git: 0d557cdf6f0e - main - kldxref: Simplify handling of ELF object files
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Date: Fri, 22 Dec 2023 15:50:12 UTC
The branch main has been updated by jhb:
URL: https://cgit.FreeBSD.org/src/commit/?id=0d557cdf6f0e94e909acea065f3de2a28437ae74
commit 0d557cdf6f0e94e909acea065f3de2a28437ae74
Author: John Baldwin <jhb@FreeBSD.org>
AuthorDate: 2023-12-22 15:49:18 +0000
Commit: John Baldwin <jhb@FreeBSD.org>
CommitDate: 2023-12-22 15:49:18 +0000
kldxref: Simplify handling of ELF object files
Unlike the backend for ELF DSOs, the object file backend allocated an
aligned chunk of memory and read all of the in-memory sections from
the file into this memory even though most of the file contents were
never used. Instead, just track a set of virtual addresses (based at
0) that each loaded section would be loaded at and only read the
necessary bits from the backing file when needed.
Reviewed by: imp
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D43126
---
usr.sbin/kldxref/ef_obj.c | 146 +++++++++++++++++++++-------------------------
1 file changed, 65 insertions(+), 81 deletions(-)
diff --git a/usr.sbin/kldxref/ef_obj.c b/usr.sbin/kldxref/ef_obj.c
index 36c0dce432b6..1274a14c10af 100644
--- a/usr.sbin/kldxref/ef_obj.c
+++ b/usr.sbin/kldxref/ef_obj.c
@@ -46,7 +46,8 @@
#include "ef.h"
typedef struct {
- char *addr;
+ GElf_Addr addr;
+ GElf_Off offset;
GElf_Off size;
int flags;
int sec; /* Original section */
@@ -69,9 +70,6 @@ struct ef_file {
char *ef_name;
struct elf_file *ef_efile;
- char *address;
- GElf_Off size;
-
Elf_progent *progtab;
int nprogtab;
@@ -113,6 +111,22 @@ static struct elf_file_ops ef_obj_file_ops = {
.lookup_set = ef_obj_lookup_set,
};
+static GElf_Off
+ef_obj_get_offset(elf_file_t ef, GElf_Addr addr)
+{
+ Elf_progent *pt;
+ int i;
+
+ for (i = 0; i < ef->nprogtab; i++) {
+ pt = &ef->progtab[i];
+ if (pt->offset == (GElf_Off)-1)
+ continue;
+ if (addr >= pt->addr && addr < pt->addr + pt->size)
+ return (pt->offset + (addr - pt->addr));
+ }
+ return (0);
+}
+
static int
ef_obj_lookup_symbol(elf_file_t ef, const char *name, GElf_Sym **sym)
{
@@ -139,9 +153,8 @@ ef_obj_lookup_set(elf_file_t ef, const char *name, GElf_Addr *startp,
for (i = 0; i < ef->nprogtab; i++) {
if ((strncmp(ef->progtab[i].name, "set_", 4) == 0) &&
strcmp(ef->progtab[i].name + 4, name) == 0) {
- *startp = ef->progtab[i].addr - ef->address;
- *stopp = ef->progtab[i].addr + ef->progtab[i].size -
- ef->address;
+ *startp = ef->progtab[i].addr;
+ *stopp = ef->progtab[i].addr + ef->progtab[i].size;
*countp = (*stopp - *startp) /
elf_pointer_size(ef->ef_efile);
return (0);
@@ -160,46 +173,50 @@ ef_obj_symaddr(elf_file_t ef, GElf_Size symidx)
sym = ef->ddbsymtab + symidx;
if (sym->st_shndx != SHN_UNDEF)
- return (sym->st_value - (GElf_Addr)ef->address);
+ return (sym->st_value);
return (0);
}
static int
ef_obj_seg_read_rel(elf_file_t ef, GElf_Addr address, size_t len, void *dest)
{
- char *memaddr;
+ GElf_Off secofs;
GElf_Rel *r;
GElf_Rela *a;
GElf_Addr secbase, dataoff;
int error, i, sec;
- if (address + len > ef->size) {
- if (ef->ef_verbose)
- warnx("ef_obj_seg_read_rel(%s): bad offset/len (%lx:%ld)",
- ef->ef_name, (long)address, (long)len);
- return (EFAULT);
- }
- bcopy(ef->address + address, dest, len);
-
/* Find out which section contains the data. */
- memaddr = ef->address + address;
sec = -1;
- secbase = dataoff = 0;
for (i = 0; i < ef->nprogtab; i++) {
- if (ef->progtab[i].addr == NULL)
+ if (address < ef->progtab[i].addr)
continue;
- if (memaddr < (char *)ef->progtab[i].addr || memaddr + len >
- (char *)ef->progtab[i].addr + ef->progtab[i].size)
+
+ dataoff = address - ef->progtab[i].addr;
+ if (dataoff + len > ef->progtab[i].size)
continue;
+
sec = ef->progtab[i].sec;
- /* We relocate to address 0. */
- secbase = (char *)ef->progtab[i].addr - ef->address;
- dataoff = memaddr - ef->address;
+ secbase = ef->progtab[i].addr;
+ secofs = ef->progtab[i].offset;
break;
}
- if (sec == -1)
+ if (sec == -1) {
+ if (ef->ef_verbose)
+ warnx("ef_obj_seg_read_rel(%s): bad address (%jx)",
+ ef->ef_name, (uintmax_t)address);
return (EFAULT);
+ }
+
+ if (secofs == (GElf_Off)-1) {
+ memset(dest, 0, len);
+ } else {
