From: Zoran Zaric Date: Tue, 22 Sep 2020 16:10:26 +0000 (+0100) Subject: Add new memory access interface to expr.c X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8b1bcaf79ca06c733393340124385c2da120b743;p=thirdparty%2Fbinutils-gdb.git Add new memory access interface to expr.c DWARF expression evaluator is currently using a few different interfaces for memory access: write_memory_with_notification, read_value_memory, read_memory. They all seem incosistent, while some of them even need a struct value typed argument to be present. This patch is simplifying that interface by replacing it with two new low level functions: read_from_memory and write_to_memory. The advantage of this new interface is that it behaves in the same way as the register access interface from the previous patch. Both of these have the same error returning policy, which will be usefull for the following patches. * dwarf2/expr.c (xfer_memory): New function. (read_from_memory): New function. (write_to_memory): New function. (rw_pieced_value): Now calls the read_from_memory and write_to_memory functions. --- diff --git a/gdb/dwarf2/expr.c b/gdb/dwarf2/expr.c index 0ca8528298a..6419294a284 100644 --- a/gdb/dwarf2/expr.c +++ b/gdb/dwarf2/expr.c @@ -33,6 +33,8 @@ #include "gdbsupport/underlying.h" #include "gdbarch.h" #include "objfiles.h" +#include "inferior.h" +#include "observable.h" /* Cookie for gdbarch data. */ @@ -189,6 +191,86 @@ write_to_register (frame_info *frame, int regnum, return; } +/* Helper for read_from_memory and write_to_memory. */ + +static void +xfer_memory (CORE_ADDR address, gdb_byte *readbuf, + const gdb_byte *writebuf, + size_t length, bool stack, int *unavailable) +{ + *unavailable = 0; + + target_object object + = stack ? TARGET_OBJECT_STACK_MEMORY : TARGET_OBJECT_MEMORY; + + ULONGEST xfered_total = 0; + + while (xfered_total < length) + { + ULONGEST xfered_partial; + + enum target_xfer_status status + = target_xfer_partial (current_inferior ()->top_target (), + object, NULL, + (readbuf != nullptr + ? readbuf + xfered_total + : nullptr), + (writebuf != nullptr + ? writebuf + xfered_total + : nullptr), + address + xfered_total, length - xfered_total, + &xfered_partial); + + if (status == TARGET_XFER_OK) + { + xfered_total += xfered_partial; + QUIT; + } + else if (status == TARGET_XFER_UNAVAILABLE) + { + *unavailable = 1; + return; + } + else if (status == TARGET_XFER_EOF) + memory_error (TARGET_XFER_E_IO, address + xfered_total); + else + memory_error (status, address + xfered_total); + } +} + +/* Read LENGTH bytes of memory contents starting at ADDRESS. + + The data read is copied to a caller-managed buffer BUF. STACK + indicates whether the memory range specified belongs to a stack + memory region. + + If the memory is unavailable, the UNAVAILABLE output is set. */ + +static void +read_from_memory (CORE_ADDR address, gdb_byte *buffer, + size_t length, bool stack, int *unavailable) +{ + xfer_memory (address, buffer, nullptr, length, stack, unavailable); +} + +/* Write LENGTH bytes of memory contents starting at ADDRESS. + + The data written is copied from a caller-managed buffer buf. STACK + indicates whether the memory range specified belongs to a stack + memory region. + + If the memory is unavailable, the UNAVAILABLE output is set. */ + +static void +write_to_memory (CORE_ADDR address, const gdb_byte *buffer, + size_t length, bool stack, int *unavailable) +{ + xfer_memory (address, nullptr, buffer, length, stack, unavailable); + + gdb::observers::memory_changed.notify (current_inferior (), address, + length, buffer); +} + struct piece_closure { /* Reference count. */ @@ -387,66 +469,86 @@ rw_pieced_value (value *v, value *from, bool check_optimized) bits_to_skip += p->offset; CORE_ADDR start_addr = p->v.mem.addr + bits_to_skip / 8; + bool in_stack_memory = p->v.mem.in_stack_memory; + int unavail = 0; if (bits_to_skip % 8 == 0 && this_size_bits % 8 == 0 && offset % 8 == 0) { /* Everything is byte-aligned; no buffer needed. */ - if (from != nullptr) - write_memory_with_notification (start_addr, - (from_contents - + offset / 8), - this_size_bits / 8); + if (from != NULL) + write_to_memory (start_addr, (from_contents + offset / 8), + this_size_bits / 8, in_stack_memory, + &unavail); else - read_value_memory (v, offset, - p->v.mem.in_stack_memory, - p->v.mem.addr + bits_to_skip / 8, - v_contents + offset / 8, - this_size_bits / 8); - break; - } - - this_size = bits_to_bytes (bits_to_skip, this_size_bits); - buffer.resize (this_size); - - if (from == nullptr) - { - /* Read mode. */ - read_value_memory (v, offset, - p->v.mem.in_stack_memory, - p->v.mem.addr + bits_to_skip / 8, - buffer.data (), this_size); - copy_bitwise (v_contents, offset, - buffer.data (), bits_to_skip % 8, - this_size_bits, bits_big_endian); + read_from_memory (start_addr, (v_contents + offset / 8), + this_size_bits / 8, in_stack_memory, + &unavail); } else { - /* Write mode. */ - if (bits_to_skip % 8 != 0 || this_size_bits % 8 != 0) + this_size = bits_to_bytes (bits_to_skip, this_size_bits); + buffer.resize (this_size); + + if (from == NULL) { - if (this_size <= 8) + /* Read mode. */ + read_from_memory (start_addr, buffer.data (), + this_size, in_stack_memory, + &unavail); + if (!unavail) + copy_bitwise (v_contents, offset, + buffer.data (), bits_to_skip % 8, + this_size_bits, bits_big_endian); + } + else + { + /* Write mode. */ + if (bits_to_skip % 8 != 0 || this_size_bits % 8 != 0) { - /* Perform a single read for small sizes. */ - read_memory (start_addr, buffer.data (), - this_size); + if (this_size <= 8) + { + /* Perform a single read for small sizes. */ + read_from_memory (start_addr, buffer.data (), + this_size, in_stack_memory, + &unavail); + } + else + { + /* Only the first and last bytes can possibly have + any bits reused. */ + read_from_memory (start_addr, buffer.data (), + 1, in_stack_memory, + &unavail); + if (!unavail) + read_from_memory (start_addr + this_size - 1, + &buffer[this_size - 1], 1, + in_stack_memory, &unavail); + } } - else + + if (!unavail) { - /* Only the first and last bytes can possibly have - any bits reused. */ - read_memory (start_addr, buffer.data (), 1); - read_memory (start_addr + this_size - 1, - &buffer[this_size - 1], 1); + copy_bitwise (buffer.data (), bits_to_skip % 8, + from_contents, offset, + this_size_bits, bits_big_endian); + write_to_memory (start_addr, buffer.data (), + this_size, in_stack_memory, + &unavail); } } + } - copy_bitwise (buffer.data (), bits_to_skip % 8, - from_contents, offset, - this_size_bits, bits_big_endian); - write_memory_with_notification (start_addr, - buffer.data (), - this_size); + if (unavail) + { + if (from == NULL) + mark_value_bits_unavailable (v, (offset + bits_to_skip % 8), + this_size_bits); + else + throw_error (NOT_AVAILABLE_ERROR, + _("Can't do read-modify-write to " + "update bitfield; containing word " + "is unavailable")); } } break;