[PATCH] kvm-userspace: x86: Support for breakpoints in ROM code

[Jan Kiszka <jan.kiszka@siemens.com>]

Align qemu-kvm-x86 with upstream kvm support /wrt software breakpoint
support in ROM code.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---

 qemu/qemu-kvm-x86.c |   29 ++++++++++++++++++++++++-----
 1 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/qemu/qemu-kvm-x86.c b/qemu/qemu-kvm-x86.c
index 06ef775..05a9c4c 100644
--- a/qemu/qemu-kvm-x86.c
+++ b/qemu/qemu-kvm-x86.c
@@ -680,12 +680,32 @@ void kvm_arch_cpu_reset(CPUState *env)
     }
 }
 
-int kvm_arch_insert_sw_breakpoint(CPUState *env, struct kvm_sw_breakpoint *bp)
+#ifdef KVM_CAP_SET_GUEST_DEBUG
+static int kvm_patch_opcode_byte(CPUState *env, target_ulong addr, uint8_t val)
 {
-    uint8_t int3 = 0xcc;
+    target_phys_addr_t phys_page_addr;
+    unsigned long pd;
+    uint8_t *ptr;
+
+    phys_page_addr = cpu_get_phys_page_debug(env, addr & TARGET_PAGE_MASK);
+    if (phys_page_addr == -1)
+        return -EINVAL;
+
+    pd = cpu_get_physical_page_desc(phys_page_addr);
+    if ((pd & ~TARGET_PAGE_MASK) != IO_MEM_RAM &&
+        (pd & ~TARGET_PAGE_MASK) != IO_MEM_ROM && !(pd & IO_MEM_ROMD))
+        return -EINVAL;
 
+    ptr = phys_ram_base + (pd & TARGET_PAGE_MASK)
+                        + (addr & ~TARGET_PAGE_MASK);
+    *ptr = val;
+    return 0;
+}
+
+int kvm_arch_insert_sw_breakpoint(CPUState *env, struct kvm_sw_breakpoint *bp)
+{
     if (cpu_memory_rw_debug(env, bp->pc, (uint8_t *)&bp->saved_insn, 1, 0) ||
-        cpu_memory_rw_debug(env, bp->pc, &int3, 1, 1))
+        kvm_patch_opcode_byte(env, bp->pc, 0xcc))
         return -EINVAL;
     return 0;
 }
@@ -695,12 +715,11 @@ int kvm_arch_remove_sw_breakpoint(CPUState *env, struct kvm_sw_breakpoint *bp)
     uint8_t int3;
 
     if (cpu_memory_rw_debug(env, bp->pc, &int3, 1, 0) || int3 != 0xcc ||
-        cpu_memory_rw_debug(env, bp->pc, (uint8_t *)&bp->saved_insn, 1, 1))
+        kvm_patch_opcode_byte(env, bp->pc, bp->saved_insn))
         return -EINVAL;
     return 0;
 }
 
-#ifdef KVM_CAP_SET_GUEST_DEBUG
 static struct {
     target_ulong addr;
     int len;