[xen staging] xen/cet: Fix __initconst_cf_clobber

[patchbot@xxxxxxx]

commit 3e56754b08871ccceff856ff634731b9b9bccbbe
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Mar 2 20:27:46 2022 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Mar 3 11:21:35 2022 +0000

    xen/cet: Fix __initconst_cf_clobber
    
    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 plain __initcall()'s.
    
    Consolidate to a single initcall using the iommu_adjust_irq_affinities()
    wrapper (satisfying the cf_clobber safety requirement by using iommu_call()
    under the hood), 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 in .text 
with
    382 (23%) being clobbered during boot.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 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 83def6541e..b15e5b67e4 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 657c7f619a..2e5bffa732 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 6a65ba1d82..f70d515806 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 58a422fb5f..57c7b26c1a 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 __init cf_check adjust_irq_affinities(void)
+{
+    return iommu_adjust_irq_affinities();
+}
+__initcall(adjust_irq_affinities);
+
 /*
  * Local variables:
  * mode: C
--
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