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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v1 10/11] xsplice: Add support for exception tables
On Tue, Nov 03, 2015 at 06:16:07PM +0000, Ross Lagerwall wrote:
> Add support for exception tables contained within xsplice modules. If an
> exception occurs search either the main exception table or a particular
> active module's exception table depending on the instruction pointer.
s/module/payload/
>
> Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
> ---
> xen/arch/x86/extable.c | 36 ++++++++++++++++++++++--------------
> xen/common/xsplice.c | 41 +++++++++++++++++++++++++++++++++++++++++
> xen/include/asm-x86/uaccess.h | 5 +++++
> xen/include/xen/xsplice.h | 2 ++
> 4 files changed, 70 insertions(+), 14 deletions(-)
>
> diff --git a/xen/arch/x86/extable.c b/xen/arch/x86/extable.c
> index 89b5bcb..2787a92 100644
> --- a/xen/arch/x86/extable.c
> +++ b/xen/arch/x86/extable.c
> @@ -4,6 +4,7 @@
> #include <xen/perfc.h>
> #include <xen/sort.h>
> #include <xen/spinlock.h>
> +#include <xen/xsplice.h>
> #include <asm/uaccess.h>
>
> #define EX_FIELD(ptr, field) ((unsigned long)&(ptr)->field + (ptr)->field)
> @@ -18,7 +19,7 @@ static inline unsigned long ex_cont(const struct
> exception_table_entry *x)
> return EX_FIELD(x, cont);
> }
>
> -static int __init cmp_ex(const void *a, const void *b)
> +static int cmp_ex(const void *a, const void *b)
> {
> const struct exception_table_entry *l = a, *r = b;
> unsigned long lip = ex_addr(l);
> @@ -33,7 +34,7 @@ static int __init cmp_ex(const void *a, const void *b)
> }
>
> #ifndef swap_ex
> -static void __init swap_ex(void *a, void *b, int size)
> +static void swap_ex(void *a, void *b, int size)
> {
> struct exception_table_entry *l = a, *r = b, tmp;
> long delta = b - a;
> @@ -46,19 +47,23 @@ static void __init swap_ex(void *a, void *b, int size)
> }
> #endif
>
> -void __init sort_exception_tables(void)
> +void sort_exception_table(struct exception_table_entry *start,
> + struct exception_table_entry *stop)
> {
> - sort(__start___ex_table, __stop___ex_table - __start___ex_table,
> - sizeof(struct exception_table_entry), cmp_ex, swap_ex);
> - sort(__start___pre_ex_table,
> - __stop___pre_ex_table - __start___pre_ex_table,
> + sort(start, stop - start,
> sizeof(struct exception_table_entry), cmp_ex, swap_ex);
> }
>
> -static inline unsigned long
> -search_one_table(const struct exception_table_entry *first,
> - const struct exception_table_entry *last,
> - unsigned long value)
> +void __init sort_exception_tables(void)
> +{
> + sort_exception_table(__start___ex_table, __stop___ex_table);
> + sort_exception_table(__start___pre_ex_table, __stop___pre_ex_table);
> +}
> +
> +unsigned long
> +search_one_extable(const struct exception_table_entry *first,
> + const struct exception_table_entry *last,
> + unsigned long value)
> {
> const struct exception_table_entry *mid;
> long diff;
> @@ -80,15 +85,18 @@ search_one_table(const struct exception_table_entry
> *first,
> unsigned long
> search_exception_table(unsigned long addr)
> {
> - return search_one_table(
> - __start___ex_table, __stop___ex_table-1, addr);
> + if ( likely(is_kernel(addr)) )
> + return search_one_extable(
> + __start___ex_table, __stop___ex_table-1, addr);
> + else
> + return search_module_extables(addr);
> }
>
> unsigned long
> search_pre_exception_table(struct cpu_user_regs *regs)
> {
> unsigned long addr = (unsigned long)regs->eip;
> - unsigned long fixup = search_one_table(
> + unsigned long fixup = search_one_extable(
