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x86/um/vdso: nommu: vdso memory update

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On !MMU mode, the address of vdso is accessible from userspace.  This
commit implements the entry point by pointing a block of page address.

This commit also add memory permission configuration of vdso page to be
executable.

Signed-off-by: Hajime Tazaki <thehajime@gmail.com>
Signed-off-by: Ricardo Koller <ricarkol@google.com>
[remove print, add comment on #endif]
Link: https://patch.msgid.link/20260723113633.6393b6b5c614.Ia508c720e53c944e663430117899fb4912021d8a@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Hajime Tazaki 2026-07-23 11:35:46 +02:00 committed by Johannes Berg
parent cf2dd04179
commit 5b4d63ca18
1 changed files with 11 additions and 2 deletions
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13
arch/x86/um/vdso/vma.c
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@ -9,6 +9,7 @@
#include <asm/page.h>
#include <asm/elf.h>
#include <linux/init.h>
#include <os.h>
unsigned long um_vdso_addr;
static struct page *um_vdso;
@ -20,18 +21,25 @@ static int __init init_vdso(void)
{
BUG_ON(vdso_end - vdso_start > PAGE_SIZE);
um_vdso_addr = task_size - PAGE_SIZE;
um_vdso = alloc_page(GFP_KERNEL);
if (!um_vdso)
panic("Cannot allocate vdso\n");
copy_page(page_address(um_vdso), vdso_start);
#ifdef CONFIG_MMU
um_vdso_addr = task_size - PAGE_SIZE;
#else
/* this is fine with NOMMU as everything is accessible */
um_vdso_addr = (unsigned long)page_address(um_vdso);
os_protect_memory((void *)um_vdso_addr, vdso_end - vdso_start, 1, 0, 1);
#endif
return 0;
}
subsys_initcall(init_vdso);
#ifdef CONFIG_MMU
int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
struct vm_area_struct *vma;
@ -53,3 +61,4 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
return IS_ERR(vma) ? PTR_ERR(vma) : 0;
}
#endif /* CONFIG_MMU */