diff options
Diffstat (limited to '0051-x86-entry-don-t-clear-DF-when-raising-UD-for-lack-of.patch')
| -rw-r--r-- | 0051-x86-entry-don-t-clear-DF-when-raising-UD-for-lack-of.patch | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/0051-x86-entry-don-t-clear-DF-when-raising-UD-for-lack-of.patch b/0051-x86-entry-don-t-clear-DF-when-raising-UD-for-lack-of.patch new file mode 100644 index 0000000..acefc8e --- /dev/null +++ b/0051-x86-entry-don-t-clear-DF-when-raising-UD-for-lack-of.patch @@ -0,0 +1,58 @@ +From 7e636b8a16412d4f0d94b2b24d7ebcd2c749afff Mon Sep 17 00:00:00 2001 +From: Jan Beulich <jbeulich@suse.com> +Date: Thu, 4 Jul 2024 14:14:49 +0200 +Subject: [PATCH 51/56] x86/entry: don't clear DF when raising #UD for lack of + syscall handler + +While doing so is intentional when invoking the actual callback, to +mimic a hard-coded SYCALL_MASK / FMASK MSR, the same should not be done +when no handler is available and hence #UD is raised. + +Fixes: ca6fcf4321b3 ("x86/pv: Inject #UD for missing SYSCALL callbacks") +Reported-by: Andrew Cooper <andrew.cooper3@citrix.com> +Signed-off-by: Jan Beulich <jbeulich@suse.com> +Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com> +master commit: d2fe9ab3048d503869ec81bc49db07e55a4a2386 +master date: 2024-07-02 12:01:21 +0200 +--- + xen/arch/x86/x86_64/entry.S | 12 +++++++++++- + 1 file changed, 11 insertions(+), 1 deletion(-) + +diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S +index 054fcb225f..d3def49ea3 100644 +--- a/xen/arch/x86/x86_64/entry.S ++++ b/xen/arch/x86/x86_64/entry.S +@@ -38,6 +38,14 @@ switch_to_kernel: + setc %cl + leal (,%rcx,TBF_INTERRUPT),%ecx + ++ /* ++ * The PV ABI hardcodes the (guest-inaccessible and virtual) ++ * SYSCALL_MASK MSR such that DF (and nothing else) would be cleared. ++ * Note that the equivalent of IF (VGCF_syscall_disables_events) is ++ * dealt with separately above. ++ */ ++ mov $~X86_EFLAGS_DF, %esi ++ + test %rax, %rax + UNLIKELY_START(z, syscall_no_callback) /* TB_eip == 0 => #UD */ + mov VCPU_trap_ctxt(%rbx), %rdi +@@ -47,12 +55,14 @@ UNLIKELY_START(z, syscall_no_callback) /* TB_eip == 0 => #UD */ + testb $4, X86_EXC_UD * TRAPINFO_sizeof + TRAPINFO_flags(%rdi) + setnz %cl + lea TBF_EXCEPTION(, %rcx, TBF_INTERRUPT), %ecx ++ or $~0, %esi /* Don't clear DF */ + UNLIKELY_END(syscall_no_callback) + + movq %rax,TRAPBOUNCE_eip(%rdx) + movb %cl,TRAPBOUNCE_flags(%rdx) + call create_bounce_frame +- andl $~X86_EFLAGS_DF,UREGS_eflags(%rsp) ++ /* Conditionally clear DF */ ++ and %esi, UREGS_eflags(%rsp) + /* %rbx: struct vcpu */ + test_all_events: + ASSERT_NOT_IN_ATOMIC +-- +2.45.2 + |