[binutils-gdb] bpf: fix relocation addend incorrect symbol value
David Faust
dfaust@sourceware.org
Fri Jan 12 17:32:19 GMT 2024
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=ba7c1e37cfb498263a4e309700c27696fa5ff1ad
commit ba7c1e37cfb498263a4e309700c27696fa5ff1ad
Author: David Faust <david.faust@oracle.com>
Date: Wed Jan 10 15:05:36 2024 -0800
bpf: fix relocation addend incorrect symbol value
Relocations installed by the BPF ELF backend were sometimes incorrectly
adding the symbol value to the relocation entry addend, when the correct
relocation value was already stored in the addend. This could lead to a
relocation effectively adding the symbol value twice.
Fix that by making bpf_elf_generic_reloc () more similar to the flow of
bfd_install_relocation in the case where howto->install_addend is set,
which is how it ought to behave.
bfd/
* bpf-reloc.def (R_BPF_64_ABS32, R_BPF_64_ABS64)
(R_BPF_64_NODYLD32): Set partial_inplace to true.
* elf64-bpf.c (bpf_elf_generic_reloc): Do not include the value
of the symbol when installing relocation. Copy some additional
logic from bfd_elf_generic_reloc.
gas/
* testsuite/gas/bpf/bpf.exp: Run new test.
* testsuite/gas/bpf/elf-relo-1.d: New.
* testsuite/gas/bpf/elf-relo-1.s: New.
Diff:
---
bfd/bpf-reloc.def | 6 +++---
bfd/elf64-bpf.c | 34 +++++++++++++++++++++++-----------
gas/testsuite/gas/bpf/bpf.exp | 3 +++
gas/testsuite/gas/bpf/elf-relo-1.d | 35 +++++++++++++++++++++++++++++++++++
gas/testsuite/gas/bpf/elf-relo-1.s | 25 +++++++++++++++++++++++++
5 files changed, 89 insertions(+), 14 deletions(-)
diff --git a/bfd/bpf-reloc.def b/bfd/bpf-reloc.def
index 42ba1a169ea..65228d44009 100644
--- a/bfd/bpf-reloc.def
+++ b/bfd/bpf-reloc.def
@@ -38,7 +38,7 @@
complain_overflow_bitfield, /* complain_on_overflow */
bpf_elf_generic_reloc, /* special_function */
"R_BPF_64_ABS32", /* name */
- false, /* partial_inplace */
+ true, /* partial_inplace */
0xffffffff, /* src_mask */
0xffffffff, /* dst_mask */
true) /* pcrel_offset */
@@ -53,7 +53,7 @@
complain_overflow_bitfield, /* complain_on_overflow */
bpf_elf_generic_reloc, /* special_function */
"R_BPF_64_ABS64", /* name */
- false, /* partial_inplace */
+ true, /* partial_inplace */
0, /* src_mask */
MINUS_ONE, /* dst_mask */
true) /* pcrel_offset */
@@ -103,7 +103,7 @@
complain_overflow_bitfield, /* complain_on_overflow */
bpf_elf_generic_reloc, /* special_function */
"R_BPF_64_NODYLD32", /* name */
- false, /* partial_inplace */
+ true, /* partial_inplace */
0xffffffff, /* src_mask */
0xffffffff, /* dst_mask */
true) /* pcrel_offset */
diff --git a/bfd/elf64-bpf.c b/bfd/elf64-bpf.c
index 0bffe2c5717..c922a3eb48e 100644
--- a/bfd/elf64-bpf.c
+++ b/bfd/elf64-bpf.c
@@ -385,8 +385,7 @@ elf64_bpf_merge_private_bfd_data (bfd *ibfd, struct bfd_link_info *info)
static bfd_reloc_status_type
bpf_elf_generic_reloc (bfd *abfd, arelent *reloc_entry, asymbol *symbol,
- void *data, asection *input_section,
- bfd *output_bfd ATTRIBUTE_UNUSED,
+ void *data, asection *input_section, bfd *output_bfd,
char **error_message ATTRIBUTE_UNUSED)
{
@@ -394,6 +393,22 @@ bpf_elf_generic_reloc (bfd *abfd, arelent *reloc_entry, asymbol *symbol,
bfd_reloc_status_type status;
bfd_byte *where;
+ /* From bfd_elf_generic_reloc. */
+ if (output_bfd != NULL
+ && (symbol->flags & BSF_SECTION_SYM) == 0
+ && (! reloc_entry->howto->partial_inplace
+ || reloc_entry->addend == 0))
+ {
+ reloc_entry->address += input_section->output_offset;
+ return bfd_reloc_ok;
+ }
+
+ if (output_bfd == NULL
+ && !reloc_entry->howto->pc_relative
+ && (symbol->section->flags & SEC_DEBUGGING) != 0
+ && (input_section->flags & SEC_DEBUGGING) != 0)
+ reloc_entry->addend -= symbol->section->output_section->vma;
+
/* Sanity check that the address is in range. */
bfd_size_type end = bfd_get_section_limit_octets (abfd, input_section);
bfd_size_type reloc_size;
@@ -407,18 +422,15 @@ bpf_elf_generic_reloc (bfd *abfd, arelent *reloc_entry, asymbol *symbol,
|| end - reloc_entry->address < reloc_size)
return bfd_reloc_outofrange;
- /* Get the symbol value. */
- if (bfd_is_com_section (symbol->section))
- relocation = 0;
- else
- relocation = symbol->value;
+ /* Behave similarly to bfd_install_relocation with install_addend set.
