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SUSE:SLE-12-SP5:GA
xen.3242
57360bcb-x86-use-optimal-NOPs-to-fill-the-SMEP-...
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File 57360bcb-x86-use-optimal-NOPs-to-fill-the-SMEP-SMAP-placeholders.patch of Package xen.3242
References: bsc#949889 # Commit 01a0bd0a7d72be638a359db3f8cf551123467d29 # Date 2016-05-13 18:15:55 +0100 # Author Jan Beulich <jbeulich@suse.com> # Committer Andrew Cooper <andrew.cooper3@citrix.com> x86: use optimal NOPs to fill the SMEP/SMAP placeholders Alternatives patching code picks the most suitable NOPs for the running system, so simply use it to replace the pre-populated ones. Use an arbitrary, always available feature to key off from, but hide this behind the new X86_FEATURE_ALWAYS. Signed-off-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com> # Commit f5610009529628314c9d1d52b00715fe855fcf06 # Date 2016-05-26 17:26:24 +0100 # Author Jan Beulich <jbeulich@suse.com> # Committer Wei Liu <wei.liu2@citrix.com> x86/compat: correct SMEP/SMAP NOPs patching Correct the number of single byte NOPs we want to be replaced in case neither SMEP nor SMAP are available. Also simplify the expression adding these NOPs - at that location . equals .Lcr4_orig, and removing that part of the expression fixes a bogus ".space or fill with negative value, ignored" warning by very old gas (which actually is what made me look at those constructs again). Signed-off-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Wei Liu <wei.liu2@citrix.com> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com> --- a/xen/arch/x86/x86_64/compat/entry.S +++ b/xen/arch/x86/x86_64/compat/entry.S @@ -175,14 +175,7 @@ compat_bad_hypercall: ENTRY(compat_restore_all_guest) ASSERT_INTERRUPTS_DISABLED .Lcr4_orig: - ASM_NOP8 /* testb $3,UREGS_cs(%rsp) */ - ASM_NOP2 /* jpe .Lcr4_alt_end */ - ASM_NOP8 /* mov CPUINFO_cr4...(%rsp), %rax */ - ASM_NOP6 /* and $..., %rax */ - ASM_NOP8 /* mov %rax, CPUINFO_cr4...(%rsp) */ - ASM_NOP3 /* mov %rax, %cr4 */ - ASM_NOP8 /* cmp %rax, CPUINFO_cr4...(%rsp) */ - ASM_NOP2 /* jne 1b */ + .skip .Lcr4_alt_end - .Lcr4_alt, 0x90 .Lcr4_orig_end: .pushsection .altinstr_replacement, "ax" .Lcr4_alt: @@ -207,6 +200,8 @@ ENTRY(compat_restore_all_guest) jne 1b .Lcr4_alt_end: .section .altinstructions, "a" + altinstruction_entry .Lcr4_orig, .Lcr4_orig, X86_FEATURE_ALWAYS, \ + (.Lcr4_orig_end - .Lcr4_orig), 0 altinstruction_entry .Lcr4_orig, .Lcr4_alt, X86_FEATURE_SMEP, \ (.Lcr4_orig_end - .Lcr4_orig), \ (.Lcr4_alt_end - .Lcr4_alt) --- a/xen/include/asm-x86/asm_defns.h +++ b/xen/include/asm-x86/asm_defns.h @@ -173,6 +173,7 @@ void ret_from_intr(void); 662: __ASM_##op; \ .popsection; \ .pushsection .altinstructions, "a"; \ + altinstruction_entry 661b, 661b, X86_FEATURE_ALWAYS, 3, 0; \ altinstruction_entry 661b, 662b, X86_FEATURE_SMAP, 3, 3; \ .popsection @@ -184,6 +185,7 @@ void ret_from_intr(void); .pushsection .altinstr_replacement, "ax"; \ 668: call cr4_pv32_restore; \ .section .altinstructions, "a"; \ + altinstruction_entry 667b, 667b, X86_FEATURE_ALWAYS, 5, 0; \ altinstruction_entry 667b, 668b, X86_FEATURE_SMEP, 5, 5; \ altinstruction_entry 667b, 668b, X86_FEATURE_SMAP, 5, 5; \ .popsection --- a/xen/include/asm-x86/cpufeature.h +++ b/xen/include/asm-x86/cpufeature.h @@ -156,6 +156,9 @@ #define X86_FEATURE_ADX (7*32+19) /* ADCX, ADOX instructions */ #define X86_FEATURE_SMAP (7*32+20) /* Supervisor Mode Access Prevention */ +/* An alias of a feature we know is always going to be present. */ +#define X86_FEATURE_ALWAYS X86_FEATURE_LM + #ifndef __ASSEMBLY__ #define cpu_has(c, bit) test_bit(bit, (c)->x86_capability) #define boot_cpu_has(bit) test_bit(bit, boot_cpu_data.x86_capability)
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