> __start___pre_ex_table, __stop___pre_ex_table-1, addr);
> if ( fixup )
> {
> diff --git a/xen/common/xsplice.c b/xen/common/xsplice.c
> index 982954b..c5a403b 100644
> --- a/xen/common/xsplice.c
> +++ b/xen/common/xsplice.c
> @@ -45,6 +45,10 @@ struct payload {
>
> struct bug_frame *start_bug_frames[4];
> struct bug_frame *stop_bug_frames[4];
> +#ifdef CONFIG_X86
> + struct exception_table_entry *start_ex_table;
> + struct exception_table_entry *stop_ex_table;
> +#endif
>
> char id[XEN_XSPLICE_NAME_SIZE + 1]; /* Name of it. */
> };
> @@ -691,6 +695,17 @@ static int find_special_sections(struct payload *payload,
> payload->stop_bug_frames[i] = (struct bug_frame *)(sec->load_addr +
> sec->sec->sh_size);
> }
>
> +#ifdef CONFIG_X86
> + sec = xsplice_elf_sec_by_name(elf, ".ex_table");
> + if ( sec )
> + {
> + payload->start_ex_table = (struct exception_table_entry
> *)sec->load_addr;
> + payload->stop_ex_table = (struct exception_table_entry
> *)(sec->load_addr + sec->sec->sh_size);
Please double-check that sh_size is not some funny value. For example it
may be 0, or worst - not aligned to the size of 'struct
exception_table_entry'!
> +
> + sort_exception_table(payload->start_ex_table,
> payload->stop_ex_table);
> + }
> +#endif
> +
> return 0;
> }
>
> @@ -999,6 +1014,32 @@ bool_t is_active_module_text(unsigned long addr)
> return false;
> }
>
> +#ifdef CONFIG_X86
> +unsigned long search_module_extables(unsigned long addr)
> +{
> + struct payload *data;
> + unsigned long ret;
> +
> + /* No locking since this list is only ever changed during apply or revert
> + * context. */
> + list_for_each_entry ( data, &applied_list, applied_list )
> + {
> + if ( !data->start_ex_table )
> + continue;
> + if ( !((void *)addr >= data->module_address &&
> + (void *)addr < (data->module_address + data->core_text_size)))
The last ')' needs to have space before it.
> + continue;
> +
> + ret = search_one_extable(data->start_ex_table, data->stop_ex_table -
> 1,
> + addr);
> + if ( ret )
> + return ret;
> + }
> +
> + return 0;
> +}
> +#endif
> +
> static int __init xsplice_init(void)
> {
> register_keyhandler('x', xsplice_printall, "print xsplicing info", 1);
> diff --git a/xen/include/asm-x86/uaccess.h b/xen/include/asm-x86/uaccess.h
> index 947470d..9e67bf0 100644
> --- a/xen/include/asm-x86/uaccess.h
> +++ b/xen/include/asm-x86/uaccess.h
> @@ -276,6 +276,11 @@ extern struct exception_table_entry
> __start___pre_ex_table[];
> extern struct exception_table_entry __stop___pre_ex_table[];
>
> extern unsigned long search_exception_table(unsigned long);
> +extern unsigned long search_one_extable(const struct exception_table_entry
> *first,
> + const struct exception_table_entry
> *last,
> + unsigned long value);
> extern void sort_exception_tables(void);
> +extern void sort_exception_table(struct exception_table_entry *start,
> + struct exception_table_entry *stop);
>
> #endif /* __X86_UACCESS_H__ */
> diff --git a/xen/include/xen/xsplice.h b/xen/include/xen/xsplice.h
> index 772fa3a..485eb08 100644
> --- a/xen/include/xen/xsplice.h
> +++ b/xen/include/xen/xsplice.h
> @@ -26,6 +26,8 @@ struct bug_frame * xsplice_find_bug(const char *eip, int
> *id);
> bool_t is_module(const void *addr);
> bool_t is_active_module_text(unsigned long addr);
>
> +unsigned long search_module_extables(unsigned long addr);
> +
> /* Arch hooks */
> int xsplice_verify_elf(uint8_t *data, ssize_t len);
> int xsplice_perform_rel(struct xsplice_elf *elf,
> --
> 2.4.3
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel
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