From: Jens Remus <jremus@linux.ibm.com>
To: Indu Bhagat <indu.bhagat@oracle.com>, binutils@sourceware.org
Cc: Andreas Krebbel <krebbel@linux.ibm.com>
Subject: Re: [PATCH v3 09/15] gas: User readable warnings if SFrame FDE is not generated
Date: Fri, 3 May 2024 14:30:13 +0200 [thread overview]
Message-ID: <b27ff422-b70a-4ba6-8ba1-6438bc0373e5@linux.ibm.com> (raw)
In-Reply-To: <5591cd7d-8464-4d71-8f02-aa88af36fcd9@oracle.com>
Am 18.04.2024 um 22:33 schrieb Indu Bhagat:
> On 4/12/24 07:47, Jens Remus wrote:
>> The following generic warning message, which is printed whenever the
>> assembler skips generation of SFrame FDE, is not very helpful for the
>> user:
>>
>> skipping SFrame FDE due to DWARF CFI op <name> (0x<hexval>)
>>
>> Whenever possible print meaningful warning messages, when the assembler
>> skips generation of SFrame FDE:
>>
>
> My intention below is to keep warning messages terse but useful.
>
>> - skipping SFrame FDE due to .cfi_def_cfa defining non-SP/FP register
>> <regno> as CFA base register
>
> .cfi_def_cfa _is_ used to specify the CFA base register. So I suggest we
> re-word this to following (and hence, removing the redundancy):
>
> skipping SFrame FDE; non-SP/FP register <regno> in .cfi_def_cfa
Done.
>
> or if (;) is unappetizing:
>
> skipping SFrame FDE due to non-SP/FP register <regno> in .cfi_def_cfa
>
> (replacing ; with "due to", if you prefer, applies to all comments below)
I like the terse format. Especially as it saves some characters for the longer reason descriptions.
>
>> - skipping SFrame FDE due to .cfi_def_cfa_register defining non-SP/FP
>> register <regno> as CFA base register
>
> skipping SFrame FDE; non-SP/FP register <regno> in .cfi_def_cfa_register
Done.
>
>> - skipping SFrame FDE due to .cfi_def_cfa_offset without CFA base
>> register in effect
>
> skipping SFrame FDE; .cfi_def_cfa_offset specified when no CFA base
> register in effect
"when no" or "without" (see "without prior SFrame FRE state" below)?
>
>> - skipping SFrame FDE due to .cfi_def_cfa_offset with non-SP/FP register
>> <regno> as CFA base register in effect
>
> I find this very confusing. Can we not add this warning? Such a case
> should not happen as we have handled the respective cases in
> sframe_xlate_do_def_cfa and sframe_xlate_do_def_cfa_register ?
Done. I finally got the point. I have added the following comment as explanation:
/* No CFA base register in effect. Non-SP/FP CFA base register should
not occur, as sframe_xlate_do_def_cfa[_register] would detect this. */
>
>> - skipping SFrame FDE due to .cfi_val_offset specifying {FP|RA} register
>
> skipping SFrame FDE; FP/RA register <regno> in .cfi_val_offset
Done.
>
>> - skipping SFrame FDE due to .cfi_remember_state without SFrame FRE
>> state
>
> skipping SFrame FDE; .cfi_remember_state without prior SFrame FRE state
Done.
>
>> - skipping SFrame FDE due to .cfi_register specifying {SP|FP|RA}
>> register
>
> skipping SFrame FDE; FP/RA register <regno> in .cfi_register
Done.
>
>> - skipping SFrame FDE due to non-default return-address register <regno>
>
> skipping SFrame FDE; non-default RA register <regno>
Done. Using the abbreviation "RA" instead of "return address" aligns well with the other warnings.
For consistency I have changed the following SFrame warnings as well:
skipping SFrame FDE; CFI insn <name> (<hexval>)
skipping SFrame FDE; FP without RA on stack
skipping SFrame FDE; .cfi_window_save
>
>>
>> gas/
>> * gen-sframe.h (SFRAME_FRE_BASE_REG_INVAL): New macro for
>> invalid SFrame FRE CFA base register value of -1.
>> * gen-sframe.c: User readable warnings if SFrame FDE is not
>> generated.
>>
>> gas/testsuite/
>> * gas/cfi-sframe/common-empty-1.d: Update generic SFrame test
>> case to updated warning message texts.
>> * gas/cfi-sframe/common-empty-2.d: Likewise.
>> * gas/cfi-sframe/common-empty-3.d: Likewise.
