Commit 3f5159a9 authored by Denys Vlasenko's avatar Denys Vlasenko Committed by Ingo Molnar
Browse files

x86/asm/entry/32: Update -ENOSYS handling to match the 64-bit logic 



Recently Andy changed the 64-bit syscall logic so that
pt_regs->ax is initially set to -ENOSYS, and on syscall exit,
it is updated with the actual return value. This simplified
the logic there.

This patch does the same for 32-bit syscall entry points.

The check for %rax being too big is moved to be just before
the call instruction which dispatches execution through the
syscall table.

There is no way to accidentally skip this check now by jumping
to a label after it. This allows us to remove redundant checks
after ptrace et al.

If %rax is too big, we just skip over the (call, write %rax to
pt_regs->ax) instruction pair. pt_regs->ax remains set to -ENOSYS,
and it gets returned to userspace.

Similar to 64-bit code, this eliminates the "ia32_badsys" code path.

Run-tested.

Signed-off-by: default avatarDenys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1429632194-13445-2-git-send-email-dvlasenk@redhat.com


[ Changelog massage. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ac7f5dfb

arch/x86/ia32/ia32entry.S

+14 −28
Original line number Diff line number Diff line
@@ -136,7 +136,7 @@ ENTRY(ia32_sysenter_target) 
	pushq_cfi_reg	rsi			/* pt_regs->si */

	pushq_cfi_reg	rdx			/* pt_regs->dx */

	pushq_cfi_reg	rcx			/* pt_regs->cx */

	pushq_cfi_reg	rax			/* pt_regs->ax */

	pushq_cfi	$-ENOSYS		/* pt_regs->ax */

	cld

	sub	$(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */

	CFI_ADJUST_CFA_OFFSET 10*8
@@ -163,8 +163,6 @@ sysenter_flags_fixed: 
	testl   $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)

	CFI_REMEMBER_STATE

	jnz  sysenter_tracesys

	cmpq	$(IA32_NR_syscalls-1),%rax

	ja	ia32_badsys

sysenter_do_call:

	/* 32bit syscall -> 64bit C ABI argument conversion */

	movl	%edi,%r8d	/* arg5 */
@@ -173,8 +171,11 @@ sysenter_do_call: 
	movl	%ebx,%edi	/* arg1 */

	movl	%edx,%edx	/* arg3 (zero extension) */

sysenter_dispatch:

	cmpq	$(IA32_NR_syscalls-1),%rax

	ja	1f

	call	*ia32_sys_call_table(,%rax,8)

	movq	%rax,RAX(%rsp)

1:

	DISABLE_INTERRUPTS(CLBR_NONE)

	TRACE_IRQS_OFF

	testl	$_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
@@ -241,9 +242,7 @@ sysexit_from_sys_call: 
	movl %ebx,%esi			/* 2nd arg: 1st syscall arg */

	movl %eax,%edi			/* 1st arg: syscall number */

	call __audit_syscall_entry

	movl RAX(%rsp),%eax	/* reload syscall number */

	cmpq $(IA32_NR_syscalls-1),%rax

	ja ia32_badsys

	movl ORIG_RAX(%rsp),%eax	/* reload syscall number */

	movl %ebx,%edi			/* reload 1st syscall arg */

	movl RCX(%rsp),%esi	/* reload 2nd syscall arg */

	movl RDX(%rsp),%edx	/* reload 3rd syscall arg */
@@ -294,13 +293,10 @@ sysenter_tracesys: 
#endif

	SAVE_EXTRA_REGS

	CLEAR_RREGS

	movq	$-ENOSYS,RAX(%rsp)/* ptrace can change this for a bad syscall */

	movq	%rsp,%rdi        /* &pt_regs -> arg1 */

	call	syscall_trace_enter

	LOAD_ARGS32  /* reload args from stack in case ptrace changed it */

	RESTORE_EXTRA_REGS

	cmpq	$(IA32_NR_syscalls-1),%rax

	ja	int_ret_from_sys_call /* sysenter_tracesys has set RAX(%rsp) */

	jmp	sysenter_do_call

	CFI_ENDPROC

ENDPROC(ia32_sysenter_target)
@@ -370,7 +366,7 @@ ENTRY(ia32_cstar_target) 
	pushq_cfi_reg	rdx			/* pt_regs->dx */

	pushq_cfi_reg	rbp			/* pt_regs->cx */

	movl	%ebp,%ecx

	pushq_cfi_reg	rax			/* pt_regs->ax */

	pushq_cfi	$-ENOSYS		/* pt_regs->ax */

	sub	$(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */

	CFI_ADJUST_CFA_OFFSET 10*8
@@ -386,8 +382,6 @@ ENTRY(ia32_cstar_target) 
	testl   $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)

