x86/vm86/32: A bugfix and a matching test improvement
Subsystems (3)
cover x86/vm86/32: A bugfix and a matching test improvement
A patch in 4.2 broke vm86's POPF emulation in a way that was somehow subtle enough that no one noticed until now. Fix it and improve the test case to exercise the code.
(The improved test case also exercises some code paths that were *not*
broken but that would have become broken if Stas' original suggested patch were applied. Go testing!)
Andy Lutomirski (3):
selftests/x86/entry_from_vm86: Exit with 1 if we fail selftests/x86/entry_from_vm86: Add test cases for POPF x86/vm86/32: Fix POPF emulation
arch/x86/kernel/vm86_32.c | 3 ++- tools/testing/selftests/x86/entry_from_vm86.c | 32 +++++++++++++++++++++++---- 2 files changed, 30 insertions(+), 5 deletions(-)
Signature · 1 line
2.14.3
PATCH 1/3 selftests/x86/entry_from_vm86: Exit with 1 if we fail
Fix a logic error that caused the test to exit with 0 even if test cases failed.
Signed-off-by Andy Lutomirski <[email protected]>
--- tools/testing/selftests/x86/entry_from_vm86.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
tools/testing/selftests/x86/entry_from_vm86.c +1 -1
@@ -318,7 +318,7 @@ int main(void)clearhandler (SIGSEGV );/* Make sure nothing explodes if we fork. */ -if (fork () >0 ) +if (fork () ==0 )return 0 ;return (nerrs ==0 ?0 :1 );
Signature · 1 line
2.14.3
tip-bot for Andy Lutomirski
merge bot[tip:x86/pti] selftests/x86/entry_from_vm86: Exit with 1 if we fail
selftests/x86/entry_from_vm86: Exit with 1 if we fail
Commit-ID: 327d53d005ca47b10eae940616ed11c569f75a9b Gitweb: https://git.kernel.org/tip/327d53d005ca47b10eae940616ed11c569f75a9b Author: Andy Lutomirski <[email protected]> AuthorDate: Tue, 13 Mar 2018 22:03:10 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Wed, 14 Mar 2018 09:21:01 +0100
selftests/x86/entry_from_vm86: Exit with 1 if we fail
Fix a logic error that caused the test to exit with 0 even if test cases failed.
Signed-off-by Andy Lutomirski <[email protected]>
Cc Borislav Petkov <[email protected]>
Cc Brian Gerst <[email protected]>
Cc Denys Vlasenko <[email protected]>
Cc H. Peter Anvin <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Stas Sergeev <[email protected]>
Cc Thomas Gleixner <[email protected]>
Link http://lkml.kernel.org/r/b1cc37144038958a469c8f70a5f47a6a5638636a.1521003603.git.luto@kernel.org open here
Signed-off-by Ingo Molnar <[email protected]>
--- tools/testing/selftests/x86/entry_from_vm86.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
tools/testing/selftests/x86/entry_from_vm86.c +1 -1
@@ -318,7 +318,7 @@ int main(void)clearhandler (SIGSEGV );/* Make sure nothing explodes if we fork. */ -if (fork () >0 ) +if (fork () ==0 )return 0 ;return (nerrs ==0 ?0 :1 );
PATCH 2/3 selftests/x86/entry_from_vm86: Add test cases for POPF
In reply to Andy LutomirskiPOPF is currently broken -- add tests to catch the error. This results in:
[RUN] POPF with VIP set and IF clear from vm86 mode
[INFO] Exited vm86 mode due to STI
[FAIL] Incorrect return reason (started at eip = 0xd, ended at eip = 0xf)
because POPF currently fails to check IF before reporting a pending interrupt.
This patch also makes the FAIL message a bit more informative.
