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dlinfo.3: Document the RTLD_DI_PHDR request

PATCH In review Florian Weimer 2 participants 4 messages Aug 28, 2024 Man-pages: manual pages for Linux -- Sections 2, 3, 4, 5, and 7

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Florian Weimer

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#0 lore raw

PATCH v2 1/1 dlinfo.3: Document the RTLD_DI_PHDR request

First added in glibc 2.36, backported upstream to glibc 2.34, so mention 2.34.1 for the first version.

Signed-off-by Florian Weimer <[email protected]>

---
v2: Fix commit IDs.

 man/man3/dlinfo.3 | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)
man/man3/dlinfo.3 +14 -1
index 84b696f8c..8158356bd 100644
@@ -194,10 +194,23 @@ If this object does not define a PT_TLS segment,
 or if the calling thread has not allocated a block for it,
 NULL is placed in
 .IR *info .
+.TP
+.BR RTLD_DI_PHDR " (\fIconst ElfW(Phdr *)\fP, since glibc 2.34.1)"
+.\" glibc commit d056c212130280c0a54d9a4f72170ec621b70ce5 (2.36)
+.\" glibc commit 28ea43f8d64f0dd1f2de75525157730e1532e600 (2.35.1)
+.\" glibc commit 91c2e6c3db44297bf4cb3a2e3c40236c5b6a0b23 (2.34.1)
+Obtain the address of this shared object's program header and place it
+in
+.IR *info .
+This
+.B dlinfo
+call returns the number of program headers in the shared object.
 .SH RETURN VALUE
 On success,
 .BR dlinfo ()
-returns 0.
+returns 0
+(if not specified explicitly),
+or a positive value corresponding to the request.
 On failure, it returns \-1; the error can be diagnosed using
 .BR dlerror (3).
 .SH ATTRIBUTES

base-commit: 6a7f1461b0e5474d50ef1920558dec103c0c058f

maintainer
#1 lore raw

Hi Florian,

Quoted 19 lines · Florian Weimer

First added in glibc 2.36, backported upstream to glibc 2.34, so mention 2.34.1 for the first version.

Signed-off-by Florian Weimer <[email protected]>

---
v2: Fix commit IDs.

 man/man3/dlinfo.3 | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)
man/man3/dlinfo.3 +1 -0
index 84b696f8c..8158356bd 100644
@@ -194,10 +194,23 @@ If this object does not define a PT_TLS segment,
 or if the calling thread has not allocated a block for it,
 NULL is placed in
 .IR *info .
+.TP

man/man3/dlinfo.3 If this object does not define a PT_TLS segment, · line 207

Quoted 10 lines
man/man3/dlinfo.3 +10 -0
+.BR RTLD_DI_PHDR " (\fIconst ElfW(Phdr *)\fP, since glibc 2.34.1)"
+.\" glibc commit d056c212130280c0a54d9a4f72170ec621b70ce5 (2.36)
+.\" glibc commit 28ea43f8d64f0dd1f2de75525157730e1532e600 (2.35.1)
+.\" glibc commit 91c2e6c3db44297bf4cb3a2e3c40236c5b6a0b23 (2.34.1)
+Obtain the address of this shared object's program header and place it
+in
+.IR *info .
+This
+.B dlinfo
+call returns the number of program headers in the shared object.

Can that number be 0?

man/man3/dlinfo.3 If this object does not define a PT_TLS segment, · line 213

Quoted 7 lines
man/man3/dlinfo.3 +3 -1
 .SH RETURN VALUE
 On success,
 .BR dlinfo ()
-returns 0.
+returns 0
+(if not specified explicitly),
+or a positive value corresponding to the request.

If so, this should be nonnegative rather than positive.

Cheers,
Alex

Quoted 7 lines
man/man3/dlinfo.3 +0 -0
 On failure, it returns \-1; the error can be diagnosed using
 .BR dlerror (3).
 .SH ATTRIBUTES

base-commit: 6a7f1461b0e5474d50ef1920558dec103c0c058f

Signature · 1 line
<https://www.alejandro-colomar.es/>
author
#2 lore raw

* Alejandro Colomar:

Quoted 26 lines

Hi Florian,

Quoted 23 lines · Florian Weimer

First added in glibc 2.36, backported upstream to glibc 2.34, so mention 2.34.1 for the first version.

Signed-off-by Florian Weimer <[email protected]>

---
v2: Fix commit IDs.

 man/man3/dlinfo.3 | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)
man/man3/dlinfo.3 +5 -0
index 84b696f8c..8158356bd 100644
@@ -194,10 +194,23 @@ If this object does not define a PT_TLS segment,
 or if the calling thread has not allocated a block for it,
 NULL is placed in
 .IR *info .
+.TP
+.BR RTLD_DI_PHDR " (\fIconst ElfW(Phdr *)\fP, since glibc 2.34.1)"
+.\" glibc commit d056c212130280c0a54d9a4f72170ec621b70ce5 (2.36)
+.\" glibc commit 28ea43f8d64f0dd1f2de75525157730e1532e600 (2.35.1)
+.\" glibc commit 91c2e6c3db44297bf4cb3a2e3c40236c5b6a0b23 (2.34.1)
Quoted 8 lines

man/man3/dlinfo.3 If this object does not define a PT_TLS segment, · line 207

Quoted 6 lines
man/man3/dlinfo.3 +6 -0
+Obtain the address of this shared object's program header and place it
+in
+.IR *info .
+This
+.B dlinfo
+call returns the number of program headers in the shared object.

Can that number be 0?

No, there has to be at least one PT_LOAD segment.

Thanks,
Florian

maintainer
#3 lore raw

Hi Florian,

Quoted 37 lines · Florian Weimer

* Alejandro Colomar:

Quoted 26 lines

Hi Florian,

Quoted 23 lines · Florian Weimer

First added in glibc 2.36, backported upstream to glibc 2.34, so mention 2.34.1 for the first version.

Signed-off-by Florian Weimer <[email protected]>

---
v2: Fix commit IDs.

 man/man3/dlinfo.3 | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)
man/man3/dlinfo.3 +5 -0
index 84b696f8c..8158356bd 100644
@@ -194,10 +194,23 @@ If this object does not define a PT_TLS segment,
 or if the calling thread has not allocated a block for it,
 NULL is placed in
 .IR *info .
+.TP
+.BR RTLD_DI_PHDR " (\fIconst ElfW(Phdr *)\fP, since glibc 2.34.1)"
+.\" glibc commit d056c212130280c0a54d9a4f72170ec621b70ce5 (2.36)
+.\" glibc commit 28ea43f8d64f0dd1f2de75525157730e1532e600 (2.35.1)
+.\" glibc commit 91c2e6c3db44297bf4cb3a2e3c40236c5b6a0b23 (2.34.1)
Quoted 8 lines

man/man3/dlinfo.3 If this object does not define a PT_TLS segment, · line 207

Quoted 6 lines
man/man3/dlinfo.3 +6 -0
+Obtain the address of this shared object's program header and place it
+in
+.IR *info .
+This
+.B dlinfo
+call returns the number of program headers in the shared object.

Can that number be 0?

Quoted 1 line

No, there has to be at least one PT_LOAD segment.

Thanks! I've applied the patch.

Cheers,
Alex

Quoted 4 lines

Thanks,
Florian

Signature · 1 line
<https://www.alejandro-colomar.es/>