[binutils-gdb] RISC-V: PR28789, Reject R_RISCV_PCREL relocations with ABS symbol in PIC/PIE.

[binutils-gdb] RISC-V: PR28789, Reject R_RISCV_PCREL relocations with ABS symbol in PIC/PIE.

[Nelson Chu]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=890744e8585ad75e4adf7b4c447301540479a885

commit 890744e8585ad75e4adf7b4c447301540479a885
Author: Palmer Dabbelt <palmer@rivosinc.com>
Date:   Sat Mar 25 08:41:13 2023 +0800

    RISC-V: PR28789, Reject R_RISCV_PCREL relocations with ABS symbol in PIC/PIE.
    
    The non-preemptible SHN_ABS symbol with a pc-relative relocation should be
    disallowed when generating shared object (pic and pie).  Generally, the
    following cases, which refer to pr25749, will cause a symbol be
    non-preemptible,
    
    * -pie, or -shared with -symbolic
    * STV_HIDDEN, STV_INTERNAL, STV_PROTECTED
    * Have dynamic symbol table, but without the symbol
    * VER_NDX_LOCAL
    
    However, PCREL_HI20/LO12 relocs are always bind locally when generating
    shared object, so not only the non-preemptible absolute symbol need to
    be disallowed, all absolute symbol references need but except that they
    are defined in linker script.  If we also disallow the absolute symbol
    in linker script, then the glibc-linux toolchain build failed, so regard
    them as pc-relative symbols, just like what x86 did.
    
    Maybe we should add this check for all pc-relative relocations, rather
    than just handle in R_RISCV_PCREL relocs.  Ideally, since the value of
    SHN_ABS symbol is a constant, only S - A relocations should be allowed
    in the shared object, so only BFD_RELOC_8/16/32/64 are allowed, which
    means R_RISCV_32/R_RISCV_64.
    
    bfd/
        PR 28789
        * elfnn-riscv.c (riscv_elf_check_relocs): The absolute symbol cannot be
        referneced with pc-relative relocation when generating shared object.
    ld/
        PR 28789
        * ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp: Updated.
        * ld/testsuite/ld-riscv-elf/pcrel-reloc*: New testcases.

Diff:
---
 bfd/elfnn-riscv.c                                 | 41 +++++++++++++++++++++++
 ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp        |  7 ++++
 ld/testsuite/ld-riscv-elf/pcrel-reloc-abs-nopie.d | 14 ++++++++
 ld/testsuite/ld-riscv-elf/pcrel-reloc-abs-pie.d   |  5 +++
 ld/testsuite/ld-riscv-elf/pcrel-reloc-abs.s       |  2 ++
 ld/testsuite/ld-riscv-elf/pcrel-reloc-rel-nopie.d | 14 ++++++++
 ld/testsuite/ld-riscv-elf/pcrel-reloc-rel-pie.d   | 14 ++++++++
 ld/testsuite/ld-riscv-elf/pcrel-reloc-rel.s       |  9 +++++
 ld/testsuite/ld-riscv-elf/pcrel-reloc.s           |  5 +++
 9 files changed, 111 insertions(+)

diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
index 00f034a6751..0dd9b27c8ae 100644
--- a/bfd/elfnn-riscv.c
+++ b/bfd/elfnn-riscv.c
@@ -862,6 +862,47 @@ riscv_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
 		 ifunc symbol.  */
 	      h->plt.refcount += 1;
 	    }
+
+	  /* The non-preemptible absolute symbol shouldn't be referneced with
+	     pc-relative relocation when generating shared object.  However,
+	     PCREL_HI20/LO12 relocs are always bind locally when generating
+	     shared object, so all absolute symbol referenced need to be
+	     disallowed, except they are defined in linker script.
+
+	     Maybe we should add this check for all pc-relative relocations,
+	     please see pr28789 and pr25749 for details.  */
+	  if (bfd_link_pic (info)
+	      /* (h == NULL || SYMBOL_REFERENCES_LOCAL (info, h))  */
+	      && is_abs_symbol)
+	    {
+	      if (h != NULL && (h)->root.ldscript_def)
+		/* Disallow the absolute symbol defined in linker script here
+		   will cause the glibc-linux toolchain build failed, so regard
+		   them as pc-relative symbols, just like what x86 did.  */
+		;
+	      else
+		{
+		  const char *name;
+		  if (h->root.root.string)
+		    name = h->root.root.string;
+		  else
+		    {
+		      Elf_Internal_Sym *sym;
+		      sym = bfd_sym_from_r_symndx (&htab->elf.sym_cache, abfd,
+						   r_symndx);
+		      name = bfd_elf_sym_name (abfd, symtab_hdr, sym, NULL);
+		    }
+
+		  reloc_howto_type *r_t =
+			riscv_elf_rtype_to_howto (abfd, r_type);
+		  _bfd_error_handler
+		    (_("%pB: relocation %s against absolute symbol `%s' can "
+		       "not be used when making a shared object"),
+		     abfd, r_t ? r_t->name : _("<unknown>"), name);
+		  bfd_set_error (bfd_error_bad_value);
+		  return false;
+		}
+	    }
 	  /* Fall through.  */
 
