git: 7756b8f25e64 - stable/13 - xen: Fix warning by adding KERNBASE to modlist_paddr before casting

[Dimitry Andric]

The branch stable/13 has been updated by dim:

URL: https://cgit.FreeBSD.org/src/commit/?id=7756b8f25e640a5428b46670aa402ebecb884e6d

commit 7756b8f25e640a5428b46670aa402ebecb884e6d
Author:     Dimitry Andric <dim at FreeBSD.org>
AuthorDate: 2021-08-29 14:02:31 +0000
Commit:     Dimitry Andric <dim at FreeBSD.org>
CommitDate: 2021-09-02 21:53:18 +0000

    xen: Fix warning by adding KERNBASE to modlist_paddr before casting
    
    Clang 13 produces the following warning for hammer_time_xen():
    
    sys/x86/xen/pv.c:183:19: error: the pointer incremented by -2147483648 refers past the last possible element for an array in 64-bit address space containing 256-bit (32-byte) elements (max possible 576460752303423488 elements) [-Werror,-Warray-bounds]
                        (vm_paddr_t)start_info->modlist_paddr + KERNBASE;
                                    ^                               ~~~~~~~~
    sys/xen/interface/arch-x86/hvm/start_info.h:131:5: note: array 'modlist_paddr' declared here
        uint64_t modlist_paddr;         /* Physical address of an array of           */
        ^
    
    This is because the expression first casts start_info->modlist_paddr to
    struct hvm_modlist_entry * (via vmpaddr_t), and *then* adds KERNBASE,
    which is then interpreted as KERNBASE * sizeof(struct
    hvm_modlist_entry).
    
    Instead, parenthesize the addition to get the intended result, and cast
    it to struct hvm_modlist_entry * afterwards. Also remove the cast to
    vmpaddr_t since it is not necessary.
    
    Reviewed by:    royger
    Differential Revision: https://reviews.freebsd.org/D31711
    
    (cherry picked from commit 8e3c56d6b676a175e974bad4c20797fb35017db8)
---
 sys/x86/xen/pv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sys/x86/xen/pv.c b/sys/x86/xen/pv.c
index 59c5b464aace..6501f4dc2c50 100644
--- a/sys/x86/xen/pv.c
+++ b/sys/x86/xen/pv.c
@@ -334,7 +334,7 @@ hammer_time_xen(vm_paddr_t start_info_paddr)
 			HYPERVISOR_shutdown(SHUTDOWN_crash);
 		}
 		mod = (struct hvm_modlist_entry *)
-		    (vm_paddr_t)start_info->modlist_paddr + KERNBASE;
+		    (start_info->modlist_paddr + KERNBASE);
 		if (mod[0].paddr >= physfree) {
 			xc_printf("ERROR: unexpected module memory address\n");
 			HYPERVISOR_shutdown(SHUTDOWN_crash);