[PATCH] kvm_show_code for ROM code

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

Userland-located ROM memory is not available via kvm->physical_memory +
guest_address. To let kvm_show_code also dump useful information when
some problem in ROM (BIOS...) occurs, this patch first tries to obtain
the memory content via the mmio_read callback - maybe not 100% clean,
but works at least for the QEMU use case. If the callback complains
about the given address, we then fall back to RAM access.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 libkvm/libkvm-x86.c |   17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

Index: b/libkvm/libkvm-x86.c
===================================================================
--- a/libkvm/libkvm-x86.c
+++ b/libkvm/libkvm-x86.c
@@ -393,14 +393,15 @@ int kvm_set_pit(kvm_context_t kvm, struc
 
 void kvm_show_code(kvm_context_t kvm, int vcpu)
 {
+#define CODE_LEN	50
 #define CR0_PE_MASK	(1ULL<<0)
 	int fd = kvm->vcpu_fd[vcpu];
 	struct kvm_regs regs;
 	struct kvm_sregs sregs;
-	int r;
-	unsigned char code[50];
+	int r, n;
 	int back_offset;
-	char code_str[sizeof(code) * 3 + 1];
+	unsigned char code;
+	char code_str[CODE_LEN * 3 + 1];
 	unsigned long rip;
 
 	r = ioctl(fd, KVM_GET_SREGS, &sregs);
@@ -420,12 +421,14 @@ void kvm_show_code(kvm_context_t kvm, in
 	back_offset = regs.rip;
 	if (back_offset > 20)
 	    back_offset = 20;
-	memcpy(code, kvm->physical_memory + rip - back_offset, sizeof code);
 	*code_str = 0;
-	for (r = 0; r < sizeof code; ++r) {
-	    	if (r == back_offset)
+	for (n = -back_offset; n < CODE_LEN-back_offset; ++n) {
+		if (n == 0)
 			strcat(code_str, " -->");
-		sprintf(code_str + strlen(code_str), " %02x", code[r]);
+		r = kvm->callbacks->mmio_read(kvm->opaque, rip + n, &code, 1);
+		if (r < 0)
+			code = *(unsigned char *)(kvm->physical_memory + rip + n);
+		sprintf(code_str + strlen(code_str), " %02x", code);
 	}
 	fprintf(stderr, "code:%s\n", code_str);
 }

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