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libdwarf: Support consumption of compressed ELF sections

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Automatically decompress zlib-compressed debug sections when loading
them.  This lets ctfcovert work on userland code after commit
c910570e75 ("Use compressed debug in standalone userland debug files
by default").

Reported by:	avg
Reviewed by:	avg, emaste
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D33139
This commit is contained in:
Mark Johnston 2021-12-06 10:37:49 -05:00
parent dadbc04250
commit dbf05458e3
5 changed files with 80 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
contrib/elftoolchain/libdwarf/_libdwarf.h
View File

@ -379,8 +379,9 @@ typedef struct _Dwarf_Rel_Section {
} *Dwarf_Rel_Section;
typedef struct {
Elf_Data *ed_data;
void *ed_alloc;
Elf_Data *ed_data;
void *ed_alloc;
size_t ed_size; /* Uncompressed size. */
} Dwarf_Elf_Data;
typedef struct {

1
contrib/elftoolchain/libdwarf/libdwarf.h
View File

@ -335,6 +335,7 @@ enum {
DW_DLE_ARANGE_OFFSET_BAD, /* Invalid arange offset. */
DW_DLE_DEBUG_MACRO_INCONSISTENT,/* Invalid macinfo data. */
DW_DLE_ELF_SECT_ERR, /* Application callback failed. */
DW_DLE_COMPRESSION, /* Section decompression error. */
DW_DLE_NUM /* Max error number. */
};

