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x86/hyperv: Use direct call to hypercall-page

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Instead of using an indirect call to the hypercall page, use a direct
call instead. This avoids all CFI problems, including the one where
the hypercall page doesn't have IBT on.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Acked-by: Sean Christopherson <seanjc@google.com>
Link: https://lkml.kernel.org/r/20250714103441.011387946@infradead.org
This commit is contained in:
Peter Zijlstra 2025-04-12 13:55:55 +02:00
parent 0e20f1f4c2
commit c8ed081264
1 changed files with 30 additions and 31 deletions
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61
arch/x86/hyperv/hv_init.c
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@ -17,7 +17,6 @@
#include <asm/desc.h> #include <asm/desc.h>
#include <asm/e820/api.h> #include <asm/e820/api.h>
#include <asm/sev.h> #include <asm/sev.h>
#include <asm/ibt.h>
#include <asm/hypervisor.h> #include <asm/hypervisor.h>
#include <hyperv/hvhdk.h> #include <hyperv/hvhdk.h>
#include <asm/mshyperv.h> #include <asm/mshyperv.h>
@ -39,23 +38,41 @@
void *hv_hypercall_pg; void *hv_hypercall_pg;
#ifdef CONFIG_X86_64 #ifdef CONFIG_X86_64
static u64 __hv_hyperfail(u64 control, u64 param1, u64 param2)
{
return U64_MAX;
}
DEFINE_STATIC_CALL(__hv_hypercall, __hv_hyperfail);
u64 hv_std_hypercall(u64 control, u64 param1, u64 param2) u64 hv_std_hypercall(u64 control, u64 param1, u64 param2)
{ {
u64 hv_status; u64 hv_status;
if (!hv_hypercall_pg)
return U64_MAX;
register u64 __r8 asm("r8") = param2; register u64 __r8 asm("r8") = param2;
asm volatile (CALL_NOSPEC asm volatile ("call " STATIC_CALL_TRAMP_STR(__hv_hypercall)
: "=a" (hv_status), ASM_CALL_CONSTRAINT, : "=a" (hv_status), ASM_CALL_CONSTRAINT,
"+c" (control), "+d" (param1), "+r" (__r8) "+c" (control), "+d" (param1), "+r" (__r8)
: THUNK_TARGET(hv_hypercall_pg) : : "cc", "memory", "r9", "r10", "r11");
: "cc", "memory", "r9", "r10", "r11");
return hv_status; return hv_status;
} }
typedef u64 (*hv_hypercall_f)(u64 control, u64 param1, u64 param2);
static inline void hv_set_hypercall_pg(void *ptr)
{
hv_hypercall_pg = ptr;
if (!ptr)
ptr = &__hv_hyperfail;
static_call_update(__hv_hypercall, (hv_hypercall_f)ptr);
}
#else #else
static inline void hv_set_hypercall_pg(void *ptr)
{
hv_hypercall_pg = ptr;
}
EXPORT_SYMBOL_GPL(hv_hypercall_pg); EXPORT_SYMBOL_GPL(hv_hypercall_pg);
#endif #endif
@ -350,7 +367,7 @@ static int hv_suspend(void)
* pointer is restored on resume. * pointer is restored on resume.
*/ */
hv_hypercall_pg_saved = hv_hypercall_pg; hv_hypercall_pg_saved = hv_hypercall_pg;
hv_hypercall_pg = NULL; hv_set_hypercall_pg(NULL);
/* Disable the hypercall page in the hypervisor */ /* Disable the hypercall page in the hypervisor */
rdmsrq(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); rdmsrq(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
@ -376,7 +393,7 @@ static void hv_resume(void)
vmalloc_to_pfn(hv_hypercall_pg_saved); vmalloc_to_pfn(hv_hypercall_pg_saved);
wrmsrq(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); wrmsrq(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
hv_hypercall_pg = hv_hypercall_pg_saved; hv_set_hypercall_pg(hv_hypercall_pg_saved);
hv_hypercall_pg_saved = NULL; hv_hypercall_pg_saved = NULL;
/* /*
@ -496,8 +513,8 @@ void __init hyperv_init(void)
if (hv_isolation_type_tdx() && !ms_hyperv.paravisor_present) if (hv_isolation_type_tdx() && !ms_hyperv.paravisor_present)
goto skip_hypercall_pg_init; goto skip_hypercall_pg_init;
hv_hypercall_pg = __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, hv_hypercall_pg = __vmalloc_node_range(PAGE_SIZE, 1, MODULES_VADDR,
VMALLOC_END, GFP_KERNEL, PAGE_KERNEL_ROX, MODULES_END, GFP_KERNEL, PAGE_KERNEL_ROX,
VM_FLUSH_RESET_PERMS, NUMA_NO_NODE, VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
__builtin_return_address(0)); __builtin_return_address(0));
if (hv_hypercall_pg == NULL) if (hv_hypercall_pg == NULL)
@ -535,27 +552,9 @@ void __init hyperv_init(void)
wrmsrq(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); wrmsrq(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
} }
skip_hypercall_pg_init: hv_set_hypercall_pg(hv_hypercall_pg);
/*
* Some versions of Hyper-V that provide IBT in guest VMs have a bug
* in that there's no ENDBR64 instruction at the entry to the
* hypercall page. Because hypercalls are invoked via an indirect call
* to the hypercall page, all hypercall attempts fail when IBT is
* enabled, and Linux panics. For such buggy versions, disable IBT.
*
* Fixed versions of Hyper-V always provide ENDBR64 on the hypercall
* page, so if future Linux kernel versions enable IBT for 32-bit
* builds, additional hypercall page hackery will be required here
* to provide an ENDBR32.
*/
#ifdef CONFIG_X86_KERNEL_IBT
if (cpu_feature_enabled(X86_FEATURE_IBT) &&
*(u32 *)hv_hypercall_pg != gen_endbr()) {
setup_clear_cpu_cap(X86_FEATURE_IBT);
pr_warn("Disabling IBT because of Hyper-V bug\n");
}
#endif
skip_hypercall_pg_init:
/* /*
* hyperv_init() is called before LAPIC is initialized: see * hyperv_init() is called before LAPIC is initialized: see
* apic_intr_mode_init() -> x86_platform.apic_post_init() and * apic_intr_mode_init() -> x86_platform.apic_post_init() and