[RFC PATCH v1 3/3] powerpc: WIP draft support to objtool check
Christophe Leroy
christophe.leroy at csgroup.eu
Fri Jun 16 23:47:52 AEST 2023
This draft messy patch is first try to add support of objtool
check for powerpc. This is in preparation of doing uaccess
validation for powerpc.
For the time being, this is implemented for PPC32 only breaking
support for other targets eventually. Will be reworked to be more
generic once a final working status has been achieved.
All assembly files have been deactivated as they require huge
work and are not really needed at the first place for uaccess validation.
Signed-off-by: Christophe Leroy <christophe.leroy at csgroup.eu>
---
arch/powerpc/Kconfig | 1 +
scripts/Makefile.lib | 2 +-
tools/objtool/arch/powerpc/decode.c | 60 +++++++++++++++++--
.../arch/powerpc/include/arch/special.h | 2 +-
tools/objtool/arch/powerpc/special.c | 44 +++++++++++++-
tools/objtool/check.c | 29 +++++----
tools/objtool/include/objtool/elf.h | 1 +
tools/objtool/include/objtool/special.h | 2 +-
8 files changed, 118 insertions(+), 23 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 542be1c3c315..3bd244784af1 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -259,6 +259,7 @@ config PPC
select HAVE_OPTPROBES
select HAVE_OBJTOOL if PPC32 || MPROFILE_KERNEL
select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
+ select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
select HAVE_PERF_EVENTS
select HAVE_PERF_EVENTS_NMI if PPC64
select HAVE_PERF_REGS
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 100a386fcd71..298e2656e911 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -267,7 +267,7 @@ objtool-args-$(CONFIG_RETHUNK) += --rethunk
objtool-args-$(CONFIG_SLS) += --sls
objtool-args-$(CONFIG_STACK_VALIDATION) += --stackval
objtool-args-$(CONFIG_HAVE_STATIC_CALL_INLINE) += --static-call
-objtool-args-$(CONFIG_HAVE_UACCESS_VALIDATION) += --uaccess
+objtool-args-$(CONFIG_HAVE_UACCESS_VALIDATION) += --uaccess --sec-address
objtool-args-$(CONFIG_GCOV_KERNEL) += --no-unreachable
objtool-args-$(CONFIG_PREFIX_SYMBOLS) += --prefix=$(CONFIG_FUNCTION_PADDING_BYTES)
diff --git a/tools/objtool/arch/powerpc/decode.c b/tools/objtool/arch/powerpc/decode.c
index 53b55690f320..e95c0470e34b 100644
--- a/tools/objtool/arch/powerpc/decode.c
+++ b/tools/objtool/arch/powerpc/decode.c
@@ -43,24 +43,72 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
unsigned long offset, unsigned int maxlen,
struct instruction *insn)
{
- unsigned int opcode;
+ unsigned int opcode, xop;
+ unsigned int rs, ra, rb, bo, bi, to, uimm, l;
enum insn_type typ;
unsigned long imm;
u32 ins;
ins = bswap_if_needed(file->elf, *(u32 *)(sec->data->d_buf + offset));
opcode = ins >> 26;
- typ = INSN_OTHER;
- imm = 0;
+ xop = (ins >> 1) & 0x3ff;
+ rs = bo = to = (ins >> 21) & 0x1f;
+ ra = bi = (ins >> 16) & 0x1f;
+ rb = (ins >> 11) & 0x1f;
+ uimm = (ins >> 0) & 0xffff;
+ l = ins & 1;
switch (opcode) {
+ case 16: /* bc[l][a] */
+ if (ins & 1) /* bcl[a] */
+ typ = INSN_OTHER;
+ else /* bc[a] */
+ typ = INSN_JUMP_CONDITIONAL;
+
+ imm = ins & 0xfffc;
+ if (imm & 0x8000)
+ imm -= 0x10000;
+ imm |= ins & 2; /* AA flag */
+ insn->immediate = imm;
+ break;
case 18: /* b[l][a] */
