From: Indu Bhagat Date: Wed, 10 Apr 2024 20:46:37 +0000 (-0700) Subject: gas: scfi: bugfixes for SCFI state propagation X-Git-Tag: gdb-15-branchpoint~440 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f1c5d46cae3fa4a3c41c05c796c69d52eef97067;p=thirdparty%2Fbinutils-gdb.git gas: scfi: bugfixes for SCFI state propagation There are two state propagation functions in SCFI machinery - forward and backward flow. The patch addresses two issues: - In forward_flow_scfi_state (), the state being compared in forward flow must be that at the exit of a prev bb and that at the entry of the next bb. The variable holding the state to be compared was previously (erroneously) stale. - In cmp_scfi_state (), the assumption that two different control flows, leading to the same basic block, cannot have a mismatched notion of CFA base register, is not true. Remove the assertion and instead return err if mismatch. Fixing these issues helps correctly synthesize CFI, when previously SCFI was erroring out for an otherwise valid input asm. gas/ * scfi.c (cmp_scfi_state): Remove assertion and return mismatch in return value as applicable. (forward_flow_scfi_state): Update state object to be the same as the exit state of the prev bb before comparing. gas/testsuite/ * gas/scfi/x86_64/scfi-x86-64.exp: Add new test. * gas/scfi/x86_64/scfi-cfg-5.d: New test. * gas/scfi/x86_64/scfi-cfg-5.l: New test. * gas/scfi/x86_64/scfi-cfg-5.s: New test. --- diff --git a/gas/scfi.c b/gas/scfi.c index 37cc85cfed7..929ea8a73e1 100644 --- a/gas/scfi.c +++ b/gas/scfi.c @@ -155,7 +155,7 @@ cmp_scfi_state (scfi_stateS *state1, scfi_stateS *state2) int ret; if (!state1 || !state2) - ret = 1; + return 1; /* Skip comparing the scratch[] value of registers. The user visible unwind information is derived from the regs[] from the SCFI state. */ @@ -164,10 +164,12 @@ cmp_scfi_state (scfi_stateS *state1, scfi_stateS *state2) /* For user functions which perform dynamic stack allocation, after switching t REG_FP based CFA tracking, it is perfectly possible to have stack usage - in some control flows. However, double-checking that all control flows - have the same idea of CFA tracking before this wont hurt. */ - gas_assert (state1->regs[REG_CFA].base == state2->regs[REG_CFA].base); - if (state1->regs[REG_CFA].base == REG_SP) + in some control flows. Further, the different control flows may even not + have the same idea of CFA tracking (likely later necessitating generation + of .cfi_remember_state / .cfi_restore_state pair). */ + ret |= state1->regs[REG_CFA].base != state2->regs[REG_CFA].base; + + if (!ret && state1->regs[REG_CFA].base == REG_SP) ret |= state1->stack_size != state2->stack_size; ret |= state1->traceable_p != state2->traceable_p; @@ -911,11 +913,11 @@ gen_scfi_ops (ginsnS *ginsn, scfi_stateS *state) return ret; } -/* Recursively perform forward flow of the (unwind information) SCFI state +/* Recursively perform forward flow of the (unwind information) SCFI STATE starting at basic block GBB. - The forward flow process propagates the SCFI state at exit of a basic block - to the successor basic block. + The core of forward flow process takes the SCFI state at the entry of a bb + and updates it incrementally as per the semantics of each ginsn in the bb. Returns error code, if any. */ @@ -961,6 +963,8 @@ forward_flow_scfi_state (gcfgS *gcfg, gbbS *gbb, scfi_stateS *state) bb_for_each_edge(gbb, gedge) { gbb = gedge->dst_bb; + /* Ensure that the state is the one from the exit of the prev bb. */ + memcpy (state, prev_bb->exit_state, sizeof (scfi_stateS)); if (gbb->visited) { ret = cmp_scfi_state (gbb->entry_state, state); diff --git a/gas/testsuite/gas/scfi/x86_64/scfi-cfg-5.d b/gas/testsuite/gas/scfi/x86_64/scfi-cfg-5.d new file mode 100644 index 00000000000..5a0a2e1f927 --- /dev/null +++ b/gas/testsuite/gas/scfi/x86_64/scfi-cfg-5.d @@ -0,0 +1,39 @@ +#as: --scfi=experimental -W +#as: +#objdump: -Wf +#name: Synthesize CFI in presence of control flow 5 +#... +Contents of the .eh_frame section: + +00000000 0+0014 0+0000 CIE + Version: 1 + Augmentation: "zR" + Code alignment factor: 1 + Data alignment factor: -8 + Return address column: 16 + Augmentation data: 1b + DW_CFA_def_cfa: r7 \(rsp\) ofs 8 + DW_CFA_offset: r16 \(rip\) at cfa-8 + DW_CFA_nop + DW_CFA_nop + +0+0018 0+002c 0000001c FDE cie=00000000 pc=0+0000..0+0017 + DW_CFA_advance_loc: 1 to 0+0001 + DW_CFA_def_cfa_offset: 16 + DW_CFA_offset: r6 \(rbp\) at cfa-16 + DW_CFA_advance_loc: 3 to 0+0004 + DW_CFA_def_cfa_register: r6 \(rbp\) + DW_CFA_advance_loc: 5 to 0+0009 + DW_CFA_remember_state + DW_CFA_advance_loc: 6 to 0+000f + DW_CFA_def_cfa_register: r7 \(rsp\) + DW_CFA_restore: r6 \(rbp\) + DW_CFA_def_cfa_offset: 8 + DW_CFA_advance_loc: 1 to 0+0010 + DW_CFA_restore_state + DW_CFA_advance_loc: 6 to 0+0016 + DW_CFA_def_cfa_register: r7 \(rsp\) + DW_CFA_restore: r6 \(rbp\) + DW_CFA_def_cfa_offset: 8 + +#pass diff --git a/gas/testsuite/gas/scfi/x86_64/scfi-cfg-5.l b/gas/testsuite/gas/scfi/x86_64/scfi-cfg-5.l new file mode 100644 index 00000000000..abca835a642 --- /dev/null +++ b/gas/testsuite/gas/scfi/x86_64/scfi-cfg-5.l @@ -0,0 +1,2 @@ +.*Assembler messages: +.*5: Warning: SCFI ignores most user-specified CFI directives diff --git a/gas/testsuite/gas/scfi/x86_64/scfi-cfg-5.s b/gas/testsuite/gas/scfi/x86_64/scfi-cfg-5.s new file mode 100644 index 00000000000..80b081ffe07 --- /dev/null +++ b/gas/testsuite/gas/scfi/x86_64/scfi-cfg-5.s @@ -0,0 +1,32 @@ + .text + .globl foo + .type foo, @function +foo: + .cfi_startproc + push %rbp + .cfi_def_cfa_offset 16 + .cfi_offset %rbp, -16 + mov %rsp, %rbp + .cfi_def_cfa_register %rbp + cmpl $-1, %eax + jne .L1 +.L2: + .cfi_remember_state + call bar + pop %rbp + .cfi_def_cfa_register %rsp + .cfi_restore %rbp + .cfi_def_cfa_offset 8 + ret + +.L1: + .cfi_restore_state + testq %rax, %rax + je .L2 + pop %rbp + .cfi_def_cfa_register %rsp + .cfi_restore %rbp + .cfi_def_cfa_offset 8 + ret + .cfi_endproc + .size foo,.-foo diff --git a/gas/testsuite/gas/scfi/x86_64/scfi-x86-64.exp b/gas/testsuite/gas/scfi/x86_64/scfi-x86-64.exp index 63f0d7e4700..a91dc9df9e5 100644 --- a/gas/testsuite/gas/scfi/x86_64/scfi-x86-64.exp +++ b/gas/testsuite/gas/scfi/x86_64/scfi-x86-64.exp @@ -82,6 +82,8 @@ if { ([istarget "x86_64-*-*"] && ![istarget "x86_64-*-linux*-gnux32"]) } then { run_list_test "scfi-cfg-3" "--scfi=experimental --warn" run_dump_test "scfi-cfg-4" run_list_test "scfi-cfg-4" "--scfi=experimental --warn" + run_dump_test "scfi-cfg-5" + run_list_test "scfi-cfg-5" "--scfi=experimental --warn" run_dump_test "scfi-asm-marker-1" run_list_test "scfi-asm-marker-1" "--scfi=experimental --warn" run_dump_test "scfi-asm-marker-2"