MFC r265613, r267649: Handle ELF files with 65280 or more sections

  If e_shnum or e_shstrndx are at least SHN_LORESERVE (0xff00) then an
  escape value is used to indicate that the actual value is found in one
  of section 0's fields.

  Don't dump core when the ELF file has no section headers. The ELF
  core files created by gcore are among those.

1 files changed, 55 insertions, 13 deletions

diff --git a/usr.bin/elfdump/elfdump.c b/usr.bin/elfdump/elfdump.c
index 23d1487..2f1461e 100644
--- a/usr.bin/elfdump/elfdump.c
+++ b/usr.bin/elfdump/elfdump.c
@@ -368,7 +368,7 @@ static u_int64_t elf_get_half(Elf32_Ehdr *e, void *base, elf_member_t member);
 static u_int64_t elf_get_word(Elf32_Ehdr *e, void *base, elf_member_t member);
 static u_int64_t elf_get_quad(Elf32_Ehdr *e, void *base, elf_member_t member);
 
-static void elf_print_ehdr(Elf32_Ehdr *e);
+static void elf_print_ehdr(Elf32_Ehdr *e, void *sh);
 static void elf_print_phdr(Elf32_Ehdr *e, void *p);
 static void elf_print_shdr(Elf32_Ehdr *e, void *sh);
 static void elf_print_symtab(Elf32_Ehdr *e, void *sh, char *str);
@@ -382,6 +382,33 @@ static void elf_print_note(Elf32_Ehdr *e, void *sh);
 
 static void usage(void);
 
+/*
+ * Helpers for ELF files with shnum or shstrndx values that don't fit in the
+ * ELF header.  If the values are too large then an escape value is used to
+ * indicate that the actual value is found in one of section 0's fields.
+ */
+static uint64_t
+elf_get_shnum(Elf32_Ehdr *e, void *sh)
+{
+	uint64_t shnum;
+
+	shnum = elf_get_quarter(e, e, E_SHNUM);
+	if (shnum == 0)
+		shnum = elf_get_word(e, (char *)sh, SH_SIZE);
+	return shnum;
+}
+
+static uint64_t
+elf_get_shstrndx(Elf32_Ehdr *e, void *sh)
+{
+	uint64_t shstrndx;
+
+	shstrndx = elf_get_quarter(e, e, E_SHSTRNDX);
+	if (shstrndx == SHN_XINDEX)
+		shstrndx = elf_get_word(e, (char *)sh, SH_LINK);
+	return shstrndx;
+}
+
 int
 main(int ac, char **av)
 {
@@ -467,12 +494,20 @@ main(int ac, char **av)
 	phentsize = elf_get_quarter(e, e, E_PHENTSIZE);
 	phnum = elf_get_quarter(e, e, E_PHNUM);
 	shentsize = elf_get_quarter(e, e, E_SHENTSIZE);
-	shnum = elf_get_quarter(e, e, E_SHNUM);
-	shstrndx = elf_get_quarter(e, e, E_SHSTRNDX);
 	p = (char *)e + phoff;
-	sh = (char *)e + shoff;
-	offset = elf_get_off(e, (char *)sh + shstrndx * shentsize, SH_OFFSET);
-	shstrtab = (char *)e + offset;
+	if (shoff > 0) {
+		sh = (char *)e + shoff;
+		shnum = elf_get_shnum(e, sh);
+		shstrndx = elf_get_shstrndx(e, sh);
+		offset = elf_get_off(e, (char *)sh + shstrndx * shentsize,
+		    SH_OFFSET);
+		shstrtab = (char *)e + offset;
+	} else {
+		sh = NULL;
+		shnum = 0;
+		shstrndx = 0;
+		shstrtab = NULL;
+	}
 	for (i = 0; (u_int64_t)i < shnum; i++) {
 		name = elf_get_word(e, (char *)sh + i * shentsize, SH_NAME);
 		offset = elf_get_off(e, (char *)sh + i * shentsize, SH_OFFSET);
@@ -482,7 +517,7 @@ main(int ac, char **av)
 			dynstr = (char *)e + offset;
 	}
 	if (flags & ED_EHDR)
-		elf_print_ehdr(e);
+		elf_print_ehdr(e, sh);
 	if (flags & ED_PHDR)
 		elf_print_phdr(e, p);
 	if (flags & ED_SHDR)
@@ -556,7 +591,7 @@ main(int ac, char **av)
 }
 
 static void
-elf_print_ehdr(Elf32_Ehdr *e)
+elf_print_ehdr(Elf32_Ehdr *e, void *sh)
 {
 	u_int64_t class;
 	u_int64_t data;
@@ -589,8 +624,6 @@ elf_print_ehdr(Elf32_Ehdr *e)
 	phentsize = elf_get_quarter(e, e, E_PHENTSIZE);
 	phnum = elf_get_quarter(e, e, E_PHNUM);
 	shentsize = elf_get_quarter(e, e, E_SHENTSIZE);
-	shnum = elf_get_quarter(e, e, E_SHNUM);
-	shstrndx = elf_get_quarter(e, e, E_SHSTRNDX);
 	fprintf(out, "\nelf header:\n");
 	fprintf(out, "\n");
 	fprintf(out, "\te_ident: %s %s %s\n", ei_classes[class], ei_data[data],
@@ -606,8 +639,12 @@ elf_print_ehdr(Elf32_Ehdr *e)
 	fprintf(out, "\te_phentsize: %jd\n", (intmax_t)phentsize);
 	fprintf(out, "\te_phnum: %jd\n", (intmax_t)phnum);
 	fprintf(out, "\te_shentsize: %jd\n", (intmax_t)shentsize);
-	fprintf(out, "\te_shnum: %jd\n", (intmax_t)shnum);
-	fprintf(out, "\te_shstrndx: %jd\n", (intmax_t)shstrndx);
+	if (sh != NULL) {
+		shnum = elf_get_shnum(e, sh);
+		shstrndx = elf_get_shstrndx(e, sh);
+		fprintf(out, "\te_shnum: %jd\n", (intmax_t)shnum);
+		fprintf(out, "\te_shstrndx: %jd\n", (intmax_t)shstrndx);
+	}
 }
 
 static void
@@ -670,8 +707,13 @@ elf_print_shdr(Elf32_Ehdr *e, void *sh)
 	void *v;
 	int i;
 
+	if (sh == NULL) {
+		fprintf(out, "\nNo section headers\n");
+		return;
+	}
+
 	shentsize = elf_get_quarter(e, e, E_SHENTSIZE);
-	shnum = elf_get_quarter(e, e, E_SHNUM);
+	shnum = elf_get_shnum(e, sh);
 	fprintf(out, "\nsection header:\n");
 	for (i = 0; (u_int64_t)i < shnum; i++) {
 		v = (char *)sh + i * shentsize;