+ error = elf_read_raw_data(ef->ef_efile, secofs + dataoff, dest,
+ len);
+ if (error != 0)
+ return (error);
+ }
/* Now do the relocations. */
for (i = 0; i < ef->nrel; i++) {
@@ -208,7 +225,7 @@ ef_obj_seg_read_rel(elf_file_t ef, GElf_Addr address, size_t len, void *dest)
for (r = ef->reltab[i].rel;
r < &ef->reltab[i].rel[ef->reltab[i].nrel]; r++) {
error = elf_reloc(ef->ef_efile, r, ELF_T_REL, secbase,
- dataoff, len, dest);
+ address, len, dest);
if (error != 0)
return (error);
}
@@ -219,7 +236,7 @@ ef_obj_seg_read_rel(elf_file_t ef, GElf_Addr address, size_t len, void *dest)
for (a = ef->relatab[i].rela;
a < &ef->relatab[i].rela[ef->relatab[i].nrela]; a++) {
error = elf_reloc(ef->ef_efile, a, ELF_T_RELA, secbase,
- dataoff, len, dest);
+ address, len, dest);
if (error != 0)
return (error);
}
@@ -230,21 +247,23 @@ ef_obj_seg_read_rel(elf_file_t ef, GElf_Addr address, size_t len, void *dest)
static int
ef_obj_seg_read_string(elf_file_t ef, GElf_Addr address, size_t len, char *dest)
{
+ GElf_Off ofs;
+ int error;
- if (address >= ef->size) {
+ ofs = ef_obj_get_offset(ef, address);
+ if (ofs == 0) {
if (ef->ef_verbose)
- warnx("ef_obj_seg_read_string(%s): bad address (%lx)",
- ef->ef_name, (long)address);
+ warnx("ef_obj_seg_read_string(%s): bad address (%jx)",
+ ef->ef_name, (uintmax_t)address);
return (EFAULT);
}
- if (ef->size - address < len)
- len = ef->size - address;
-
- if (strnlen(ef->address + address, len) == len)
+ error = elf_read_raw_data(ef->ef_efile, ofs, dest, len);
+ if (error != 0)
+ return (error);
+ if (strnlen(dest, len) == len)
return (EFAULT);
- memcpy(dest, ef->address + address, len);
return (0);
}
@@ -255,8 +274,8 @@ ef_obj_open(struct elf_file *efile, int verbose)
GElf_Ehdr *hdr;
GElf_Shdr *shdr;
GElf_Sym *es;
- char *mapbase;
- size_t i, mapsize, alignmask, max_addralign, nshdr;
+ GElf_Addr mapbase;
+ size_t i, nshdr;
int error, pb, ra, rl;
int j, nsym, symstrindex, symtabindex;
@@ -359,59 +378,26 @@ ef_obj_open(struct elf_file *efile, int verbose)
}
}
- /* Size up code/data(progbits) and bss(nobits). */
- alignmask = 0;
- max_addralign = 0;
- mapsize = 0;
- for (i = 0; i < nshdr; i++) {
- switch (shdr[i].sh_type) {
- case SHT_PROGBITS:
- case SHT_NOBITS:
- alignmask = shdr[i].sh_addralign - 1;
- if (shdr[i].sh_addralign > max_addralign)
- max_addralign = shdr[i].sh_addralign;
- mapsize += alignmask;
- mapsize &= ~alignmask;
- mapsize += shdr[i].sh_size;
- break;
- }
- }
-
- /* We know how much space we need for the text/data/bss/etc. */
- ef->size = mapsize;
- if (posix_memalign((void **)&ef->address, max_addralign, mapsize)) {
- printf("posix_memalign failed\n");
- goto out;
- }
- mapbase = ef->address;
-
/*
- * Now load code/data(progbits), zero bss(nobits), allocate
- * space for and load relocs
+ * Now allocate address space for code/data(progbits) and
+ * bss(nobits) and allocate space for and load relocs.
*/
pb = 0;
rl = 0;
ra = 0;
- alignmask = 0;
+ mapbase = 0;
for (i = 0; i < nshdr; i++) {
switch (shdr[i].sh_type) {
case SHT_PROGBITS:
case SHT_NOBITS:
- alignmask = shdr[i].sh_addralign - 1;
- mapbase += alignmask;
- mapbase = (char *)((uintptr_t)mapbase & ~alignmask);
- ef->progtab[pb].addr = (void *)(uintptr_t)mapbase;
+ mapbase = roundup2(mapbase, shdr[i].sh_addralign);
+ ef->progtab[pb].addr = mapbase;
if (shdr[i].sh_type == SHT_PROGBITS) {
ef->progtab[pb].name = "<<PROGBITS>>";
- if (elf_read_raw_data(efile,
- shdr[i].sh_offset, ef->progtab[pb].addr,
- shdr[i].sh_size) != 0) {
- printf("failed to read progbits\n");
- goto out;
- }
+ ef->progtab[pb].offset = shdr[i].sh_offset;
} else {
ef->progtab[pb].name = "<<NOBITS>>";
- bzero(ef->progtab[pb].addr, shdr[i].sh_size);
+ ef->progtab[pb].offset = (GElf_Off)-1;
}
ef->progtab[pb].size = shdr[i].sh_size;
ef->progtab[pb].sec = i;
@@ -424,7 +410,7 @@ ef_obj_open(struct elf_file *efile, int verbose)
es = &ef->ddbsymtab[j];
if (es->st_shndx != i)
continue;
- es->st_value += (GElf_Addr)ef->progtab[pb].addr;
+ es->st_value += ef->progtab[pb].addr;
}
mapbase += shdr[i].sh_size;
pb++;
@@ -464,8 +450,6 @@ ef_obj_close(elf_file_t ef)
if (ef->ef_name)
free(ef->ef_name);
- if (ef->size != 0)
- free(ef->address);
if (ef->nprogtab != 0)
free(ef->progtab);
if (ef->nrel != 0) {