>>
>> Reviewed-by: Andreas Krebbel <krebbel@linux.ibm.com>
>> Signed-off-by: Jens Remus <jremus@linux.ibm.com>
>> ---
>>
>> Notes (jremus):
>> Changes v2 -> v3:
>> - Updated SFrame warning message texts as suggested by Indu,
>> except for
>> the .cfi_def_cfa[_register] ones. I think it would be helpful
>> for the
>> user to know that the issue is caused by a non-SP/FP register. But
>> maybe that is because I am new to CFI and those that would
>> actually
>> debug the cause for these warnings would not need this extra
>> information? Anyhow, Indu, if you still prefer your suggestions I
>> would go with yours.
>> The ".cfi_remember_state without SFrame FRE state" warning
>> needs to
>> remain, as there would otherwise not be any warning at all. The
>> reason
>> is that sframe_do_cfi_insn now expects any of its called CFI
>> processing functions to emit a warning, if they return with an
>> error,
>> such as SFRAME_XLATE_ERR_NOTREPRESENTED. Silently skipping
>> SFrame FDE
>> does not seem an acceptable approach to me.
>> - Do not test sframe_ra_tracking_p when determining the SFrame
>> register
>> name in sframe_register_name. The RA register name does not
>> depend on
>> whether RA tracking is used or not.
>> - Corrected formatting of ChangeLog in commit message.
>>
>> gas/gen-sframe.c | 95 ++++++++++++++-----
>> gas/gen-sframe.h | 2 +
>> gas/testsuite/gas/cfi-sframe/common-empty-1.d | 2 +-
>> gas/testsuite/gas/cfi-sframe/common-empty-2.d | 2 +-
>> gas/testsuite/gas/cfi-sframe/common-empty-3.d | 2 +-
>> 5 files changed, 75 insertions(+), 28 deletions(-)
>>
>> diff --git a/gas/gen-sframe.c b/gas/gen-sframe.c
>> index f47f51c7a354..a3b6f75cfe85 100644
>> --- a/gas/gen-sframe.c
>> +++ b/gas/gen-sframe.c
>> @@ -867,7 +867,7 @@ sframe_row_entry_new (void)
>> struct sframe_row_entry *fre = XCNEW (struct sframe_row_entry);
>> /* Reset cfa_base_reg to -1. A value of 0 will imply some valid
>> register
>> for the supported arches. */
>> - fre->cfa_base_reg = -1;
>> + fre->cfa_base_reg = SFRAME_FRE_BASE_REG_INVAL;
>> fre->merge_candidate = true;
>> /* Reset the mangled RA status bit to zero by default. We will
>> initialize it in
>> sframe_row_entry_initialize () with the sticky bit if set. */
>> @@ -922,6 +922,23 @@ sframe_row_entry_initialize (struct
>> sframe_row_entry *cur_fre,
>> cur_fre->mangled_ra_p = prev_fre->mangled_ra_p;
>> }
>> +/* Return SFrame register name for SP, FP, and RA, or NULL if other. */
>> +
>> +static const char *
>> +sframe_register_name (unsigned int reg)
>> +{
>> + if (reg == SFRAME_CFA_SP_REG)
>> + return "SP";
>> + else if (reg == SFRAME_CFA_FP_REG)
>> + return "FP";
>> +#ifdef SFRAME_FRE_RA_TRACKING
>> + else if (reg == SFRAME_CFA_RA_REG)
>> + return "RA";
>> +#endif
>> + else
>> + return NULL;
>> +}
>> +
>> /* Translate DW_CFA_advance_loc into SFrame context.
