From: Jens Remus Date: Wed, 15 Oct 2025 15:45:48 +0000 (+0200) Subject: gas: sframe: Represent .cfi_undefined RA as FRE without offsets X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=5079bf895955c6f7f40c1846ae38ecb26cde1be6;p=thirdparty%2Fbinutils-gdb.git gas: sframe: Represent .cfi_undefined RA as FRE without offsets In DWARF CFI an "undefined" register rule for the return address (RA) register indicates that there is no return address and the stack trace is complete. Represent DW_CFA_undefined as SFrame FRE without any offsets, so that a stack tracer implementation can use this as indication that an outermost frame has been reached and the stack trace is complete. This representation is backward compatible, as existing stack tracers should already deal with the case, that an SFrame FRE a so far invalid offset count of zero and stop the trace. include/ * sframe.h (SFRAME_V2_FRE_RA_UNDEFINED_P): New macro to test FRE info word for RA undefined (FRE without any offsets). binutils/ * NEWS: Mention SFrame can represent an undefined RA as FRE without any offsets. gas/ * gen-sframe.h (struct sframe_row_entry): Add ra_undefined_p flag. * gen-sframe.c (sframe_row_entry_new): Initialize ra_undefined_p flag to not set. (sframe_row_entry_initialize): Treat ra_undefined_p flag as sticky. (sframe_fre_set_ra_track): Reset ra_undefined_p flag. (sframe_xlate_do_restore): Reset ra_undefined_p flag to saved state. (sframe_xlate_do_same_value): Reset ra_undefined_p flag. (sframe_xlate_do_cfi_undefined): For RA set ra_undefined_p flag. (output_sframe_row_entry): Represent RA undefined as SFrame FRE without any offsets and FRE info word fields zeroed. * NEWS: Mention assembler represents .cfi_undefined RA in SFrame as FRE without any offsets. libsframe/ * doc/sframe-spec.texi (Changes from Version 1 to Version 2): Mention that a SFrame FRE without any offsets flag indicates an outermost frame with an undefined RA. (fre_offset_count): Document that a FRE offset count of zero indicates an outermost frame with an undefined RA. * sframe.c (sframe_get_fre_ra_undefined_p): Use macro SFRAME_V2_FRE_RA_UNDEFINED_P. (sframe_fre_get_fp_offset, sframe_fre_get_ra_offset): Do not return fixed FP/RA offset if RA undefined. * sframe-dump.c (dump_sframe_func_with_fres): Show FRE without any offsets as "RA undefined". gas/testsuite/ * gas/cfi-sframe/cfi-sframe.exp: Run tests for .cfi_undefined RA on AArch64, s390x, and x86-64. * gas/cfi-sframe/cfi-sframe-aarch64-ra-undefined-1.d: Add test for .cfi_undefined RA on AArch64. * gas/cfi-sframe/cfi-sframe-aarch64-ra-undefined-1.s: Likewise. * as/cfi-sframe/cfi-sframe-s390x-ra-undefined-1.d: Add test for .cfi_undefined RA on s390x. * gas/cfi-sframe/cfi-sframe-s390x-ra-undefined-1.s: Likewise. * gas/cfi-sframe/cfi-sframe-x86_64-ra-undefined-1.d: Add test for .cfi_undefined RA on x86-64. * gas/cfi-sframe/cfi-sframe-x86_64-ra-undefined-1.s: Likewise. Signed-off-by: Jens Remus --- diff --git a/binutils/NEWS b/binutils/NEWS index 0a4ed3bcc43..c7c44a708d2 100644 --- a/binutils/NEWS +++ b/binutils/NEWS @@ -1,5 +1,10 @@ -*- text -*- +* SFrame stack trace format now represents an undefined return address as + an SFrame FRE without any offsets. libsframe provides a new API to test + for RA undefined, which is used when dumping SFrame information (e.g. using + objdump and readelf) to show such FREs as "RA undefined". + * Add --got-contents option to readelf to display the contents of Global Offset Table (GOT) sections. diff --git a/gas/NEWS b/gas/NEWS index 4de0cfbcc91..4bd3d747aa5 100644 --- a/gas/NEWS +++ b/gas/NEWS @@ -1,5 +1,8 @@ -*- text -*- +* Emit an SFrame FRE with zero offsets to convey an undefined return address + in the SFrame stack