script has always been using: 0x20 bytes. Not only does this bring the kernel loader in line with the toolchain, but it also fixes a swath of gcc tests which try to force larger alignment values but randomly fail when the FLAT loader fails to deliver. Signed-off-by: Mike Frysinger vap...@gentoo.org Acked-by: Greg Ungerer g...@uclinux.org --- v2 - split changes document better fs/binfmt_flat.c | 23 +++ 1 files changed, 15 insertions(+), 8 deletions(-) diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c index 49566c1..b865622 100644 --- a/fs/binfmt_flat.c +++ b/fs/binfmt_flat.c @@ -56,15 +56,22 @@ #endif /* - * User data (stack, data section and bss) needs to be aligned - * for the same reasons as SLAB memory is, and to the same amount. - * Avoid duplicating architecture specific code by using the same - * macro as with SLAB allocation: + * User data (data section and bss) needs to be aligned. + * We pick 0x20 here because it is the max value elf2flt has always + * used in producing FLAT files, and because it seems to be large + * enough to make all the gcc alignment related tests happy. + */ +#define FLAT_DATA_ALIGN(0x20) + +/* + * User data (stack) also needs to be aligned. + * Here we can be a bit looser than the data sections since this + * needs to only meet arch ABI requirements. */ #ifdef ARCH_SLAB_MINALIGN -#define FLAT_DATA_ALIGN(ARCH_SLAB_MINALIGN) +#define FLAT_STACK_ALIGN (ARCH_SLAB_MINALIGN) #else -#define FLAT_DATA_ALIGN(sizeof(void *)) +#define FLAT_STACK_ALIGN (sizeof(void *)) #endif #define RELOC_FAILED 0xff00ff01 /* Relocation incorrect somewhere */ @@ -129,7 +136,7 @@ static unsigned long create_flat_tables( sp = (unsigned long *)p; sp -= (envc + argc + 2) + 1 + (flat_argvp_envp_on_stack() ? 2 : 0); - sp = (unsigned long *) ((unsigned long)sp -FLAT_DATA_ALIGN); + sp = (unsigned long *) ((unsigned long)sp -FLAT_STACK_ALIGN); argv = sp + 1 + (flat_argvp_envp_on_stack() ? 2 : 0); envp = argv + (argc + 1); @@ -876,7 +883,7 @@ static int load_flat_binary(struct linux_binprm * bprm, struct pt_regs * regs) stack_len = TOP_OF_ARGS - bprm-p; /* the strings */ stack_len += (bprm-argc + 1) * sizeof(char *); /* the argv array */ stack_len += (bprm-envc + 1) * sizeof(char *); /* the envp array */ - stack_len += FLAT_DATA_ALIGN - 1; /* reserve for upcoming alignment */ + stack_len += FLAT_STACK_ALIGN - 1; /* reserve for upcoming alignment */ res = load_flat_file(bprm, libinfo, 0, stack_len); if (IS_ERR_VALUE(res)) -- Greg Ungerer -- Principal EngineerEMAIL: g...@snapgear.com SnapGear Group, McAfee PHONE: +61 7 3435 2888 8 Gardner Close FAX: +61 7 3217 5323 Milton, QLD, 4064, AustraliaWEB: http://www.SnapGear.com ___ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
[uClinux-dev] Re: [PATCH 1/2 v2] FLAT: split the stack data alignments
On Wed, May 26, 2010 at 04:45, Mike Frysinger wrote: The stack and data have different alignment requirements, so don't force them to wear the same shoe. Increase the data alignment to match that which the elf2flt linker script has always been using: 0x20 bytes. Not only does this bring the kernel loader in line with the toolchain, but it also fixes a swath of gcc tests which try to force larger alignment values but randomly fail when the FLAT loader fails to deliver. btw, a follow up patch might be to move the shared lib identifiers from the start of the data section to the end of it so that the re-aligning isnt necessary (we'd get a 4k page alignment from mmap and such). but i cant seem to figure out how these identifiers are being read/written. otherwise, the fact that we're force aligning to 0x20 bytes means that there is always room for 8 identifiers ... no point in flipping between 1 or 4, at least from this point of view ... -mike ___ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