- if ((ins & 3) == 1) /* bl */
+ if (ins & 1) /* bl[a] */
typ = INSN_CALL;
+ else /* b[a] */
+ typ = INSN_JUMP_UNCONDITIONAL;
imm = ins & 0x3fffffc;
if (imm & 0x2000000)
imm -= 0x4000000;
+ imm |= ins & 2; /* AA flag */
+ insn->immediate = imm;
+ break;
+ case 19:
+ if (xop == 16 && bo == 20 && bi == 0) /* blr */
+ typ = INSN_RETURN;
+ else if (xop == 50) /* rfi */
+ typ = INSN_JUMP_DYNAMIC;
+ else if (xop == 528 && bo == 20 && bi ==0 && !l) /* bctr */
+ typ = INSN_JUMP_DYNAMIC;
+ else if (xop == 528 && bo == 20 && bi ==0 && l) /* bctrl */
+ typ = INSN_CALL_DYNAMIC;
+ else
+ typ = INSN_OTHER;
+ break;
+ case 24:
+ if (rs == 0 && ra == 0 && uimm == 0)
+ typ = INSN_NOP;
+ else
+ typ = INSN_OTHER;
+ break;
+ case 31:
+ if (xop == 4 && to == 31 && ra == 0 && rb == 0) /* trap */
+ typ = INSN_BUG;
+ else
+ typ = INSN_OTHER;
+ break;
+ default:
+ typ = INSN_OTHER;
break;
}
@@ -70,13 +118,15 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
insn->len = 4;
insn->type = typ;
- insn->immediate = imm;
return 0;
}
unsigned long arch_jump_destination(struct instruction *insn)
{
+ if (insn->immediate & 2)
+ return insn->immediate & ~2;
+
return insn->offset + insn->immediate;
}
diff --git a/tools/objtool/arch/powerpc/include/arch/special.h b/tools/objtool/arch/powerpc/include/arch/special.h
index ffef9ada7133..a679b36307a9 100644
--- a/tools/objtool/arch/powerpc/include/arch/special.h
+++ b/tools/objtool/arch/powerpc/include/arch/special.h
@@ -6,7 +6,7 @@
#define EX_ORIG_OFFSET 0
#define EX_NEW_OFFSET 4
-#define JUMP_ENTRY_SIZE 16
+#define JUMP_ENTRY_SIZE 12
#define JUMP_ORIG_OFFSET 0
#define JUMP_NEW_OFFSET 4
#define JUMP_KEY_OFFSET 8
diff --git a/tools/objtool/arch/powerpc/special.c b/tools/objtool/arch/powerpc/special.c
index d33868147196..0e301b3a5b71 100644
--- a/tools/objtool/arch/powerpc/special.c
+++ b/tools/objtool/arch/powerpc/special.c
@@ -13,7 +13,47 @@ bool arch_support_alt_relocation(struct special_alt *special_alt,
}
struct reloc *arch_find_switch_table(struct objtool_file *file,
- struct instruction *insn)
+ struct instruction *insn, bool *is_rel)
{
- exit(-1);
+ struct reloc *text_reloc, *rodata_reloc;
+ struct section *table_sec;
+ unsigned long table_offset;
+
+ /* look for a relocation which references .rodata */
+ text_reloc = find_reloc_by_dest_range(file->elf, insn->sec,
+ insn->offset, insn->len);
+ if (!text_reloc || text_reloc->sym->type != STT_SECTION ||
+ !text_reloc->sym->sec->rodata)
+ return NULL;
+
+ table_offset = text_reloc->addend;
+ table_sec = text_reloc->sym->sec;
+
+ /*
+ * Make sure the .rodata address isn't associated with a
+ * symbol. GCC jump tables are anonymous data.
+ *
+ * Also support C jump tables which are in the same format as
+ * switch jump tables. For objtool to recognize them, they
+ * need to be placed in the C_JUMP_TABLE_SECTION section. They
+ * have symbols associated with them.
+ */
+ if (find_symbol_containing(table_sec, table_offset)) {
+ *is_rel = false;
+ if (strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
+ return NULL;
+ } else {
+ *is_rel = true;
+ }
+
+ /*
+ * Each table entry has a rela associated with it. The rela
+ * should reference text in the same function as the original
+ * instruction.
