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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v3 19/23] xsplice, symbols: Implement symbol name resolution on address. (v2)
From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
If in the payload we do not have the old_addr we can resolve
the virtual address based on the UNDEFined symbols.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
---
v1: Ross original version.
v2: Include test-case and document update.
---
docs/misc/xsplice.markdown | 1 -
xen/arch/x86/Makefile | 6 +-
xen/arch/x86/test/Makefile | 4 +-
xen/arch/x86/test/xen_hello_world.c | 5 +-
xen/common/symbols.c | 23 ++++++
xen/common/xsplice.c | 151 ++++++++++++++++++++++++++++++++++++
xen/common/xsplice_elf.c | 19 ++++-
xen/include/xen/symbols.h | 2 +
xen/include/xen/xsplice.h | 7 ++
9 files changed, 208 insertions(+), 10 deletions(-)
diff --git a/docs/misc/xsplice.markdown b/docs/misc/xsplice.markdown
index c06cd9d..1a982f2 100644
--- a/docs/misc/xsplice.markdown
+++ b/docs/misc/xsplice.markdown
@@ -932,7 +932,6 @@ This is for further development of xSplice.
The design must also have a mechanism for:
- * Be able to lookup in the Xen hypervisor the symbol names of functions from
the ELF payload.
* Be able to patch .rodata, .bss, and .data sections.
* Further safety checks (blacklist of which functions cannot be patched, check
the stack, etc).
diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 4a19ae9..5f7c57e 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -119,12 +119,14 @@ $(TARGET)-syms: prelink.o xen.lds
$(BASEDIR)/common/symbols-dummy.o
$(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
$(BASEDIR)/common/symbols-dummy.o -o $(@D)/.$(@F).0
$(NM) -pa --format=sysv $(@D)/.$(@F).0 \
- | $(BASEDIR)/tools/symbols --sysv --sort >$(@D)/.$(@F).0.S
+ | $(BASEDIR)/tools/symbols --all-symbols --sysv --sort \
+ >$(@D)/.$(@F).0.S
$(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).0.o
$(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
$(@D)/.$(@F).0.o -o $(@D)/.$(@F).1
$(NM) -pa --format=sysv $(@D)/.$(@F).1 \
- | $(BASEDIR)/tools/symbols --sysv --sort --warn-dup
>$(@D)/.$(@F).1.S
+ | $(BASEDIR)/tools/symbols --all-symbols --sysv --sort
--warn-dup \
+ >$(@D)/.$(@F).1.S
$(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).1.o
$(LD) $(LDFLAGS) -T xen.lds -N prelink.o $(build_id_linker) \
$(@D)/.$(@F).1.o -o $@
diff --git a/xen/arch/x86/test/Makefile b/xen/arch/x86/test/Makefile
index de9693f..57c5189 100644
--- a/xen/arch/x86/test/Makefile
+++ b/xen/arch/x86/test/Makefile
@@ -32,14 +32,12 @@ clean::
