This patch does a lot of cleanup in comments and formatting,
but it does not change any code.
Rename save_paranoid to paranoid_entry: this makes naming
similar to its "non-paranoid" sibling, error_entry,
and to its counterpart, paranoid_exit.
Use the same CFI annotation atop paranoid_entry and error_entry.
Fix irregular indentation of assembler operands.
Add/fix comments on top of paranoid_entry and error_entry.
Remove stale comment about "oldrax".
Make comments about "no swapgs" flag in ebx more prominent.
Deindent wrongly indented top-level comment atop paranoid_exit.
Indent wrongly deindented comment inside error_entry.
Signed-off-by: Denys Vlasenko <dvlas...@redhat.com>
CC: Linus Torvalds <torva...@linux-foundation.org>
CC: Oleg Nesterov <o...@redhat.com>
CC: Borislav Petkov <b...@alien8.de>
CC: "H. Peter Anvin" <h...@zytor.com>
CC: Andy Lutomirski <l...@amacapital.net>
CC: Frederic Weisbecker <fweis...@gmail.com>
CC: X86 ML <x...@kernel.org>
CC: Alexei Starovoitov <a...@plumgrid.com>
CC: Will Drewry <w...@chromium.org>
CC: Kees Cook <keesc...@chromium.org>
CC: linux-kernel@vger.kernel.org
---
arch/x86/kernel/entry_64.S | 104 +++++++++++++++++++++++----------------------
1 file changed, 54 insertions(+), 50 deletions(-)
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index d72e46e..aacfa2c 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -968,10 +968,11 @@ ENTRY(\sym)
testl $3, CS(%rsp) /* If coming from userspace, switch */
jnz 1f /* stacks. */
.endif
- call save_paranoid
+ call paranoid_entry
.else
call error_entry
.endif
+ /* returned flag: ebx=0: need swapgs on exit, ebx=1: don't need it */
DEFAULT_FRAME 0
@@ -1002,10 +1003,11 @@ ENTRY(\sym)
addq $EXCEPTION_STKSZ, INIT_TSS_IST(\shift_ist)
.endif
+ /* these procedures expect "no swapgs" flag in ebx */
.if \paranoid
- jmp paranoid_exit /* %ebx: no swapgs flag */
+ jmp paranoid_exit
.else
- jmp error_exit /* %ebx: no swapgs flag */
+ jmp error_exit
.endif
.if \paranoid == 1
@@ -1240,8 +1242,13 @@ idtentry async_page_fault do_async_page_fault
has_error_code=1
idtentry machine_check has_error_code=0 paranoid=1
do_sym=*machine_check_vector(%rip)
#endif
-ENTRY(save_paranoid)
- XCPT_FRAME 1 RDI+8
+/*
+ * Save all registers in pt_regs, and switch gs if needed.
+ * Use slow, but surefire "are we in kernel?" check.
+ * Return: ebx=0: need swapgs on exit, ebx=1: otherwise
+ */
+ENTRY(paranoid_entry)
+ XCPT_FRAME 1 15*8
cld
SAVE_C_REGS 8
SAVE_EXTRA_REGS 8
@@ -1254,20 +1261,19 @@ ENTRY(save_paranoid)
xorl %ebx,%ebx
1: ret
CFI_ENDPROC
-END(save_paranoid)
+END(paranoid_entry)
- /*
- * "Paranoid" exit path from exception stack. This is invoked
- * only on return from non-NMI IST interrupts that came
- * from kernel space.
- *
- * We may be returning to very strange contexts (e.g. very early
- * in syscall entry), so checking for preemption here would
- * be complicated. Fortunately, we there's no good reason
- * to try to handle preemption here.
- */
-
- /* ebx: no swapgs flag */
+/*
+ * "Paranoid" exit path from exception stack. This is invoked
+ * only on return from non-NMI IST interrupts that came
+ * from kernel space.
+ *
+ * We may be returning to very strange contexts (e.g. very early
+ * in syscall entry), so checking for preemption here would
+ * be complicated. Fortunately, we there's no good reason
+ * to try to handle preemption here.
