* [PATCH] libdwfl: Handle unaligned Phdr in dwfl_segment_report_module
@ 2021-12-19 23:45 Mark Wielaard
0 siblings, 0 replies; 2+ messages in thread
From: Mark Wielaard @ 2021-12-19 23:45 UTC (permalink / raw)
To: elfutils-devel; +Cc: Mark Wielaard
The xlate functions only handle correctly aligned buffers. But they do
handle src == dest. So if the source buffer isn't aligned correctly
just copy it first into the destination (which is already correctly
aligned).
Signed-off-by: Mark Wielaard <mark@klomp.org>
---
libdwfl/ChangeLog | 6 ++++++
libdwfl/dwfl_segment_report_module.c | 12 ++++++++++++
2 files changed, 18 insertions(+)
diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index 6c7e0c4a..ac0fbe0f 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,9 @@
+2021-12-19 Mark Wielaard <mark@klomp.org>
+
+ * dwfl_segment_report_module.c (dwfl_segment_report_module): Copy
+ ph_buffer and set xlatefrom.d_buf to phdrsp when ph_buffer is not
+ aligned.
+
2021-12-19 Mark Wielaard <mark@klomp.org>
* dwfl_segment_report_module.c (dwfl_segment_report_module): Copy
diff --git a/libdwfl/dwfl_segment_report_module.c b/libdwfl/dwfl_segment_report_module.c
index 7f756392..de190e90 100644
--- a/libdwfl/dwfl_segment_report_module.c
+++ b/libdwfl/dwfl_segment_report_module.c
@@ -461,6 +461,18 @@ dwfl_segment_report_module (Dwfl *dwfl, int ndx, const char *name,
xlateto.d_buf = phdrsp;
xlateto.d_size = phdrsp_bytes;
+ /* ph_ buffer may be unaligned, in which case xlatetom would not work.
+ xlatetom does work when the in and out d_buf are equal (but not
+ for any other overlap). */
+ size_t phdr_align = (class32
+ ? __alignof__ (Elf32_Phdr)
+ : __alignof__ (Elf64_Phdr));
+ if (((uintptr_t) ph_buffer & (phdr_align - 1)) != 0)
+ {
+ memcpy (phdrsp, ph_buffer, phdrsp_bytes);
+ xlatefrom.d_buf = phdrsp;
+ }
+
/* Track the bounds of the file visible in memory. */
GElf_Off file_trimmed_end = 0; /* Proper p_vaddr + p_filesz end. */
GElf_Off file_end = 0; /* Rounded up to effective page size. */
--
2.30.2
^ permalink raw reply [flat|nested] 2+ messages in thread
* [PATCH] libdwfl: Handle unaligned Phdr in dwfl_segment_report_module
@ 2021-12-20 0:40 Mark Wielaard
0 siblings, 0 replies; 2+ messages in thread
From: Mark Wielaard @ 2021-12-20 0:40 UTC (permalink / raw)
To: elfutils-devel; +Cc: Mark Wielaard
The xlate functions only handle correctly aligned buffers. But they do
handle src == dest. So if the source buffer isn't aligned correctly
just copy it first into the destination (which is already correctly
aligned).
Signed-off-by: Mark Wielaard <mark@klomp.org>
---
libdwfl/ChangeLog | 5 +++++
libdwfl/dwfl_segment_report_module.c | 12 ++++++++++++
2 files changed, 17 insertions(+)
diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index ac0fbe0f..6015f6b7 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,8 @@
+2021-12-19 Mark Wielaard <mark@klomp.org>
+
+ * dwfl_segment_report_module.c (dwfl_segment_report_module): Copy
+ data and set xlatefrom.d_buf to notes when data is not aligned.
+
2021-12-19 Mark Wielaard <mark@klomp.org>
* dwfl_segment_report_module.c (dwfl_segment_report_module): Copy
diff --git a/libdwfl/dwfl_segment_report_module.c b/libdwfl/dwfl_segment_report_module.c
index de190e90..72c85070 100644
--- a/libdwfl/dwfl_segment_report_module.c
+++ b/libdwfl/dwfl_segment_report_module.c
@@ -573,6 +573,18 @@ dwfl_segment_report_module (Dwfl *dwfl, int ndx, const char *name,
xlatefrom.d_size = filesz;
xlateto.d_buf = notes;
xlateto.d_size = filesz;
+
+ /* data may be unaligned, in which case xlatetom would not work.
+ xlatetom does work when the in and out d_buf are equal (but not
+ for any other overlap). */
+ if ((uintptr_t) data != (align == 8
+ ? NOTE_ALIGN8 ((uintptr_t) data)
+ : NOTE_ALIGN4 ((uintptr_t) data)))
+ {
+ memcpy (notes, data, filesz);
+ xlatefrom.d_buf = notes;
+ }
+
if (elf32_xlatetom (&xlateto, &xlatefrom, xencoding) == NULL)
{
free (notes);
--
2.30.2
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