x86/idt: Generate bsp_idt[] at build time

... rather than dynamically at boot time.  Aside from less runtime overhead,
this approach is less fragile than the preexisting autogen stubs mechanism.

We can manage this with some linker calculations.  See patch comments for full
details.

For simplicity, we create a new set of entry stubs here, and clean up the old
ones in the subsequent patch.  bsp_idt[] needs to move from .bss to .data.

No functional change yet; the boot path still rewrites bsp_idt[] at this
juncture.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/xen/arch/x86/include/asm/gen-idt.h b/xen/arch/x86/include/asm/gen-idt.h
new file mode 100644 (file)
index 0000000..9d2ae36
--- /dev/null
+++ b/xen/arch/x86/include/asm/gen-idt.h
@@ -0,0 +1,105 @@
+/*
+ * Generator for IDT entries.
+ *
+ * Caller to provide GEN(vector, symbol, dpl, auto) macro
+ *
+ * Symbols of the form 'entry_0xYY' set auto=1 and want a stub generating
+ * automatically.  Other symbols are ones with a more specific name, and most
+ * are provided elsewhere rather than autogenerated.
+ */
+
+#define GEN16(i) \
+    GEN(0x ## i ## 0, entry_0x ## i ## 0, 0, 1) \
+    GEN(0x ## i ## 1, entry_0x ## i ## 1, 0, 1) \
+    GEN(0x ## i ## 2, entry_0x ## i ## 2, 0, 1) \
+    GEN(0x ## i ## 3, entry_0x ## i ## 3, 0, 1) \
+    GEN(0x ## i ## 4, entry_0x ## i ## 4, 0, 1) \
+    GEN(0x ## i ## 5, entry_0x ## i ## 5, 0, 1) \
+    GEN(0x ## i ## 6, entry_0x ## i ## 6, 0, 1) \
+    GEN(0x ## i ## 7, entry_0x ## i ## 7, 0, 1) \
+    GEN(0x ## i ## 8, entry_0x ## i ## 8, 0, 1) \
+    GEN(0x ## i ## 9, entry_0x ## i ## 9, 0, 1) \
+    GEN(0x ## i ## a, entry_0x ## i ## a, 0, 1) \
+    GEN(0x ## i ## b, entry_0x ## i ## b, 0, 1) \
+    GEN(0x ## i ## c, entry_0x ## i ## c, 0, 1) \
+    GEN(0x ## i ## d, entry_0x ## i ## d, 0, 1) \
+    GEN(0x ## i ## e, entry_0x ## i ## e, 0, 1) \
+    GEN(0x ## i ## f, entry_0x ## i ## f, 0, 1)
+
+
+GEN(0x00, entry_DE,   0, 0)
+GEN(0x01, entry_DB,   0, 0)
+GEN(0x02, entry_NMI,  0, 0)
+GEN(0x03, entry_BP,   3, 0)
+GEN(0x04, entry_OF,   3, 0)
+GEN(0x05, entry_BR,   0, 0)
+GEN(0x06, entry_UD,   0, 0)
+GEN(0x07, entry_NM,   0, 0)
+GEN(0x08, entry_DF,   0, 0)
+GEN(0x09, entry_0x09, 0, 1) /* Coprocessor Segment Overrun */
+GEN(0x0a, entry_TS,   0, 0)
+GEN(0x0b, entry_NP,   0, 0)
+GEN(0x0c, entry_SS,   0, 0)
+GEN(0x0d, entry_GP,   0, 0)
+GEN(0x0e, early_page_fault, 0, 0)
+GEN(0x0f, entry_0x0f, 0, 1) /* PIC Spurious Interrupt Vector */
+
+GEN(0x10, entry_MF,   0, 0)
+GEN(0x11, entry_AC,   0, 0)
+GEN(0x12, entry_MC,   0, 0)
+GEN(0x13, entry_XM,   0, 0)
+GEN(0x14, entry_VE,   0, 1)
+GEN(0x15, entry_CP,   0, 0)
+GEN(0x16, entry_0x16, 0, 1)
+GEN(0x17, entry_0x17, 0, 1)
+GEN(0x18, entry_0x18, 0, 1)
+GEN(0x19, entry_0x19, 0, 1)
+GEN(0x1a, entry_0x1a, 0, 1)
+GEN(0x1b, entry_0x1b, 0, 1)
+GEN(0x1c, entry_HV,   0, 1)
+GEN(0x1d, entry_VC,   0, 1)
+GEN(0x1e, entry_SX,   0, 1)
+GEN(0x1f, entry_0x1f, 0, 1)
+
+GEN16(2)
+GEN16(3)
+GEN16(4)
+GEN16(5)
+GEN16(6)
+GEN16(7)
+
+#ifdef CONFIG_PV
+GEN(0x80, entry_int80, 0, 0)
+#else
+GEN(0x80, entry_0x80, 0, 1)
+#endif
+
+GEN(0x81, entry_0x81, 0, 1)
+
+#ifdef CONFIG_PV32
+GEN(0x82, entry_int82, 1, 0)
+#else
+GEN(0x82, entry_0x82, 0, 1)
+#endif
+
+GEN(0x83, entry_0x83, 0, 1)
+GEN(0x84, entry_0x84, 0, 1)
+GEN(0x85, entry_0x85, 0, 1)
+GEN(0x86, entry_0x86, 0, 1)
+GEN(0x87, entry_0x87, 0, 1)
+GEN(0x88, entry_0x88, 0, 1)
+GEN(0x89, entry_0x89, 0, 1)
+GEN(0x8a, entry_0x8a, 0, 1)
+GEN(0x8b, entry_0x8b, 0, 1)
+GEN(0x8c, entry_0x8c, 0, 1)
+GEN(0x8d, entry_0x8d, 0, 1)
+GEN(0x8e, entry_0x8e, 0, 1)
+GEN(0x8f, entry_0x8f, 0, 1)
+
+GEN16(9)
+GEN16(a)
+GEN16(b)
+GEN16(c)
+GEN16(d)
+GEN16(e)
+GEN16(f)