trace format. + * ELF targets can now have section entity size specified for arbitrary sections, using the new attribute letter 'E'. diff --git a/gas/gen-sframe.c b/gas/gen-sframe.c index 8643ee8731e..b1aa8072410 100644 --- a/gas/gen-sframe.c +++ b/gas/gen-sframe.c @@ -164,6 +164,7 @@ sframe_fre_set_ra_track (struct sframe_row_entry *fre, offsetT ra_offset) { fre->ra_loc = SFRAME_FRE_ELEM_LOC_STACK; fre->ra_offset = ra_offset; + fre->ra_undefined_p = false; fre->merge_candidate = false; } @@ -511,6 +512,8 @@ sframe_row_entry_new (void) initialize it in sframe_row_entry_initialize () with the sticky bit if set. */ fre->mangled_ra_p = false; + /* Reset the RA undefined status by to zero by default. */ + fre->ra_undefined_p = false; return fre; } @@ -552,6 +555,7 @@ output_sframe_row_entry (symbolS *fde_start_addr, unsigned int fre_num_offsets; unsigned int fre_offset_size; unsigned int fre_base_reg; + bool fre_mangled_ra_p; expressionS exp; unsigned int fre_addr_size; @@ -581,14 +585,30 @@ output_sframe_row_entry (symbolS *fde_start_addr, } /* Create the fre_info using the CFA base register, number of offsets and max - size of offset in this frame row entry. */ - fre_base_reg = get_fre_base_reg_id (sframe_fre); - fre_num_offsets = get_fre_num_offsets (sframe_fre); - fre_offset_size = sframe_get_fre_offset_size (sframe_fre); + size of offset in this frame row entry. Represent RA undefined as FRE + without any offsets and all FRE info word fields zeroed. */ + if (sframe_fre->ra_undefined_p) + { + fre_base_reg = 0; + fre_num_offsets = 0; + fre_offset_size = 0; + fre_mangled_ra_p = 0; + } + else + { + fre_base_reg = get_fre_base_reg_id (sframe_fre); + fre_num_offsets = get_fre_num_offsets (sframe_fre); + fre_offset_size = sframe_get_fre_offset_size (sframe_fre); + fre_mangled_ra_p = sframe_fre->mangled_ra_p; + } fre_info = sframe_set_fre_info (fre_base_reg, fre_num_offsets, - fre_offset_size, sframe_fre->mangled_ra_p); + fre_offset_size, fre_mangled_ra_p); out_one (fre_info); + /* Represent RA undefined as FRE without any offsets. */ + if (sframe_fre->ra_undefined_p) + return; + idx = sframe_fre_offset_func_map_index (fre_offset_size); gas_assert (idx < SFRAME_FRE_OFFSET_FUNC_MAP_INDEX_MAX); @@ -944,6 +964,10 @@ sframe_row_entry_initialize (struct sframe_row_entry *cur_fre, /* Treat RA mangling as a sticky bit. It retains its value until another .cfi_negate_ra_state is seen. */ cur_fre->mangled_ra_p = prev_fre->mangled_ra_p; + /* Treat RA undefined as a sticky bit. It retains its value until a + .cfi_offset RA, .cfi_register RA, .cfi_restore RA, or .cfi_same_value RA + is seen. */ + cur_fre->ra_undefined_p = prev_fre->ra_undefined_p; } /* Return SFrame register name for SP, FP, and RA, or NULL if other. */ @@ -1319,6 +1343,7 @@ sframe_xlate_do_restore (struct sframe_xlate_ctx *xlate_ctx, gas_assert (cur_fre); cur_fre->ra_loc = cie_fre->ra_loc; cur_fre->ra_offset = cie_fre->ra_offset; + cur_fre->ra_undefined_p = cie_fre->ra_undefined_p; cur_fre->merge_candidate = false; } return SFRAME_XLATE_OK; @@ -1665,9 +1690,15 @@ sframe_xlate_do_cfi_escape (const struct sframe_xlate_ctx *xlate_ctx, /* Translate DW_CFA_undefined into SFrame context. DW_CFA_undefined op indicates that from now on, the previous value of - register can’t be restored anymore. In SFrame stack trace, we cannot - represent such a semantic. So, we skip generating an SFrame FDE for this, - when a register of interest is used with DW_CFA_undefined. + register can’t be restored anymore. In DWARF, for the return address (RA) + register, this indicates to an unwinder that there is no return address + and the unwind is complete. + + In SFrame, represent the use of the RA register with DW_CFA_undefined as + SFrame FRE without any offsets. Stack tracers can use this as indication + that an outermost frame has been reached and the stack trace is complete. + The use of other registers of interest with DW_CFA_undefined cannot be + represented in SFrame. Therefore skip generating an SFrame FDE. Return SFRAME_XLATE_OK if success. */ @@ -1676,15 +1707,24 @@ sframe_xlate_do_cfi_undefined (const struct sframe_xlate_ctx *xlate_ctx ATTRIBUT const struct cfi_insn_data *cfi_insn) { if (cfi_insn->u.r == SFRAME_CFA_FP_REG - || cfi_insn->u.r == SFRAME_CFA_RA_REG || cfi_insn->u.r == SFRAME_CFA_SP_REG) { as_warn (_("no SFrame FDE emitted; %s reg %u in .cfi_undefined"), sframe_register_name (cfi_insn->u.r), cfi_insn->u.r); return SFRAME_XLATE_ERR_NOTREPRESENTED; /* Not represented. */ } + else if (cfi_insn->u.r == SFRAME_CFA_RA_REG) + { + /* Represent RA undefined (i.e. outermost frame) as FRE without any + offsets. */ + struct sframe_row_entry *cur_fre = xlate_ctx->cur_fre; + + gas_assert (cur_fre); + /* Set RA undefined status bit. */ + cur_fre->ra_undefined_p = true; + cur_fre->merge_candidate = false; + } - /* Safe to skip. */ return SFRAME_XLATE_OK; } @@ -1732,6 +1772,7 @@ sframe_xlate_do_same_value (const struct sframe_xlate_ctx *xlate_ctx, { cur_fre->ra_loc = SFRAME_FRE_ELEM_LOC_REG; cur_fre->ra_offset = 0; + cur_fre->ra_undefined_p = false; cur_fre->merge_candidate = false; } else if (cfi_insn->u.r == SFRAME_CFA_FP_REG) diff --git a/gas/gen-sframe.h b/gas/gen-sframe.h index 8ad521b5cbe..cf9f5987bf5 100644 --- a/gas/gen-sframe.h +++ b/gas/gen-sframe.h @@ -65,6 +65,9 @@ struct sframe_row_entry /* Whether the return address is mangled with pauth code. */ bool mangled_ra_p; + /* Whether RA is undefined. */ + bool ra_undefined_p; + /* Track CFA base (architectural) register ID. */ unsigned int cfa_base_reg; /* Offset from the CFA base register for recovering CFA. */ diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-ra-undefined-1.d b/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-ra-undefined-1.d new file mode 100644 index 00000000000..f6bd6d71008 --- /dev/null +++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-ra-undefined-1.d @@ -0,0 +1,20 @@ +#as: --gsframe +#objdump: --sframe=.sframe +#name: SFrame generation on aarch64 - .cfi_undefined RA +#... +Contents of the SFrame section .sframe: + Header : + + Version: SFRAME_VERSION_2 + Flags: SFRAME_F_FDE_FUNC_START_PCREL + Num FDEs: 1 + Num FREs: 4 + + Function Index : + + func idx \[0\]: pc = 0x0, size = 16 bytes + STARTPC +CFA +FP +RA + + 0+0000 +sp\+0 +u +u + + 0+0004 +sp\+16 +c\-16 +c\-8 + + 0+0008 +RA undefined + 0+000c +RA undefined diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-ra-undefined-1.s b/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-ra-undefined-1.s new file mode 100644 index 00000000000..7b28ab8f652 --- /dev/null +++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-ra-undefined-1.s @@ -0,0 +1,13 @@ + .cfi_startproc + stp fp, lr, [sp, #-16]! + .cfi_def_cfa_offset 16 + .cfi_offset 29, -16 + .cfi_offset 30, -8 + nop + .cfi_undefined 30 + ldp fp, lr, [sp], #16 + .cfi_restore 20 + .cfi_restore 19 + .cfi_def_cfa_offset 0 + ret lr + .cfi_endproc diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe-s390x-ra-undefined-1.d b/gas/testsuite/gas/cfi-sframe/cfi-sframe-s390x-ra-undefined-1.d new file mode 100644 index 00000000000..dfd47e30bbe --- /dev/null +++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe-s390x-ra-undefined-1.d @@ -0,0 +1,21 @@ +#name: SFrame generation on s390x - .cfi_undefined RA +#as: --gsframe +#objdump: --sframe=.sframe +#... +Contents of the SFrame section .sframe: + + Header : + + Version: SFRAME_VERSION_2 + Flags: SFRAME_F_FDE_FUNC_START_PCREL + Num FDEs: 1 + Num FREs: 4 + + Function Index : + + func idx \[0\]: pc = 0x0, size = 18 bytes + STARTPC +CFA +FP +RA + + 0+0000 +sp\+160 +u +u + + 0+0006 +sp\+160 +u +c\-48 + + 0+000a +RA undefined + 0+0010 +sp\+160 +u +u + diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe-s390x-ra-undefined-1.s b/gas/testsuite/gas/cfi-sframe/cfi-sframe-s390x-ra-undefined-1.s new file mode 100644 index 00000000000..2117a4ca2f0 --- /dev/null +++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe-s390x-ra-undefined-1.s @@ -0,0 +1,11 @@ + .cfi_startproc + stmg %r14,%r15,112(%r15) + .cfi_offset 14, -48 + .cfi_offset 15, -40 + nop + .cfi_undefined 14 + lmg %r14,%r15,112(%r15) + .cfi_restore 15 + .cfi_restore 14 + br %r14 + .cfi_endproc diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-ra-undefined-1.d b/gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-ra-undefined-1.d new file mode 100644 index 00000000000..a635c3cd9cb --- /dev/null +++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-ra-undefined-1.d @@ -0,0 +1,22 @@ +#as: --gsframe -O0 +#objdump: --sframe=.sframe +#name: SFrame generation on x86_64 - .cfi_undefined RA +#... +Contents of the SFrame section .sframe: + + Header : + + Version: SFRAME_VERSION_2 + Flags: SFRAME_F_FDE_FUNC_START_PCREL + CFA fixed RA offset: \-8 + Num FDEs: 1 + Num FREs: 4 + + Function Index : + + func idx \[0\]: pc = 0x0, size = 6 bytes + STARTPC +CFA +FP +RA + + 0+0000 +sp\+8 +u +f + + 0+0001 +sp\+16 +c\-16 +f + + 0+0004 +fp\+16 +c\-16 +f + + 0+0005 +RA undefined diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-ra-undefined-1.s b/gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-ra-undefined-1.s new file mode 100644 index 00000000000..0f5b9c71715 --- /dev/null +++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-ra-undefined-1.s @@ -0,0 +1,11 @@ + .cfi_startproc + pushq %rbp + .cfi_def_cfa_offset 16 + .cfi_offset 6, -16 + movq %rsp, %rbp + .cfi_def_cfa_register 6 + nop + .cfi_undefined 16 + .cfi_def_cfa 7, 8 + ret + .cfi_endproc diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp b/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp index 7c93164c4c6..20828516546 100644 --- a/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp +++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp @@ -66,6 +66,7 @@ if { [istarget "x86_64-*-*"] && [gas_sframe_check] } then { run_dump_test "cfi-sframe-x86_64-empty-2" run_dump_test "cfi-sframe-x86_64-empty-3" run_dump_test "cfi-sframe-x86_64-empty-4" + run_dump_test "cfi-sframe-x86_64-ra-undefined-1" set ASFLAGS "$old_ASFLAGS" } } @@ -77,6 +78,7 @@ if { [istarget "aarch64*-*-*"] && [gas_sframe_check] } then { run_dump_test "cfi-sframe-aarch64-3" run_dump_test "cfi-sframe-aarch64-4" run_dump_test "cfi-sframe-aarch64-pac-ab-key-1" + run_dump_test "cfi-sframe-aarch64-ra-undefined-1" } # s390x specific tests @@ -91,4 +93,5 @@ if { [istarget "s390x*-*-*"] && [gas_sframe_check] } then { run_dump_test "cfi-sframe-s390x-fpra-offset-2" run_dump_test "cfi-sframe-s390x-fpra-register-1" run_dump_test "cfi-sframe-s390x-fpra-register-2" + run_dump_test "cfi-sframe-s390x-ra-undefined-1" } diff --git a/include/sframe.h b/include/sframe.h index 7523adbef3a..127bf375057 100644 --- a/include/sframe.h +++ b/include/sframe.h @@ -287,6 +287,7 @@ typedef struct sframe_fre_info #define SFRAME_V1_FRE_OFFSET_COUNT(data) (((data) >> 1) & 0xf) #define SFRAME_V1_FRE_OFFSET_SIZE(data) (((data) >> 5) & 0x3) #define SFRAME_V1_FRE_MANGLED_RA_P(data) (((data) >> 7) & 0x1) +#define SFRAME_V2_FRE_RA_UNDEFINED_P(data) (SFRAME_V1_FRE_OFFSET_COUNT (data) == 0) /* SFrame Frame Row Entry definitions. diff --git a/libsframe/doc/sframe-spec.texi b/libsframe/doc/sframe-spec.texi index 73060ff8451..689cc28add7 