Bug 497861 - ARM: SUBW Rd, Rn, #uimm12 should accept SP as Rn
Summary: ARM: SUBW Rd, Rn, #uimm12 should accept SP as Rn
Status: REPORTED
Alias: None
Product: valgrind
Classification: Developer tools
Component: vex (other bugs)
Version First Reported In: 3.24 GIT
Platform: unspecified Other
: NOR normal
Target Milestone: ---
Assignee: Julian Seward
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2024-12-24 12:10 UTC by Angelos Oikonomopoulos
Modified: 2024-12-24 12:10 UTC (History)
0 users

See Also:
Latest Commit:
Version Fixed/Implemented In:
Sentry Crash Report:

Attachments
A trivial fix. (586 bytes, patch)
2024-12-24 12:10 UTC, Angelos Oikonomopoulos 		Details
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Description Angelos Oikonomopoulos 2024-12-24 12:10:06 UTC 
Created attachment 176865 [details]
A trivial fix.

SUMMARY
The ARM manual specifies (https://developer.arm.com/documentation/dui0489/i/arm-and-thumb-instructions/sub) that SUBW Rd, Rn, #uimm12 accepts SP as Rn. However, the (T4) SUBW Rd, Rn, #uimm12 case in guest_arm_toIR.c only accepts this form when SP is both Rd and Rn.

STEPS TO REPRODUCE
1. Manually code up a program that uses such an instruction, e.g. I ran into subw    r3, sp, #8 in WebKit's JavaScriptCore.
2. Run the program natively, observe that it doesn't hit a SIGILL.
3. Run the program under valgrind, observe that it takes a SIGILL.

OBSERVED RESULT

SIGILL.

EXPECTED RESULT

No SIGILL.

SOFTWARE/OS VERSIONS
Valgrind at commit 04edd792bd707bace8ccbf947b48b0c70b7dc5d0.

ADDITIONAL INFORMATION