From 85344cf524cccc7b8e10bf04ed38a0f586bffd10 Mon Sep 17 00:00:00 2001

From: Sumanth Korikkar <sumanthk@linux.ibm.com>

Date: Tue, 21 Feb 2023 15:28:21 +0100

Subject: [PATCH] support ubsan for kpatch

ubsan generates .data..Lubsan_data* sections as follows:

1. int main(int argc, char **argv) {

        int arr[100];

        arr[101] = 1;

        printf("arr[101] = %d", arr[101]);

        return 0;

}

2. 1a:   50 10 b0 ac          st      %r1,172(%r11)

      int arr[100];

      arr[101] = 1;

1e:   a7 39 00 65             lghi    %r3,101

22:   c0 20 00 00 00 00       larl    %r2,22 <main+0x22>

            24: R_390_PC32DBL       .data..Lubsan_data1+0x2

28:   c0 e5 00 00 00 00       brasl   %r14,28 <main+0x28>

            2a: R_390_PLT32DBL      __ubsan_handle_out_of_bounds+0x2

3. 0000000000000000 <.data..Lubsan_data1>:

0: R_390_64     .rodata              <=== source_location.location->file_name

8: 00 00 00 04  .long   0x00000004   <=== source_location.location->line

c: 00 00 00 05  .long   0x00000005   <=== source_location.location->column

10: R_390_64    .data..Lubsan_type0   <== source_location->array_type

18: R_390_64    .data..Lubsan_type1   <=== source_location->index_type

4. Avoid correlating the *.data.Lubsan* sections. This means

   included function points to new *.data.Lubsan* sections.

Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>

---

 kpatch-build/create-diff-object.c | 13 +++++++++++++

 kpatch-build/kpatch-elf.c         | 12 ++++++++++++

 kpatch-build/kpatch-elf.h         |  1 +

 kpatch-build/lookup.c             |  3 ++-

 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c

index 707b0a9..454783a 100644

--- a/kpatch-build/create-diff-object.c

+++ b/kpatch-build/create-diff-object.c

@@ -1036,6 +1036,9 @@ static void kpatch_correlate_sections(struct list_head *seclist_orig,

 			    sec_patched->twin)

 				continue;

+			if (is_ubsan_sec(sec_orig->name))

+				continue;

+

 			if (is_special_static(is_rela_section(sec_orig) ?

 					      sec_orig->base->secsym :

 					      sec_orig->secsym))

@@ -1072,6 +1075,9 @@ static void kpatch_correlate_symbols(struct list_head *symlist_orig,

 			    sym_orig->type != sym_patched->type || sym_patched->twin)

 				continue;

+			if (is_ubsan_sec(sym_orig->name))

+				continue;

+

 			if (is_special_static(sym_orig))

 				continue;

@@ -1547,6 +1553,13 @@ static void kpatch_replace_sections_syms(struct kpatch_elf *kelf)

 			if (rela->sym->type != STT_SECTION || !rela->sym->sec)

 				continue;

+			/*

+			 * UBSAN data will be taken wholesale, no need to

+			 * replace section symbols.

+			 */

+			if (is_ubsan_sec(rela->sym->name))

+				continue;

+

 			/*

 			 * These sections don't have symbols associated with

 			 * them:

diff --git a/kpatch-build/kpatch-elf.c b/kpatch-build/kpatch-elf.c

index c7d12ec..405e0d3 100644

--- a/kpatch-build/kpatch-elf.c

+++ b/kpatch-build/kpatch-elf.c

@@ -587,6 +587,18 @@ bool is_local_sym(struct symbol *sym)

 	return sym->bind == STB_LOCAL;

 }

+bool is_ubsan_sec(const char *name) {

+	if (!strncmp(name, ".data.rel.local..Lubsan_data", 28) ||

+		!strncmp(name, ".data..Lubsan_type", 18) ||

+		!strncmp(name, ".Lubsan_data", 12) ||

+		!strncmp(name, ".data..Lubsan_data", 18) ||

+		!strncmp(name, ".rela.data..Lubsan_data", 23) ||

+		!strncmp(name, ".rela.data.rel.local..Lubsan_data", 33))

+		return true;

+	else

+		return false;

+}

+

 void print_strtab(char *buf, size_t size)

 {

 	size_t i;

diff --git a/kpatch-build/kpatch-elf.h b/kpatch-build/kpatch-elf.h

index cd2900c..187b1d1 100644

--- a/kpatch-build/kpatch-elf.h

+++ b/kpatch-build/kpatch-elf.h

@@ -170,6 +170,7 @@ bool is_null_sym(struct symbol *sym);

 bool is_file_sym(struct symbol *sym);

 bool is_local_func_sym(struct symbol *sym);

 bool is_local_sym(struct symbol *sym);

+bool is_ubsan_sec(const char *name);

 void print_strtab(char *buf, size_t size);

 void kpatch_create_shstrtab(struct kpatch_elf *kelf);

diff --git a/kpatch-build/lookup.c b/kpatch-build/lookup.c

index f2596b1..2ccc181 100644

--- a/kpatch-build/lookup.c

+++ b/kpatch-build/lookup.c

@@ -84,7 +84,8 @@ static bool maybe_discarded_sym(const char *name)

 	    !strncmp(name, "__func_stack_frame_non_standard_", 32) ||

 	    strstr(name, "__addressable_") ||

 	    strstr(name, "__UNIQUE_ID_") ||

-	    !strncmp(name, ".L.str", 6))

+	    !strncmp(name, ".L.str", 6) ||

+	    is_ubsan_sec(name))

 		return true;

 	return false;

-- 

2.37.3