Made this work on i386's at least. It wants ELF section headers for

symbol table sections.  Reconstruct the necessary section headers from
(ksym_start, ksym_end).  This was much easier than converting to use
module metadata, and just works for static symbols, unlike db_kld when
there is no module metadata.  Initialize (ksym_start, ksym_end) from
bootinfo on i386's only.

The boot loader should load section headers for all sections that it
loads, and apparently did this for at least the symbol table sections
when this file last worked under FreeBSD (on alphas only) and always
did this under NetBSD (where this file was obtained from).  At least
on i386's, boot2 discards the section headers (except for converting
them to (bootinfo.bi_symtab, bootinfo.bi_esymtab), and as far as I can
tell, loader(8) discards them apart from converting them to the bootinfo
values and module metadata.

1 files changed, 34 insertions, 2 deletions

diff --git a/sys/ddb/db_elf.c b/sys/ddb/db_elf.c
index 3a77089..f683a35 100644
--- a/sys/ddb/db_elf.c
+++ b/sys/ddb/db_elf.c
@@ -49,6 +49,9 @@
 #include <sys/systm.h>  
 #include <sys/proc.h>
 
+#ifdef __i386__
+#include <machine/bootinfo.h>
+#endif
 #include <machine/db_machdep.h>
 
 #include <ddb/ddb.h>
@@ -385,9 +388,38 @@ extern void *ksym_start, *ksym_end;
 void
 kdb_init(void)
 {
+	static Elf_Ehdr elf;
+	static Elf_Shdr sh[2];
+
+#ifdef __i386__
+	ksym_start = (void *)bootinfo.bi_symtab;
+	ksym_end = (void *)bootinfo.bi_esymtab;
+#endif
+	if (ksym_end <= ksym_start)
+		return;
 
-	if (ksym_end > ksym_start)
-		X_db_sym_init(ksym_start, ksym_end, "kernel");
+	/*
+	 * The FreeBSD boot program doesn't actually load any headers, so
+	 * fake just enough for the routines in this file to work.
+	 */
+	elf.e_ident[EI_MAG0] = ELFMAG0;
+	elf.e_ident[EI_MAG1] = ELFMAG1;
+	elf.e_ident[EI_MAG2] = ELFMAG2;
+	elf.e_ident[EI_MAG3] = ELFMAG3;
+	elf.e_machine = EM_486;
+	elf.e_shoff = (uintptr_t)(void *)&sh[0] - (uintptr_t)(void *)&elf;
+	sh[0].sh_type = SHT_SYMTAB;
+	sh[0].sh_offset = (uintptr_t)ksym_start + sizeof(long) -
+	    (uintptr_t)(void *)&elf;
+	sh[0].sh_size = *(int *)ksym_start;
+	sh[1].sh_type = SHT_STRTAB;
+	sh[1].sh_offset = sh[0].sh_offset + sh[0].sh_size + sizeof(long);
+	sh[1].sh_size = (uintptr_t)ksym_end - (uintptr_t)ksym_start -
+	    sizeof(long) - sh[0].sh_size - sizeof(long);
+	elf.e_shstrndx = -1;
+	elf.e_shnum = 2;
+
+	X_db_sym_init(&elf, ksym_end, "kernel");
 }
 
 #endif /* DDB_NOKLDSYM */