+ */
+/* On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it) */
ENTRY(paranoid_exit)
DEFAULT_FRAME
DISABLE_INTERRUPTS(CLBR_NONE)
@@ -1288,18 +1294,16 @@ paranoid_restore1:
END(paranoid_exit)
/*
- * Exception entry point. This expects an error code/orig_rax on the stack.
- * returns in "no swapgs flag" in %ebx.
+ * Save all registers in pt_regs, and switch gs if needed.
+ * Return: ebx=0: need swapgs on exit, ebx=1: otherwise
*/
ENTRY(error_entry)
- XCPT_FRAME
- CFI_ADJUST_CFA_OFFSET 15*8
- /* oldrax contains error code */
+ XCPT_FRAME 1 15*8
cld
SAVE_C_REGS 8
SAVE_EXTRA_REGS 8
- xorl %ebx,%ebx
- testl $3,CS+8(%rsp)
+ xorl %ebx,%ebx
+ testl $3,CS+8(%rsp)
je error_kernelspace
error_swapgs:
SWAPGS
@@ -1307,42 +1311,42 @@ error_sti:
TRACE_IRQS_OFF
ret
-/*
- * There are two places in the kernel that can potentially fault with
- * usergs. Handle them here. B stepping K8s sometimes report a
- * truncated RIP for IRET exceptions returning to compat mode. Check
- * for these here too.
- */
+ /*
+ * There are two places in the kernel that can potentially fault with
+ * usergs. Handle them here. B stepping K8s sometimes report a
+ * truncated RIP for IRET exceptions returning to compat mode. Check
+ * for these here too.
+ */
error_kernelspace:
CFI_REL_OFFSET rcx, RCX+8
- incl %ebx
- leaq native_irq_return_iret(%rip),%rcx
- cmpq %rcx,RIP+8(%rsp)
- je error_bad_iret
- movl %ecx,%eax /* zero extend */
- cmpq %rax,RIP+8(%rsp)
- je bstep_iret
- cmpq $gs_change,RIP+8(%rsp)
- je error_swapgs
- jmp error_sti
+ incl %ebx
+ leaq native_irq_return_iret(%rip),%rcx
+ cmpq %rcx,RIP+8(%rsp)
+ je error_bad_iret
+ movl %ecx,%eax /* zero extend */
+ cmpq %rax,RIP+8(%rsp)
+ je bstep_iret
+ cmpq $gs_change,RIP+8(%rsp)
+ je error_swapgs
+ jmp error_sti
bstep_iret:
/* Fix truncated RIP */
- movq %rcx,RIP+8(%rsp)
+ movq %rcx,RIP+8(%rsp)
/* fall through */
error_bad_iret:
SWAPGS
- mov %rsp,%rdi
- call fixup_bad_iret
- mov %rax,%rsp
- decl %ebx /* Return to usergs */
- jmp error_sti
+ mov %rsp,%rdi
+ call fixup_bad_iret
+ mov %rax,%rsp
+ decl %ebx /* Return to usergs */
+ jmp error_sti
CFI_ENDPROC
END(error_entry)
-/* ebx: no swapgs flag (1: don't need swapgs, 0: need it) */
+/* On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it) */
ENTRY(error_exit)
DEFAULT_FRAME
movl %ebx,%eax
@@ -1568,13 +1572,13 @@ end_repeat_nmi:
ALLOC_PT_GPREGS_ON_STACK
/*
- * Use save_paranoid to handle SWAPGS, but no need to use paranoid_exit
+ * Use paranoid_entry to handle SWAPGS, but no need to use paranoid_exit
* as we should not be calling schedule in NMI context.
* Even with normal interrupts enabled. An NMI should not be
* setting NEED_RESCHED or anything that normal interrupts and
* exceptions might do.
*/
- call save_paranoid
+ call paranoid_entry
DEFAULT_FRAME 0
/*
--
1.8.1.4
--
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