* [PATCH] x86-64: restrict PC32 -> PLT32 conversion
@ 2022-01-05 11:14 Jan Beulich
2022-01-05 14:54 ` H.J. Lu
0 siblings, 1 reply; 2+ messages in thread
From: Jan Beulich @ 2022-01-05 11:14 UTC (permalink / raw)
To: Binutils
Neither non-64-bit code nor uses with a non-zero offset from a symbol
should be converted to PLT32, as an eventual PLT entry would not express
what was requested.
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -8857,6 +8857,8 @@ output_branch (void)
off = 0;
}
+ frag_now->tc_frag_data.code64 = flag_code == CODE_64BIT;
+
/* 1 possible extra opcode + 4 byte displacement go in var part.
Pass reloc in fr_var. */
frag_var (rs_machine_dependent, 5, i.reloc[0], subtype, sym, off, p);
@@ -8985,8 +8987,8 @@ output_jump (void)
}
#if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
- if (size == 4
- && jump_reloc == NO_RELOC
+ if (flag_code == CODE_64BIT && size == 4
+ && jump_reloc == NO_RELOC && i.op[0].disps->X_add_number == 0
&& need_plt32_p (i.op[0].disps->X_add_symbol))
jump_reloc = BFD_RELOC_X86_64_PLT32;
#endif
@@ -12289,7 +12291,8 @@ md_estimate_size_before_relax (fragS *fr
else if (size == 2)
reloc_type = BFD_RELOC_16_PCREL;
#if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
- else if (need_plt32_p (fragP->fr_symbol))
+ else if (fragP->tc_frag_data.code64 && fragP->fr_offset == 0
+ && need_plt32_p (fragP->fr_symbol))
reloc_type = BFD_RELOC_X86_64_PLT32;
#endif
else
--- a/gas/config/tc-i386.h
+++ b/gas/config/tc-i386.h
@@ -283,6 +283,7 @@ struct i386_tc_frag_data
unsigned int mf_type : 3;
unsigned int classified : 1;
unsigned int branch_type : 3;
+ unsigned int code64 : 1; /* Only set by output_branch for now. */
};
/* We need to emit the right NOP pattern in .align frags. This is
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] x86-64: restrict PC32 -> PLT32 conversion
2022-01-05 11:14 [PATCH] x86-64: restrict PC32 -> PLT32 conversion Jan Beulich
@ 2022-01-05 14:54 ` H.J. Lu
0 siblings, 0 replies; 2+ messages in thread
From: H.J. Lu @ 2022-01-05 14:54 UTC (permalink / raw)
To: Jan Beulich; +Cc: Binutils
On Wed, Jan 5, 2022 at 3:14 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> Neither non-64-bit code nor uses with a non-zero offset from a symbol
> should be converted to PLT32, as an eventual PLT entry would not express
> what was requested.
>
> --- a/gas/config/tc-i386.c
> +++ b/gas/config/tc-i386.c
> @@ -8857,6 +8857,8 @@ output_branch (void)
> off = 0;
> }
>
> + frag_now->tc_frag_data.code64 = flag_code == CODE_64BIT;
> +
> /* 1 possible extra opcode + 4 byte displacement go in var part.
> Pass reloc in fr_var. */
> frag_var (rs_machine_dependent, 5, i.reloc[0], subtype, sym, off, p);
> @@ -8985,8 +8987,8 @@ output_jump (void)
> }
>
> #if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
> - if (size == 4
> - && jump_reloc == NO_RELOC
> + if (flag_code == CODE_64BIT && size == 4
> + && jump_reloc == NO_RELOC && i.op[0].disps->X_add_number == 0
> && need_plt32_p (i.op[0].disps->X_add_symbol))
> jump_reloc = BFD_RELOC_X86_64_PLT32;
> #endif
> @@ -12289,7 +12291,8 @@ md_estimate_size_before_relax (fragS *fr
> else if (size == 2)
> reloc_type = BFD_RELOC_16_PCREL;
> #if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
> - else if (need_plt32_p (fragP->fr_symbol))
> + else if (fragP->tc_frag_data.code64 && fragP->fr_offset == 0
> + && need_plt32_p (fragP->fr_symbol))
> reloc_type = BFD_RELOC_X86_64_PLT32;
> #endif
> else
> --- a/gas/config/tc-i386.h
> +++ b/gas/config/tc-i386.h
> @@ -283,6 +283,7 @@ struct i386_tc_frag_data
> unsigned int mf_type : 3;
> unsigned int classified : 1;
> unsigned int branch_type : 3;
> + unsigned int code64 : 1; /* Only set by output_branch for now. */
> };
>
> /* We need to emit the right NOP pattern in .align frags. This is
>
OK.
Thanks.
--
H.J.
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