Messages in this thread | | | From | Dmitry Mishin <> | Subject | Re: [Devel] Re: [PATCH 1/2] iptables 32bit compat layer | Date | Tue, 21 Feb 2006 12:04:49 +0300 |
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On Monday 20 February 2006 18:55, Arnd Bergmann wrote: > On Monday 20 February 2006 09:10, Mishin Dmitry wrote: > > --- ./include/linux/netfilter/x_tables.h.iptcompat 2006-02-15 > > 16:16:02.000000000 +0300 +++ > > ./include/linux/netfilter/x_tables.h 2006-02-15 18:53:09.000000000 > > +0300 struct xt_match > > { > > struct list_head list; > > @@ -118,6 +125,10 @@ struct xt_match > > /* Called when entry of this type deleted. */ > > void (*destroy)(void *matchinfo, unsigned int matchinfosize); > > > > +#ifdef CONFIG_COMPAT > > + /* Called when userspace align differs from kernel space one */ > > + int (*compat)(void *match, void **dstptr, int *size, int > > convert); +#endif > > /* Set this to THIS_MODULE if you are a module, otherwise NULL */ > > struct module *me; > > }; > > Is CONFIG_COMPAT the right conditional here? If the code is only used > for architectures that have different aligments, it should not need be > compiled in for the other architectures. So, I'll define ARCH_HAS_FUNNY_64_ALIGNMENT in x86_64 and ia64 code and will check it, as Andi suggested.
> > > @@ -154,6 +165,10 @@ struct xt_target > > /* Called when entry of this type deleted. */ > > void (*destroy)(void *targinfo, unsigned int targinfosize); > > > > +#ifdef CONFIG_COMPAT > > + /* Called when userspace align differs from kernel space one */ > > + int (*compat)(void *target, void **dstptr, int *size, int > > convert); +#endif > > /* Set this to THIS_MODULE if you are a module, otherwise NULL */ > > struct module *me; > > }; > > @@ -233,6 +248,34 @@ extern void xt_proto_fini(int af); > > extern struct xt_table_info *xt_alloc_table_info(unsigned int size); > > extern void xt_free_table_info(struct xt_table_info *info); > > > > +#ifdef CONFIG_COMPAT > > +#include <net/compat.h> > > + > > +/* FIXME: this works only on 32 bit tasks > > + * need to change whole approach in order to calculate align as function > > of + * current task alignment */ > > + > > +struct compat_xt_counters > > +{ > > + u_int32_t cnt[4]; > > +}; > > Hmm, maybe we should have something like > > typedef u64 __attribute__((aligned(4))) compat_u64; > > in order to get the right alignment on the architectures > where it makes a difference. Do all compiler versions > get that right? good point. I don't know this and that's why tried to avoid use of 'aligned' attribute.
> > > --- > > ./include/linux/netfilter_ipv4/ip_tables.h.iptcompat 2006-02-15 > > 16:06:41.000000000 +0300 +++ > > ./include/linux/netfilter_ipv4/ip_tables.h 2006-02-15 16:37:12.000000000 > > +0300 @@ -364,5 +365,62 @@ extern unsigned int ipt_do_table(struct > > void *userdata); > > > > #define IPT_ALIGN(s) XT_ALIGN(s) > > + > > +#ifdef CONFIG_COMPAT > > +#include <net/compat.h> > > + > > +struct compat_ipt_getinfo > > +{ > > + char name[IPT_TABLE_MAXNAMELEN]; > > + compat_uint_t valid_hooks; > > + compat_uint_t hook_entry[NF_IP_NUMHOOKS]; > > + compat_uint_t underflow[NF_IP_NUMHOOKS]; > > + compat_uint_t num_entries; > > + compat_uint_t size; > > +}; > > This structure looks like it does not need any > conversions. You should probably just use > struct ipt_getinfo then. I just saw compat_uint_t use in net/compat.c and thought, that it is a good style to use it. Does anybody know arch, where sizeof(compat_uint_t) != 4?