# the last entry in the build target.
#
.PHONY: config.h
-config.h: OLD_CODE=$(call CODE_ADDR,$(BASEDIR)/xen-syms,xen_extra_version)
config.h: OLD_CODE_SZ=$(call CODE_SZ,$<,xen_hello_world)
config.h: NEW_CODE_SZ=$(call CODE_SZ,$(BASEDIR)/xen-syms,xen_extra_version)
config.h: xen_hello_world_func.o
(set -e; \
echo "#define NEW_CODE_SZ $(NEW_CODE_SZ)"; \
- echo "#define OLD_CODE_SZ $(OLD_CODE_SZ)"; \
- echo "#define OLD_CODE $(OLD_CODE)") > $@
+ echo "#define OLD_CODE_SZ $(OLD_CODE_SZ)") > $@
#
# This target is only accessible if CONFIG_XSPLICE is defined, which
diff --git a/xen/arch/x86/test/xen_hello_world.c
b/xen/arch/x86/test/xen_hello_world.c
index 6a1775b..6200fbe 100644
--- a/xen/arch/x86/test/xen_hello_world.c
+++ b/xen/arch/x86/test/xen_hello_world.c
@@ -6,10 +6,13 @@
static char name[] = "xen_hello_world";
extern const char *xen_hello_world(void);
+/* External symbol. */
+extern const char *xen_extra_version(void);
+
struct xsplice_patch_func __section(".xsplice.funcs") xsplice_xen_hello_world
= {
.name = name,
.new_addr = (unsigned long)(xen_hello_world),
- .old_addr = OLD_CODE,
+ .old_addr = (unsigned long)(xen_extra_version),
.new_size = NEW_CODE_SZ,
.old_size = OLD_CODE_SZ,
};
diff --git a/xen/common/symbols.c b/xen/common/symbols.c
index bf5623f..406e5be 100644
--- a/xen/common/symbols.c
+++ b/xen/common/symbols.c
@@ -209,3 +209,26 @@ int xensyms_read(uint32_t *symnum, char *type,
return 0;
}
+
+uint64_t symbols_lookup_by_name(const char *symname)
+{
+ uint32_t symnum = 0;
+ uint64_t addr = 0, outaddr = 0;
+ int rc;
+ char type;
+ char name[KSYM_NAME_LEN + 1] = {0};
+
+ do {
+ rc = xensyms_read(&symnum, &type, &addr, name);
+ if ( rc )
+ break;
+
+ if ( !strcmp(name, symname) )
+ {
+ outaddr = addr;
+ break;
+ }
+ } while ( name[0] != '\0' );
+
+ return outaddr;
+}
diff --git a/xen/common/xsplice.c b/xen/common/xsplice.c
index 3f1da13..0b42a16 100644
--- a/xen/common/xsplice.c
+++ b/xen/common/xsplice.c
@@ -14,6 +14,7 @@
#include <xen/smp.h>
#include <xen/softirq.h>
#include <xen/spinlock.h>
+#include <xen/symbols.h>
#include <xen/version.h>
#include <xen/version.h>
#include <xen/wait.h>
@@ -55,6 +56,9 @@ struct payload {
#endif
struct xsplice_build_id id; /* ELFNOTE_DESC(.note.gnu.build-id)
of the payload. */
struct xsplice_build_id dep; /* ELFNOTE_DESC(.xsplice.depends). */
+ struct xsplice_symbol *symtab; /* All symbols. */
+ char *strtab; /* Pointer to .strtab. */
+ unsigned int nsyms; /* Nr of entries in .strtab and
symbols. */
char name[XEN_XSPLICE_NAME_SIZE + 1];/* Name of it. */
};
@@ -232,6 +236,8 @@ static void free_payload(struct payload *data)
payload_cnt--;
payload_version++;
free_payload_data(data);
+ xfree(data->symtab);
+ xfree(data->strtab);
xfree(data);
}
@@ -290,6 +296,8 @@ static int xsplice_upload(xen_sysctl_xsplice_upload_t
*upload)
err_raw:
free_xenheap_pages(raw_data, get_order_from_bytes(upload->size));
err_data:
+ xfree(data->symtab);
+ xfree(data->strtab);
xfree(data);
return rc;
}
@@ -716,6 +724,24 @@ static int find_special_sections(struct payload *payload,
