From: Jeff Dike From: Bodo Stroesser To make the vsyscall-page available for copy_from_user() and ptrace(), we should use kernel's "gate-vma" mechanism. Therefore we need a valid page structure. To have this, one page (or more) is allocated at boot time, the contents of the vsyscall-page is copied into this page and the page's pte is inserted in swapper's pagetables. Now it will be copied into the pagetables of all processes. Note: this alone doesn't work, since FIXADDR_USER_START and FIXADDR_USER_END are not yet defined correctly. Also access_ok_skas() does not yet grant read accesses to pages not in the normal user area. Risks: Please check the first hunk! I don't know, whether this change is OK. Maybe fixrange_init() is wrong anyway with 3-level-pagetables? Here access_ok_skas() and FIXADDR_USER_XXXX are fixed. Now everything should work fine, while the processes are running. But if a process crashes, the vsyscall-page will not be dumped. Signed-off-by: Bodo Stroesser Signed-off-by: Jeff Dike Signed-off-by: Andrew Morton --- 25-akpm/arch/um/kernel/mem.c | 25 +++++++++++++++++++++ 25-akpm/arch/um/kernel/skas/include/uaccess-skas.h | 7 +++++ 25-akpm/include/asm-um/fixmap.h | 6 ++--- 25-akpm/include/asm-um/pgtable.h | 2 + 4 files changed, 36 insertions(+), 4 deletions(-) diff -puN arch/um/kernel/mem.c~uml-make-vsyscall-page-into-process-page-tables arch/um/kernel/mem.c --- 25/arch/um/kernel/mem.c~uml-make-vsyscall-page-into-process-page-tables Fri Dec 3 13:50:28 2004 +++ 25-akpm/arch/um/kernel/mem.c Fri Dec 3 13:50:28 2004 @@ -174,6 +174,29 @@ static void init_highmem(void) } #endif /* CONFIG_HIGHMEM */ +static void __init fixaddr_user_init( void) +{ + long size = FIXADDR_USER_END - FIXADDR_USER_START; + pgd_t *pgd; + pmd_t *pmd; + pte_t *pte; + unsigned long paddr, vaddr = FIXADDR_USER_START; + + if ( ! size ) + return; + + fixrange_init( FIXADDR_USER_START, FIXADDR_USER_END, swapper_pg_dir); + paddr = (unsigned long)alloc_bootmem_low_pages( size); + memcpy( (void *)paddr, (void *)FIXADDR_USER_START, size); + paddr = __pa(paddr); + for ( ; size > 0; size-=PAGE_SIZE, vaddr+=PAGE_SIZE, paddr+=PAGE_SIZE) { + pgd = swapper_pg_dir + pgd_index(vaddr); + pmd = pmd_offset(pgd, vaddr); + pte = pte_offset_kernel(pmd, vaddr); + pte_set_val( (*pte), paddr, PAGE_READONLY); + } +} + void paging_init(void) { unsigned long zones_size[MAX_NR_ZONES], vaddr; @@ -194,6 +217,8 @@ void paging_init(void) vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK; fixrange_init(vaddr, FIXADDR_TOP, swapper_pg_dir); + fixaddr_user_init(); + #ifdef CONFIG_HIGHMEM init_highmem(); #endif diff -puN arch/um/kernel/skas/include/uaccess-skas.h~uml-make-vsyscall-page-into-process-page-tables arch/um/kernel/skas/include/uaccess-skas.h --- 25/arch/um/kernel/skas/include/uaccess-skas.h~uml-make-vsyscall-page-into-process-page-tables Fri Dec 3 13:50:28 2004 +++ 25-akpm/arch/um/kernel/skas/include/uaccess-skas.h Fri Dec 3 13:50:28 2004 @@ -7,11 +7,16 @@ #define __SKAS_UACCESS_H #include "asm/errno.h" +#include "asm/fixmap.h" #define access_ok_skas(type, addr, size) \ ((segment_eq(get_fs(), KERNEL_DS)) || \ (((unsigned long) (addr) < TASK_SIZE) && \ - ((unsigned long) (addr) + (size) <= TASK_SIZE))) + ((unsigned long) (addr) + (size) <= TASK_SIZE)) || \ + ((type == VERIFY_READ ) && \ + (size <= (FIXADDR_USER_END - FIXADDR_USER_START)) && \ + ((unsigned long) (addr) >= FIXADDR_USER_START) && \ + ((unsigned long) (addr) + (size) <= FIXADDR_USER_END))) static inline int verify_area_skas(int type, const void * addr, unsigned long size) diff -puN include/asm-um/fixmap.h~uml-make-vsyscall-page-into-process-page-tables include/asm-um/fixmap.h --- 25/include/asm-um/fixmap.h~uml-make-vsyscall-page-into-process-page-tables Fri Dec 3 13:50:28 2004 +++ 25-akpm/include/asm-um/fixmap.h Fri Dec 3 13:50:28 2004 @@ -3,6 +3,7 @@ #include #include +#include /* * Here we define all the compile-time 'special' virtual @@ -34,7 +35,6 @@ enum fixed_addresses { FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */ FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1, #endif - FIX_VSYSCALL, __end_of_fixed_addresses }; @@ -68,8 +68,8 @@ extern unsigned long get_kmem_end(void); * This is the range that is readable by user mode, and things * acting like user mode such as get_user_pages. */ -#define FIXADDR_USER_START (__fix_to_virt(FIX_VSYSCALL)) -#define FIXADDR_USER_END (FIXADDR_USER_START + PAGE_SIZE) +#define FIXADDR_USER_START VSYSCALL_BASE +#define FIXADDR_USER_END VSYSCALL_END extern void __this_fixmap_does_not_exist(void); diff -puN include/asm-um/pgtable.h~uml-make-vsyscall-page-into-process-page-tables include/asm-um/pgtable.h --- 25/include/asm-um/pgtable.h~uml-make-vsyscall-page-into-process-page-tables Fri Dec 3 13:50:28 2004 +++ 25-akpm/include/asm-um/pgtable.h Fri Dec 3 13:50:28 2004 @@ -355,6 +355,8 @@ extern unsigned long page_to_phys(struct extern pte_t mk_pte(struct page *page, pgprot_t pgprot); +#define pte_set_val(p, phys, prot) pte_val(p) = (phys | pgprot_val(prot)) + static inline pte_t pte_modify(pte_t pte, pgprot_t newprot) { pte_val(pte) = (pte_val(pte) & _PAGE_CHG_MASK) | pgprot_val(newprot); _