Reported-by Bart Oldeman <[email protected]>
Signed-off-by Andy Lutomirski <[email protected]>
--- tools/testing/selftests/x86/entry_from_vm86.c | 30 ++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-)
tools/testing/selftests/x86/entry_from_vm86.c +27 -3
@@ -95,6 +95,10 @@ asm ("int3\n\t" "vmcode_int80:\n\t" "int $0x80\n\t" +"vmcode_popf_hlt:\n\t" +"push %ax\n\t" +"popf\n\t" +"hlt\n\t" "vmcode_umip:\n\t" /* addressing via displacements */ "smsw (2052)\n\t"
@@ -124,8 +128,8 @@ asm (extern unsigned char vmcode[], end_vmcode[];extern unsigned char vmcode_bound[], vmcode_sysenter[], vmcode_syscall[], - vmcode_sti[], vmcode_int3[], vmcode_int80[], vmcode_umip[], - vmcode_umip_str[], vmcode_umip_sldt[]; + vmcode_sti[], vmcode_int3[], vmcode_int80[], vmcode_popf_hlt[], + vmcode_umip[], vmcode_umip_str[], vmcode_umip_sldt[];/* Returns false if the test was skipped. */ static bool do_test(struct vm86plus_struct *v86, unsigned long eip,
@@ -175,7 +179,7 @@ static bool do_test(struct vm86plus_struct *v86, unsigned long eip, (VM86_TYPE(ret) == rettype && VM86_ARG(ret) == retarg)) { printf("[OK]\tReturned correctly\n"); } else { -printf ("[FAIL]\tIncorrect return reason\n" ); +printf ("[FAIL]\tIncorrect return reason (started at eip = 0x%lx, ended at eip = 0x%lx)\n" , eip, v86->regs.eip); nerrs++; }
@@ -264,6 +268,9 @@ int main(void) v86.regs.ds = load_addr /16 ; v86.regs.es = load_addr /16 ; +/* Use the end of the page as our stack. */ + v86.regs.esp =4096 ; +assert ((v86.regs.cs &3 ) ==0 );/* Looks like RPL = 0 */ /* #BR -- should deliver SIG??? */
@@ -295,6 +302,23 @@ int main(void) v86.regs.eflags &= ~X86_EFLAGS_IF ;do_test (&v86, vmcode_sti - vmcode,VM86_STI ,0 ,"STI with VIP set" ); +/* POPF with VIP set but IF clear: should not trap */ + v86.regs.eflags =X86_EFLAGS_VIP ; + v86.regs.eax =0 ; +do_test (&v86, vmcode_popf_hlt - vmcode,VM86_UNKNOWN ,0 ,"POPF with VIP set and IF clear" ); + +/* POPF with VIP set and IF set: should trap */ + v86.regs.eflags =X86_EFLAGS_VIP ; + v86.regs.eax =X86_EFLAGS_IF ; +do_test (&v86, vmcode_popf_hlt - vmcode,VM86_STI ,0 ,"POPF with VIP and IF set" ); + +/* POPF with VIP clear and IF set: should not trap */ + v86.regs.eflags =0 ; + v86.regs.eax =X86_EFLAGS_IF ; +do_test (&v86, vmcode_popf_hlt - vmcode,VM86_UNKNOWN ,0 ,"POPF with VIP clear and IF set" ); + + v86.regs.eflags =0 ; +/* INT3 -- should cause #BP */ do_test (&v86, vmcode_int3 - vmcode,VM86_TRAP ,3 ,"INT3" );
Signature · 1 line
2.14.3
tip-bot for Andy Lutomirski
merge bot[tip:x86/pti] selftests/x86/entry_from_vm86: Add test cases for POPF
selftests/x86/entry_from_vm86: Add test cases for POPF
Commit-ID: 78393fdde2a456cafa414b171c90f26a3df98b20 Gitweb: https://git.kernel.org/tip/78393fdde2a456cafa414b171c90f26a3df98b20 Author: Andy Lutomirski <[email protected]> AuthorDate: Tue, 13 Mar 2018 22:03:11 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Wed, 14 Mar 2018 09:21:01 +0100
selftests/x86/entry_from_vm86: Add test cases for POPF
POPF is currently broken -- add tests to catch the error. This results in:
[RUN] POPF with VIP set and IF clear from vm86 mode
[INFO] Exited vm86 mode due to STI
[FAIL] Incorrect return reason (started at eip = 0xd, ended at eip = 0xf)
because POPF currently fails to check IF before reporting a pending interrupt.
This patch also makes the FAIL message a bit more informative.
Reported-by Bart Oldeman <[email protected]>
Signed-off-by Andy Lutomirski <[email protected]>
Cc Borislav Petkov <[email protected]>
Cc Brian Gerst <[email protected]>
Cc Denys Vlasenko <[email protected]>
Cc H. Peter Anvin <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Stas Sergeev <[email protected]>
Cc Thomas Gleixner <[email protected]>
Link http://lkml.kernel.org/r/a16270b5cfe7832d6d00c479d0f871066cbdb52b.1521003603.git.luto@kernel.org open here
Signed-off-by Ingo Molnar <[email protected]>
--- tools/testing/selftests/x86/entry_from_vm86.c | 30 ++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-)
tools/testing/selftests/x86/entry_from_vm86.c +27 -3
@@ -95,6 +95,10 @@ asm ("int3\n\t" "vmcode_int80:\n\t" "int $0x80\n\t" +"vmcode_popf_hlt:\n\t" +"push %ax\n\t" +"popf\n\t" +"hlt\n\t" "vmcode_umip:\n\t" /* addressing via displacements */ "smsw (2052)\n\t"