>> Return SFRAME_XLATE_OK if success. */
>> @@ -990,7 +1007,12 @@ sframe_xlate_do_def_cfa (struct sframe_xlate_ctx
>> *xlate_ctx,
>> SFrame stack trace info for the function. */
>> if (cfi_insn->u.r != SFRAME_CFA_SP_REG
>> && cfi_insn->u.r != SFRAME_CFA_FP_REG)
>> - return SFRAME_XLATE_ERR_NOTREPRESENTED; /* Not represented. */
>> + {
>> + as_warn (_("skipping SFrame FDE due to .cfi_def_cfa defining "
>> + "non-SP/FP register %u as CFA base register"),
>> + cfi_insn->u.r);
>> + return SFRAME_XLATE_ERR_NOTREPRESENTED; /* Not represented. */
>> + }
>> sframe_fre_set_cfa_base_reg (cur_fre, cfi_insn->u.ri.reg);
>> sframe_fre_set_cfa_offset (cur_fre, cfi_insn->u.ri.offset);
>> cur_fre->merge_candidate = false;
>> @@ -1015,7 +1037,12 @@ sframe_xlate_do_def_cfa_register (struct
>> sframe_xlate_ctx *xlate_ctx,
>> skip creating SFrame stack trace info for the function. */
>> if (cfi_insn->u.r != SFRAME_CFA_SP_REG
>> && cfi_insn->u.r != SFRAME_CFA_FP_REG)
>> - return SFRAME_XLATE_ERR_NOTREPRESENTED; /* Not represented. */
>> + {
>> + as_warn (_("skipping SFrame FDE due to .cfi_def_cfa_register
>> defining "
>> + "non-SP/FP register %u as CFA base register"),
>> + cfi_insn->u.r);
>> + return SFRAME_XLATE_ERR_NOTREPRESENTED; /* Not represented. */
>> + }
>> sframe_fre_set_cfa_base_reg (cur_fre, cfi_insn->u.ri.reg);
>> sframe_fre_set_cfa_offset (cur_fre, last_fre->cfa_offset);
>> cur_fre->merge_candidate = false;
>> @@ -1046,7 +1073,16 @@ sframe_xlate_do_def_cfa_offset (struct
>> sframe_xlate_ctx *xlate_ctx,
>> cur_fre->merge_candidate = false;
>> }
>> else
>> - return SFRAME_XLATE_ERR_NOTREPRESENTED;
>> + {
>> + if (cur_fre->cfa_base_reg == SFRAME_FRE_BASE_REG_INVAL)
>> + as_warn (_("skipping SFrame FDE due to .cfi_def_cfa_offset without "
>> + "CFA base register in effect"));
>> + else
>> + as_warn (_("skipping SFrame FDE due to .cfi_def_cfa_offset with "
>> + "non-SP/FP register %u as CFA base register in effect"),
>> + cur_fre->cfa_base_reg);
>> + return SFRAME_XLATE_ERR_NOTREPRESENTED;
>> + }
>> return SFRAME_XLATE_OK;
>> }
>> @@ -1096,13 +1132,16 @@ sframe_xlate_do_val_offset (struct
>> sframe_xlate_ctx *xlate_ctx ATTRIBUTE_UNUSED,
>> register is not interesting (FP or RA reg), the current
>> DW_CFA_val_offset
>> instruction can be safely skipped without sacrificing the
>> asynchronicity of
>> stack trace information. */
>> - if (cfi_insn->u.r == SFRAME_CFA_FP_REG)
>> - return SFRAME_XLATE_ERR_NOTREPRESENTED; /* Not represented. */
>> + if (cfi_insn->u.r == SFRAME_CFA_FP_REG
>> #ifdef SFRAME_FRE_RA_TRACKING
>> - else if (sframe_ra_tracking_p ()
>> - && cfi_insn->u.r == SFRAME_CFA_RA_REG)
>> - return SFRAME_XLATE_ERR_NOTREPRESENTED; /* Not represented. */
>> + || (sframe_ra_tracking_p () && cfi_insn->u.r == SFRAME_CFA_RA_REG)
>> #endif
>> + )
>> + {
>> + as_warn (_("skipping SFrame FDE due to .cfi_val_offset
>> specifying %s register"),
>> + sframe_register_name (cfi_insn->u.r));
>> + return SFRAME_XLATE_ERR_NOTREPRESENTED; /* Not represented. */
>> + }
>> /* Safe to skip. */
>> return SFRAME_XLATE_OK;
>> @@ -1124,7 +1163,11 @@ sframe_xlate_do_register (struct
>> sframe_xlate_ctx *xlate_ctx ATTRIBUTE_UNUSED,
>> || (cfi_insn->u.rr.reg1 == SFRAME_CFA_RA_REG)
>> #endif
>> || cfi_insn->u.rr.reg1 == SFRAME_CFA_FP_REG)
>> - return SFRAME_XLATE_ERR_NOTREPRESENTED; /* Not represented. */
>> + {
>> + as_warn (_("skipping SFrame FDE due to .cfi_register specifying
>> %s register"),
>> + sframe_register_name (cfi_insn->u.rr.reg1));
>> + return SFRAME_XLATE_ERR_NOTREPRESENTED; /* Not represented. */
>> + }
>> /* Safe to skip. */
>> return SFRAME_XLATE_OK;
>> @@ -1142,7 +1185,10 @@ sframe_xlate_do_remember_state (struct
>> sframe_xlate_ctx *xlate_ctx)
>> early with non-zero error code, this will cause no SFrame stack
>> trace
>> info for the function involved. */
>> if (!last_fre)
>> - return SFRAME_XLATE_ERR_INVAL;
>> + {
>> + as_warn (_("skipping SFrame FDE due to .cfi_remember_state
>> without SFrame FRE state"));
>
> "without SFrame FRE state" --> "without prior SFrame FRE state" ?