87
contrib/elftoolchain/libdwarf/libdwarf_elf_init.c
View File

@ -25,6 +25,7 @@
*/
#include "_libdwarf.h"
#include <zlib.h>
ELFTC_VCSID("$Id: libdwarf_elf_init.c 3475 2016-05-18 18:11:26Z emaste $");
@ -168,21 +169,28 @@ _dwarf_elf_relocate(Dwarf_Debug dbg, Elf *elf, Dwarf_Elf_Data *ed, size_t shndx,
return (DW_DLE_NONE);
}
ed->ed_alloc = malloc(ed->ed_data->d_size);
/*
* A copy may already have been created if the section
* is compressed.
*/
if (ed->ed_alloc == NULL) {
DWARF_SET_ERROR(dbg, error, DW_DLE_MEMORY);
return (DW_DLE_MEMORY);
ed->ed_alloc = malloc(ed->ed_size);
if (ed->ed_alloc == NULL) {
DWARF_SET_ERROR(dbg, error,
DW_DLE_MEMORY);
return (DW_DLE_MEMORY);
}
memcpy(ed->ed_alloc, ed->ed_data->d_buf,
ed->ed_size);
}
memcpy(ed->ed_alloc, ed->ed_data->d_buf,
ed->ed_data->d_size);
if (sh.sh_type == SHT_REL)
_dwarf_elf_apply_rel_reloc(dbg,
ed->ed_alloc, ed->ed_data->d_size,
ed->ed_alloc, ed->ed_size,
rel, symtab_data, eh.e_ident[EI_DATA]);
else
_dwarf_elf_apply_rela_reloc(dbg,
ed->ed_alloc, ed->ed_data->d_size,
rel, symtab_data, eh.e_ident[EI_DATA]);
ed->ed_alloc, ed->ed_size, rel, symtab_data,
eh.e_ident[EI_DATA]);
return (DW_DLE_NONE);
}
@ -196,13 +204,58 @@ _dwarf_elf_relocate(Dwarf_Debug dbg, Elf *elf, Dwarf_Elf_Data *ed, size_t shndx,
return (DW_DLE_NONE);
}
static int
_dwarf_elf_decompress(Dwarf_Debug dbg, Dwarf_Elf_Object *e, Elf_Scn *scn,
Dwarf_Elf_Data *ed, GElf_Shdr *shdr, Dwarf_Error *error)
{
GElf_Chdr chdr;
size_t hsize;
unsigned long csize;
if (gelf_getchdr(scn, &chdr) == NULL) {
DWARF_SET_ELF_ERROR(dbg, error);
return (DW_DLE_ELF);
}
if (chdr.ch_type != ELFCOMPRESS_ZLIB) {
DWARF_SET_ERROR(dbg, error, DW_DLE_COMPRESSION);
return (DW_DLE_COMPRESSION);
}
if ((ed->ed_alloc = malloc(chdr.ch_size)) == NULL) {
DWARF_SET_ERROR(dbg, error, DW_DLE_MEMORY);
return (DW_DLE_MEMORY);
}
csize = chdr.ch_size;
hsize = e->eo_ehdr.e_ident[EI_CLASS] == ELFCLASS64 ?
sizeof(Elf64_Chdr) : sizeof(Elf32_Chdr);
if (uncompress(ed->ed_alloc, &csize, (char *)ed->ed_data->d_buf + hsize,
ed->ed_data->d_size - hsize) != Z_OK) {
DWARF_SET_ERROR(dbg, error, DW_DLE_COMPRESSION);
return (DW_DLE_COMPRESSION);
}
/* Sanity check. */
if (csize != chdr.ch_size) {
DWARF_SET_ERROR(dbg, error, DW_DLE_COMPRESSION);
return (DW_DLE_COMPRESSION);
}
ed->ed_size = chdr.ch_size;
shdr->sh_size = chdr.ch_size;
shdr->sh_addralign = chdr.ch_addralign;
return (DW_DLE_NONE);
}
int
_dwarf_elf_init(Dwarf_Debug dbg, Elf *elf, Dwarf_Error *error)
{
Dwarf_Obj_Access_Interface *iface;
Dwarf_Elf_Data *ed;
Dwarf_Elf_Object *e;
const char *name;
GElf_Shdr sh;
GElf_Shdr *es, sh;
Elf_Scn *scn;
Elf_Data *symtab_data;
size_t symtab_ndx;
@ -319,8 +372,6 @@ _dwarf_elf_init(Dwarf_Debug dbg, Elf *elf, Dwarf_Error *error)
if (sh.sh_type == SHT_NOBITS)
continue;
memcpy(&e->eo_shdr[j], &sh, sizeof(sh));
if ((name = elf_strptr(elf, e->eo_strndx, sh.sh_name)) ==
NULL) {
DWARF_SET_ELF_ERROR(dbg, error);
@ -328,13 +379,15 @@ _dwarf_elf_init(Dwarf_Debug dbg, Elf *elf, Dwarf_Error *error)
goto fail_cleanup;
}
ed = &e->eo_data[j];
es = &e->eo_shdr[j];
memcpy(es, &sh, sizeof(sh));
for (i = 0; debug_name[i] != NULL; i++) {
if (strcmp(name, debug_name[i]))
continue;
(void) elf_errno();
if ((e->eo_data[j].ed_data = elf_getdata(scn, NULL)) ==
NULL) {
if ((ed->ed_data = elf_getdata(scn, NULL)) == NULL) {
elferr = elf_errno();
if (elferr != 0) {
_DWARF_SET_ERROR(dbg, error,
@ -344,6 +397,14 @@ _dwarf_elf_init(Dwarf_Debug dbg, Elf *elf, Dwarf_Error *error)
}
}
if ((sh.sh_flags & SHF_COMPRESSED) != 0) {
if (_dwarf_elf_decompress(dbg, e, scn, ed,
es, error) != DW_DLE_NONE)
goto fail_cleanup;
} else {
ed->ed_size = ed->ed_data->d_size;
}
if (_libdwarf.applyreloc) {
if (_dwarf_elf_relocate(dbg, elf,
&e->eo_data[j], elf_ndxscn(scn), symtab_ndx,

2
lib/libdwarf/Makefile
View File

@ -98,7 +98,7 @@ sys/elf32.h sys/elf64.h sys/elf_common.h: ${SRCTOP}/sys/${.TARGET} .NOMETA
mkdir -p ${.OBJDIR}/sys
ln -sf ${.ALLSRC} ${.TARGET}
LIBADD+= elf
LIBADD+= elf z
SHLIB_MAJOR= 4

2
share/mk/src.libnames.mk
View File

@ -329,7 +329,7 @@ _DP_fetch= ssl crypto
_DP_fetch= md
.endif
_DP_execinfo= elf
_DP_dwarf= elf
_DP_dwarf= elf z
_DP_dpv= dialog figpar util tinfow ncursesw
_DP_dialog= tinfow ncursesw m
_DP_cuse= pthread