From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Thu, 15 Apr 2021 01:03:00 +0000 (+0100)
Subject: various: Fix scan-build deadcode.DeadStores issues
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=8b9b625d0bb309f2771c290033114dcbbcec3434;p=xtf.git

various: Fix scan-build deadcode.DeadStores issues

Scan-build complains:

  main.c:164:15: warning: Although the value stored to 'cr4' is used in the enclosing expression, the value is never actually read from 'cr4' [deadcode.DeadStores]
      write_cr4(cr4 &= ~X86_CR4_DE);
                ^      ~~~~~~~~~~~

Rework all impacted logic avoid dead stores of this form.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---

diff --git a/tests/debug-regs/main.c b/tests/debug-regs/main.c
index 9d4b74e..19c8889 100644
--- a/tests/debug-regs/main.c
+++ b/tests/debug-regs/main.c
@@ -138,7 +138,7 @@ static void test_pv_dr7_io_breakpoints(void)
     printk("Test PV %%dr7 IO breakpoints\n");
 
     if ( !(cr4 & X86_CR4_DE) )
-        write_cr4(cr4 |= X86_CR4_DE);
+        write_cr4(cr4 | X86_CR4_DE);
 
     /* Active IO breakpoint in %dr0. */
     io0 = DR7_SYM(0, G, IO, 32) | X86_DR7_GE | X86_DR7_DEFAULT;
@@ -161,7 +161,7 @@ static void test_pv_dr7_io_breakpoints(void)
     write_dr7(io0);
 
     /* Clear %cr4.de, after which IO breakpoints are invalid. */
-    write_cr4(cr4 &= ~X86_CR4_DE);
+    write_cr4(cr4);
 
     /* Attempt to reload an IO breakpoint in %dr0, which should fail ... */
     exinfo_t fault = 0;
diff --git a/tests/nested-vmx/vmxon.c b/tests/nested-vmx/vmxon.c
index 74b1182..e101288 100644
--- a/tests/nested-vmx/vmxon.c
+++ b/tests/nested-vmx/vmxon.c
@@ -181,7 +181,7 @@ void test_vmxon(void)
     test_vmxon_novmxe();
     test_vmxon_novmxe_in_user();
 
-    write_cr4(cr4 |= X86_CR4_VMXE);
+    write_cr4(cr4 | X86_CR4_VMXE);
 
     test_vmxon_in_user();
     test_vmxon_overly_wide_paddr();
diff --git a/tests/pv-fsgsbase/main.c b/tests/pv-fsgsbase/main.c
index d354238..de966c9 100644
--- a/tests/pv-fsgsbase/main.c
+++ b/tests/pv-fsgsbase/main.c
@@ -174,7 +174,9 @@ void test_main(void)
     {
         xtf_failure("Fail: Initial CR4.FSGSBASE state should be clear\n");
 
-        if ( pv_write_cr4_safe(cr4 &= ~X86_CR4_FSGSBASE) )
+        /* Try turning CR4.FSGSBASE off, to continue the test. */
+        cr4 &= ~X86_CR4_FSGSBASE;
+        if ( pv_write_cr4_safe(cr4) )
             return xtf_failure("Fail: Fault while trying to clear CR4.FSGSBASE\n");
     }
 
@@ -187,14 +189,14 @@ void test_main(void)
     if ( !cpu_has_fsgsbase )
     {
         /* If the FSGSBASE feature isn't visible, check we can't turn it on. */
-        if ( !pv_write_cr4_safe(cr4 |= X86_CR4_FSGSBASE) )
+        if ( !pv_write_cr4_safe(cr4 | X86_CR4_FSGSBASE) )
             xtf_failure("Fail: Able to set CR4.FSGSBASE without the feature\n");
 
         return;
     }
 
     /* Check we can turn CR4.FSGSBASE on. */
-    if ( pv_write_cr4_safe(cr4 |= X86_CR4_FSGSBASE) )
+    if ( pv_write_cr4_safe(cr4 | X86_CR4_FSGSBASE) )
         xtf_failure("Fail: Unable to enable CR4.FSGSBASE\n");
 
     /* Check that {RD,WR}{FS,GS}BASE instructions are enabled. */
@@ -204,7 +206,7 @@ void test_main(void)
     test_wrfsbase_values();
 
     /* Check we can turn CR4.FSGSBASE off again. */
-    if ( pv_write_cr4_safe(cr4 &= ~X86_CR4_FSGSBASE) )
+    if ( pv_write_cr4_safe(cr4) )
         xtf_failure("Fail: Unable to enable CR4.FSGSBASE\n");
 
     /* Check that {RD,WR}{FS,GS}BASE instructions are disabled again. */
diff --git a/tests/xsa-269/main.c b/tests/xsa-269/main.c
index d633d50..164a602 100644
--- a/tests/xsa-269/main.c
+++ b/tests/xsa-269/main.c
@@ -43,7 +43,7 @@ void test_main(void)
      */
     wrmsr_safe(MSR_DEBUGCTL, val |= DEBUGCTL_TR);
     wrmsr_safe(MSR_DEBUGCTL, val |= DEBUGCTL_BTS);
-    wrmsr_safe(MSR_DEBUGCTL, val |= DEBUGCTL_BTINT);
+    wrmsr_safe(MSR_DEBUGCTL, val |  DEBUGCTL_BTINT);
 
     /*
      * If we're still alive, generate a billion jumps to check that BTS really