diff --git a/xen/arch/x86/include/asm/gen-idt.lds.h b/xen/arch/x86/include/asm/gen-idt.lds.h
new file mode 100644 (file)
index 0000000..110f494
--- /dev/null
+++ b/xen/arch/x86/include/asm/gen-idt.lds.h
@@ -0,0 +1,27 @@
+/*
+ * Linker file fragment to help format the IDT correctly
+ *
+ * The IDT, having grown compatibly since the 16 bit days, has the entrypoint
+ * address field split into 3.  x86 ELF lacks the @lo/@hi/etc relocation forms
+ * commonly found in other architectures for accessing a part of a resolved
+ * symbol address.
+ *
+ * However, the linker can perform the necessary calculations and provide them
+ * under new symbol names.  We use this to generate the low and next 16 bits
+ * of the address for each handler.
+ *
+ * We could do this for the upper 32 bits too, but they're always constant as
+ * Xen's .text/data/rodata all sits in a single 1G range.
+ */
+#ifndef X86_IDT_GEN_LDS_H
+#define X86_IDT_GEN_LDS_H
+
+#define GEN(vec, sym, dpl, auto)                                        \
+    PROVIDE_HIDDEN(IDT_ ## sym ## _ADDR1 = ((sym) & 0xffff));           \
+    PROVIDE_HIDDEN(IDT_ ## sym ## _ADDR2 = ((sym >> 16) & 0xffff));
+
+#include <asm/gen-idt.h>
+
+#undef GEN
+
+#endif /* X86_IDT_GEN_LDS_H */

diff --git a/xen/arch/x86/traps-init.c b/xen/arch/x86/traps-init.c
index ae600526cbe3d9c70a11945dbbca1e769d5cad9a..ab00bf9a748cccf2875ad34e56120f72bff532b6 100644 (file)
--- a/xen/arch/x86/traps-init.c
+++ b/xen/arch/x86/traps-init.c
@@ -5,7 +5,4 @@
 #include <asm/idt.h>
 #include <asm/page.h>
 