 	case R_RISCV_JAL:
diff --git a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
index 1b2a5ce2cb2..43572c5286b 100644
--- a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
+++ b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
@@ -308,4 +308,11 @@ if [istarget "riscv*-*-*"] {
     run_dump_test "ifunc-seperate-plt-pic"
     run_dump_test "ifunc-seperate-pcrel-pie"
     run_dump_test "ifunc-seperate-pcrel-pic"
+
+    # Tests related to mixing medany code into position-independent targets,
+    # where it's not always possible to generate correct addressing sequences.
+    run_dump_test "pcrel-reloc-rel-nopie"
+    run_dump_test "pcrel-reloc-rel-pie"
+    run_dump_test "pcrel-reloc-abs-nopie"
+    run_dump_test "pcrel-reloc-abs-pie"
 }
diff --git a/ld/testsuite/ld-riscv-elf/pcrel-reloc-abs-nopie.d b/ld/testsuite/ld-riscv-elf/pcrel-reloc-abs-nopie.d
new file mode 100644
index 00000000000..54026388b7a
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/pcrel-reloc-abs-nopie.d
@@ -0,0 +1,14 @@
+#source: pcrel-reloc.s
+#source: pcrel-reloc-abs.s
+#as: -march=rv64i -mabi=lp64
+#ld: -melf64lriscv --no-pie --no-relax
+#objdump: -d
+
+.*:[ 	]+file format .*
+
+Disassembly of section \.text:
+
+[0-9a-f]+ <_start>:
+.*auipc.*
+.*lw.*# [0-9a-f]* <sym>
+#pass
diff --git a/ld/testsuite/ld-riscv-elf/pcrel-reloc-abs-pie.d b/ld/testsuite/ld-riscv-elf/pcrel-reloc-abs-pie.d
new file mode 100644
index 00000000000..7f5eaa321f7
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/pcrel-reloc-abs-pie.d
@@ -0,0 +1,5 @@
+#source: pcrel-reloc.s
+#source: pcrel-reloc-abs.s
+#as: -march=rv64i -mabi=lp64
+#ld: -melf64lriscv --pie --no-relax
+#error: .*relocation R_RISCV_PCREL_HI20 against absolute symbol `sym' can not be used when making a shared objec.*t
diff --git a/ld/testsuite/ld-riscv-elf/pcrel-reloc-abs.s b/ld/testsuite/ld-riscv-elf/pcrel-reloc-abs.s
new file mode 100644
index 00000000000..1df32a1a3fb
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/pcrel-reloc-abs.s
@@ -0,0 +1,2 @@
+.global sym
+.set sym,0x8000
diff --git a/ld/testsuite/ld-riscv-elf/pcrel-reloc-rel-nopie.d b/ld/testsuite/ld-riscv-elf/pcrel-reloc-rel-nopie.d
new file mode 100644
index 00000000000..ab2a3774cdd
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/pcrel-reloc-rel-nopie.d
@@ -0,0 +1,14 @@
+#source: pcrel-reloc.s
+#source: pcrel-reloc-rel.s
+#as: -march=rv64i -mabi=lp64
+#ld: -melf64lriscv --no-pie --no-relax
+#objdump: -d
+
+.*:[ 	]+file format .*
+
+Disassembly of section \.text:
+
+[0-9a-f]+ <_start>:
+.*auipc.*
+.*lw.*# [0-9a-f]* <sym>
+#pass
diff --git a/ld/testsuite/ld-riscv-elf/pcrel-reloc-rel-pie.d b/ld/testsuite/ld-riscv-elf/pcrel-reloc-rel-pie.d
new file mode 100644
index 00000000000..aec612d4d2c
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/pcrel-reloc-rel-pie.d
@@ -0,0 +1,14 @@
+#source: pcrel-reloc.s
+#source: pcrel-reloc-rel.s
+#as: -march=rv64i -mabi=lp64
+#ld: -melf64lriscv --pie --no-relax
+#objdump: -d
+
+.*:[ 	]+file format .*
+
+Disassembly of section \.text:
+
+[0-9a-f]+ <_start>:
+.*auipc.*
+.*lw.*# [0-9a-f]* <sym>
+#pass
diff --git a/ld/testsuite/ld-riscv-elf/pcrel-reloc-rel.s b/ld/testsuite/ld-riscv-elf/pcrel-reloc-rel.s
new file mode 100644
index 00000000000..fb0e6c09f22
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/pcrel-reloc-rel.s
@@ -0,0 +1,9 @@
+.data
+# Makes sure "sym" doesn't end up at the beginning of ".data", as that makes it
+# tough to then later detect it from scripts.
+.global buf
+buf:
+    .fill 8192, 4, 1
+.global sym
+sym:
+    .fill 8192, 4, 2
diff --git a/ld/testsuite/ld-riscv-elf/pcrel-reloc.s b/ld/testsuite/ld-riscv-elf/pcrel-reloc.s
new file mode 100644
index 00000000000..db2103bafd1
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/pcrel-reloc.s
@@ -0,0 +1,5 @@
+.text
+.global _start
+_start:
+    auipc t0, %pcrel_hi(sym)
+    lw t0, %pcrel_lo(_start)(t0)