From f8e3fe0d2764e2976fec6a0ac48921893dc62bbf Mon Sep 17 00:00:00 2001 From: Luis Machado Date: Mon, 10 Aug 2020 11:56:19 -0300 Subject: [AArch64] Improve prologue handling (and fix PR26310) I initially noticed the problem with the addition of gdb.dwarf2/dw2-line-number-zero.exp. The following failures showed up: FAIL: gdb.dwarf2/dw2-line-number-zero.exp: continue to breakpoint: bar1 FAIL: gdb.dwarf2/dw2-line-number-zero.exp: bar1, 1st next FAIL: gdb.dwarf2/dw2-line-number-zero.exp: bar1, 2nd next FAIL: gdb.dwarf2/dw2-line-number-zero.exp: continue to breakpoint: bar2 FAIL: gdb.dwarf2/dw2-line-number-zero.exp: bar2, 1st next FAIL: gdb.dwarf2/dw2-line-number-zero.exp: bar2, 2nd next They happen because AArch64's prologue analyzer skips too many instructions and ends up indicating a stopping point further into user code. Dump of assembler code for function bar1: 0x00000000000006f8 <+0>: stp x29, x30, [sp, #-16]! 0x00000000000006fc <+4>: mov x29, sp 0x0000000000000700 <+8>: mov w0, #0x1 // #1 0x0000000000000704 <+12>: bl 0x6e4 0x0000000000000708 <+16>: mov w0, #0x2 // #2 We should've stopped at 0x700, but the analyzer actually skips that instruction and stops at 0x704. Then GDB ends up adjusting the address further, and pushes the stopping point to 0x708 based on the SAL information. I'm not sure if this adjustment to 0x708 is correct though, as it ends up skipping past a branch. But I'm leaving that aside for now. One other complicating factor is that GCC seems to be hoisting up instructions from user code, mixing them up with prologue instructions. The following patch adjusts the heuristics a little bit, and tracks when the SP and FP get used. If we notice an instruction that is not supposed to be in the prologue, and this happens *after* SP/FP adjustments and saving of registers, we stop the analysis. This means, for PR26310, that we will now stop at 0x700. I've also added a few more unit tests to make sure the updated behavior is validated. gdb/ChangeLog: 2020-08-10 Luis Machado PR gdb/26310 * aarch64-tdep.c (aarch64_analyze_prologue): Track use of SP/FP and act accordingly. (aarch64_analyze_prologue_test): Add more unit tests to exercise movz/str/stur/stp skipping behavior. --- gdb/ChangeLog | 9 ++++ gdb/aarch64-tdep.c | 139 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 148 insertions(+) (limited to 'gdb') diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 463847f..1306bd5 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,5 +1,14 @@ 2020-08-10 Luis Machado + PR gdb/26310 + + * aarch64-tdep.c (aarch64_analyze_prologue): Track use of SP/FP and + act accordingly. + (aarch64_analyze_prologue_test): Add more unit tests to exercise + movz/str/stur/stp skipping behavior. + +2020-08-10 Luis Machado + * nat/aarch64-sve-linux-sigcontext.h (SVE_PT_REGS_OFFSET): Use struct user_sve_header instead of struct sve_context. diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c index 5e7d0d0..106939a 100644 --- a/gdb/aarch64-tdep.c +++ b/gdb/aarch64-tdep.c @@ -287,6 +287,12 @@ aarch64_analyze_prologue (struct gdbarch *gdbarch, { enum bfd_endian byte_order_for_code = gdbarch_byte_order_for_code (gdbarch); int i; + + /* Whether the stack has been set. This should be true when we notice a SP + to FP move or if we are using the SP as the base register for storing + data, in case the FP is ommitted. */ + bool seen_stack_set = false; + /* Track X registers and D registers in prologue. */ pv_t regs[AARCH64_X_REGISTER_COUNT + AARCH64_D_REGISTER_COUNT]; @@ -326,6 +332,10 @@ aarch64_analyze_prologue (struct gdbarch *gdbarch, regs[rd] = pv_add_constant (regs[rn], -inst.operands[2].imm.value); } + + /* Did we move SP to FP? */ + if (rn == AARCH64_SP_REGNUM && rd == AARCH64_FP_REGNUM) + seen_stack_set = true; } else if (inst.opcode->iclass == pcreladdr && inst.operands[1].type == AARCH64_OPND_ADDR_ADRP) @@ -358,6 +368,12 @@ aarch64_analyze_prologue (struct gdbarch *gdbarch, else if (inst.opcode->op == OP_MOVZ) { gdb_assert (inst.operands[0].type == AARCH64_OPND_Rd); + + /* If this shows up before we set the stack, keep going. Otherwise + stop the analysis. */ + if (seen_stack_set) + break; + regs[inst.operands[0].reg.regno] = pv_unknown (); } else if (inst.opcode->iclass == log_shift @@ -399,6 +415,10 @@ aarch64_analyze_prologue (struct gdbarch *gdbarch, stack.store (pv_add_constant (regs[rn], inst.operands[1].addr.offset.imm), size, regs[rt]); + + /* Are we storing with SP as a base? */ + if (rn == AARCH64_SP_REGNUM) + seen_stack_set = true; } else if ((inst.opcode->iclass == ldstpair_off || (inst.opcode->iclass == ldstpair_indexed @@ -442,6 +462,10 @@ aarch64_analyze_prologue (struct gdbarch *gdbarch, if (inst.operands[2].addr.writeback) regs[rn] = pv_add_constant (regs[rn], imm); + /* Ignore the instruction that allocates stack space and sets + the SP. */ + if (rn == AARCH64_SP_REGNUM && !inst.operands[2].addr.writeback) + seen_stack_set = true; } else if ((inst.opcode->iclass == ldst_imm9 /* Signed immediate. */ || (inst.opcode->iclass == ldst_pos /* Unsigned immediate. */ @@ -464,6 +488,10 @@ aarch64_analyze_prologue (struct gdbarch *gdbarch, stack.store (pv_add_constant (regs[rn], imm), size, regs[rt]); if (inst.operands[1].addr.writeback) regs[rn] = pv_add_constant (regs[rn], imm); + + /* Are we storing with SP as a base? */ + if (rn == AARCH64_SP_REGNUM) + seen_stack_set = true; } else if (inst.opcode->iclass == testbranch) { @@ -690,6 +718,117 @@ aarch64_analyze_prologue_test (void) } } + /* Test handling of movz before setting the frame pointer. */ + { + static const uint32_t insns[] = { + 0xa9bf7bfd, /* stp x29, x30, [sp, #-16]! */ + 0x52800020, /* mov w0, #0x1 */ + 0x910003fd, /* mov x29, sp */ + 0x528000a2, /* mov w2, #0x5 */ + 0x97fffff8, /* bl 6e4 */ + }; + + instruction_reader_test reader (insns); + + trad_frame_reset_saved_regs (gdbarch, cache.saved_regs); + CORE_ADDR end = aarch64_analyze_prologue (gdbarch, 0, 128, &cache, reader); + + /* We should stop at the 4th instruction. */ + SELF_CHECK (end == (4 - 1) * 4); + SELF_CHECK (cache.framereg == AARCH64_FP_REGNUM); + SELF_CHECK (cache.framesize == 16); + } + + /* Test handling of movz/stp when using the stack pointer as frame + pointer. */ + { + static const uint32_t insns[] = { + 0xa9bc7bfd, /* stp x29, x30, [sp, #-64]! */ + 0x52800020, /* mov w0, #0x1 */ + 0x290207e0, /* stp w0, w1, [sp, #16] */ + 0xa9018fe2, /* stp x2, x3, [sp, #24] */ + 0x528000a2, /* mov w2, #0x5 */ + 0x97fffff8, /* bl 6e4 */ + }; + + instruction_reader_test reader (insns); + + trad_frame_reset_saved_regs (gdbarch, cache.saved_regs); + CORE_ADDR end = aarch64_analyze_prologue (gdbarch, 0, 128, &cache, reader); + + /* We should stop at the 5th instruction. */ + SELF_CHECK (end == (5 - 1) * 4); + SELF_CHECK (cache.framereg == AARCH64_SP_REGNUM); + SELF_CHECK (cache.framesize == 64); + } + + /* Test handling of movz/str when using the stack pointer as frame + pointer */ + { + static const uint32_t insns[] = { + 0xa9bc7bfd, /* stp x29, x30, [sp, #-64]! */ + 0x52800020, /* mov w0, #0x1 */ + 0xb9002be4, /* str w4, [sp, #40] */ + 0xf9001be5, /* str x5, [sp, #48] */ + 0x528000a2, /* mov w2, #0x5 */ + 0x97fffff8, /* bl 6e4 */ + }; + + instruction_reader_test reader (insns); + + trad_frame_reset_saved_regs (gdbarch, cache.saved_regs); + CORE_ADDR end = aarch64_analyze_prologue (gdbarch, 0, 128, &cache, reader); + + /* We should stop at the 5th instruction. */ + SELF_CHECK (end == (5 - 1) * 4); + SELF_CHECK (cache.framereg == AARCH64_SP_REGNUM); + SELF_CHECK (cache.framesize == 64); + } + + /* Test handling of movz/stur when using the stack pointer as frame + pointer. */ + { + static const uint32_t insns[] = { + 0xa9bc7bfd, /* stp x29, x30, [sp, #-64]! */ + 0x52800020, /* mov w0, #0x1 */ + 0xb80343e6, /* stur w6, [sp, #52] */ + 0xf80383e7, /* stur x7, [sp, #56] */ + 0x528000a2, /* mov w2, #0x5 */ + 0x97fffff8, /* bl 6e4 */ + }; + + instruction_reader_test reader (insns); + + trad_frame_reset_saved_regs (gdbarch, cache.saved_regs); + CORE_ADDR end = aarch64_analyze_prologue (gdbarch, 0, 128, &cache, reader); + + /* We should stop at the 5th instruction. */ + SELF_CHECK (end == (5 - 1) * 4); + SELF_CHECK (cache.framereg == AARCH64_SP_REGNUM); + SELF_CHECK (cache.framesize == 64); + } + + /* Test handling of movz when there is no frame pointer set or no stack + pointer used. */ + { + static const uint32_t insns[] = { + 0xa9bf7bfd, /* stp x29, x30, [sp, #-16]! */ + 0x52800020, /* mov w0, #0x1 */ + 0x528000a2, /* mov w2, #0x5 */ + 0x97fffff8, /* bl 6e4 */ + }; + + instruction_reader_test reader (insns); + + trad_frame_reset_saved_regs (gdbarch, cache.saved_regs); + CORE_ADDR end = aarch64_analyze_prologue (gdbarch, 0, 128, &cache, reader); + + /* We should stop at the 4th instruction. */ + SELF_CHECK (end == (4 - 1) * 4); + SELF_CHECK (cache.framereg == AARCH64_SP_REGNUM); + SELF_CHECK (cache.framesize == 16); + } + /* Test a prologue in which there is a return address signing instruction. */ if (tdep->has_pauth ()) { -- cgit v1.1