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* [glibc/release/2.39/master] arm: Remove wrong ldr from _dl_start_user (BZ 31339)
@ 2024-02-05 19:06 Adhemerval Zanella
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From: Adhemerval Zanella @ 2024-02-05 19:06 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=63295e4fda1f6dab4bf7442706fe303bf283036c
commit 63295e4fda1f6dab4bf7442706fe303bf283036c
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Mon Feb 5 16:10:24 2024 +0000
arm: Remove wrong ldr from _dl_start_user (BZ 31339)
The commit 49d877a80b29d3002887b084eec6676d9f5fec18 (arm: Remove
_dl_skip_args usage) removed the _SKIP_ARGS literal, which was
previously loader to r4 on loader _start. However, the cleanup did not
remove the following 'ldr r4, [sl, r4]' on _dl_start_user, used to check
to skip the arguments after ld self-relocations.
In my testing, the kernel initially set r4 to 0, which makes the
ldr instruction just read the _GLOBAL_OFFSET_TABLE_. However, since r4
is a callee-saved register; a different runtime might not zero
initialize it and thus trigger an invalid memory access.
Checked on arm-linux-gnu.
Reported-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
(cherry picked from commit 1e25112dc0cb2515d27d8d178b1ecce778a9d37a)
Diff:
---
sysdeps/arm/dl-machine.h | 1 -
1 file changed, 1 deletion(-)
diff --git a/sysdeps/arm/dl-machine.h b/sysdeps/arm/dl-machine.h
index b857bbc868..dd1a0f6b6e 100644
--- a/sysdeps/arm/dl-machine.h
+++ b/sysdeps/arm/dl-machine.h
@@ -139,7 +139,6 @@ _start:\n\
_dl_start_user:\n\
adr r6, .L_GET_GOT\n\
add sl, sl, r6\n\
- ldr r4, [sl, r4]\n\
@ save the entry point in another register\n\
mov r6, r0\n\
@ get the original arg count\n\
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