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| 1 | +From 8e2c350f870f8cd99122c62efd023820e563e935 Mon Sep 17 00:00:00 2001 |
| 2 | +From: Moritz Angermann < [email protected]> |
| 3 | +Date: Thu, 16 May 2019 13:35:31 +0800 |
| 4 | +Subject: [PATCH] Add _GLOBAL_OFFSET_TABLE_ support |
| 5 | + |
| 6 | +This adds lookup logic for _GLOBAL_OFFSET_TABLE_ as well as |
| 7 | +relocation logic for R_ARM_BASE_PREL and R_ARM_GOT_BREL which |
| 8 | +the gnu toolchain (gas, gcc, ...) prefers to produce. Apparently |
| 9 | +recent llvm toolchains will produce those as well. |
| 10 | +--- |
| 11 | + rts/linker/Elf.c | 33 +++++++++++++++++++++++++++++++-- |
| 12 | + rts/linker/elf_got.c | 10 +++++++--- |
| 13 | + 2 files changed, 38 insertions(+), 5 deletions(-) |
| 14 | + |
| 15 | +diff --git a/rts/linker/Elf.c b/rts/linker/Elf.c |
| 16 | +index b647d207cb..c6f82af72a 100644 |
| 17 | +--- a/rts/linker/Elf.c |
| 18 | ++++ b/rts/linker/Elf.c |
| 19 | +@@ -1023,6 +1023,19 @@ do_Elf_Rel_relocations ( ObjectCode* oc, char* ehdrC, |
| 20 | + return 1; |
| 21 | + } |
| 22 | + |
| 23 | ++ /* The following nomenclature is used for the operation: |
| 24 | ++ * - S -- (when used on its own) is the address of the symbol. |
| 25 | ++ * - A -- is the addend for the relocation. |
| 26 | ++ * - P -- is the address of the place being relocated (derived from r_offset). |
| 27 | ++ * - Pa - is the adjusted address of the place being relocated, defined as (P & 0xFFFFFFFC). |
| 28 | ++ * - T -- is 1 if the target symbol S has type STT_FUNC and the symbol addresses a Thumb instruction; it is 0 otherwise. |
| 29 | ++ * - B(S) is the addressing origin of the output segment defining the symbol S. The origin is not required to be the |
| 30 | ++ * base address of the segment. This value must always be word-aligned. |
| 31 | ++ * - GOT_ORG is the addressing origin of the Global Offset Table (the indirection table for imported data addresses). |
| 32 | ++ * This value must always be word-aligned. See §4.6.1.8, Proxy generating relocations. |
| 33 | ++ * - GOT(S) is the address of the GOT entry for the symbol S. |
| 34 | ++ */ |
| 35 | ++ |
| 36 | + for (j = 0; j < nent; j++) { |
| 37 | + Elf_Addr offset = rtab[j].r_offset; |
| 38 | + Elf_Addr info = rtab[j].r_info; |
| 39 | +@@ -1117,19 +1130,35 @@ do_Elf_Rel_relocations ( ObjectCode* oc, char* ehdrC, |
| 40 | + # endif |
| 41 | + |
| 42 | + # ifdef arm_HOST_ARCH |
| 43 | +- case COMPAT_R_ARM_ABS32: |
| 44 | ++ case COMPAT_R_ARM_ABS32: /* (S + A) | T */ |
| 45 | + // Specified by Linux ARM ABI to be equivalent to ABS32 |
| 46 | + case COMPAT_R_ARM_TARGET1: |
| 47 | + *(Elf32_Word *)P += S; |
| 48 | + *(Elf32_Word *)P |= T; |
| 49 | + break; |
| 50 | + |
| 51 | +- case COMPAT_R_ARM_REL32: |
| 52 | ++ case COMPAT_R_ARM_REL32: /* ((S + A) | T) – P */ |
| 53 | + *(Elf32_Word *)P += S; |
| 54 | + *(Elf32_Word *)P |= T; |
| 55 | + *(Elf32_Word *)P -= P; |
| 56 | + break; |
| 57 | + |
| 58 | ++ case COMPAT_R_ARM_BASE_PREL: /* B(S) + A – P */ |
| 59 | ++ { |
| 60 | ++ int32_t A = *pP; |
| 61 | ++ // bfd used to encode sb (B(S)) as 0. |
| 62 | ++ *(uint32_t *)P += 0 + A - P; |
| 63 | ++ break; |
| 64 | ++ } |
| 65 | ++ |
| 66 | ++ case COMPAT_R_ARM_GOT_BREL: /* GOT(S) + A – GOT_ORG */ |
| 67 | ++ { |
| 68 | ++ int32_t A = *pP; |
| 69 | ++ void* GOT_S = symbol->got_addr; |
| 70 | ++ *(uint32_t *)P = (uint32_t) GOT_S + A - (uint32_t) oc->info->got_start; |
| 71 | ++ break; |
| 72 | ++ } |
| 73 | ++ |
| 74 | + case COMPAT_R_ARM_CALL: |
| 75 | + case COMPAT_R_ARM_JUMP24: |
| 76 | + { |
| 77 | +diff --git a/rts/linker/elf_got.c b/rts/linker/elf_got.c |
| 78 | +index 10ea25b98b..162fff3161 100644 |
| 79 | +--- a/rts/linker/elf_got.c |
| 80 | ++++ b/rts/linker/elf_got.c |
| 81 | +@@ -83,9 +83,13 @@ fillGot(ObjectCode * oc) { |
| 82 | + if(0x0 == symbol->addr) { |
| 83 | + symbol->addr = lookupSymbol_(symbol->name); |
| 84 | + if(0x0 == symbol->addr) { |
| 85 | +- errorBelch("Failed to lookup symbol: %s\n", |
| 86 | +- symbol->name); |
| 87 | +- return EXIT_FAILURE; |
| 88 | ++ if(0 == strncmp(symbol->name,"_GLOBAL_OFFSET_TABLE_",21)) { |
| 89 | ++ symbol->addr = oc->info->got_start; |
| 90 | ++ } else { |
| 91 | ++ errorBelch("Failed to lookup symbol: %s\n", |
| 92 | ++ symbol->name); |
| 93 | ++ return EXIT_FAILURE; |
| 94 | ++ } |
| 95 | + } |
| 96 | + } else { |
| 97 | + // we already have the address. |
| 98 | +-- |
| 99 | +2.21.0 |
| 100 | + |
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