114 lines
4.0 KiB
Diff
114 lines
4.0 KiB
Diff
From eb6bd05766f54dc921018de1f93fcfa290e4a19d Mon Sep 17 00:00:00 2001
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From: Yonghong Song <yhs@fb.com>
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Date: Thu, 23 Aug 2018 14:04:13 -0700
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Subject: [PATCH] dwarf_loader: Process DW_AT_count in DW_TAG_subrange_type
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For array type, gcc and clang generates dwarf info with different tags. For
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example, with existing pahole,
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$ cat test.c
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int a[5][5];
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$ gcc -c -g test.c
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$ llvm-dwarfdump test.o
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...
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0x0000001d: DW_TAG_array_type
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DW_AT_type (0x0000003a "int")
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DW_AT_sibling (0x00000033)
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0x00000026: DW_TAG_subrange_type
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DW_AT_type (0x00000033 "long unsigned int")
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DW_AT_upper_bound (0x04)
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0x0000002c: DW_TAG_subrange_type
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DW_AT_type (0x00000033 "long unsigned int")
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DW_AT_upper_bound (0x04)
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$ pahole -JV test.o
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[1] ARRAY (anon) type_id=3 index_type_id=3 nr_elems=25
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[2] INT long unsigned int size=8 bit_offset=0 nr_bits=64 encoding=(none)
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[3] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
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$ clang -c -g test.c
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$ llvm-dwarfdump test.o
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...
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0x00000033: DW_TAG_array_type
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DW_AT_type (0x00000045 "int")
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0x00000038: DW_TAG_subrange_type
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DW_AT_type (0x0000004c "__ARRAY_SIZE_TYPE__")
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DW_AT_count (0x05)
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0x0000003e: DW_TAG_subrange_type
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DW_AT_type (0x0000004c "__ARRAY_SIZE_TYPE__")
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DW_AT_count (0x05)
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$ pahole -JV test.o
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[1] ARRAY (anon) type_id=2 index_type_id=2 nr_elems=0
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[2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
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[3] INT __ARRAY_SIZE_TYPE__ size=8 bit_offset=0 nr_bits=64 encoding=(none)
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Current pahole processed DW_AT_upper_bound under DW_TAG_subrange_type to
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get array range, but it did not process DW_AT_count so during pahole
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dwarf2btf conversion, the flattened array size is 0.
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This patch fixed the issue by processing DW_AT_count properly.
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With the change, for clang generated test.o, pahole btf conversion output is:
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$ pahole -JV test.o
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[1] ARRAY (anon) type_id=2 index_type_id=2 nr_elems=25
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[2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
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[3] INT __ARRAY_SIZE_TYPE__ size=8 bit_offset=0 nr_bits=64 encoding=(none)
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Committer testing:
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Before:
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# pahole -C augmented_enter_connect_args augmented_syscalls.bpf.o
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struct augmented_enter_connect_args {
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struct syscall_enter_connect_args args; /* 0 40 */
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char addr[0]; /* 40 0 */
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/* size: 56, cachelines: 1, members: 2 */
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/* padding: 16 */
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/* last cacheline: 56 bytes */
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};
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# file augmented_syscalls.bpf.o
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augmented_syscalls.bpf.o: ELF 64-bit LSB relocatable, *unknown arch 0xf7* version 1 (SYSV), with debug_info, not stripped
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#
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After:
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# pahole -C augmented_enter_connect_args augmented_syscalls.bpf.o
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struct augmented_enter_connect_args {
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struct syscall_enter_connect_args args; /* 0 40 */
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char addr[14]; /* 40 14 */
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/* size: 56, cachelines: 1, members: 2 */
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/* padding: 2 */
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/* last cacheline: 56 bytes */
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};
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#
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Signed-off-by: Yonghong Song <yhs@fb.com>
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Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Cc: Martin KaFai Lau <kafai@fb.com>
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Cc: Okash Khawaja <osk@fb.com>
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Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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---
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dwarf_loader.c | 6 ++++++
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1 file changed, 6 insertions(+)
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diff --git a/src/struct/dwarf_loader.c b/src/struct/dwarf_loader.c
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index 037e005..23dfdfb 100644
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--- a/src/struct/dwarf_loader.c
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+++ b/src/struct/dwarf_loader.c
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@@ -933,6 +933,12 @@ static uint64_t attr_upper_bound(Dwarf_Die *die)
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if (dwarf_formudata(&attr, &num) == 0) {
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return (uintmax_t)num + 1;
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}
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+ } else if (dwarf_attr(die, DW_AT_count, &attr) != NULL) {
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+ Dwarf_Word num;
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+
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+ if (dwarf_formudata(&attr, &num) == 0) {
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+ return (uintmax_t)num;
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+ }
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}
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return 0;
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