> > > + > > +struct compat_ipt_entry_match > > +{ > > + union { > > + struct { > > + u_int16_t match_size; > > + char name[IPT_FUNCTION_MAXNAMELEN]; > > + } user; > > + u_int16_t match_size; > > + } u; > > + unsigned char data[0]; > > +}; > > + > > +struct compat_ipt_entry_target > > +{ > > + union { > > + struct { > > + u_int16_t target_size; > > + char name[IPT_FUNCTION_MAXNAMELEN]; > > + } user; > > + u_int16_t target_size; > > + } u; > > + unsigned char data[0]; > > +}; > > Dito Disagree, ipt_entry_match and ipt_entry_target contain pointers which make their alignment equal 8 byte on 64bits architectures.
> > > +#define COMPAT_IPT_ALIGN(s) COMPAT_XT_ALIGN(s) > > + > > +extern int ipt_match_align_compat(void *match, void **dstptr, > > + int *size, int off, int convert); > > +extern int ipt_target_align_compat(void *target, void **dstptr, > > + int *size, int off, int convert); > > + > > +#endif /* CONFIG_COMPAT */ > > #endif /*__KERNEL__*/ > > #endif /* _IPTABLES_H */ > > --- ./include/net/compat.h.iptcompat 2006-01-03 06:21:10.000000000 > > +0300 +++ ./include/net/compat.h 2006-02-15 18:45:49.000000000 +0300 > > @@ -23,6 +23,14 @@ struct compat_cmsghdr { > > compat_int_t cmsg_type; > > }; > > > > +#if defined(CONFIG_X86_64) > > +#define is_current_32bits() (current_thread_info()->flags & _TIF_IA32) > > +#elif defined(CONFIG_IA64) > > +#define is_current_32bits() (IS_IA32_PROCESS(ia64_task_regs(current))) > > +#else > > +#define is_current_32bits() 0 > > +#endif > > + > > This definition looks very wrong to me. For x86_64, the right thing to > check should be TS_COMPAT, no _TIF_IA32, since you can also call the 64 bit > syscall entry point from a i386 task running on x86_64. For most other > architectures, is_current_32bits returns something that is not reflected in > the name. I would e.g. expect the function to return '1' on i386 and the > correct task state on other compat platforms, instead of a bogus '0'. > > There have been long discussions about the inclusions of the > 'is_compat_task' macro. Let's at least not define a second function that > does almost the same but gets it wrong. > > I would much rather have either an extra 'compat' argument to to > sock_setsockopt and proto_ops->setsockopt than to spread the use > of is_compat_task further. Another weak place in my code. is_compat_task() approach has one advantage - it doesn't require a lot of current code modifications. > > > #else /* defined(CONFIG_COMPAT) */ > > #define compat_msghdr msghdr /* to avoid compiler warnings */ > > #endif /* defined(CONFIG_COMPAT) */ > > --- ./net/compat.c.iptcompat 2006-01-03 06:21:10.000000000 +0300 > > +++ ./net/compat.c 2006-02-15 16:38:45.000000000 +0300 > > @@ -308,107 +308,6 @@ void scm_detach_fds_compat(struct msghdr > > } > > > > /* > > - * For now, we assume that the compatibility and native version > > - * of struct ipt_entry are the same - sfr. FIXME > > - */ > > -struct compat_ipt_replace { > > - char name[IPT_TABLE_MAXNAMELEN]; > > - u32 valid_hooks; > > - u32 num_entries; > > - u32 size; > > - u32 hook_entry[NF_IP_NUMHOOKS]; > > - u32 underflow[NF_IP_NUMHOOKS]; > > - u32 num_counters; > > - compat_uptr_t counters; /* struct ipt_counters * > > */ - struct ipt_entry entries[0]; > > -}; > > Is the FIXME above the only reason that the code needs to be changed? > What is the reason that you did not just address this in the > compat_sys_setsockopt implementation? Code above doesn't work. iptables with version >= 1.3 does alignment checks as well as kernel does. So, we can't simply put entries with 8 bytes alignment to userspace or with 4 bytes alignment to kernel - we need translate them entry by entry. So, I tried to do this the most correct way - that userspace will hide its alignment from kernel and vice versa, with not only SET_REPLACE, but also GET_INFO, GET_ENTRIES and SET_COUNTERS translation. First implementation was exactly in compat_sys_setsockopt, but David asked me to do this in netfilter code itself.
> > Arnd <>< > > _______________________________________________ > Devel mailing list > Devel@openvz.org > https://openvz.org/mailman/listinfo/devel
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