[XEN PATCH][for-4.19 v5 2/8] x86: add deviation for asm-only functions

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

As stated in rules.rst, functions used only in asm modules
are allowed to have no prior declaration visible when being
defined, hence these functions are marked with an
'asmlinkage' macro, which is then deviated for MISRA C:2012
Rule 8.4.

'current_stack_pointer' in x86/asm_defns is a declaration, not a definition,
and is thus marked as safe for ECLAIR.

Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
---
Changes in v3:
- added SAF deviations for vmx counterparts to svm functions.
Changes in v5:
- drop SAF deviations in favour of the pseudo-attribute asmlinkage
---
 automation/eclair_analysis/ECLAIR/deviations.ecl | 9 +++++++++
 docs/misra/deviations.rst                        | 6 ++++++
 xen/arch/x86/hvm/svm/intr.c                      | 2 +-
 xen/arch/x86/hvm/svm/nestedsvm.c                 | 2 +-
 xen/arch/x86/hvm/svm/svm.c                       | 4 ++--
 xen/arch/x86/hvm/vmx/intr.c                      | 2 +-
 xen/arch/x86/hvm/vmx/vmx.c                       | 4 ++--
 xen/arch/x86/hvm/vmx/vvmx.c                      | 2 +-
 xen/arch/x86/traps.c                             | 2 +-
 xen/arch/x86/x86_64/traps.c                      | 2 +-
 xen/include/xen/compiler.h                       | 3 +++
 11 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
b/automation/eclair_analysis/ECLAIR/deviations.ecl
index fa56e5c00a27..28369174458d 100644
--- a/automation/eclair_analysis/ECLAIR/deviations.ecl
+++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
@@ -163,6 +163,15 @@ Therefore the absence of prior declarations is safe."
 -config=MC3R1.R8.4,reports+={safe, "first_area(any_loc(file(gcov)))"}
 -doc_end
 
+-doc_begin="Recognize the occurrence of current_stack_pointer as a 
declaration."
+-file_tag+={asm_defns, "^xen/arch/x86/include/asm/asm_defns\\.h$"}
+-config=MC3R1.R8.4,declarations+={safe, 
"loc(file(asm_defns))&&^current_stack_pointer$"}
+-doc_end
+
+-doc_begin="asmlinkage is a marker to indicate that the function is only used 
from asm modules."
+-config=MC3R1.R8.4,declarations+={safe,"loc(text(^.*asmlinkage.*$, -1..0))"}
+-doc_end
+
 -doc_begin="The following variables are compiled in multiple translation units
 belonging to different executables and therefore are safe."
 -config=MC3R1.R8.6,declarations+={safe, 
"name(current_stack_pointer||bsearch||sort)"}
diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
index 8511a189253b..d468da2f5ce9 100644
--- a/docs/misra/deviations.rst
+++ b/docs/misra/deviations.rst
@@ -133,6 +133,12 @@ Deviations related to MISRA C:2012 Rules:
        configuration. Therefore, the absence of prior declarations is safe.
      - Tagged as `safe` for ECLAIR.
 
+   * - R8.4
+     - Functions and variables used only by asm modules are either marked with
+       the `asmlinkage` macro or with a SAF-1-safe textual deviation
+       (see safe.json).
+     - Tagged as `safe` for ECLAIR.
+
    * - R8.6
      - The following variables are compiled in multiple translation units
        belonging to different executables and therefore are safe.
diff --git a/xen/arch/x86/hvm/svm/intr.c b/xen/arch/x86/hvm/svm/intr.c
index 192e17ebbfbb..34e5ff886e47 100644
--- a/xen/arch/x86/hvm/svm/intr.c
+++ b/xen/arch/x86/hvm/svm/intr.c
@@ -123,7 +123,7 @@ static void svm_enable_intr_window(struct vcpu *v, struct 
hvm_intack intack)
         vmcb, general1_intercepts | GENERAL1_INTERCEPT_VINTR);
 }
 
-void svm_intr_assist(void)
+asmlinkage void svm_intr_assist(void)
 {
     struct vcpu *v = current;
     struct vmcb_struct *vmcb = v->arch.hvm.svm.vmcb;
diff --git a/xen/arch/x86/hvm/svm/nestedsvm.c b/xen/arch/x86/hvm/svm/nestedsvm.c
index a09b6abaaeaf..222dfbe28781 100644
--- a/xen/arch/x86/hvm/svm/nestedsvm.c
+++ b/xen/arch/x86/hvm/svm/nestedsvm.c
@@ -1441,7 +1441,7 @@ nestedsvm_vcpu_vmexit(struct vcpu *v, struct 
cpu_user_regs *regs,
 }
 