-idt_entry_t __section(".bss.page_aligned") __aligned(PAGE_SIZE)
-    bsp_idt[X86_IDT_VECTORS];
-
 DEFINE_PER_CPU_READ_MOSTLY(idt_entry_t *, idt);

diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 5b712e292f885b26b938635528e6e9bdd22e4829..3c9073f292b8e66680f6c5d06ccd63a92fc02220 100644 (file)
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -1232,6 +1232,82 @@ FUNC(trap_nop, 0)
         iretq
 END(trap_nop)
 
+/*
+ * Automatically generated entrypoints, and IDT
+ */
+
+        .pushsection .data.page_aligned, "aw", @progbits
+DATA(bsp_idt, PAGE_SIZE)
+        .popsection
+
+/*
+ * Write an IDT Entry.  The linker provides us new _ADDR1/2 symbols calculated
+ * from \sym.
+ */
+.macro write_idte sym, dpl
+        .pushsection .data.page_aligned, "aw", @progbits
+        .word IDT_\sym\()_ADDR1
+        .word __HYPERVISOR_CS
+        .word 0x8e00 | (\dpl << 13) /* Present, DPL, Interrupt Gate */
+        .word IDT_\sym\()_ADDR2
+        .long __XEN_VIRT_START >> 32
+        .long 0
+        .popsection
+.endm
+
+/*
+ * Write an automatically generated stub.  Vectors in the exception range keep
+ * the stack properly aligned by judging whether the CPU pushed an error code
+ * or not.
+ *
+ * Alignment is forced to 16 because that's the size of the interrupt stub
+ * with CET active.
+ */
+.macro gen_entry vec, sym
+
+FUNC(\sym, 16)
+        ENDBR64
+
+        .if \vec < 0x20 /* Exception. */
+
+            test  $8, %spl       /* 64bit exception frames are 16 byte aligned, but the word */
+            jz    1f             /* size is 8 bytes.  Check whether the processor gave us an */
+            pushq $0             /* error code, and insert an empty one if not.              */
+1:          movb  $\vec, EFRAME_entry_vector(%rsp)
+            jmp   handle_exception
+
+        .else /* Interrupt. */
+
+            pushq $0
+            movb  $\vec, EFRAME_entry_vector(%rsp)
+            jmp   common_interrupt
+
+        .endif
+END(\sym)
+.endm
+
+/*
+ * Generator.  Write an entrypoint if necessary, and record an IDT entry.
+ */
+.macro gen vec, sym, dpl, auto
+
+        .if \auto
+            gen_entry \vec, \sym
+        .endif
+
+        write_idte \sym, \dpl
+.endm
+#define GEN(v, s, d, a) gen vec=v, sym=s, dpl=d auto=a;
+#include <asm/gen-idt.h>
+#undef GEN
+
+        .pushsection .data.page_aligned, "aw", @progbits
+END(bsp_idt)
+        .if . - bsp_idt != PAGE_SIZE
+        .error "Bad bsp_idt size, should be PAGE_SIZE"
+        .endif
+        .popsection
+
 /* Table of automatically generated entry points.  One per vector. */
         .pushsection .init.rodata, "a", @progbits
 DATA(autogen_entrypoints, 8)

diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 42217eaf2485ebc221749c1cf12794af8a153616..d4dd6434c466ada97d39eafe784983697d0b6e12 100644 (file)
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -8,6 +8,8 @@
 # define DECL_SECTION_WITH_LADDR
 #endif
 #include <xen/xen.lds.h>
+
+#include <asm/gen-idt.lds.h>
 #include <asm/page.h>
 #include <asm/trampoline.h>