+ That is, just install the addend and do not include the value of
+ the symbol. */
+ relocation = reloc_entry->addend;
if (symbol->flags & BSF_SECTION_SYM)
/* Relocation against a section symbol: add in the section base address. */
relocation += BASEADDR (symbol->section);
- relocation += reloc_entry->addend;
-
where = (bfd_byte *) data + reloc_entry->address;
status = bfd_check_overflow (reloc_entry->howto->complain_on_overflow,
@@ -449,8 +461,8 @@ bpf_elf_generic_reloc (bfd *abfd, arelent *reloc_entry, asymbol *symbol,
where + reloc_entry->howto->bitpos / 8);
}
- reloc_entry->addend = relocation;
- reloc_entry->address += input_section->output_offset;
+ if (output_bfd != NULL)
+ reloc_entry->address += input_section->output_offset;
return bfd_reloc_ok;
}
diff --git a/gas/testsuite/gas/bpf/bpf.exp b/gas/testsuite/gas/bpf/bpf.exp
index 44b050e2a00..dae8bd924d0 100644
--- a/gas/testsuite/gas/bpf/bpf.exp
+++ b/gas/testsuite/gas/bpf/bpf.exp
@@ -83,4 +83,7 @@ if {[istarget bpf*-*-*]} {
# Test that parser does not create undefined symbols
run_dump_test asm-extra-sym-1
+
+ # Test relocation installation
+ run_dump_test elf-relo-1
}
diff --git a/gas/testsuite/gas/bpf/elf-relo-1.d b/gas/testsuite/gas/bpf/elf-relo-1.d
new file mode 100644
index 00000000000..4a1c7944882
--- /dev/null
+++ b/gas/testsuite/gas/bpf/elf-relo-1.d
@@ -0,0 +1,35 @@
+#as: -EL -mdialect=normal
+#objdump: -tdr
+#source elf-relo-1.s
+#name: eBPF ELF relocations 1
+
+.*: +file format elf64-bpfle
+
+SYMBOL TABLE:
+0000000000000000 l d .text 0000000000000000 .text
+0000000000000000 l d .data 0000000000000000 .data
+0000000000000000 l d .bss 0000000000000000 .bss
+0000000000000006 l .data 0000000000000000 bar
+0000000000000000 l F .text 0000000000000000 baz
+0000000000000030 l F .text 0000000000000000 qux
+0000000000000004 g .data 0000000000000000 foo
+0000000000000000 \*UND\* 0000000000000000 somefunc
+
+
+
+Disassembly of section .text:
+
+0+ <baz>:
+ 0: 18 01 00 00 00 00 00 00 lddw %r1,0
+ 8: 00 00 00 00 00 00 00 00
+ 0: R_BPF_64_64 foo
+ 10: b7 02 00 00 06 00 00 00 mov %r2,6
+ 14: R_BPF_64_ABS32 .data
+ 18: 18 03 00 00 30 00 00 00 lddw %r3,48
+ 20: 00 00 00 00 00 00 00 00
+ 18: R_BPF_64_64 .text
+ 28: 85 10 00 00 ff ff ff ff call -1
+ 28: R_BPF_64_32 somefunc
+
+0+30 <qux>:
+ 30: 95 00 00 00 00 00 00 00 exit
diff --git a/gas/testsuite/gas/bpf/elf-relo-1.s b/gas/testsuite/gas/bpf/elf-relo-1.s
new file mode 100644
index 00000000000..23424e05907
--- /dev/null
+++ b/gas/testsuite/gas/bpf/elf-relo-1.s
@@ -0,0 +1,25 @@
+ .global foo
+ .data
+ .byte 1
+ .byte 2
+ .byte 3
+ .byte 4
+foo:
+ .byte 5
+ .byte 6
+bar:
+ .byte 7
+ .byte 8
+
+ .text
+ .align 3
+ .type baz, @function
+baz:
+ lddw %r1, foo
+ mov %r2, bar
+ lddw %r3, qux
+ call somefunc
+
+ .type qux, @function
+qux:
+ exit
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