From 019808c95c540a830a64c132257bde018abf6a1e Mon Sep 17 00:00:00 2001 From: Ian Lance Taylor Date: Wed, 2 May 2018 21:53:30 +0000 Subject: [PATCH] libgo: break dependence on libgcc unwind-pe.h The C portion of the Go runtime includes the header "unwind-pe.h" from libgcc, which contains some constants and a few small routines for decoding pointer values within unwind info. This patch gets rid of that include and instead adds a re-implementation of that functionality in the single file that uses it. The intent is to allow the C runtime portion of libgo to be built without a companion GCC installation. Reviewed-on: https://go-review.googlesource.com/90235 From-SVN: r259861 --- libgo/runtime/go-unwind.c | 167 +++++++++++++++++++++++++++++++++++++- 1 file changed, 165 insertions(+), 2 deletions(-) diff --git a/libgo/runtime/go-unwind.c b/libgo/runtime/go-unwind.c index 4c9fb49c994..536a619d298 100644 --- a/libgo/runtime/go-unwind.c +++ b/libgo/runtime/go-unwind.c @@ -10,11 +10,30 @@ #include #include "unwind.h" -#define NO_SIZE_OF_ENCODED_VALUE -#include "unwind-pe.h" #include "runtime.h" +/* These constants are documented here: + https://refspecs.linuxfoundation.org/LSB_3.0.0/LSB-PDA/LSB-PDA/dwarfext.html + */ + +#define DW_EH_PE_omit 0xff +#define DW_EH_PE_absptr 0x00 +#define DW_EH_PE_uleb128 0x01 +#define DW_EH_PE_udata2 0x02 +#define DW_EH_PE_udata4 0x03 +#define DW_EH_PE_udata8 0x04 +#define DW_EH_PE_sleb128 0x09 +#define DW_EH_PE_sdata2 0x0A +#define DW_EH_PE_sdata4 0x0B +#define DW_EH_PE_sdata8 0x0C +#define DW_EH_PE_pcrel 0x10 +#define DW_EH_PE_textrel 0x20 +#define DW_EH_PE_datarel 0x30 +#define DW_EH_PE_funcrel 0x40 +#define DW_EH_PE_aligned 0x50 +#define DW_EH_PE_indirect 0x80 + /* The code for a Go exception. */ #ifdef __ARM_EABI_UNWINDER__ @@ -109,6 +128,150 @@ throwException () abort (); } +static inline _Unwind_Ptr +encoded_value_base (uint8_t encoding, struct _Unwind_Context *context) +{ + if (encoding == DW_EH_PE_omit) + return 0; + switch (encoding & 0x70) + { + case DW_EH_PE_absptr: + case DW_EH_PE_pcrel: + case DW_EH_PE_aligned: + return 0; + case DW_EH_PE_textrel: + return _Unwind_GetTextRelBase(context); + case DW_EH_PE_datarel: + return _Unwind_GetDataRelBase(context); + case DW_EH_PE_funcrel: + return _Unwind_GetRegionStart(context); + } + abort (); +} + +/* Read an unsigned leb128 value. */ + +static inline const uint8_t * +read_uleb128 (const uint8_t *p, _uleb128_t *val) +{ + unsigned int shift = 0; + _uleb128_t result = 0; + uint8_t byte; + + do + { + byte = *p++; + result |= ((_uleb128_t)byte & 0x7f) << shift; + shift += 7; + } + while (byte & 0x80); + + *val = result; + return p; +} + +/* Similar, but read a signed leb128 value. */ + +static inline const uint8_t * +read_sleb128 (const uint8_t *p, _sleb128_t *val) +{ + unsigned int shift = 0; + _uleb128_t result = 0; + uint8_t byte; + + do + { + byte = *p++; + result |= ((_uleb128_t)byte & 0x7f) << shift; + shift += 7; + } + while (byte & 0x80); + + /* sign extension */ + if (shift < (8 * sizeof(result)) && (byte & 0x40) != 0) + result |= (((_uleb128_t)~0) << shift); + + *val = (_sleb128_t)result; + return p; +} + +#define ROUND_UP_TO_PVB(x) (x + sizeof(void *) - 1) &- sizeof(void *) + +#define COPY_AND_ADVANCE(dst, ptr, typ) \ + (dst = *((const typ*)ptr), \ + ptr += sizeof(typ)) + +static inline const uint8_t * +read_encoded_value (struct _Unwind_Context *context, uint8_t encoding, + const uint8_t *p, _Unwind_Ptr *val) +{ + _Unwind_Ptr base = encoded_value_base (encoding, context); + _Unwind_Internal_Ptr decoded = 0; + const uint8_t *origp = p; + + if (encoding == DW_EH_PE_aligned) + { + _Unwind_Internal_Ptr uip = (_Unwind_Internal_Ptr)p; + uip = ROUND_UP_TO_PVB (uip); + decoded = *(_Unwind_Internal_Ptr *)uip; + p = (const uint8_t *)(uip + sizeof(void *)); + } + else + { + switch (encoding & 0x0f) + { + case DW_EH_PE_sdata2: + case DW_EH_PE_udata2: + COPY_AND_ADVANCE (decoded, p, uint16_t); + break; + case DW_EH_PE_sdata4: + case DW_EH_PE_udata4: + COPY_AND_ADVANCE (decoded, p, uint32_t); + break; + case DW_EH_PE_sdata8: + case DW_EH_PE_udata8: + COPY_AND_ADVANCE (decoded, p, uint64_t); + break; + case DW_EH_PE_uleb128: + { + _uleb128_t value; + p = read_uleb128 (p, &value); + decoded = (_Unwind_Internal_Ptr)value; + break; + } + case DW_EH_PE_sleb128: + { + _sleb128_t value; + p = read_sleb128 (p, &value); + decoded = (_Unwind_Internal_Ptr)value; + break; + } + case DW_EH_PE_absptr: + decoded = (_Unwind_Internal_Ptr)(*(const void *const *)p); + p += sizeof(void *); + break; + default: + abort (); + } + + if (decoded == 0) + { + *val = decoded; + return p; + } + + if ((encoding & 0x70) == DW_EH_PE_pcrel) + decoded += ((_Unwind_Internal_Ptr)origp); + else + decoded += base; + + if ((encoding & DW_EH_PE_indirect) != 0) + decoded = *(_Unwind_Internal_Ptr *)decoded; + } + *val = decoded; + return p; +} + /* The rest of this code is really similar to gcc/unwind-c.c and libjava/exception.cc. */