	CFI_REMEMBER_STATE

	jnz   cstar_tracesys

	cmpq $IA32_NR_syscalls-1,%rax

	ja  ia32_badsys

cstar_do_call:

	/* 32bit syscall -> 64bit C ABI argument conversion */

	movl	%edi,%r8d	/* arg5 */
@@ -396,8 +390,11 @@ cstar_do_call: 
	movl	%ebx,%edi	/* arg1 */

	movl	%edx,%edx	/* arg3 (zero extension) */

cstar_dispatch:

	cmpq	$(IA32_NR_syscalls-1),%rax

	ja	1f

	call *ia32_sys_call_table(,%rax,8)

	movq %rax,RAX(%rsp)

1:

	DISABLE_INTERRUPTS(CLBR_NONE)

	TRACE_IRQS_OFF

	testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
@@ -444,14 +441,11 @@ cstar_tracesys: 
	xchgl %r9d,%ebp

	SAVE_EXTRA_REGS

	CLEAR_RREGS r9

	movq $-ENOSYS,RAX(%rsp)	/* ptrace can change this for a bad syscall */

	movq %rsp,%rdi        /* &pt_regs -> arg1 */

	call syscall_trace_enter

	LOAD_ARGS32 1	/* reload args from stack in case ptrace changed it */

	RESTORE_EXTRA_REGS

	xchgl %ebp,%r9d

	cmpq $(IA32_NR_syscalls-1),%rax

	ja int_ret_from_sys_call /* cstar_tracesys has set RAX(%rsp) */

	jmp cstar_do_call

END(ia32_cstar_target)
@@ -510,7 +504,7 @@ ENTRY(ia32_syscall) 
	pushq_cfi_reg	rsi			/* pt_regs->si */

	pushq_cfi_reg	rdx			/* pt_regs->dx */

	pushq_cfi_reg	rcx			/* pt_regs->cx */

	pushq_cfi_reg	rax			/* pt_regs->ax */

	pushq_cfi	$-ENOSYS		/* pt_regs->ax */

	cld

	sub	$(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */

	CFI_ADJUST_CFA_OFFSET 10*8
@@ -518,8 +512,6 @@ ENTRY(ia32_syscall) 
	orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)

	testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)

	jnz ia32_tracesys

	cmpq $(IA32_NR_syscalls-1),%rax

	ja ia32_badsys

ia32_do_call:

	/* 32bit syscall -> 64bit C ABI argument conversion */

	movl %edi,%r8d	/* arg5 */
@@ -527,9 +519,12 @@ ia32_do_call: 
	xchg %ecx,%esi	/* rsi:arg2, rcx:arg4 */

	movl %ebx,%edi	/* arg1 */

	movl %edx,%edx	/* arg3 (zero extension) */

	cmpq	$(IA32_NR_syscalls-1),%rax

	ja	1f

	call *ia32_sys_call_table(,%rax,8) # xxx: rip relative

ia32_sysret:

	movq %rax,RAX(%rsp)

1:

ia32_ret_from_sys_call:

	CLEAR_RREGS

	jmp int_ret_from_sys_call
@@ -537,22 +532,13 @@ ia32_ret_from_sys_call: 
ia32_tracesys:

	SAVE_EXTRA_REGS

	CLEAR_RREGS

	movq $-ENOSYS,RAX(%rsp)	/* ptrace can change this for a bad syscall */

	movq %rsp,%rdi        /* &pt_regs -> arg1 */

	call syscall_trace_enter

	LOAD_ARGS32	/* reload args from stack in case ptrace changed it */

	RESTORE_EXTRA_REGS

	cmpq $(IA32_NR_syscalls-1),%rax

	ja  int_ret_from_sys_call	/* ia32_tracesys has set RAX(%rsp) */

	jmp ia32_do_call

END(ia32_syscall)



ia32_badsys:

	movq $0,ORIG_RAX(%rsp)

	movq $-ENOSYS,%rax

	jmp ia32_sysret



	CFI_ENDPROC

END(ia32_syscall)



	.macro PTREGSCALL label, func

	ALIGN

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