>
>> + return SFRAME_XLATE_ERR_INVAL;
>> + }
>> if (!xlate_ctx->remember_fre)
>> xlate_ctx->remember_fre = sframe_row_entry_new ();
>> @@ -1330,21 +1376,19 @@ sframe_do_cfi_insn (struct sframe_xlate_ctx
>> *xlate_ctx,
>> default:
>> /* Following skipped operations do, however, impact the
>> asynchronicity:
>> - CFI_escape. */
>> - err = SFRAME_XLATE_ERR_NOTREPRESENTED;
>> - }
>> -
>> - /* An error here will cause no SFrame FDE later. Warn the user
>> because this
>> - will affect the overall coverage and hence, asynchronicity. */
>> - if (err)
>> - {
>> - const char *cfi_name = sframe_get_cfi_name (op);
>> -
>> - if (!cfi_name)
>> - cfi_name = _("(unknown)");
>> - as_warn (_("skipping SFrame FDE due to DWARF CFI op %s (%#x)"),
>> - cfi_name, op);
>> + {
>> + const char *cfi_name = sframe_get_cfi_name (op);
>> +
>> + if (!cfi_name)
>> + cfi_name = _("(unknown)");
>> + as_warn (_("skipping SFrame FDE due to DWARF CFI op %s (%#x)"),
>> + cfi_name, op);
>> + err = SFRAME_XLATE_ERR_NOTREPRESENTED;
>
> <>/GCC/gcc-upstream/gcc/contrib/check_GNU_style.py patch gives:
>
> === ERROR type #1: blocks of 8 spaces should be replaced with tabs (1
> error(s)) ===
> gas/gen-sframe.c:1386:0: err = SFRAME_XLATE_ERR_NOTREPRESENTED;
Corrected.
>
> I dont think it is a must-be-used-script for binutils project, but for
> my commits I have used this script to keep code base aligned to same
> formatting style.
Thanks for sharing! That is really helful!
>
> PS: Not all errors reported by the script need to be fixed.
>
>> + }
>> }
>> + /* Any error will cause no SFrame FDE later. The user has already
>> been
>> + warned. */
>> return err;
>> }
>> @@ -1361,7 +1405,8 @@ sframe_do_fde (struct sframe_xlate_ctx *xlate_ctx,
>> /* SFrame format cannot represent a non-default DWARF return
>> column reg. */
>> if (xlate_ctx->dw_fde->return_column != DWARF2_DEFAULT_RETURN_COLUMN)
>> {
>> - as_warn (_("skipping SFrame FDE due to non-default DWARF return
>> column"));
>> + as_warn (_("skipping SFrame FDE due to non-default
>> return-address register %u"),
>> + xlate_ctx->dw_fde->return_column);
>
> return-address -> "return address" or even just RA.
>
>> return SFRAME_XLATE_ERR_NOTREPRESENTED;
>> }
>> diff --git a/gas/gen-sframe.h b/gas/gen-sframe.h
>> index fbe2fd5d9368..8ed46dbb087b 100644
>> --- a/gas/gen-sframe.h
>> +++ b/gas/gen-sframe.h
>> @@ -24,6 +24,8 @@
>> #define SFRAME_FRE_ELEM_LOC_REG 0
>> #define SFRAME_FRE_ELEM_LOC_STACK 1
>> +#define SFRAME_FRE_BASE_REG_INVAL ((unsigned int)-1)
>> +
>> /* SFrame Frame Row Entry (FRE).
>> A frame row entry is a slice of the frame and can be valid for a
>> set of
>> diff --git a/gas/testsuite/gas/cfi-sframe/common-empty-1.d
>> b/gas/testsuite/gas/cfi-sframe/common-empty-1.d
>> index d7756302b559..08731b069229 100644
>> --- a/gas/testsuite/gas/cfi-sframe/common-empty-1.d
>> +++ b/gas/testsuite/gas/cfi-sframe/common-empty-1.d
>> @@ -1,5 +1,5 @@
>> #as: --gsframe
>> -#warning: skipping SFrame FDE due to DWARF CFI op
>> DW_CFA_remember_state \(0xa\)
>> +#warning: skipping SFrame FDE due to \.cfi_remember_state without
>> SFrame FRE state
>> #objdump: --sframe=.sframe
>> #name: Uninteresting cfi directives generate an empty SFrame section
>> #...
