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Date:      Thu, 7 Feb 2019 02:17:35 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r343852 - in head/sys: i386/i386 kern x86/include
Message-ID:  <201902070217.x172HZmA073270@repo.freebsd.org>
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Author: kib
Date: Thu Feb  7 02:17:34 2019
New Revision: 343852
URL: https://svnweb.freebsd.org/changeset/base/343852

Log:
  Port sysctl kern.elf32.read_exec from amd64 to i386.
  
  Make it more comprehensive on i386, by not setting nx bit for any
  mapping, not just adding PF_X to all kernel-loaded ELF segments.  This
  is needed for the compatibility with older i386 programs that assume
  that read access implies exec, e.g. old X servers with hand-rolled
  module loader.
  
  Reported and tested by:	bde
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

Modified:
  head/sys/i386/i386/pmap.c
  head/sys/kern/imgact_elf.c
  head/sys/x86/include/x86_var.h

Modified: head/sys/i386/i386/pmap.c
==============================================================================
--- head/sys/i386/i386/pmap.c	Thu Feb  7 02:09:34 2019	(r343851)
+++ head/sys/i386/i386/pmap.c	Thu Feb  7 02:17:34 2019	(r343852)
@@ -3247,7 +3247,7 @@ retry:
 	if ((prot & VM_PROT_WRITE) == 0)
 		newpde &= ~(PG_RW | PG_M);
 #ifdef PMAP_PAE_COMP
-	if ((prot & VM_PROT_EXECUTE) == 0)
+	if ((prot & VM_PROT_EXECUTE) == 0 && !i386_read_exec)
 		newpde |= pg_nx;
 #endif
 	if (newpde != oldpde) {
@@ -3389,7 +3389,7 @@ retry:
 				pbits &= ~(PG_RW | PG_M);
 			}
 #ifdef PMAP_PAE_COMP
-			if ((prot & VM_PROT_EXECUTE) == 0)
+			if ((prot & VM_PROT_EXECUTE) == 0 && !i386_read_exec)
 				pbits |= pg_nx;
 #endif
 
@@ -3604,7 +3604,7 @@ __CONCAT(PMTYPE, enter)(pmap_t pmap, vm_offset_t va, v
 	KASSERT((newpte & (PG_M | PG_RW)) != PG_M,
 	    ("pmap_enter: flags includes VM_PROT_WRITE but prot doesn't"));
 #ifdef PMAP_PAE_COMP
-	if ((prot & VM_PROT_EXECUTE) == 0)
+	if ((prot & VM_PROT_EXECUTE) == 0 && !i386_read_exec)
 		newpte |= pg_nx;
 #endif
 	if ((flags & PMAP_ENTER_WIRED) != 0)
@@ -3841,7 +3841,7 @@ pmap_enter_4mpage(pmap_t pmap, vm_offset_t va, vm_page
 	if ((m->oflags & VPO_UNMANAGED) == 0)
 		newpde |= PG_MANAGED;
 #ifdef PMAP_PAE_COMP
-	if ((prot & VM_PROT_EXECUTE) == 0)
+	if ((prot & VM_PROT_EXECUTE) == 0 && !i386_read_exec)
 		newpde |= pg_nx;
 #endif
 	if (pmap != kernel_pmap)
@@ -4099,7 +4099,7 @@ pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va, v
 	if ((m->oflags & VPO_UNMANAGED) == 0)
 		newpte |= PG_MANAGED;
 #ifdef PMAP_PAE_COMP
-	if ((prot & VM_PROT_EXECUTE) == 0)
+	if ((prot & VM_PROT_EXECUTE) == 0 && !i386_read_exec)
 		newpte |= pg_nx;
 #endif
 	if (pmap != kernel_pmap)

Modified: head/sys/kern/imgact_elf.c
==============================================================================
--- head/sys/kern/imgact_elf.c	Thu Feb  7 02:09:34 2019	(r343851)
+++ head/sys/kern/imgact_elf.c	Thu Feb  7 02:17:34 2019	(r343852)
@@ -130,13 +130,11 @@ SYSCTL_INT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_A
     nxstack, CTLFLAG_RW, &__elfN(nxstack), 0,
     __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE)) ": enable non-executable stack");
 
-#if __ELF_WORD_SIZE == 32
-#if defined(__amd64__)
+#if __ELF_WORD_SIZE == 32 && (defined(__amd64__) || defined(__i386__))
 int i386_read_exec = 0;
 SYSCTL_INT(_kern_elf32, OID_AUTO, read_exec, CTLFLAG_RW, &i386_read_exec, 0,
     "enable execution from readable segments");
 #endif
-#endif
 
 static Elf_Brandinfo *elf_brand_list[MAX_BRANDS];
 
@@ -2516,11 +2514,9 @@ __elfN(trans_prot)(Elf_Word flags)
 		prot |= VM_PROT_WRITE;
 	if (flags & PF_R)
 		prot |= VM_PROT_READ;
-#if __ELF_WORD_SIZE == 32
-#if defined(__amd64__)
+#if __ELF_WORD_SIZE == 32 && (defined(__amd64__) || defined(__i386__))
 	if (i386_read_exec && (flags & PF_R))
 		prot |= VM_PROT_EXECUTE;
-#endif
 #endif
 	return (prot);
 }

Modified: head/sys/x86/include/x86_var.h
==============================================================================
--- head/sys/x86/include/x86_var.h	Thu Feb  7 02:09:34 2019	(r343851)
+++ head/sys/x86/include/x86_var.h	Thu Feb  7 02:17:34 2019	(r343852)
@@ -83,6 +83,7 @@ extern	int	_ugssel;
 extern	int	use_xsave;
 extern	uint64_t xsave_mask;
 extern	u_int	max_apic_id;
+extern	int	i386_read_exec;
 extern	int	pti;
 extern	int	hw_ibrs_active;
 extern	int	hw_ssb_active;

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