[Xen-devel] [PATCH v2 13/13] xsplice: Add support for alternatives

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>

Add support for applying alternative sections within xsplice modules. At
module load time, apply an alternative sections that are found.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 xen/arch/x86/Makefile             |  2 +-
 xen/arch/x86/alternative.c        | 12 ++++++------
 xen/common/xsplice.c              | 10 +++++++++-
 xen/include/asm-x86/alternative.h |  1 +
 4 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index f7d3e39..60249ab 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -6,7 +6,7 @@ subdir-y += mm
 subdir-y += oprofile
 subdir-y += x86_64
 
-obj-bin-y += alternative.init.o
+obj-bin-y += alternative.o
 obj-y += apic.o
 obj-y += bitops.o
 obj-bin-y += bzimage.init.o
diff --git a/xen/arch/x86/alternative.c b/xen/arch/x86/alternative.c
index 46ac0fd..8d895ad 100644
--- a/xen/arch/x86/alternative.c
+++ b/xen/arch/x86/alternative.c
@@ -28,7 +28,7 @@
 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
 
 #ifdef K8_NOP1
-static const unsigned char k8nops[] __initconst = {
+static const unsigned char k8nops[] = {
     K8_NOP1,
     K8_NOP2,
     K8_NOP3,
@@ -52,7 +52,7 @@ static const unsigned char * const k8_nops[ASM_NOP_MAX+1] = {
 #endif
 
 #ifdef P6_NOP1
-static const unsigned char p6nops[] __initconst = {
+static const unsigned char p6nops[] = {
     P6_NOP1,
     P6_NOP2,
     P6_NOP3,
@@ -75,7 +75,7 @@ static const unsigned char * const p6_nops[ASM_NOP_MAX+1] = {
 };
 #endif
 
-static const unsigned char * const *ideal_nops __initdata = k8_nops;
+static const unsigned char * const *ideal_nops = k8_nops;
 
 static int __init mask_nmi_callback(const struct cpu_user_regs *regs, int cpu)
 {
@@ -100,7 +100,7 @@ static void __init arch_init_ideal_nops(void)
 }
 
 /* Use this to add nops to a buffer, then text_poke the whole buffer. */
-static void __init add_nops(void *insns, unsigned int len)
+static void add_nops(void *insns, unsigned int len)
 {
     while ( len > 0 )
     {
@@ -127,7 +127,7 @@ static void __init add_nops(void *insns, unsigned int len)
  *
  * This routine is called with local interrupt disabled.
  */
-static void *__init text_poke_early(void *addr, const void *opcode, size_t len)
+static void *text_poke_early(void *addr, const void *opcode, size_t len)
 {
     memcpy(addr, opcode, len);
     sync_core();
@@ -142,7 +142,7 @@ static void *__init text_poke_early(void *addr, const void 
*opcode, size_t len)
  * APs have less capabilities than the boot processor are not handled.
  * Tough. Make sure you disable such features by hand.
  */
-static void __init apply_alternatives(struct alt_instr *start, struct 
alt_instr *end)
+void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
 {
     struct alt_instr *a;
     u8 *instr, *replacement;
diff --git a/xen/common/xsplice.c b/xen/common/xsplice.c
index 53a67a9..7866162 100644
--- a/xen/common/xsplice.c
+++ b/xen/common/xsplice.c
@@ -677,7 +677,7 @@ static int find_special_sections(struct payload *payload,
     if ( sec )
     {
         if ( ( !sec->sec->sh_size ) ||
-             ( sec->sec->sh_size % sizeof *sec->load_addr ) )
+             ( sec->sec->sh_size % sizeof (struct exception_table_entry) ) )
             return -EINVAL;
 
         payload->start_ex_table = (struct exception_table_entry 
*)sec->load_addr;
@@ -685,6 +685,14 @@ static int find_special_sections(struct payload *payload,
 
         sort_exception_table(payload->start_ex_table, payload->stop_ex_table);
     }
+    sec = xsplice_elf_sec_by_name(elf, ".altinstructions");
+    if ( sec )
+    {
+        local_irq_disable();
+        apply_alternatives((struct alt_instr *)sec->load_addr,
+                           (struct alt_instr *)(sec->load_addr + 
sec->sec->sh_size));
+        local_irq_enable();
+    }
 #endif
     return 0;
 }
diff --git a/xen/include/asm-x86/alternative.h 
b/xen/include/asm-x86/alternative.h
index 7d11354..95c2f7e 100644
--- a/xen/include/asm-x86/alternative.h
+++ b/xen/include/asm-x86/alternative.h
@@ -23,6 +23,7 @@ struct alt_instr {
     u8  replacementlen;     /* length of new instruction, <= instrlen */
 };
 
+extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
 extern void alternative_instructions(void);
 
 #define OLDINSTR(oldinstr)      "661:\n\t" oldinstr "\n662:\n"
-- 
2.1.0


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