@@ -124,8 +128,8 @@ asm (extern unsigned char vmcode[], end_vmcode[];extern unsigned char vmcode_bound[], vmcode_sysenter[], vmcode_syscall[], - vmcode_sti[], vmcode_int3[], vmcode_int80[], vmcode_umip[], - vmcode_umip_str[], vmcode_umip_sldt[]; + vmcode_sti[], vmcode_int3[], vmcode_int80[], vmcode_popf_hlt[], + vmcode_umip[], vmcode_umip_str[], vmcode_umip_sldt[];/* Returns false if the test was skipped. */ static bool do_test(struct vm86plus_struct *v86, unsigned long eip,
@@ -175,7 +179,7 @@ static bool do_test(struct vm86plus_struct *v86, unsigned long eip, (VM86_TYPE(ret) == rettype && VM86_ARG(ret) == retarg)) { printf("[OK]\tReturned correctly\n"); } else { -printf ("[FAIL]\tIncorrect return reason\n" ); +printf ("[FAIL]\tIncorrect return reason (started at eip = 0x%lx, ended at eip = 0x%lx)\n" , eip, v86->regs.eip); nerrs++; }
@@ -264,6 +268,9 @@ int main(void) v86.regs.ds = load_addr /16 ; v86.regs.es = load_addr /16 ; +/* Use the end of the page as our stack. */ + v86.regs.esp =4096 ; +assert ((v86.regs.cs &3 ) ==0 );/* Looks like RPL = 0 */ /* #BR -- should deliver SIG??? */
@@ -295,6 +302,23 @@ int main(void) v86.regs.eflags &= ~X86_EFLAGS_IF ;do_test (&v86, vmcode_sti - vmcode,VM86_STI ,0 ,"STI with VIP set" ); +/* POPF with VIP set but IF clear: should not trap */ + v86.regs.eflags =X86_EFLAGS_VIP ; + v86.regs.eax =0 ; +do_test (&v86, vmcode_popf_hlt - vmcode,VM86_UNKNOWN ,0 ,"POPF with VIP set and IF clear" ); + +/* POPF with VIP set and IF set: should trap */ + v86.regs.eflags =X86_EFLAGS_VIP ; + v86.regs.eax =X86_EFLAGS_IF ; +do_test (&v86, vmcode_popf_hlt - vmcode,VM86_STI ,0 ,"POPF with VIP and IF set" ); + +/* POPF with VIP clear and IF set: should not trap */ + v86.regs.eflags =0 ; + v86.regs.eax =X86_EFLAGS_IF ; +do_test (&v86, vmcode_popf_hlt - vmcode,VM86_UNKNOWN ,0 ,"POPF with VIP clear and IF set" ); + + v86.regs.eflags =0 ; +/* INT3 -- should cause #BP */ do_test (&v86, vmcode_int3 - vmcode,VM86_TRAP ,3 ,"INT3" );
PATCH 3/3 x86/vm86/32: Fix POPF emulation
In reply to Andy LutomirskiPOPF would trap if VIP was set regardless of whether IF was set. Fix it.
Reported-by Bart Oldeman <[email protected]>
Suggested-by Stas Sergeev <[email protected]>
Fixes 5ed92a8ab71f ("x86/vm86: Use the normal pt_regs area for vm86")
Signed-off-by Andy Lutomirski <[email protected]>
--- arch/x86/kernel/vm86_32.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
arch/x86/kernel/vm86_32.c +2 -1
@@ -727,7 +727,8 @@ void handle_vm86_fault(struct kernel_vm86_regs *regs, long error_code)return ; check_vip: -if (VEFLAGS &X86_EFLAGS_VIP ) { +if ((VEFLAGS & (X86_EFLAGS_VIP |X86_EFLAGS_VIF )) == + (X86_EFLAGS_VIP |X86_EFLAGS_VIF )) {save_v86_state (regs,VM86_STI );return ; }
Signature · 1 line
2.14.3
tip-bot for Andy Lutomirski
merge bot[tip:x86/pti] x86/vm86/32: Fix POPF emulation
x86/vm86/32: Fix POPF emulation
Commit-ID: b5069782453459f6ec1fdeb495d9901a4545fcb5 Gitweb: https://git.kernel.org/tip/b5069782453459f6ec1fdeb495d9901a4545fcb5 Author: Andy Lutomirski <[email protected]> AuthorDate: Tue, 13 Mar 2018 22:03:12 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Wed, 14 Mar 2018 09:21:01 +0100
x86/vm86/32: Fix POPF emulation
POPF would trap if VIP was set regardless of whether IF was set. Fix it.
Suggested-by Stas Sergeev <[email protected]>
Reported-by Bart Oldeman <[email protected]>
Signed-off-by Andy Lutomirski <[email protected]>
Cc Borislav Petkov <[email protected]>
Cc Brian Gerst <[email protected]>
Cc Denys Vlasenko <[email protected]>
Cc H. Peter Anvin <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Thomas Gleixner <[email protected]>
Fixes 5ed92a8ab71f ("x86/vm86: Use the normal pt_regs area for vm86")
Link http://lkml.kernel.org/r/ce95f40556e7b2178b6bc06ee9557827ff94bd28.1521003603.git.luto@kernel.org open here
Signed-off-by Ingo Molnar <[email protected]>
--- arch/x86/kernel/vm86_32.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
arch/x86/kernel/vm86_32.c +2 -1
@@ -727,7 +727,8 @@ void handle_vm86_fault(struct kernel_vm86_regs *regs, long error_code)return ; check_vip: -if (VEFLAGS &X86_EFLAGS_VIP ) { +if ((VEFLAGS & (X86_EFLAGS_VIP |X86_EFLAGS_VIF )) == + (X86_EFLAGS_VIP |X86_EFLAGS_VIF )) {save_v86_state (regs,VM86_STI );return ; }