>> diff --git a/gas/testsuite/gas/cfi-sframe/common-empty-2.d
>> b/gas/testsuite/gas/cfi-sframe/common-empty-2.d
>> index 20282c7854e8..e759cddfcc20 100644
>> --- a/gas/testsuite/gas/cfi-sframe/common-empty-2.d
>> +++ b/gas/testsuite/gas/cfi-sframe/common-empty-2.d
>> @@ -1,5 +1,5 @@
>> #as: --gsframe
>> -#warning: skipping SFrame FDE due to DWARF CFI op
>> DW_CFA_def_cfa_offset \(0xe\)
>> +#warning: skipping SFrame FDE due to \.cfi_def_cfa_offset without CFA
>> base register in effect
>> #objdump: --sframe=.sframe
>> #name: SFrame supports only FP/SP based CFA
>> #...
>> diff --git a/gas/testsuite/gas/cfi-sframe/common-empty-3.d
>> b/gas/testsuite/gas/cfi-sframe/common-empty-3.d
>> index d17521dd88ea..5cc37d5ff440 100644
>> --- a/gas/testsuite/gas/cfi-sframe/common-empty-3.d
>> +++ b/gas/testsuite/gas/cfi-sframe/common-empty-3.d
>> @@ -1,5 +1,5 @@
>> #as: --gsframe
>> -#warning: skipping SFrame FDE due to non-default DWARF return column
>> +#warning: skipping SFrame FDE due to non-default return-address
>> register 0
>> #objdump: --sframe=.sframe
>> #name: SFrame supports only default return column
>> #...
>
Regards,
Jens
--
Jens Remus
Linux on Z Development (D3303) and z/VSE Support
+49-7031-16-1128 Office
jremus@de.ibm.com
IBM
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next prev parent reply other threads:[~2024-05-03 12:30 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-12 14:47 [PATCH v3 00/15] sframe: Enhancements to SFrame info generation Jens Remus
2024-04-12 14:47 ` [PATCH v3 01/15] x86: Remove unused SFrame CFI RA register variable Jens Remus
2024-04-12 14:47 ` [PATCH v3 02/15] gas: Enhance arch-specific SFrame configuration descriptions Jens Remus
2024-04-18 7:39 ` Indu Bhagat
2024-05-03 12:30 ` Jens Remus
2024-04-12 14:47 ` [PATCH v3 03/15] readelf/objdump: Dump SFrame CFA fixed FP and RA offsets Jens Remus
2024-04-18 7:39 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 04/15] readelf/objdump: Display SFrame fixed RA offset as 'f' in dump Jens Remus
2024-04-18 7:40 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 05/15] gas: Print DWARF call frame insn name in SFrame warning message Jens Remus
2024-04-18 7:40 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 06/15] gas: Skip SFrame FDE if CFI specifies non-FP/SP base register Jens Remus
2024-04-18 7:40 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 07/15] gas: Warn if SFrame FDE is skipped due to non-default return column Jens Remus
2024-04-18 7:40 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 08/15] gas: Refactor SFrame CFI opcode DW_CFA_register processing Jens Remus
2024-04-18 7:40 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 09/15] gas: User readable warnings if SFrame FDE is not generated Jens Remus
2024-04-18 20:33 ` Indu Bhagat
2024-05-03 12:30 ` Jens Remus [this message]
2024-05-03 23:41 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 10/15] gas: Skip SFrame FDE if FP without RA on stack Jens Remus
2024-04-16 13:14 ` Jens Remus
2024-04-17 23:56 ` Indu Bhagat
2024-04-18 10:27 ` Jens Remus
2024-04-18 20:35 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 11/15] gas: Skip SFrame FDE if .cfi_window_save Jens Remus
2024-04-18 20:36 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 12/15] gas: Don't skip SFrame FDE if .cfi_register specifies RA w/o tracking Jens Remus
2024-04-18 20:36 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 13/15] gas: Don't skip SFrame FDE if .cfi_register specifies SP register Jens Remus
2024-04-18 20:37 ` Indu Bhagat
2024-04-19 13:13 ` Jens Remus
2024-04-23 8:15 ` Indu Bhagat
2024-04-25 22:22 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 14/15] gas: Test predicate whether SFrame RA tracking is used Jens Remus
2024-04-18 20:37 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 15/15] gas: Validate SFrame RA tracking and fixed RA offset Jens Remus
2024-04-18 20:38 ` Indu Bhagat
2024-05-03 16:40 ` Jens Remus
2024-05-04 0:22 ` Indu Bhagat
2024-05-06 11:41 ` Jens Remus
2024-05-06 14:39 ` Jens Remus
2024-05-16 20:45 ` Indu Bhagat
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