 /* VCPU switch */
-void nsvm_vcpu_switch(void)
+asmlinkage void nsvm_vcpu_switch(void)
 {
     struct cpu_user_regs *regs = guest_cpu_user_regs();
     struct vcpu *v = current;
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 24c417ca7199..c1d83fe8af70 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -1056,7 +1056,7 @@ static void noreturn cf_check svm_do_resume(void)
     reset_stack_and_jump(svm_asm_do_resume);
 }
 
-void svm_vmenter_helper(void)
+asmlinkage void svm_vmenter_helper(void)
 {
     const struct cpu_user_regs *regs = guest_cpu_user_regs();
     struct vcpu *curr = current;
@@ -2586,7 +2586,7 @@ const struct hvm_function_table * __init start_svm(void)
     return &svm_function_table;
 }
 
-void svm_vmexit_handler(void)
+asmlinkage void svm_vmexit_handler(void)
 {
     struct cpu_user_regs *regs = guest_cpu_user_regs();
     uint64_t exit_reason;
diff --git a/xen/arch/x86/hvm/vmx/intr.c b/xen/arch/x86/hvm/vmx/intr.c
index fd719c4c01d2..4f2ac1db3e83 100644
--- a/xen/arch/x86/hvm/vmx/intr.c
+++ b/xen/arch/x86/hvm/vmx/intr.c
@@ -224,7 +224,7 @@ void vmx_sync_exit_bitmap(struct vcpu *v)
     }
 }
 
-void vmx_intr_assist(void)
+asmlinkage void vmx_intr_assist(void)
 {
     struct hvm_intack intack;
     struct vcpu *v = current;
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 1edc7f1e919f..af7e4e997c75 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -4035,7 +4035,7 @@ static void undo_nmis_unblocked_by_iret(void)
               guest_info | VMX_INTR_SHADOW_NMI);
 }
 
-void vmx_vmexit_handler(struct cpu_user_regs *regs)
+asmlinkage void vmx_vmexit_handler(struct cpu_user_regs *regs)
 {
     unsigned long exit_qualification, exit_reason, idtv_info, intr_info = 0;
     unsigned int vector = 0;
@@ -4787,7 +4787,7 @@ static void lbr_fixup(void)
 }
 
 /* Returns false if the vmentry has to be restarted */
-bool vmx_vmenter_helper(const struct cpu_user_regs *regs)
+asmlinkage bool vmx_vmenter_helper(const struct cpu_user_regs *regs)
 {
     struct vcpu *curr = current;
     struct domain *currd = curr->domain;
diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
index 16b0ef82b6c8..f234057b88ae 100644
--- a/xen/arch/x86/hvm/vmx/vvmx.c
+++ b/xen/arch/x86/hvm/vmx/vvmx.c
@@ -1490,7 +1490,7 @@ static void nvmx_eptp_update(void)
     __vmwrite(EPT_POINTER, get_shadow_eptp(curr));
 }
 
-void nvmx_switch_guest(void)
+asmlinkage void nvmx_switch_guest(void)
 {
     struct vcpu *v = current;
     struct nestedvcpu *nvcpu = &vcpu_nestedhvm(v);
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index e1356f696aba..b516da7b80f0 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -2265,7 +2265,7 @@ void asm_domain_crash_synchronous(unsigned long addr)
 }
 
 #ifdef CONFIG_DEBUG
-void check_ist_exit(const struct cpu_user_regs *regs, bool ist_exit)
+asmlinkage void check_ist_exit(const struct cpu_user_regs *regs, bool ist_exit)
 {
     const unsigned int ist_mask =
         (1U << X86_EXC_NMI) | (1U << X86_EXC_DB) |
diff --git a/xen/arch/x86/x86_64/traps.c b/xen/arch/x86/x86_64/traps.c
index e03e80813e36..ab5959daa887 100644
--- a/xen/arch/x86/x86_64/traps.c
+++ b/xen/arch/x86/x86_64/traps.c
@@ -266,7 +266,7 @@ void show_page_walk(unsigned long addr)
            l1_table_offset(addr), l1e_get_intpte(l1e), pfn);
 }
 
-void do_double_fault(struct cpu_user_regs *regs)
+asmlinkage void do_double_fault(struct cpu_user_regs *regs)
 {
     unsigned int cpu;
     unsigned long crs[8];
diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h
index dd99e573083f..39d696176f3d 100644
--- a/xen/include/xen/compiler.h
+++ b/xen/include/xen/compiler.h
@@ -159,6 +159,9 @@
 # define ASM_FLAG_OUT(yes, no) no
 #endif
 
+/* Mark a function or variable as used only from asm */
+#define asmlinkage
+
 /*
  * NB: we need to disable the gcc-compat warnings for clang in some places or
  * else it will complain with: "'break' is bound to loop, GCC binds it to
-- 
2.34.1