[PATCH] x86: ld: sframe: Remove SFrame NULL FRE template

[Jens Remus]

A SFrame NULL FRE template is used as NULL value in some but not all
instances to initialize unused elements of SFrame FRE pointer arrays of
fixed size.  Additionally it is erroneously used as SFrame FRE template
for PLT GOT entries.

Define a separate SFrame FRE template for PLT GOT entries with the same
properties as the SFrame NULL FRE and use that for all PLT GOT entries.
Remove the SFrame NULL FRE template, as initialization of unused array
elements is not required, as demonstrated by the instances where it was
not done.

bfd/
	* elf64-x86-64.c (elf_x86_64_sframe_null_fre): Remove.
	(elf_x86_64_sframe_pltgot_fre1): New SFrame FRE template for
	PLT GOT entries.
	(elf_x86_64_sframe_non_lazy_plt,
	elf_x86_64_sframe_non_lazy_ibt_plt): Do not initialize unused
	FRE array elements with elf_x86_64_sframe_null_fre.  Use
	elf_x86_64_sframe_pltgot_fre1 for PLT GOT.
	(elf_x86_64_sframe_plt, elf_x86_64_sframe_ibt_plt): Use
	elf_x86_64_sframe_pltgot_fre1 for PLT GOT.

Signed-off-by: Jens Remus <jremus@linux.ibm.com>
---

Notes (jremus):
    This was noticed when wrongly using the term SFrame NULL FRE in my s390
    SFrame support series:
    https://inbox.sourceware.org/binutils/41c78ff7-d35d-4e70-8719-a6024d8882d2@linux.ibm.com/

 bfd/elf64-x86-64.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index 6867d4934695..b9b3cf831c44 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -868,13 +868,6 @@ static const bfd_byte elf_x86_64_eh_frame_non_lazy_plt[] =
   DW_CFA_nop, DW_CFA_nop, DW_CFA_nop
 };
 
-static const sframe_frame_row_entry elf_x86_64_sframe_null_fre =
-{
-  0,
-  {16, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, /* 12 bytes.  */
-  SFRAME_V1_FRE_INFO (SFRAME_BASE_REG_SP, 1, SFRAME_FRE_OFFSET_1B) /* FRE info.  */
-};
-
 /* .sframe FRE covering the .plt section entry.  */
 static const sframe_frame_row_entry elf_x86_64_sframe_plt0_fre1 =
 {
@@ -923,6 +916,14 @@ static const sframe_frame_row_entry elf_x86_64_sframe_sec_pltn_fre1 =
   SFRAME_V1_FRE_INFO (SFRAME_BASE_REG_SP, 1, SFRAME_FRE_OFFSET_1B) /* FRE info.  */
 };
 
+/* .sframe FRE covering the .plt.got section entry.  */
+static const sframe_frame_row_entry elf_x86_64_sframe_pltgot_fre1 =
+{
+  0, /* SFrame FRE start address.  */
+  {16, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, /* 12 bytes.  */
+  SFRAME_V1_FRE_INFO (SFRAME_BASE_REG_SP, 1, SFRAME_FRE_OFFSET_1B) /* FRE info.  */
+};
+
 /* SFrame helper object for non-lazy PLT.  */
 static const struct elf_x86_sframe_plt elf_x86_64_sframe_non_lazy_plt =
 {
@@ -933,14 +934,14 @@ static const struct elf_x86_sframe_plt elf_x86_64_sframe_non_lazy_plt =
   LAZY_PLT_ENTRY_SIZE,
   1, /* Number of FREs for PLTn.  */
   /* Array of SFrame FREs for plt.  */
-  { &elf_x86_64_sframe_sec_pltn_fre1, &elf_x86_64_sframe_null_fre },
+  { &elf_x86_64_sframe_sec_pltn_fre1 },
   0,
   0, /* There is no second PLT necessary.  */
-  { &elf_x86_64_sframe_null_fre },
+  { },
   NON_LAZY_PLT_ENTRY_SIZE,
   1, /* Number of FREs for PLT GOT.  */
   /* Array of SFrame FREs for PLT GOT.  */
-  { &elf_x86_64_sframe_null_fre },
+  { &elf_x86_64_sframe_pltgot_fre1 },
 };
 
 /* SFrame helper object for non-lazy IBT enabled PLT.  */
@@ -953,14 +954,14 @@ static const struct elf_x86_sframe_plt elf_x86_64_sframe_non_lazy_ibt_plt =
   LAZY_PLT_ENTRY_SIZE,
   1, /* Number of FREs for PLTn.  */
   /* Array of SFrame FREs for plt.  */
-  { &elf_x86_64_sframe_sec_pltn_fre1, &elf_x86_64_sframe_null_fre },
+  { &elf_x86_64_sframe_sec_pltn_fre1 },
   0,
   0, /* There is no second PLT necessary.  */
-  { &elf_x86_64_sframe_null_fre },
+  { },
   LAZY_PLT_ENTRY_SIZE,
   1, /* Number of FREs for PLT GOT.  */
   /* Array of SFrame FREs for PLT GOT.  */
-  { &elf_x86_64_sframe_null_fre },
+  { &elf_x86_64_sframe_pltgot_fre1 },
 };
 
 /* SFrame helper object for lazy PLT. */
@@ -981,7 +982,7 @@ static const struct elf_x86_sframe_plt elf_x86_64_sframe_plt =
   NON_LAZY_PLT_ENTRY_SIZE,
   1, /* Number of FREs for PLT GOT.  */
   /* Array of SFrame FREs for PLT GOT.  */
-  { &elf_x86_64_sframe_null_fre },
+  { &elf_x86_64_sframe_pltgot_fre1 },
 };
 
 /* SFrame helper object for lazy PLT with IBT. */
@@ -1002,7 +1003,7 @@ static const struct elf_x86_sframe_plt elf_x86_64_sframe_ibt_plt =
   LAZY_PLT_ENTRY_SIZE,
   1, /* Number of FREs for PLT GOT.  */
   /* Array of SFrame FREs for PLT GOT.  */
-  { &elf_x86_64_sframe_null_fre },
+  { &elf_x86_64_sframe_pltgot_fre1 },
 };
 
 /* These are the standard parameters.  */
-- 
2.48.1