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dtrace: correctly map sections to addresses in elf object modules (amd64)

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Unlike for modules with dso type, in elf object modules all the sections
have virtual address of zero.  So, it is insufficient to add module base
address to section virtual address (as recorded in section header) to
get section address in kernel memory.
Instead, we should apply the same calculations that are performed by
kernel loaders (in boot code and in kernel) when they lay out sections
in memory.
Also, unlike OpenSolaris, the sections are not collapsed into just .text,
.data and .bss by module loaders, so we need to take additional care
about other sections.

Note that in-kernel symbol-to-address mapping worked just fine, e.g. fbt
provider could correctly find the functions, etc.  It's only in userland
that the mapping in both direction worked incorrectly, e.g. in stack()
output addresses of functions in kernel modules were not translated to
their names.

Reviewed by:	rpaulo
MFC after:	3 weeks
This commit is contained in:
Andriy Gapon 2010-07-23 17:32:47 +00:00
parent 7996bf419b
commit 556cb98d95
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=210425
2 changed files with 70 additions and 6 deletions
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1
cddl/contrib/opensolaris/lib/libdtrace/common/dt_impl.h
View File

@ -137,6 +137,7 @@ typedef struct dt_module {
dt_idhash_t *dm_extern; /* external symbol definitions */
#if !defined(sun)
caddr_t dm_reloc_offset; /* Symbol relocation offset. */
uintptr_t *dm_sec_offsets;
#endif
} dt_module_t;

75
cddl/contrib/opensolaris/lib/libdtrace/common/dt_module.c
View File

@ -83,6 +83,14 @@ dt_module_syminit32(dt_module_t *dmp)
uint_t i, n = dmp->dm_nsymelems;
uint_t asrsv = 0;
#if defined(__FreeBSD__)
GElf_Ehdr ehdr;
int is_elf_obj;
gelf_getehdr(dmp->dm_elf, &ehdr);
is_elf_obj = (ehdr.e_type == ET_REL);
#endif
for (i = 0; i < n; i++, sym++) {
const char *name = base + sym->st_name;
uchar_t type = ELF32_ST_TYPE(sym->st_info);
@ -97,8 +105,12 @@ dt_module_syminit32(dt_module_t *dmp)
(ELF32_ST_BIND(sym->st_info) != STB_LOCAL || sym->st_size)) {
asrsv++; /* reserve space in the address map */
#if !defined(sun)
#if defined(__FreeBSD__)
sym->st_value += (Elf_Addr) dmp->dm_reloc_offset;
if (is_elf_obj && sym->st_shndx != SHN_UNDEF &&
sym->st_shndx < ehdr.e_shnum)
sym->st_value +=
dmp->dm_sec_offsets[sym->st_shndx];
#endif
}
@ -117,6 +129,14 @@ dt_module_syminit64(dt_module_t *dmp)
uint_t i, n = dmp->dm_nsymelems;
uint_t asrsv = 0;
#if defined(__FreeBSD__)
GElf_Ehdr ehdr;
int is_elf_obj;
gelf_getehdr(dmp->dm_elf, &ehdr);
is_elf_obj = (ehdr.e_type == ET_REL);
#endif
for (i = 0; i < n; i++, sym++) {
const char *name = base + sym->st_name;
uchar_t type = ELF64_ST_TYPE(sym->st_info);
@ -130,9 +150,12 @@ dt_module_syminit64(dt_module_t *dmp)
if (sym->st_value != 0 &&
(ELF64_ST_BIND(sym->st_info) != STB_LOCAL || sym->st_size)) {
asrsv++; /* reserve space in the address map */
#if !defined(sun)
#if defined(__FreeBSD__)
sym->st_value += (Elf_Addr) dmp->dm_reloc_offset;
if (is_elf_obj && sym->st_shndx != SHN_UNDEF &&
sym->st_shndx < ehdr.e_shnum)
sym->st_value +=
dmp->dm_sec_offsets[sym->st_shndx];
#endif
}
@ -722,7 +745,12 @@ dt_module_unload(dtrace_hdl_t *dtp, dt_module_t *dmp)
free(dmp->dm_asmap);
dmp->dm_asmap = NULL;
}
#if defined(__FreeBSD__)
if (dmp->dm_sec_offsets != NULL) {
free(dmp->dm_sec_offsets);
dmp->dm_sec_offsets = NULL;
}
#endif
dmp->dm_symfree = 0;
dmp->dm_nsymbuckets = 0;
dmp->dm_nsymelems = 0;
@ -846,9 +874,12 @@ dt_module_update(dtrace_hdl_t *dtp, struct kld_file_stat *k_stat)
(void) snprintf(fname, sizeof (fname),
"%s/%s/object", OBJFS_ROOT, name);
#else
GElf_Ehdr ehdr;
GElf_Phdr ph;
char name[MAXPATHLEN];
uintptr_t mapbase, alignmask;
int i = 0;
int is_elf_obj;
(void) strlcpy(name, k_stat->name, sizeof(name));
(void) strlcpy(fname, k_stat->pathname, sizeof(fname));
@ -893,7 +924,20 @@ dt_module_update(dtrace_hdl_t *dtp, struct kld_file_stat *k_stat)
dt_module_destroy(dtp, dmp);
return;
}
#if defined(__FreeBSD__)
mapbase = (uintptr_t)k_stat->address;
gelf_getehdr(dmp->dm_elf, &ehdr);
is_elf_obj = (ehdr.e_type == ET_REL);
if (is_elf_obj) {
dmp->dm_sec_offsets =
malloc(ehdr.e_shnum * sizeof(*dmp->dm_sec_offsets));
if (dmp->dm_sec_offsets == NULL) {
dt_dprintf("failed to allocate memory\n");
dt_module_destroy(dtp, dmp);
return;
}
}
#endif
/*
* Iterate over the section headers locating various sections of
* interest and use their attributes to flesh out the dt_module_t.
@ -902,7 +946,19 @@ dt_module_update(dtrace_hdl_t *dtp, struct kld_file_stat *k_stat)
if (gelf_getshdr(sp, &sh) == NULL || sh.sh_type == SHT_NULL ||
(s = elf_strptr(dmp->dm_elf, shstrs, sh.sh_name)) == NULL)
continue; /* skip any malformed sections */
#if defined(__FreeBSD__)
if (sh.sh_size == 0)
continue;
if (is_elf_obj && (sh.sh_type == SHT_PROGBITS ||
sh.sh_type == SHT_NOBITS)) {
alignmask = sh.sh_addralign - 1;
mapbase += alignmask;
mapbase &= ~alignmask;
sh.sh_addr = mapbase;
dmp->dm_sec_offsets[elf_ndxscn(sp)] = sh.sh_addr;
mapbase += sh.sh_size;
}
#endif
if (strcmp(s, ".text") == 0) {
dmp->dm_text_size = sh.sh_size;
dmp->dm_text_va = sh.sh_addr;
@ -927,6 +983,13 @@ dt_module_update(dtrace_hdl_t *dtp, struct kld_file_stat *k_stat)
#if defined(sun)
dmp->dm_modid = (int)OBJFS_MODID(st.st_ino);
#else
/*
* Include .rodata and special sections into .text.
* This depends on default section layout produced by GNU ld
* for ELF objects and libraries:
* [Text][R/O data][R/W data][Dynamic][BSS][Non loadable]
*/
dmp->dm_text_size = dmp->dm_data_va - dmp->dm_text_va;
#if defined(__i386__)
/*
* Find the first load section and figure out the relocation