100644 --- a/libsframe/doc/sframe-spec.texi +++ b/libsframe/doc/sframe-spec.texi @@ -171,6 +171,11 @@ by CFA offset alignment factor and then revert CFA offset adjustment). @end itemize @item [Errata 1] An ELF SFrame section has the type SHT_GNU_SFRAME. +@item +[Errata 2] An SFrame FRE info word offset count of zero indicates that the +return address (RA) is undefined for the range of PCs covered by the SFrame FRE. +A stack tracer may use this as indication that an outermost frame has been +reached and the stack trace is complete. @end itemize SFrame version 1 is now obsolete and should not be used. @@ -777,7 +782,10 @@ SFRAME_FRE_OFFSET_4B. @item 1-4 @tab @code{fre_offset_count} @tab A max value of 15 is allowed. Typically, a value of upto 3 is sufficient -for most ABIs to track all three of CFA, FP and RA. +for most ABIs to track all three of CFA, FP and RA. A value of zero indicates +that the return address (RA) is undefined. A stack tracer may use this as +indication that an outermost frame has been reached and the stack trace is +complete. @item 0 @tab @code{fre_cfa_base_reg_id} diff --git a/libsframe/sframe-dump.c b/libsframe/sframe-dump.c index d55d3847194..1290966439f 100644 --- a/libsframe/sframe-dump.c +++ b/libsframe/sframe-dump.c @@ -130,6 +130,7 @@ dump_sframe_func_with_fres (sframe_decoder_ctx *sfd_ctx, uint64_t func_start_pc_vma = 0; uint64_t fre_start_pc_vma = 0; const char *base_reg_str[] = {"fp", "sp"}; + bool ra_undefined_p = false; int32_t cfa_offset = 0; int32_t fp_offset = 0; int32_t ra_offset = 0; @@ -180,15 +181,25 @@ dump_sframe_func_with_fres (sframe_decoder_ctx *sfd_ctx, : func_start_pc_vma + fre.fre_start_addr); /* FIXME - fixup the err caching in array. - assert no error for base reg id. */ + assert no error for base reg id and RA undefined. */ base_reg_id = sframe_fre_get_base_reg_id (&fre, &err[0]); + ra_undefined_p = sframe_fre_get_ra_undefined_p (sfd_ctx, &fre, &err[0]); cfa_offset = sframe_fre_get_cfa_offset (sfd_ctx, &fre, &err[0]); fp_offset = sframe_fre_get_fp_offset (sfd_ctx, &fre, &err[1]); ra_offset = sframe_fre_get_ra_offset (sfd_ctx, &fre, &err[2]); - /* Dump CFA info. */ + /* Dump VMA. */ printf ("\n"); printf (" %016"PRIx64, fre_start_pc_vma); + + /* Dump RA undefined (FRE without any offsets). */ + if (ra_undefined_p) + { + printf (" RA undefined"); + continue; + } + + /* Dump CFA info. */ sprintf (temp, "%s+%d", base_reg_str[base_reg_id], cfa_offset); printf (" %-10s", temp); diff --git a/libsframe/sframe.c b/libsframe/sframe.c index bd39780a913..9d20f2e2d71 100644 --- a/libsframe/sframe.c +++ b/libsframe/sframe.c @@ -134,7 +134,7 @@ sframe_get_fre_ra_mangled_p (uint8_t fre_info) static bool sframe_get_fre_ra_undefined_p (uint8_t fre_info) { - return SFRAME_V1_FRE_OFFSET_COUNT (fre_info) == 0; + return SFRAME_V2_FRE_RA_UNDEFINED_P (fre_info); } /* Access functions for info from function descriptor entry. */ @@ -729,7 +729,8 @@ sframe_fre_get_fp_offset (sframe_decoder_ctx *dctx, int8_t fp_offset = sframe_decoder_get_fixed_fp_offset (dctx); /* If the FP offset is not being tracked, return the fixed FP offset from the SFrame header. */ - if (fp_offset != SFRAME_CFA_FIXED_FP_INVALID) + if (fp_offset != SFRAME_CFA_FIXED_FP_INVALID + && !sframe_get_fre_ra_undefined_p (fre->fre_info)) { if (errp) *errp = 0; @@ -760,7 +761,8 @@ sframe_fre_get_ra_offset (sframe_decoder_ctx *dctx, int8_t ra_offset = sframe_decoder_get_fixed_ra_offset (dctx); /* If the RA offset was not being tracked, return the fixed RA offset from the SFrame header. */ - if (ra_offset != SFRAME_CFA_FIXED_RA_INVALID) + if (ra_offset != SFRAME_CFA_FIXED_RA_INVALID + && !sframe_get_fre_ra_undefined_p (fre->fre_info)) { if (errp) *errp = 0;