+ */
+ rodata_reloc = find_reloc_by_dest(file->elf, table_sec, table_offset);
+ if (!rodata_reloc)
+ return NULL;
+
+ return rodata_reloc;
}
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 0fcf99c91400..f945fe271706 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -236,6 +236,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
"x86_64_start_reservations",
"xen_cpu_bringup_again",
"xen_start_kernel",
+ "longjmp",
};
if (!func)
@@ -2060,13 +2061,12 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
* instruction.
*/
list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
-
/* Check for the end of the table: */
if (reloc != table && reloc->jump_table_start)
break;
/* Make sure the table entries are consecutive: */
- if (prev_offset && reloc->offset != prev_offset + 8)
+ if (prev_offset && reloc->offset != prev_offset + 4)
break;
/* Detect function pointers from contiguous objects: */
@@ -2074,7 +2074,10 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
reloc->addend == pfunc->offset)
break;
- dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
+ if (table->jump_table_is_rel)
+ dest_insn = find_insn(file, reloc->sym->sec, reloc->addend + table->offset - reloc->offset);
+ else
+ dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
if (!dest_insn)
break;
@@ -2108,7 +2111,7 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
*/
static struct reloc *find_jump_table(struct objtool_file *file,
struct symbol *func,
- struct instruction *insn)
+ struct instruction *insn, bool *is_rel)
{
struct reloc *table_reloc;
struct instruction *dest_insn, *orig_insn = insn;
@@ -2125,14 +2128,7 @@ static struct reloc *find_jump_table(struct objtool_file *file,
if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
break;
- /* allow small jumps within the range */
- if (insn->type == INSN_JUMP_UNCONDITIONAL &&
- insn->jump_dest &&
- (insn->jump_dest->offset <= insn->offset ||
- insn->jump_dest->offset > orig_insn->offset))
- break;
-
- table_reloc = arch_find_switch_table(file, insn);
+ table_reloc = arch_find_switch_table(file, insn, is_rel);
if (!table_reloc)
continue;
dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
@@ -2154,6 +2150,7 @@ static void mark_func_jump_tables(struct objtool_file *file,
{
struct instruction *insn, *last = NULL;
struct reloc *reloc;
+ bool is_rel;
func_for_each_insn(file, func, insn) {
if (!last)
@@ -2176,9 +2173,10 @@ static void mark_func_jump_tables(struct objtool_file *file,
if (insn->type != INSN_JUMP_DYNAMIC)
continue;
- reloc = find_jump_table(file, func, insn);
+ reloc = find_jump_table(file, func, insn, &is_rel);
if (reloc) {
reloc->jump_table_start = true;
+ reloc->jump_table_is_rel = is_rel;
insn->_jump_table = reloc;
}
}
@@ -4024,6 +4022,11 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
return true;
+ /* powerpc relocatable files have a word in front of each relocatable function */
+ if ((file->elf->ehdr.e_machine == EM_PPC || file->elf->ehdr.e_machine == EM_PPC64) &&
+ (file->elf->ehdr.e_flags & EF_PPC_RELOCATABLE_LIB) &&
+ insn_func(next_insn_same_sec(file, insn)))
+ return true;
/*
* Ignore alternative replacement instructions. This can happen
* when a whitelisted function uses one of the ALTERNATIVE macros.
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index e1ca588eb69d..64aac87a4825 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -80,6 +80,7 @@ struct reloc {
s64 addend;
int idx;
bool jump_table_start;
+ bool jump_table_is_rel;
};
#define ELF_HASH_BITS 20
diff --git a/tools/objtool/include/objtool/special.h b/tools/objtool/include/objtool/special.h
index 86d4af9c5aa9..803c6d3ba389 100644
--- a/tools/objtool/include/objtool/special.h
+++ b/tools/objtool/include/objtool/special.h
@@ -38,5 +38,5 @@ bool arch_support_alt_relocation(struct special_alt *special_alt,
struct instruction *insn,
struct reloc *reloc);
struct reloc *arch_find_switch_table(struct objtool_file *file,
- struct instruction *insn);
+ struct instruction *insn, bool *is_rel);
#endif /* _SPECIAL_H */
--
2.40.1
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