Commit 2717c6b6 authored by Tiwei Bie's avatar Tiwei Bie Committed by Johannes Berg
Browse files

um: Abandon the _PAGE_NEWPROT bit 



When a PTE is updated in the page table, the _PAGE_NEWPAGE bit will
always be set. And the corresponding page will always be mapped or
unmapped depending on whether the PTE is present or not. The check
on the _PAGE_NEWPROT bit is not really reachable. Abandoning it will
allow us to simplify the code and remove the unreachable code.

Reviewed-by: default avatarBenjamin Berg <benjamin.berg@intel.com>
Signed-off-by: default avatarTiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20241011102354.1682626-2-tiwei.btw@antgroup.com


Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent 90daca7c

arch/um/include/asm/pgtable.h

+6 −31
Original line number Diff line number Diff line
@@ -12,7 +12,6 @@ 


#define _PAGE_PRESENT	0x001

#define _PAGE_NEWPAGE	0x002

#define _PAGE_NEWPROT	0x004

#define _PAGE_RW	0x020

#define _PAGE_USER	0x040

#define _PAGE_ACCESSED	0x080
@@ -151,23 +150,12 @@ static inline int pte_newpage(pte_t pte) 
	return pte_get_bits(pte, _PAGE_NEWPAGE);

}



static inline int pte_newprot(pte_t pte)

{

	return(pte_present(pte) && (pte_get_bits(pte, _PAGE_NEWPROT)));

}



/*

 * =================================

 * Flags setting section.

 * =================================

 */



static inline pte_t pte_mknewprot(pte_t pte)

{

	pte_set_bits(pte, _PAGE_NEWPROT);

	return(pte);

}



static inline pte_t pte_mkclean(pte_t pte)

{

	pte_clear_bits(pte, _PAGE_DIRTY);
@@ -182,19 +170,14 @@ static inline pte_t pte_mkold(pte_t pte) 


static inline pte_t pte_wrprotect(pte_t pte)

{

	if (likely(pte_get_bits(pte, _PAGE_RW)))

	pte_clear_bits(pte, _PAGE_RW);

	else

	return pte;

	return(pte_mknewprot(pte));

}



static inline pte_t pte_mkread(pte_t pte)

{

	if (unlikely(pte_get_bits(pte, _PAGE_USER)))

		return pte;

	pte_set_bits(pte, _PAGE_USER);

	return(pte_mknewprot(pte));

	return pte;

}



static inline pte_t pte_mkdirty(pte_t pte)
@@ -211,18 +194,14 @@ static inline pte_t pte_mkyoung(pte_t pte) 


static inline pte_t pte_mkwrite_novma(pte_t pte)

{

	if (unlikely(pte_get_bits(pte,  _PAGE_RW)))

		return pte;

	pte_set_bits(pte, _PAGE_RW);

	return(pte_mknewprot(pte));

	return pte;

}



static inline pte_t pte_mkuptodate(pte_t pte)

{

	pte_clear_bits(pte, _PAGE_NEWPAGE);

	if(pte_present(pte))

		pte_clear_bits(pte, _PAGE_NEWPROT);

	return(pte);

	return pte;

}



static inline pte_t pte_mknewpage(pte_t pte)
@@ -236,12 +215,10 @@ static inline void set_pte(pte_t *pteptr, pte_t pteval) 
	pte_copy(*pteptr, pteval);



	/* If it's a swap entry, it needs to be marked _PAGE_NEWPAGE so

	 * fix_range knows to unmap it.  _PAGE_NEWPROT is specific to

	 * mapped pages.

	 * update_pte_range knows to unmap it.

	 */



	*pteptr = pte_mknewpage(*pteptr);

	if(pte_present(*pteptr)) *pteptr = pte_mknewprot(*pteptr);

}



#define PFN_PTE_SHIFT		PAGE_SHIFT
@@ -298,8 +275,6 @@ static inline int pte_same(pte_t pte_a, pte_t pte_b) 
	({ pte_t pte;					\

							\

	pte_set_val(pte, page_to_phys(page), (pgprot));	\

	if (pte_present(pte))				\

		pte_mknewprot(pte_mknewpage(pte));	\

	pte;})



static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)

arch/um/include/asm/tlbflush.h

+2 −2
Original line number Diff line number Diff line
@@ -9,8 +9,8 @@ 
#include <linux/mm.h>



/*

 * In UML, we need to sync the TLB over by using mmap/munmap/mprotect syscalls

 * from the process handling the MM (which can be the kernel itself).

 * In UML, we need to sync the TLB over by using mmap/munmap syscalls from

 * the process handling the MM (which can be the kernel itself).

 *

 * To track updates, we can hook into set_ptes and flush_tlb_*. With set_ptes

 * we catch all PTE transitions where memory that was unusable becomes usable.

arch/um/include/shared/os.h

+0 −2
Original line number Diff line number Diff line
@@ -279,8 +279,6 @@ int map(struct mm_id *mm_idp, unsigned long virt, 
	unsigned long len, int prot, int phys_fd,

	unsigned long long offset);

int unmap(struct mm_id *mm_idp, unsigned long addr, unsigned long len);

int protect(struct mm_id *mm_idp, unsigned long addr,

	    unsigned long len, unsigned int prot);



/* skas/process.c */

extern int is_skas_winch(int pid, int fd, void *data);

arch/um/include/shared/skas/stub-data.h

+0 −1
Original line number Diff line number Diff line
@@ -30,7 +30,6 @@ enum stub_syscall_type { 
	STUB_SYSCALL_UNSET = 0,

	STUB_SYSCALL_MMAP,

	STUB_SYSCALL_MUNMAP,

	STUB_SYSCALL_MPROTECT,

};



struct stub_syscall {

arch/um/kernel/skas/stub.c

+0 −10
Original line number Diff line number Diff line
@@ -35,16 +35,6 @@ static __always_inline int syscall_handler(struct stub_data *d) 
				return -1;

			}

			break;

		case STUB_SYSCALL_MPROTECT:

			res = stub_syscall3(__NR_mprotect,

					    sc->mem.addr, sc->mem.length,

					    sc->mem.prot);

			if (res) {

				d->err = res;

				d->syscall_data_len = i;

				return -1;

			}

			break;

		default:

			d->err = -95; /* EOPNOTSUPP */

			d->syscall_data_len = i;