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KVM: selftests: Compare insn opcodes directly in fix_hypercall_test
Directly compare the expected versus observed hypercall instructions when
verifying that KVM patched in the native hypercall (FIX_HYPERCALL_INSN
quirk enabled). gcc rightly complains that doing a 4-byte memcpy() with
an "unsigned char" as the source generates an out-of-bounds accesses.
Alternatively, "exp" and "obs" could be declared as 3-byte arrays, but
there's no known reason to copy locally instead of comparing directly.
In function ‘assert_hypercall_insn’,
inlined from ‘guest_main’ at x86_64/fix_hypercall_test.c:91:2:
x86_64/fix_hypercall_test.c:63:9: error: array subscript ‘unsigned int[0]’
is partly outside array bounds of ‘unsigned char[1]’ [-Werror=array-bounds]
63 | memcpy(&exp, exp_insn, sizeof(exp));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
x86_64/fix_hypercall_test.c: In function ‘guest_main’:
x86_64/fix_hypercall_test.c:42:22: note: object ‘vmx_hypercall_insn’ of size 1
42 | extern unsigned char vmx_hypercall_insn;
| ^~~~~~~~~~~~~~~~~~
x86_64/fix_hypercall_test.c:25:22: note: object ‘svm_hypercall_insn’ of size 1
25 | extern unsigned char svm_hypercall_insn;
| ^~~~~~~~~~~~~~~~~~
In function ‘assert_hypercall_insn’,
inlined from ‘guest_main’ at x86_64/fix_hypercall_test.c:91:2:
x86_64/fix_hypercall_test.c:64:9: error: array subscript ‘unsigned int[0]’
is partly outside array bounds of ‘unsigned char[1]’ [-Werror=array-bounds]
64 | memcpy(&obs, obs_insn, sizeof(obs));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
x86_64/fix_hypercall_test.c: In function ‘guest_main’:
x86_64/fix_hypercall_test.c:25:22: note: object ‘svm_hypercall_insn’ of size 1
25 | extern unsigned char svm_hypercall_insn;
| ^~~~~~~~~~~~~~~~~~
x86_64/fix_hypercall_test.c:42:22: note: object ‘vmx_hypercall_insn’ of size 1
42 | extern unsigned char vmx_hypercall_insn;
| ^~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make: *** [../lib.mk:135: tools/testing/selftests/kvm/x86_64/fix_hypercall_test] Error 1
Fixes: 6c2fa8b20d
("selftests: KVM: Test KVM_X86_QUIRK_FIX_HYPERCALL_INSN")
Cc: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Message-Id: <20220928233652.783504-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
parent
6b6f71484b
commit
394265079b
1 changed files with 16 additions and 18 deletions
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@ -14,6 +14,9 @@
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#include "kvm_util.h"
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#include "processor.h"
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/* VMCALL and VMMCALL are both 3-byte opcodes. */
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#define HYPERCALL_INSN_SIZE 3
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static bool ud_expected;
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static void guest_ud_handler(struct ex_regs *regs)
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@ -22,7 +25,7 @@ static void guest_ud_handler(struct ex_regs *regs)
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GUEST_DONE();
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}
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extern unsigned char svm_hypercall_insn;
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extern uint8_t svm_hypercall_insn[HYPERCALL_INSN_SIZE];
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static uint64_t svm_do_sched_yield(uint8_t apic_id)
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{
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uint64_t ret;
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return ret;
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}
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extern unsigned char vmx_hypercall_insn;
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extern uint8_t vmx_hypercall_insn[HYPERCALL_INSN_SIZE];
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static uint64_t vmx_do_sched_yield(uint8_t apic_id)
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{
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uint64_t ret;
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@ -56,30 +59,20 @@ static uint64_t vmx_do_sched_yield(uint8_t apic_id)
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return ret;
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}
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static void assert_hypercall_insn(unsigned char *exp_insn, unsigned char *obs_insn)
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{
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uint32_t exp = 0, obs = 0;
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memcpy(&exp, exp_insn, sizeof(exp));
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memcpy(&obs, obs_insn, sizeof(obs));
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GUEST_ASSERT_EQ(exp, obs);
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}
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static void guest_main(void)
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{
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unsigned char *native_hypercall_insn, *hypercall_insn;
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uint8_t *native_hypercall_insn, *hypercall_insn;
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uint8_t apic_id;
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apic_id = GET_APIC_ID_FIELD(xapic_read_reg(APIC_ID));
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if (is_intel_cpu()) {
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native_hypercall_insn = &vmx_hypercall_insn;
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hypercall_insn = &svm_hypercall_insn;
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native_hypercall_insn = vmx_hypercall_insn;
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hypercall_insn = svm_hypercall_insn;
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svm_do_sched_yield(apic_id);
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} else if (is_amd_cpu()) {
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native_hypercall_insn = &svm_hypercall_insn;
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hypercall_insn = &vmx_hypercall_insn;
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native_hypercall_insn = svm_hypercall_insn;
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hypercall_insn = vmx_hypercall_insn;
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vmx_do_sched_yield(apic_id);
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} else {
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GUEST_ASSERT(0);
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@ -87,8 +80,13 @@ static void guest_main(void)
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return;
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}
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/*
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* The hypercall didn't #UD (guest_ud_handler() signals "done" if a #UD
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* occurs). Verify that a #UD is NOT expected and that KVM patched in
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* the native hypercall.
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*/
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GUEST_ASSERT(!ud_expected);
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assert_hypercall_insn(native_hypercall_insn, hypercall_insn);
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GUEST_ASSERT(!memcmp(native_hypercall_insn, hypercall_insn, HYPERCALL_INSN_SIZE));
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GUEST_DONE();
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}
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