[PATCH] xen/CET: Fix __initconst_cf_clobber

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

The linker script collecting .init.rodata.* ahead of .init.rodata.cf_clobber
accidentally causes __initconst_cf_clobber to be a no-op.

Rearrange the linker script to unbreak this.

The IOMMU adjust_irq_affinities() hooks currently violate the safety
requirement for being cf_clobber, by also being __initcall().

Consolidate to a single initcall using iommu_call() (satisfying the cf_clobber
safety requirement), and also removes the dubious property that we'd call into
both vendors IOMMU drivers on boot, relying on the for_each_*() loops to be
empty for safety.

With this fixed, an all-enabled build of Xen has 1681 endbr64's (1918
including .init.text) with 382 (23%) being clobbered during boot.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>

I was unsure whether to go common or x86 spefific IOMMU code, so went with the
conservative option.  The final hunk can trivially move if preferred.
---
 xen/arch/x86/xen.lds.S                   | 12 ++++++------
 xen/drivers/passthrough/amd/iommu_init.c |  1 -
 xen/drivers/passthrough/vtd/iommu.c      |  1 -
 xen/drivers/passthrough/x86/iommu.c      |  6 ++++++
 4 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 83def6541ebd..b15e5b67e4a4 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -210,6 +210,12 @@ SECTIONS
   DECL_SECTION(.init.data) {
 #endif
 
+       . = ALIGN(POINTER_ALIGN);
+       __initdata_cf_clobber_start = .;
+       *(.init.data.cf_clobber)
+       *(.init.rodata.cf_clobber)
+       __initdata_cf_clobber_end = .;
+
        *(.init.rodata)
        *(.init.rodata.*)
 
@@ -224,12 +230,6 @@ SECTIONS
        *(.initcall1.init)
        __initcall_end = .;
 
-       . = ALIGN(POINTER_ALIGN);
-       __initdata_cf_clobber_start = .;
-       *(.init.data.cf_clobber)
-       *(.init.rodata.cf_clobber)
-       __initdata_cf_clobber_end = .;
-
        *(.init.data)
        *(.init.data.rel)
        *(.init.data.rel.*)
diff --git a/xen/drivers/passthrough/amd/iommu_init.c 
b/xen/drivers/passthrough/amd/iommu_init.c
index 657c7f619a51..2e5bffa732e7 100644
--- a/xen/drivers/passthrough/amd/iommu_init.c
+++ b/xen/drivers/passthrough/amd/iommu_init.c
@@ -831,7 +831,6 @@ int cf_check iov_adjust_irq_affinities(void)
 
     return 0;
 }
-__initcall(iov_adjust_irq_affinities);
 
 /*
  * Family15h Model 10h-1fh erratum 746 (IOMMU Logging May Stall Translations)
diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index 6a65ba1d8271..f70d51580657 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -2119,7 +2119,6 @@ static int cf_check adjust_vtd_irq_affinities(void)
 
     return 0;
 }
-__initcall(adjust_vtd_irq_affinities);
 
 static int __must_check init_vtd_hw(bool resume)
 {
diff --git a/xen/drivers/passthrough/x86/iommu.c 
b/xen/drivers/passthrough/x86/iommu.c
index 58a422fb5f88..6ef580215bc2 100644
--- a/xen/drivers/passthrough/x86/iommu.c
+++ b/xen/drivers/passthrough/x86/iommu.c
@@ -462,6 +462,12 @@ bool arch_iommu_use_permitted(const struct domain *d)
             likely(!p2m_get_hostp2m(d)->global_logdirty));
 }
 
+static int cf_check __init adjust_irq_affinities(void)
+{
+    return iommu_call(&iommu_ops, adjust_irq_affinities);
+}
+__initcall(adjust_irq_affinities);
+
 /*
  * Local variables:
  * mode: C
-- 
2.11.0