for ( j = 0; j < 24; j ++ )
if ( f->pad[j] )
return -EINVAL;
+
+ /* Lookup function's old address if not already resolved. */
+ if ( !f->old_addr )
+ {
+ f->old_addr = symbols_lookup_by_name(f->name);
+ if ( !f->old_addr )
+ {
+ f->old_addr = xsplice_symbols_lookup_by_name(f->name);
+ if ( !f->old_addr )
+ {
+ printk(XENLOG_ERR "%s: Could not resolve old address of
%s\n",
+ elf->name, f->name);
+ return -ENOENT;
+ }
+ }
+ printk(XENLOG_DEBUG "%s: Resolved old address %s => 0x%"PRIx64"\n",
+ elf->name, f->name, f->old_addr);
+ }
}
sec = xsplice_elf_sec_by_name(elf, ".note.gnu.build-id");
@@ -798,6 +824,102 @@ static int find_special_sections(struct payload *payload,
return 0;
}
+static bool_t is_core_symbol(struct xsplice_elf *elf,
+ struct xsplice_elf_sym *sym)
+{
+ if ( sym->sym->st_shndx == SHN_UNDEF ||
+ sym->sym->st_shndx >= elf->hdr->e_shnum )
+ return 0;
+
+ return !!( (elf->sec[sym->sym->st_shndx].sec->sh_flags & SHF_ALLOC) &&
+ (ELF64_ST_TYPE(sym->sym->st_info) == STT_OBJECT ||
+ ELF64_ST_TYPE(sym->sym->st_info) == STT_FUNC) );
+}
+
+static int build_symbol_table(struct payload *payload, struct xsplice_elf *elf)
+{
+ unsigned int i, j, nsyms = 0;
+ size_t strtab_len = 0;
+ struct xsplice_symbol *symtab;
+ char *strtab;
+
+ /* Recall that 0 is always NULL. */
+ for ( i = 1; i < elf->nsym; i++ )
+ {
+ if ( is_core_symbol(elf, elf->sym + i) )
+ {
+ nsyms++;
+ strtab_len += strlen(elf->sym[i].name) + 1;
+ }
+ }
+
+ symtab = xmalloc_array(struct xsplice_symbol, nsyms);
+ if ( !symtab )
+ return -ENOMEM;
+
+ strtab = xmalloc_bytes(strtab_len);
+ if ( !strtab )
+ {
+ xfree(symtab);
+ return -ENOMEM;
+ }
+
+ nsyms = 0;
+ strtab_len = 0;
+ for ( i = 1; i < elf->nsym; i++ )
+ {
+ if ( is_core_symbol(elf, elf->sym + i) )
+ {
+ symtab[nsyms].name = strtab + strtab_len;
+ symtab[nsyms].size = elf->sym[i].sym->st_size;
+ symtab[nsyms].value = elf->sym[i].sym->st_value;
+ symtab[nsyms].flags = 0;
+ strtab_len += strlcpy(strtab + strtab_len, elf->sym[i].name,
+ KSYM_NAME_LEN) + 1;
+ nsyms++;
+ }
+ }
+
+ for ( i = 0; i < nsyms; i++ )
+ {
+ bool_t found = 0;
+
+ for ( j = 0; j < payload->nfuncs; j++ )
+ {
+ if ( symtab[i].value == payload->funcs[j].new_addr )
+ {
+ found = 1;
+ break;
+ }
+ }
+
+ if ( !found )
+ {
+ if ( xsplice_symbols_lookup_by_name(symtab[i].name) )
+ {
+ printk(XENLOG_ERR "%s: duplicate new symbol: %s\n", elf->name,
+ symtab[i].name);
+ xfree(symtab);
+ xfree(strtab);
+ return -EEXIST;
+ }
+ printk(XENLOG_DEBUG "%s: new symbol %s\n", elf->name,
+ symtab[i].name);
+ }
+ else
+ {
+ printk(XENLOG_DEBUG "%s: overriding symbol %s\n", elf->name,
+ symtab[i].name);
+ }
+ }
+
+ payload->symtab = symtab;
+ payload->strtab = strtab;
+ payload->nsyms = nsyms;
+
+ return 0;
+}
+
static int load_payload_data(struct payload *payload, uint8_t *raw, ssize_t
len)
{
struct xsplice_elf elf;
@@ -831,6 +953,10 @@ static int load_payload_data(struct payload *payload,
uint8_t *raw, ssize_t len)
if ( rc )
goto err_payload;
+ rc = build_symbol_table(payload, &elf);
+ if ( rc )
+ goto err_payload;
+
rc = find_special_sections(payload, &elf);
if ( rc )
goto err_payload;
@@ -1234,6 +1360,31 @@ unsigned long search_module_extables(unsigned long addr)
}
#endif
+uint64_t xsplice_symbols_lookup_by_name(const char *symname)
+{
+ struct payload *data;
+ unsigned int i;
+ uint64_t value = 0;
+
+ spin_lock(&payload_lock);
+
+ list_for_each_entry ( data, &payload_list, list )
+ {
+ for ( i = 0; i < data->nsyms; i++ )
+ {
+ if ( !strcmp(data->symtab[i].name, symname) )
+ {
+ value = data->symtab[i].value;
+ goto out;
+ }
+ }
+ }
+
+out:
+ spin_unlock(&payload_lock);
+ return value;
+}
+
static int __init xsplice_init(void)
{
register_keyhandler('x', xsplice_printall, "print xsplicing info", 1);
diff --git a/xen/common/xsplice_elf.c b/xen/common/xsplice_elf.c
index ad70797..dade9fd 100644
--- a/xen/common/xsplice_elf.c
+++ b/xen/common/xsplice_elf.c
@@ -1,5 +1,6 @@
#include <xen/errno.h>
#include <xen/lib.h>
+#include <xen/symbols.h>
#include <xen/xsplice_elf.h>
#include <xen/xsplice.h>
@@ -223,9 +224,21 @@ int xsplice_elf_resolve_symbols(struct xsplice_elf *elf)
return_(-EINVAL);
break;
case SHN_UNDEF:
- printk(XENLOG_ERR "%s: Unknown symbol: %s\n", elf->name,
- elf->sym[i].name);
- return_(-ENOENT);
+ elf->sym[i].sym->st_value =
symbols_lookup_by_name(elf->sym[i].name);
+ if ( !elf->sym[i].sym->st_value )
+ {
+ elf->sym[i].sym->st_value =
+ xsplice_symbols_lookup_by_name(elf->sym[i].name);
+ if ( !elf->sym[i].sym->st_value )
+ {
+ printk(XENLOG_ERR "%s: Unknown symbol: %s\n",
elf->name,
+ elf->sym[i].name);
+ return_(-ENOENT);
+ }
+ }
+ printk(XENLOG_DEBUG "%s: Undefined symbol resolved: %s =>
0x%"PRIx64"\n",
+ elf->name, elf->sym[i].name,
+ elf->sym[i].sym->st_value);
break;
case SHN_ABS:
printk(XENLOG_DEBUG "%s: Absolute symbol: %s => 0x%"PRIx64"\n",
diff --git a/xen/include/xen/symbols.h b/xen/include/xen/symbols.h
index 1fa0537..f8ea1dc 100644
--- a/xen/include/xen/symbols.h
+++ b/xen/include/xen/symbols.h
@@ -14,4 +14,6 @@ const char *symbols_lookup(unsigned long addr,
int xensyms_read(uint32_t *symnum, char *type,
uint64_t *address, char *name);
+uint64_t symbols_lookup_by_name(const char *symname);
+
#endif /*_XEN_SYMBOLS_H*/
diff --git a/xen/include/xen/xsplice.h b/xen/include/xen/xsplice.h
index 061a1a1..1045213 100644
--- a/xen/include/xen/xsplice.h
+++ b/xen/include/xen/xsplice.h
@@ -30,12 +30,19 @@ struct xsplice_build_id {
unsigned int len;
};
+struct xsplice_symbol {
+ const char *name;
+ uint64_t value;
+ size_t size;
+};
+
int xsplice_control(struct xen_sysctl_xsplice_op *);
void do_xsplice(void);
struct bug_frame *xsplice_find_bug(const char *eip, int *id);
bool_t is_module(const void *addr);
bool_t is_active_module_text(unsigned long addr);
unsigned long search_module_extables(unsigned long addr);
+uint64_t xsplice_symbols_lookup_by_name(const char *symname);
/* Arch hooks */
int xsplice_verify_elf(struct xsplice_elf *elf, uint8_t *data);
--
2.1.0
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